Synthesis, structure and tropicity of an 1113fulvalene derivative

摘要

J. Chem. Soc. Perkin Trans. 1 1997 3183 Synthesis structure and tropicity of an 1113fulvalene derivative Gaku Yamamoto,*,a Yasuhiro Mazaki,a Ryoji Kobayashi,b Hiroyuki Higuchi b and Ju�ro Ojima *,b a Department of Chemistry School of Science Kitasato University Kitasato Sagamihara Kanagawa 228 Japan b Department of Chemistry Faculty of Science Toyama University Gofuku Toyama 930 Japan An 1113fulvalene derivative 13-(4,9-methanocycloundeca-2,4,6,8,10-pentaenylidene)-4,9-dimethylcyclotrideca- 1,3,9,11-tetraene-5,7-diyne has been synthesized. Examination of 1H and 13C NMR spectra indicates that the compound shows no detectable ring-current effect in nonpolar solvents arising from 10�- and 14�-electron systems which is verified by X-ray crystallographic structural analysis. In a polar solvent 2H6dimethyl sulfoxide a small contribution of the dipolar resonance structure is suggested.Introduction An extension of our interests in ring-expanded fulvalenes led us to the preparation of fulvalene derivatives composed of two large-membered rings.1 The only known macrocyclic compound of this type was a tetra(cyclohexane)-annulated 1313- fulvalene derivative 1,2 which was prepared by Howes and Sondheimer in 1978 and was found to be thermally unstable and completely atropic. The fact that compound 1 carries two rings of the same size can be associated with the absence of any cross-conjugation of p-electrons or any contribution from a dipolar resonance structure. Then we considered that the 1315fulvalene 2,3 in which one ring is 13-membered and the other is 15-membered is potentially aromatic as is sesquifulvalene 3,4 since polarization of the pinch bond would make both rings 14p-electron aromatic systems as shown in a dipolar structure 2a.However although compound 2 was isolated as thermally relatively stable crystals unlike compound 1 the compound shows no ring-current effect but instead a polyolefinic character indicating the absence of any contribution from a dipolar structure. It is recognized 5 that tropicity of annulenes usually increases with a decrease in the ring size. We considered that the replacement of one ring in compound 2 by a smaller ring with larger tropicity would facilitate polarization of the pinch bond. Thus we chose a fulvalene derivative 4 with 11- and 13-membered rings. Polarization of the pinch bond of compound 4 would afford a 10p/14p aromatic system.Another expectation was that the compound would give thermally stable crystals that would be suitable for X-ray crystallographic study. Results and discussion Synthesis A successful preparation of compound 2 stimulated us to elaborate an acyclic exocyclic moiety leading to a 13-membered conjugated system upon the methano-bridged 11-membered ring of compound 5. Thus the synthesis of compound 4 was planned and performed according to the reaction sequence outlined in Scheme 1. Reduction of the dicyanofulvene 5 6 with diisobutylaluminium hydride (DIBAH) in toluene at 210 8C afforded the cyano(formyl)fulvene 6 in 40 yield. Treatment of 3-methylpent- 2-en-4-ynyltriphenylphosphonium bromide 7 7 in tetrahydrofuran (THF) with butyllithium led to the corresponding ylide which was allowed to react with the cyano(formyl)fulvene 6 to afford a mixture of the E-isomer 8a and the Z-isomer 8b of the newly formed double bond in a ratio of 5 3 which were separately isolated by chromatography on silica gel.Individual reduction of compounds 8a and 8b with DIBAH in toluene at 210 8C afforded the E-isomer 9a (40) and Zisomer 9b (30) of the ethynyl(formyl)fulvene respectively retaining the stereochemistry of the substrates 8. However the Z-isomer 9b proved to be less stable than the E-isomer 9a and gradually isomerized to the E-isomer during chromatography. The ylide derived from the salt 7 was treated with an isomeric mixture of compounds 9 to afford a stereoisomeric mixture of the acyclic diethynylfulvene 10 as a semi-solid in 37 yield which was too unstable to give satisfactory spectral and analytical data.The structure of a desirable isomer of com- 1 Me Me Me Me 2 2 3 4 12 13 11 Me Me Me Me + 2a ndash; 3 Me Me 14 15 13 3 5 6 2 4 7 8 10 11 24 23 b a 22 3184 J. Chem. Soc. Perkin Trans. 1 1997 Scheme 1 CN CN CHO CN 5 a b 2 3 5 6 7 8 10 11 6 CN Me Me CH2PPh3 Br b a 6 5 3 2 7 8 10 11 13 14 15 7 8a + CN Me a b 6 7 5 8 3 10 2 11 13 14 15 8b CHO Me CHO Me a b b a 14 15 13 2 3 5 6 7 8 10 11 15 13 2 3 6 8 10 5 7 14 11 9b 9a + Me Me 10 4 7 + ndash; pound 10 is shown in Scheme 1. An intramolecular oxidative coupling of compound 10 as a mixture with its stereoisomers using anhydrous copper(II) acetate in pyridinendash;diethyl ether at 50 8C under relatively dilute conditions afforded the desired 1113fulvalene 13-(4,9-methanocycloundeca-2,4,6,8,- 10-pentaenylidene)-4,9-dimethylcyclotrideca-1,3,9,11-tetraene- 5,7-diyne 4 in 25 yield as relatively stable blackndash;purple needles.NMR spectral studies The 1H NMR spectrum of compound 4 obtained in CDCl3 was analysed with the aid of homonuclear double resonance and nuclear Overhauser effect (NOE) experiments and the data are given in Table 1. The chemical shift data in CDCl3 indicate that no appreciable ring-current effect is detected judging from a comparison with the data for the precursors 8 and 9 and with those for the 1315fulvalene 23 and 1,6-methano11annulen- 9-one 11,8 both of which have been concluded to be atropic. Thus it should be concluded that compound 4 is atropic and the O 11 Table 1 1H NMR data of compound 4 a Proton CH3 CH2 a b 2 3 5 6 13 14 15 in CDCl3 1.915s 0.161d (11.1) 3.266d (11.1) 6.674d (11.8) 6.058d (11.8) 6.604m 7.031m 6.777d (15.9) 7.071dd (15.9 10.4) 6.757d (10.4) in 2H6DMSO 1.907s 0.041d (10.8) 3.082d (10.8) 6.774d (11.8) 6.168d (11.8) 6.730m 7.072m 6.889d (16.3) 6.788dd (16.3 9.7) 6.998d (9.7) Dd b/ppm 20.01 20.12 20.18 0.10 0.11 0.13 0.04 0.11 20.28 0.24 a Chemical shifts are given in d-values.Coupling constants (J/Hz) are given in parentheses. b Negative values mean upfield shifts upon going from CDCl3 to 2H6DMSO. contribution of the dipolar resonance structure 4a is negligibly small if any. The 13C chemical shifts of compound 4 were also thoroughly assigned on the basis of the CH-chemical shift correlation spectroscopy (CH-COSY) 1H-coupled and selectively 1Hdecoupled spectra and are compiled in Table 2.The chemical shift difference between the pinch bond carbons is 8.1 ppm in CDCl3 a similar value to that in sesquifulvalene 34 (7.9 ppm) but it would be dangerous to consider that the large chemical shift difference is an indication of the contribution of the dipolar structure. The contribution of the dipolar structure 4a was naturally expected to increase in more polar media and thus the 1H and 13C NMR spectra were examined in 2H6dimethyl sulfoxide (2H6DMSO) and the data are included in Tables 1 and 2. In the 1H spectrum the signals of the methylene protons shift upfield by ~0.15 ppm and those of the olefinic protons of the 11-membered ring shift downfield by ~0.1 ppm upon going from CDCl3 to 2H6DMSO. Similarly the signal of the inner olefinic protons of the 13-membered ring moves upfield and those of the outer olefinic protons downfield though the methyl proton signal shows no significant shift.These shifts Table 2 13C NMR data of compound 4a Carbon CH3 CH2 1 2 3 4 5 6 12 13 14 15 16 17 18 in CDCl3 19.84 31.11 142.23 130.84 118.51 121.10 124.53 130.04 134.15 125.71 131.56 142.19 120.35 100.72 85.30 in 2H6DMSO 19.16 30.83 143.52 131.04 118.21 119.93 124.56 130.10 132.93 125.94 130.44 142.86 119.25 100.96 84.55 Dd b/ppm 20.7 20.3 1.3 0.2 20.3 21.2 0.0 0.1 21.2 0.2 21.1 0.7 21.1 0.2 20.8 a Chemical shifts are given in d-values. b Negative values mean upfield shifts upon going from CDCl3 to 2H6DMSO. J. Chem. Soc. Perkin Trans. 1 1997 3185 clearly indicate the increase in diatropicity in a more polar solvent although the extent is very small.The solvent effect on the 13C chemical shifts seems compatible with the increased contribution of the dipolar structure 4a in 2H6DMSO. The arithmetic average of the shifts upon the solvent change is 20.38 ppm for the 13-membered ring carbd 20.10 ppm for the 11-membered ring carbons. The larger upfield shifts for the 13-membered ring carbons presumably reflect the increase in the negative charge in this ring due to the increased contribution of the dipolar structure. The C-4 signal moves upfield by 1.2 ppm and we have no explanation for this. If it is assumed that the solvent shift reflects the change in the p-electron density at that carbon the data suggest that the increase in the positive charge is almost localized at C-1 while the increase in the negative charge is delocalized at one-carbon intervals i.e.at C-12 C-14 C-16 and C-18 as shown by the resonance structures 4bndash;4e. X-Ray crystallographic study Single crystals of compound 4 suitable for X-ray crystallography were obtained by recrystallization from hexanendash; dichloromethane and one of them was submitted for the analysis. The molecular structure is shown in Fig. 1 and selected bond lengths and angles are compiled in Table 3. The geometry around the pinch bond (C-1C-12) is almost planar though C-1 is slightly pyramidalized the angle sum being 358.58. The 13-membered ring is slightly twisted from planarity while retaining the local C2 symmetry. The 11- membered ring part is significantly folded. The interplanar Me Me Me Me Me Me Me Me Me Me Me Me 4 4a 4b 4c 4d 4e + ndash; + + ndash; ndash; ndash; + + bull; bull; bull;bull; bull;bull; bull; bull; ndash; angle between the C-1C-2C-11 and C-2C-3C-10C11 planes is 41.58.This large folding might be responsible for the localization of the positive charge in the resonance structures 4bndash;4e. The length of the pinch bond is 1.384 Aring; and thus is signifi- cantly longer than the usual C C double bonds. The lengths of the formal double bonds other than the pinch bond range from 1.308 to 1.383 Aring; while those of the sp2sp2 single bonds range from 1.414 to 1.496 Aring;. These structural features seem to be consistent with the polyolefinic nature of compound 4 as suggested by NMR spectroscopy mentioned above. In conclusion the 1113fulvalene 4 shows no detectable tropicity in a medium with low polarity such as CDCl3 and behaves as a polyolefin and the molecular structure obtained by X-ray crystallography is compatible with this feature.Meanwhile in a polar medium such as DMSO the dipolar resonance structure 4a is stabilized and contributes to some very small extent. Experimental Mps were determined on a hot-stage apparatus and are uncorrected. IR spectra were taken with a JASCO-7300 spectrophotometer as KBr discs unless otherwise specified; only significant maxima are described. Electronic (UV/visible) spectra were measured in THF solution with a Shimadzu 2200A spectrophotometer. Mass spectra were recorded with a JEOL JMS-D 300 spectrometer operating at 75 eV using a direct-inlet system. 1H NMR spectra at ambient temperature were recorded in CDCl3 unless otherwise indicated on a Bruker ARX-300 spectrometer at 300.13 MHz with internal SiMe4 (TMS) as the reference.J Values are given in Hz. 13C NMR spectra were recorded in CDCl3 on the ARX-300 at 75.48 MHz with CDCl3 at dC 77.0 as the reference. The letters p s t and q given with the 13C NMR chemical shifts refer to primary secondary tertiary and quaternary respectively. Progress of all reactions was followed by TLC on Merck precoated silica gel plates. Alumina (Merck activity IIndash;III) and silica gel (Daiso gel 1001 W or Daiso gel 1002 W) were used for column chromatography. Compounds were pre-adsorbed from Fig. 1 Top and side views of the molecular structure of compound 4 with crystallographic numbering scheme 3186 J. Chem. Soc. Perkin Trans. 1 1997 Table 3 Selected bond lengths (Aring;) bond angles (8) and torsional angles (8) 12 111 112 23 34 45 425 56 67 78 89 910 925 1011 1213 1224 1314 1415 1516 1617 1626 1718 1819 1920 2021 2122 2127 2223 2324 1.496(6) 1.468(7) 1.384(6) 1.318(6) 1.454(6) 1.383(6) 1.482(6) 1.412(8) 1.344(9) 1.435(9) 1.363(7) 1.436(8) 1.505(8) 1.351(7) 1.464(7) 1.454(7) 1.316(7) 1.431(8) 1.358(6) 1.419(7) 1.510(7) 1.210(7) 1.377(8) 1.197(8) 1.423(8) 1.356(7) 1.498(7) 1.445(7) 1.308(7) 2111 2112 11112 123 234 345 3425 5425 456 567 678 789 8910 8925 10925 91011 11110 11213 11224 131224 121314 131415 141516 151617 161718 171819 181920 192021 202122 212223 222324 122423 117.9(4) 119.4(4) 121.2(4) 132.1(5) 127.1(5) 122.0(5) 119.8(4) 117.8(5) 123.7(6) 126.4(6) 126.3(6) 123.2(7) 122.5(6) 118.3(6) 118.9(5) 127.5(6) 132.2(6) 119.7(5) 118.6(5) 121.8(5) 129.4(5) 127.7(6) 123.4(6) 117.2(5) 165.0(6) 160.7(5) 162.1(6) 163.8(5) 115.3(5) 125.6(5) 127.5(6) 130.8(6) 11123 12123 211110 1211110 211213 211224 1111213 1111224 1234 2345 23425 3456 25456 34259 54259 4567 5678 6789 78910 78925 891011 2591011 89254 109254 910111 1121314 24121314 1122423 13122423 12131415 13141516 14151617 20212223 21222324 22232412 55.9 2137.9 256.8 137.2 5.9 2173.6 171.7 27.8 4.4 2160.6 11.8 156.7 215.9 293.7 79.0 229.7 0.9 27.6 2156.2 17.5 160.9 212.7 280.2 93.7 22.6 2161.1 18.4 2175.4 5.1 179.9 167.2 21.8 22.0 167.6 2176.2 benzene solution onto the adsorbent before column chromatography.Organic extracts were washed with saturated aq. sodium chloride and dried over anhydrous sodium sulfate prior to the removal of solvent.Solvents were evaporated under water-pump pressure. Ether refers to diethyl ether. 12,12-Dicyano-4,9-methanoundecafulvene 5 6 A stirred mixture of 1,6-methano11annulen-9-one 11 8 (150 mg 0.89 mmol) and malononitrile (117 mg 1.78 mmol) in acetic anhydride (4 cm3) was refluxed for 2.5 h. The solution was cooled to room temperature poured onto water and extracted with dichloromethane. The combined extracts were washed with aq. NaHCO3 and dried. The residue obtained after removal of solvent was chromatographed on silica gel (3.5 times; 10 cm). The fractions eluted with benzene afforded the undecafulvene 5 (101 mg 52) as red needles mp 248ndash;250 8C (from hexanendash;dichloromethane) (lit.,6 mp 250ndash;252 8C). 12-Cyano-12-formyl-4,9-methanoundecafulvene 6 To a stirred solution of the dicyanofulvene 5 (100 mg 0.453 mmol) in toluene (70 cm3) at 28 8C was added dropwise a solution of DIBAH (1.5 mol dm23; 0.9 cm3 1.4 mmol) in toluene by a syringe under argon during 10 min and the solution was then stirred for 1 h at the same temperature.Then 5 sulfuric acid (20 cm3) was added dropwise to the mixture below 0 8C and the mixture was extracted with benzene. The combined extracts were washed with aq. NaHCO3 and dried. The residue obtained after removal of solvent was chromatographed on silica gel (3.2 times; 10 cm). The initial fractions eluted with benzenendash;dichloromethane (1 1) afforded the unchanged dicyanofulvene 5 (3 mg recovery). The following fractions eluted with benzenendash;dichloromethane (1 4) afforded the cyano( formyl ) fulvene 6 (40 mg 40) as dark red needles mp 213ndash;214 8C (from hexanendash;dichloromethane); m/z 221 (M1 100) (C15H11NO requires M 221.2); nmax/cm21 2923 2884 (CHO) 2209 (C N) 1655 (C O) and 1582 (C C); lmax/nm 239 (e/dm3 mol21 cm21 18 900) 330 (17 000) and 451 (12 600); dH 9.977 (1 H s CHO) 7.390 (2 H m 6- and 7-H) 7.276 (1 H d J 12 10- H) 7.234 (1 H d J 12 3-H) 7.001 (2 H m 5- and 8-H) 6.873 (1 H d J 12 2-H) 6.582 (1 H d J 12 11-H) 2.167 (1 H dt J 11.3 and 1.5 Hb) and 0.173 (1 H d J 11.3 Ha); dC 185.46 (CHO) 161.95 (q) 139.29 (t) 139.27 (t) 132.67 (t) 132.62 (t) 127.76 (t) 127.62 (t) 122.95 (q) 122.45 (q) 116.70 (t) 115.86 (q) 114.98 (t) 111.99 (q) and 33.87 (s) (Found C 81.3; H 5.2; N 6.3.C15H11NO requires C 81.4; H 5.0; N 6.3). Isomeric 2-(4,9-methanocycloundeca-2,4,6,8,10-pentaenylidene)- 6-methylocta-3,5-dien-7-ynenitriles 8a and 8b To a stirred suspension of 3-methylpent-2-en-4-ynyltriphenylphosphonium bromide 7 7 (1.58 g 3.75 mmol) in dry THF (45 cm3) at 240 8C was added dropwise a solution of butyllithium (1.6 mol dm23; 2.34 cm3 3.75 mmol) in hexane by a syringe during 20 min under argon.After the mixture had been stirred for 1 h at 240 8C a solution of the cyano(formyl)fulvene 6 (166 mg 0.750 mmol) in THF (30 cm3) was added dropwise during 1.5 h below 230 8C and the solution was stirred for further 2 h at 215 8C. After addition of ethyl acetate (14 cm3) the mixture was poured into icendash;water and extracted with benzene. The combined organic layers were washed with brine and dried. The product obtained after removal of solvent was chromatographed on silica gel (3.2 times; 12 cm).The initial fractions eluted with hexanendash;ether (9 1) afforded the Z-isomer 8b (53 mg 25) as dark red needles mp 137ndash;140 8C (decomp.) (from hexanendash; dichloromethane); m/z 283 (M1 100) (C21H17N requires M 283.3); nmax/cm21 3290 (C CH) 2203 (C N) 2083 (C C) 1600 (C C) and 768 (Z)-HC CH; lmax/nm 239 (e 32 100) 285 (13 300) 343 (31 600) and 427 (29 000); dH 7.416 (1 H d J 12.2 15-H) 7.17ndash;7.07 (2 H m 6- and 7-H) 6.879 (1 H d J 11.9 3- H) 6.809 (1 H d J 11.8 10-H) 6.751 (1 H t J 12 14-H) 6.70ndash; 6.62 (2 H m 5- and 8-H) 6.242 (1 H d J 12 2-H) 6.164 (1 H d J 11.8 13-H) 5.817 (1 H d J 11.9 11-H) 3.422 (1 H s C CH) 2.923 (1 H dt J 11.3 and 1.3 Hb) 2.046 (3 H s Me) J. Chem. Soc. Perkin Trans. 1 1997 3187 and 0.371 (1 H d J 11.3 Ha); dC 134.71 (t) 134.62 (t) 132.42 (t) 131.38 (t) 131.01 (t) 129.76 (t) 125.64 (t) 125.32 (t) 123.38 (q) 121.67 (q) 121.55 (q) 120.11 (t) 118.58 (q) 118.54 (t) 116.46 (t) 110.67 (q C N) 85.17 (t C CH) 82.59 (q ndash;C ) 32.54 (s) and 23.68 (p) (Found C 88.9; H 6.2; N 5.0.C21H17N requires C 89.0; H 6.05; N 4.9). The following fractions eluted with hexanendash;ether (9 1) afforded the E-isomer 8a (32 mg 15) as dark red needles mp 163ndash;164 8C (decomp.) (from hexanendash;dichloromethane); m/z 283 (M1 100); nmax/cm21 3287 (C CH) 2214 (C N) 2080 (C C) 1603 (C C) and 960 (E)-HC CH; lmax/nm 234 (e 32 900) 283 (12 300) 345 (36 100) and 429 (38 200); dH 7.209 (1 H dd J 15.2 and 11.2 14-H) 7.13ndash;7.04 (2 H m 6- and 7-H) 6.823 (1 H d J 11.7 3-H) 6.783 (1 H d J 11.7 10-H) 6.676 (1 H d J 15.2 13-H) 6.65ndash;6.63 (2 H m 5- and 8-H) 6.443 (1 H d J 11.2 15-H) 6.231 (1 H d J 11.9 2-H) 5.881 (1 H d J 11.9 11-H) 3.436 (1 H s C CH) 3.054 (1 H dt J 11.3 and 1.3 Hb) 2.006 (3 H s Me) and 0.441 (1 H d J 11.3 Ha); dC 136.73 (t) 134.71 (t) 134.29 (t) 131.40 (t) 131.29 (t) 131.0 (t) 125.50 (t) 125.19 (t) 124.84 (t) 121.88 (q) 121.74 (q) 121.59 (q) 119.14 (t) 116.35 (q) 116.14 (t) 114.66 (q C N) 84.98 (t C CH) 82.55 (q C ) 32.56 (s) and 23.48 (p) (Found C 89.3; H 6.05; N 4.8).(3Z,5Z)-2-(4,9-Methanocycloundeca-2,4,6,8,10-pentaenylidene)- 6-methylocta-3,5-dien-7-ynal 9b To a stirred solution of the Z-isomer 8b of the cyanofulvene (104 mg 0.367 mmol) in dry toluene (56 cm3) at 210 8C was added dropwise a solution of DIBAH (1.5 mol dm23; 1.2 cm3 1.84 mmol) in toluene during 15 min by a syringe under argon and the solution was then stirred for 30 min at the same temperature.Then 5 sulfuric acid (13 cm3) was added dropwise to the mixture below 0 8C and the mixture was extracted with benzene. The combined extracts were washed with aq. NaHCO3 and dried. The product obtained after removal of solvent was chromatographed on silica gel (3.5 times; 10 cm). The fractions eluted with benzene afforded the Z-isomer 9b of the formylfulvene (32 mg 30) as orange needles mp 94ndash;96 8C (from hexanendash;benzene); m/z 286 (M1 100) (C21H18O requires M 286.3); nmax/cm21 3295 (C CH) 2923 2852 (CHO) 2092 (C C) 1659 (C O) 1596 (C C) and 741 (Z)-HC CH; lmax/ nm 246 (e 11 500) 332 (7200) and 421 (4900); dH 10.231 (1 H s CHO) 7.18ndash;7.10 (2 H m 6- and 7-H) 6.877 (1 H d J 12 10-H) 6.842 (1 H t J 11.4 14-H) 6.761 (1 H d J 11.9 3- H) 6.732 (1 H m 8-H) 6.694 (1 H m 5-H) 6.455 (1 H dd J 11.9 and 1.7 11-H) 6.225 (1 H d J 11.3 15-H) 6.067 (1 H d J 11.4 13-H) 5.822 (1 H dd J 11.8 and 1.4 2-H) 3.353 (1 H s C CH) 3.004 (1 H dt J 11.2 and 1.3 Hb) 1.895 (3 H s Me) and 0.265 (1 H d J 11.1 Ha); dC 191.84 (t CHO) 151.18 (q) 134.81 (t) 134.17 (q) 133.84 (t) 132.54 (t) 131.35 (t) 130.86 (t) 130.86 (t) 125.45 (t) 125.42 (t) 123.99 (t) 121.05 (q) 120.98 (q) 120.77 (q) 117.52 (t) 115.26 (t) 83.93 (t C CH) 82.71 (q C ) 32.15 (s) and 23.39 (p) (Found C 88.0; H 6.5.C21H18O requires C 88.1; H 6.3). (3E,5Z)-2-(4,9-Methanocycloundeca-2,4,6,8,10-pentaenylidene)- 6-methylocta-3,5-dien-7-ynal 9a The conversion of the cyanofulvene 8a into the formylfulvene 9a was carried out in the exactly same manner as that of 8b into 9b using substrate 8a (47 mg 0.17 mmol) in dry toluene (65 cm3) with DIBAH (0.91 mmol) in toluene.The product obtained after removal of solvent was chromatographed on silica gel (3.5 times; 10 cm). The fractions eluted with benzene afforded the E-isomer 9a of the formylfulvene (20 mg 41) as dark red needles mp 136ndash;140 8C (decomp.) (from hexanendash; benzene); m/z 286 (M1 96) and 115 (100) (C21H18O requires M 286.3); nmax/cm21 3285 (C CH) 2931 2851 (CHO) 2081 (C C) 1664 (C O) 1598 (C C) and 983 (E)-HC CH; lmax/nm 239 (e 13 100) 293 (8900) 338 (9300) and 431 (8200); dH 10.402 (1 H d J 1.3 CHO) 7.554 (1 H dd J 15.8 and 11.1 14-H) 7.18ndash;7.00 (2 H m 6- and 7-H) 6.841 (1 H d J 11.8 10-H) 6.816 (1 H d J 11.8 3-H) 6.75ndash;6.68 (2 H m 5- and 8-H) 6.577 (1 H d J 15.8 13-H) 6.430 (1 H d J 11.0 15-H) 6.288 (1 H d J 11.9 11-H) 5.979 (1 H d J 11.8 2-H) 3.385 (1 H s C CH) 2.990 (1 H dt J 11.2 and 1.3 Hb) 1.993 (3 H s Me) and 0.161 (1 H d J 11.5 Ha); dC 192.65 (t CHO) 149.74 (q) 138.98 (t) 133.27 (t) 132.46 (t) 132.46 (t) 131.19 (q) 130.68 (t) 130.64 (t) 125.52 (t) 125.33 (t) 125.33 (t) 121.03 (q) 120.91 (q) 120.16 (q) 115.97 (t) 114.59 (t) 83.67 (t C CH) 83.06 (q C ) 31.74 (s) and 23.25 (p) (Found C 88.0; H 6.3).Isomeric 7-(4,9-methanocycloundeca-2,4,6,8,10-pentaenylidene)- 3,11-dimethyltrideca-3,5,8,10-tetraene-1,12-diyne 10 To a stirred suspension of the salt 7 7 (2.37 g 5.60 mmol) in dry THF (70 cm3) at 250 8C was added dropwise a solution of butyllithium (1.6 mol dm23; 3.6 cm3 5.60 mmol) in hexane by a syringe during 20 min under argon.After the mixture had been stirred for 1 h at 250 8C a solution of a stereoisomeric mixture of the formylfulvene 9 (161 mg 0.560 mmol) in dry THF (110 cm3) was added dropwise during 1.5 h at 230 8C and the solution was stirred for further 2 h at the same temperature. After addition of ethyl acetate (15 cm3) the mixture was worked up as for the isolation of the nitrile 6. The product obtained after removal of solvent was passed through a short column of alumina (3.2 times; 5 cm). The fractions eluted with hexanendash;ether (4 1) afforded the acyclic diacetylene 10 (72 mg 37) as a dark brown semi-solid. Since compound 10 proved to be extremely unstable towards diffused light and air it was used for the following reaction without further purification.13-(4,9-Methanocycloundeca-2,4,6,8,10-pentaenylidene)-4,9- dimethylcyclotrideca-1,3,9,11-tetraene-5,7-diyne 4 A solution of a stereoisomeric mixture of the acyclic diacetylene 10 (72 mg 0.21 mmol) in a mixture of pyridine (20 cm3) and ether (7 cm3) was added dropwise during 2.5 h to a stirred solution of anhydrous copper(II) acetate (262 mg 1.45 mmol) in a mixture of pyridine (43 cm3) and ether (14 cm3) at 50 8C and the mixture was stirred for further 1 h before being poured into water and extracted with benzene. The extracts were washed with 5 HCl until they turned acidic (to litmus) and then with aq. NaHCO3 and dried. The product obtained after removal of solvent was chromatographed on silica gel (3.8 times; 12 cm). The fractions eluted with 5 benzene in hexane afforded the 1113 fulvalene 4 (18 mg 25) as black-purple needles mp 182ndash;185 8C (decomp.) (from hexanendash;dichloromethane); m/z 346 (M1 36) and 28 (100) (C27H22 requires M 346.4); nmax/ cm21 2148 (C C) 970 (E)-HC CH and 756 (Z)-HC CH; lmax/nm 237 (e 28 300) 267 (26 200) 308 (26 800) and 452 (24 300) (Found C 93.8; H 6.5.C27H22 requires C 93.6; H 6.4). X-Ray crystallographic analysis of compound 4 Crystals of compound 4 were grown from hexanendash;dichloromethane. Intensity data were collected on a Rigaku AFC-7R diffractometer using graphite-monochromated Mo-Ka radiation (l = 0.710 73 Aring;) with w scan mode. Accurate unit-cell dimensions and crystal-orientated matrix were obtained from least-squares refinement of 25 strong reflections in the range 218 2q 258. The structure was solved by direct methods using SHELXS-869 and subsequent calculations were carried out by the SHELXL-9310 program.The positions of all hydrogen atoms were located by difference Fourier synthesis. The refinement was accomplished on Fo 2 by means of full-matrix least-squares methods anisotropically for all carbons and isotropically for all hydrogens. Final difference map peaks were in the range from 0.150 to 20.16 Aring;23 and the maximal D/s being 0.001. The crystal data and parameters for data collection, 3188 J. Chem. Soc. Perkin Trans. 1 1997 structure determination and refinement are summarized in Table 4.dagger; Acknowledgements Financial support by Grant-in-Aids for Scientific Research Nos. 07246111 and 08454199 from the Ministry of Education Table 4 Crystal data for compound 4 and parameters for data collection structure determination and refinement Empirical formula Relative molecular mass Crystal dimension (mm) Crystal system Space group a (Aring;) b (Aring;) c (Aring;) V (Aring;3) Z Dc (g cm23) F(000) m(Mo-Ka) (cm21) Temp.(8C) Scan width (8) 2qmax (8) No. of reflections measured Total With I 2s(I) No. of refinement variables Final R; Rw a C27H22 346.45 0.6 times; 0.3 times; 0.1 Orthorhombic P212121 (No. 19) 11.745(2) 26.259(4) 6.334(2) 1953.6(6) 4 1.178 736 0.066 20.0 0.997 plusmn; 0.30 tan q 55 2598 1062 332 0.050; 0.097 a R= S(verbar;Foverbar;2verbar;Fcverbar;)/Sverbar;Foverbar; Rw = Sw(Fo 2 2 Fc 2)2/Sw(Fo 2)2� �� w = s2(Fo 2) 1 (0.0422P)221 where P = (Fo 2 1 2Fc 2)/3. dagger; Atomic coordinates thermal parameters and bond lengths and angles have been deposited at the Cambridge Crystallographic Data Centre (CCDC). See Instructions for Authors J.Chem. Soc. Perkin Trans. 1 1997 Issue 1. Any request to the CCDC for this material should quote the full literature citation and the reference number 207/139. Science Sports and Culture (Japan) is gratefully acknowledged. References 1 T. Asao N. Morita J. Ojima and M. Fujiyoshi Tetrahedron Lett. 1978 2795; N. Morita T. Asao J. Ojima and K. Wada Chem. Lett. 1981 57; N. Morita T. Asao J. Ojima and S. Hamai Chem. Lett. 1983 1887; T. Asao N. Morita J. Ojima M. Fujiyoshi K. Wada and S. Hamai Bull. Chem. Soc. Jpn. 1986 59 1713; J. Ojima K. Itagawa and T. Nakada Tetrahedron Lett. 1983 24 5273; Bull. Chem. Soc. Jpn. 1986 59 1723. 2 P. D. Howes and F. Sondheimer J. Org. Chem. 1978 43 2158. 3 H. Higuchi K. Kitamura J. Ojima K. Yamamoto and G. Yamamoto Chem. Lett. 1992 257; J.Chem. Soc. Perkin Trans. 1 1992 1343. 4 W. K. Schenck R. Kyburg and M. Neuenschwander Helv. Chim. Acta 1975 58 1099; M. Neuenschwander Pure Appl. Chem. 1986 58 55. 5 M. Nakagawa Pure Appl. Chem. 1975 44 885; A. T. Balaban M. Banciu and V. Ciorba Annulenes Benzo- Hetero- Homo- Derivatives and their Valence Isomers CRC Press Florida 1987 vol. 1 p. 67; J. Ojima S. Fujita M. Masumoto E. Ejiri T. Kato S. Kuroda Y. Nozawa S. Hirooka and H. Tatemitsu J. Chem. Soc. Perkin Trans. 1 1988 385; H. Higuchi H. Yamamoto J. Ojima M. Iyoda M. Yoshida and G. Yamamoto J. Chem. Soc. Perkin Trans. 1 1993 983. 6 E. Vogel and J. Reisdorf unpublished results; J. Reisdorf Ph.D. Dissertation Kouml;ln 1970. 7 J. Ojima E. Ejiri T. Kato M. Nakamura S. Kuroda S. Hirooka and M. Shibutani J. Chem. Soc. Perkin Trans.1 1987 831. 8 W. Grimme J. Reisdorf W. Junemann and E. Vogel J. Am. Chem. Soc. 1970 92 6355. 9 G. M. Sheldrick Acta Crystallogr. Sect. A 1990 46 467. 10 G. M. Sheldrick SHELXL-93 Program for Crystal Structure Refinement University of Gouml;ttingen Germany 1993. Paper 7/04071G Received 10th June 1997 Accepted 26th June 1997 J. Chem. Soc. Perkin Trans. 1 1997 3183 Synthesis structure and tropicity of an 1113fulvalene derivative Gaku Yamamoto,*,a Yasuhiro Mazaki,a Ryoji Kobayashi,b Hiroyuki Higuchi b and Ju�ro Ojima *,b a Department of Chemistry School of Science Kitasato University Kitasato Sagamihara Kanagawa 228 Japan b Department of Chemistry Faculty of Science Toyama University Gofuku Toyama 930 Japan An 1113fulvalene derivative 13-(4,9-methanocycloundeca-2,4,6,8,10-pentaenylidene)-4,9-dimethylcyclotrideca- 1,3,9,11-tetraene-5,7-diyne has been synthesized.Examination of 1H and 13C NMR spectra indicates that the compound shows no detectable ring-current effect in nonpolar solvents arising from 10�- and 14�-electron systems which is verified by X-ray crystallographic structural analysis. In a polar solvent 2H6dimethyl sulfoxide a small contribution of the dipolar resonance structure is suggested. Introduction An extension of our interests in ring-expanded fulvalenes led us to the preparation of fulvalene derivatives composed of two large-membered rings.1 The only known macrocyclic compound of this type was a tetra(cyclohexane)-annulated 1313- fulvalene derivative 1,2 which was prepared by Howes and Sondheimer in 1978 and was found to be thermally unstable and completely atropic.The fact that compound 1 carries two rings of the same size can be associated with the absence of any cross-conjugation of p-electrons or any contribution from a dipolar resonance structure. Then we considered that the 1315fulvalene 2,3 in which one ring is 13-membered and the other is 15-membered is potentially aromatic as is sesquifulvalene 3,4 since polarization of the pinch bond would make both rings 14p-electron aromatic systems as shown in a dipolar structure 2a. However although compound 2 was isolated as thermally relatively stable crystals unlike compound 1 the compound shows no ring-current effect but instead a polyolefinic character indicating the absence of any contribution from a dipolar structure. It is recognized 5 that tropicity of annulenes usually increases with a decrease in the ring size.We considered that the replacement of one ring in compound 2 by a smaller ring with larger tropicity would facilitate polarization of the pinch bond. Thus we chose a fulvalene derivative 4 with 11- and 13-membered rings. Polarization of the pinch bond of compound 4 would afford a 10p/14p aromatic system. Another expectation was that the compound would give thermally stable crystals that would be suitable for X-ray crystallographic study. Results and discussion Synthesis A successful preparation of compound 2 stimulated us to elaborate an acyclic exocyclic moiety leading to a 13-membered conjugated system upon the methano-bridged 11-membered ring of compound 5. Thus the synthesis of compound 4 was planned and performed according to the reaction sequence outlined in Scheme 1.Reduction of the dicyanofulvene 5 6 with diisobutylaluminium hydride (DIBAH) in toluene at 210 8C afforded the cyano(formyl)fulvene 6 in 40 yield. Treatment of 3-methylpent- 2-en-4-ynyltriphenylphosphonium bromide 7 7 in tetrahydrofuran (THF) with butyllithium led to the corresponding ylide which was allowed to react with the cyano(formyl)fulvene 6 to afford a mixture of the E-isomer 8a and the Z-isomer 8b of the newly formed double bond in a ratio of 5 3 which were separately isolated by chromatography on silica gel. Individual reduction of compounds 8a and 8b with DIBAH in toluene at 210 8C afforded the E-isomer 9a (40) and Zisomer 9b (30) of the ethynyl(formyl)fulvene respectively retaining the stereochemistry of the substrates 8.However the Z-isomer 9b proved to be less stable than the E-isomer 9a and gradually isomerized to the E-isomer during chromatography. The ylide derived from the salt 7 was treated with an isomeric mixture of compounds 9 to afford a stereoisomeric mixture of the acyclic diethynylfulvene 10 as a semi-solid in 37 yield which was too unstable to give satisfactory spectral and analytical data. The structure of a desirable isomer of com- 1 Me Me Me Me 2 2 3 4 12 13 11 Me Me Me Me + 2a ndash; 3 Me Me 14 15 13 3 5 6 2 4 7 8 10 11 24 23 b a 22 3184 J. Chem. Soc. Perkin Trans. 1 1997 Scheme 1 C5 a b 2 3 5 6 7 8 10 11 6 CN Me Me CH2PPh3 Br b a 6 5 3 2 7 8 10 11 13 14 15 7 8a + CN Me a b 6 7 5 8 3 10 2 11 13 14 15 8b CHO Me CHO Me a b b a 14 15 13 2 3 5 6 7 8 10 11 15 13 2 3 6 8 10 5 7 14 11 9b 9a + Me Me 10 4 7 + ndash; pound 10 is shown in Scheme 1.An intramolecular oxidative coupling of compound 10 as a mixture with its stereoisomers using anhydrous copper(II) acetate in pyridinendash;diethyl ether at 50 8C under relatively dilute conditions afforded the desired 1113fulvalene 13-(4,9-methanocycloundeca-2,4,6,8,- 10-pentaenylidene)-4,9-dimethylcyclotrideca-1,3,9,11-tetraene- 5,7-diyne 4 in 25 yield as relatively stable blackndash;purple needles. NMR spectral studies The 1H NMR spectrum of compound 4 obtained in CDCl3 was analysed with the aid of homonuclear double resonance and nuclear Overhauser effect (NOE) experiments and the data are given in Table 1. The chemical shift data in CDCl3 indicate that no appreciable ring-current effect is detected judging from a comparison with the data for the precursors 8 and 9 and with those for the 1315fulvalene 23 and 1,6-methano11annulen- 9-one 11,8 both of which have been concluded to be atropic.Thus it should be concluded that compound 4 is atropic and the O 11 Table 1 1H NMR data of compound 4 a Proton CH3 CH2 a b 2 3 5 6 13 14 15 in CDCl3 1.915s 0.161d (11.1) 3.266d (11.1) 6.674d (11.8) 6.058d (11.8) 6.604m 7.031m 6.777d (15.9) 7.071dd (15.9 10.4) 6.757d (10.4) in 2H6DMSO 1.907s 0.041d (10.8) 3.082d (10.8) 6.774d (11.8) 6.168d (11.8) 6.730m 7.072m 6.889d (16.3) 6.788dd (16.3 9.7) 6.998d (9.7) Dd b/ppm 20.01 20.12 20.18 0.10 0.11 0.13 0.04 0.11 20.28 0.24 a Chemical shifts are given in d-values. Coupling constants (J/Hz) are given in parentheses. b Negative values mean upfield shifts upon going from CDCl3 to 2H6DMSO.contribution of the dipolar resonance structure 4a is negligibly small if any. The 13C chemical shifts of compound 4 were also thoroughly assigned on the basis of the CH-chemical shift correlation spectroscopy (CH-COSY) 1H-coupled and selectively 1Hdecoupled spectra and are compiled in Table 2. The chemical shift difference between the pinch bond carbons is 8.1 ppm in CDCl3 a similar value to that in sesquifulvalene 34 (7.9 ppm) but it would be dangerous to consider that the large chemical shift difference is an indication of the contribution of the dipolar structure. The contribution of the dipolar structure 4a was naturally expected to increase in more polar media and thus the 1H and 13C NMR spectra were examined in 2H6dimethyl sulfoxide (2H6DMSO) and the data are included in Tables 1 and 2.In the 1H spectrum the signals of the methylene protons shift upfield by ~0.15 ppm and those of the olefinic protons of the 11-membered ring shift downfield by ~0.1 ppm upon going from CDCl3 to 2H6DMSO. Similarly the signal of the inner olefinic protons of the 13-membered ring moves upfield and those of the outer olefinic protons downfield though the methyl proton signal shows no significant shift. These shifts Table 2 13C NMR data of compound 4a Carbon CH3 CH2 1 2 3 4 5 6 12 13 14 15 16 17 18 in CDCl3 19.84 31.11 142.23 130.84 118.51 121.10 124.53 130.04 134.15 125.71 131.56 142.19 120.35 100.72 85.30 in 2H6DMSO 19.16 30.83 143.52 131.04 118.21 119.93 124.56 130.10 132.93 125.94 130.44 142.86 119.25 100.96 84.55 Dd b/ppm 20.7 20.3 1.3 0.2 20.3 21.2 0.0 0.1 21.2 0.2 21.1 0.7 21.1 0.2 20.8 a Chemical shifts are given in d-values.b Negative values mean upfield shifts upon going from CDCl3 to 2H6DMSO. J. Chem. Soc. Perkin Trans. 1 1997 3185 clearly indicate the increase in diatropicity in a more polar solvent although the extent is very small. The solvent effect on the 13C chemical shifts seems compatible with the increased contribution of the dipolar structure 4a in 2H6DMSO. The arithmetic average of the shifts upon the solvent change is 20.38 ppm for the 13-membered ring carbons and 20.10 ppm for the 11-membered ring carbons. The larger upfield shifts for the 13-membered ring carbons presumably reflect the increase in the negative charge in this ring due to the increased contribution of the dipolar structure.The C-4 signal moves upfield by 1.2 ppm and we have no explanation for this. If it is assumed that the solvent shift reflects the change in the p-electron density at that carbon the data suggest that the increase in the positive charge is almost localized at C-1 while the increase in the negative charge is delocalized at one-carbon intervals i.e. at C-12 C-14 C-16 and C-18 as shown by the resonance structures 4bndash;4e. X-Ray crystallographic study Single crystals of compound 4 suitable for X-ray crystallography were obtained by recrystallization from hexanendash; dichloromethane and one of them was submitted for the analysis. The molecular structure is shown in Fig. 1 and selected bond lengths and angles are compiled in Table 3. The geometry around the pinch bond (C-1C-12) is almost planar though C-1 is slightly pyramidalized the angle sum being 358.58.The 13-membered ring is slightly twisted from planarity while retaining the local C2 symmetry. The 11- membered ring part is significantly folded. The interplanar Me Me Me Me Me Me Me Me Me Me Me Me 4 4a 4b 4c 4d 4e + ndash; + + ndash; ndash; ndash; + + bull; bull; bull;bull; bull;bull; bull; bull; ndash; angle between the C-1C-2C-11 and C-2C-3C-10C11 planes is 41.58. This large folding might be responsible for the localization of the positive charge in the resonance structures 4bndash;4e. The length of the pinch bond is 1.384 Aring; and thus is signifi- cantly longer than the usual C C double bonds. The lengths of the formal double bonds other than the pinch bond range from 1.308 to 1.383 Aring; while those of the sp2sp2 single bonds range from 1.414 to 1.496 Aring;.These structural features seem to be consistent with the polyolefinic nature of compound 4 as suggested by NMR spectroscopy mentioned above. In conclusion the 1113fulvalene 4 shows no detectable tropicity in a medium with low polarity such as CDCl3 and behaves as a polyolefin and the molecular structure obtained by X-ray crystallography is compatible with this feature. Meanwhile in a polar medium such as DMSO the dipolar resonance structure 4a is stabilized and contributes to some very small extent. Experimental Mps were determined on a hot-stage apparatus and are uncorrected. IR spectra were taken with a JASCO-7300 spectrophotometer as KBr discs unless otherwise specified; only significant maxima are described. Electronic (UV/visible) spectra were measured in THF solution with a Shimadzu 2200A spectrophotometer.Mass spectra were recorded with a JEOL JMS-D 300 spectrometer operating at 75 eV using a direct-inlet system. 1H NMR spectra at ambient temperature were recorded in CDCl3 unless otherwise indicated on a Bruker ARX-300 spectrometer at 300.13 MHz with internal SiMe4 (TMS) as the reference. J Values are given in Hz. 13C NMR spectra were recorded in CDCl3 on the ARX-300 at 75.48 MHz with CDCl3 at dC 77.0 as the reference. The letters p s t and q given with the 13C NMR chemical shifts refer to primary secondary tertiary and quaternary respectively. Progress of all reactions was followed by TLC on Merck precoated silica gel plates. Alumina (Merck activity IIndash;III) and silica gel (Daiso gel 1001 W or Daiso gel 1002 W) were used for column chromatography.Compounds were pre-adsorbed from Fig. 1 Top and side views of the molecular structure of compound 4 with crystallographic numbering scheme 3186 J. Chem. Soc. Perkin Trans. 1 1997 Table 3 Selected bond lengths (Aring;) bond angles (8) and torsional angles (8) 12 111 112 23 34 45 425 56 67 78 89 910 925 1011 1213 1224 1314 1415 1516 1617 1626 1718 1819 1920 2021 2122 2127 2223 2324 1.496(6) 1.468(7) 1.384(6) 1.318(6) 1.454(6) 1.383(6) 1.482(6) 1.412(8) 1.344(9) 1.435(9) 1.363(7) 1.436(8) 1.505(8) 1.351(7) 1.464(7) 1.454(7) 1.316(7) 1.431(8) 1.358(6) 1.419(7) 1.510(7) 1.210(7) 1.377(8) 1.197(8) 1.423(8) 1.356(7) 1.498(7) 1.445(7) 1.308(7) 2111 2112 11112 123 234 345 3425 5425 456 567 678 789 8910 8925 10925 91011 11110 11213 11224 131224 121314 131415 141516 151617 161718 171819 181920 192021 202122 212223 222324 122423 117.9(4) 119.4(4) 121.2(4) 132.1(5) 127.1(5) 122.0(5) 119.8(4) 117.8(5) 123.7(6) 126.4(6) 126.3(6) 123.2(7) 122.5(6) 118.3(6) 118.9(5) 127.5(6) 132.2(6) 119.7(5) 118.6(5) 121.8(5) 129.4(5) 127.7(6) 123.4(6) 117.2(5) 165.0(6) 160.7(5) 162.1(6) 163.8(5) 115.3(5) 125.6(5) 127.5(6) 130.8(6) 11123 12123 211110 1211110 211213 211224 1111213 1111224 1234 2345 23425 3456 25456 34259 54259 4567 5678 6789 78910 78925 891011 2591011 89254 109254 910111 1121314 24121314 1122423 13122423 12131415 13141516 14151617 20212223 21222324 22232412 55.9 2137.9 256.8 137.2 5.9 2173.6 171.7 27.8 4.4 2160.6 11.8 156.7 215.9 293.7 79.0 229.7 0.9 27.6 2156.2 17.5 160.9 212.7 280.2 93.7 22.6 2161.1 18.4 2175.4 5.1 179.9 167.2 21.8 22.0 167.6 2176.2 benzene solution onto the adsorbent before column chromatography.Organic extracts were washed with saturated aq. sodium chloride and dried over anhydrous sodium sulfate prior to the removal of solvent. Solvents were evaporated under water-pump pressure. Ether refers to diethyl ether. 12,12-Dicyano-4,9-methanoundecafulvene 5 6 A stirred mixture of 1,6-methano11annulen-9-one 11 8 (150 mg 0.89 mmol) and malononitrile (117 mg 1.78 mmol) in acetic anhydride (4 cm3) was refluxed for 2.5 h. The solution was cooled to room temperature poured onto water and extracted with dichloromethane. The combined extracts were washed with aq.NaHCO3 and dried. The residue obtained after removal of solvent was chromatographed on silica gel (3.5 times; 10 cm). The fractions eluted with benzene afforded the undecafulvene 5 (101 mg 52) as red needles mp 248ndash;250 8C (from hexanendash;dichloromethane) (lit.,6 mp 250ndash;252 8C). 12-Cyano-12-formyl-4,9-methanoundecafulvene 6 To a stirred solution of the dicyanofulvene 5 (100 mg 0.453 mmol) in toluene (70 cm3) at 28 8C was added dropwise a solution of DIBAH (1.5 mol dm23; 0.9 cm3 1.4 mmol) in toluene by a syringe under argon during 10 min and the solution was then stirred for 1 h at the same temperature. Then 5 sulfuric acid (20 cm3) was added dropwise to the mixture below 0 8C and the mixture was extracted with benzene. The combined extracts were washed with aq.NaHCO3 and dried. The residue obtained after removal of solvent was chromatographed on silica gel (3.2 times; 10 cm). The initial fractions eluted with benzenendash;dichloromethane (1 1) afforded the unchanged dicyanofulvene 5 (3 mg recovery). The following fractions eluted with benzenendash;dichloromethane (1 4) afforded the cyano( formyl ) fulvene 6 (40 mg 40) as dark red needles mp 213ndash;214 8C (from hexanendash;dichloromethane); m/z 221 (M1 100) (C15H11NO requires M 221.2); nmax/cm21 2923 2884 (CHO) 2209 (C N) 1655 (C O) and 1582 (C C); lmax/nm 239 (e/dm3 mol21 cm21 18 900) 330 (17 000) and 451 (12 600); dH 9.977 (1 H s CHO) 7.390 (2 H m 6- and 7-H) 7.276 (1 H d J 12 10- H) 7.234 (1 H d J 12 3-H) 7.001 (2 H m 5- and 8-H) 6.873 (1 H d J 12 2-H) 6.582 (1 H d J 12 11-H) 2.167 (1 H dt J 11.3 and 1.5 Hb) and 0.173 (1 H d J 11.3 Ha); dC 185.46 (CHO) 161.95 (q) 139.29 (t) 139.27 (t) 132.67 (t) 132.62 (t) 127.76 (t) 127.62 (t) 122.95 (q) 122.45 (q) 116.70 (t) 115.86 (q) 114.98 (t) 111.99 (q) and 33.87 (s) (Found C 81.3; H 5.2; N 6.3.C15H11NO requires C 81.4; H 5.0; N 6.3). Isomeric 2-(4,9-methanocycloundeca-2,4,6,8,10-pentaenylidene)- 6-methylocta-3,5-dien-7-ynenitriles 8a and 8b To a stirred suspension of 3-methylpent-2-en-4-ynyltriphenylphosphonium bromide 7 7 (1.58 g 3.75 mmol) in dry THF (45 cm3) at 240 8C was added dropwise a solution of butyllithium (1.6 mol dm23; 2.34 cm3 3.75 mmol) in hexane by a syringe during 20 min under argon. After the mixture had been stirred for 1 h at 240 8C a solution of the cyano(formyl)fulvene 6 (166 mg 0.750 mmol) in THF (30 cm3) was added dropwise during 1.5 h below 230 8C and the solution was stirred for further 2 h at 215 8C.After addition of ethyl acetate (14 cm3) the mixture was poured into icendash;water and extracted with benzene. The combined organic layers were washed with brine and dried. The product obtained after removal of solvent was chromatographed on silica gel (3.2 times; 12 cm). The initial fractions eluted with hexanendash;ether (9 1) afforded the Z-isomer 8b (53 mg 25) as dark red needles mp 137ndash;140 8C (decomp.) (from hexanendash; dichloromethane); m/z 283 (M1 100) (C21H17N requires M 283.3); nmax/cm21 3290 (C CH) 2203 (C N) 2083 (C C) 1600 (C C) and 768 (Z)-HC CH; lmax/nm 239 (e 32 100) 285 (13 300) 343 (31 600) and 427 (29 000); dH 7.416 (1 H d J 12.2 15-H) 7.17ndash;7.07 (2 H m 6- and 7-H) 6.879 (1 H d J 11.9 3- H) 6.809 (1 H d J 11.8 10-H) 6.751 (1 H t J 12 14-H) 6.70ndash; 6.62 (2 H m 5- and 8-H) 6.242 (1 H d J 12 2-H) 6.164 (1 H d J 11.8 13-H) 5.817 (1 H d J 11.9 11-H) 3.422 (1 H s C CH) 2.923 (1 H dt J 11.3 and 1.3 Hb) 2.046 (3 H s Me) J.Chem. Soc. Perkin Trans. 1 1997 3187 and 0.371 (1 H d J 11.3 Ha); dC 134.71 (t) 134.62 (t) 132.42 (t) 131.38 (t) 131.01 (t) 129.76 (t) 125.64 (t) 125.32 (t) 123.38 (q) 121.67 (q) 121.55 (q) 120.11 (t) 118.58 (q) 118.54 (t) 116.46 (t) 110.67 (q C N) 85.17 (t C CH) 82.59 (q ndash;C ) 32.54 (s) and 23.68 (p) (Found C 88.9; H 6.2; N 5.0. C21H17N requires C 89.0; H 6.05; N 4.9). The following fractions eluted with hexanendash;ether (9 1) afforded the E-isomer 8a (32 mg 15) as dark red needles mp 163ndash;164 8C (decomp.) (from hexanendash;dichloromethane); m/z 283 (M1 100); nmax/cm21 3287 (C CH) 2214 (C N) 2080 (C C) 1603 (C C) and 960 (E)-HC CH; lmax/nm 234 (e 32 900) 283 (12 300) 345 (36 100) and 429 (38 200); dH 7.209 (1 H dd J 15.2 and 11.2 14-H) 7.13ndash;7.04 (2 H m 6- and 7-H) 6.823 (1 H d J 11.7 3-H) 6.783 (1 H d J 11.7 10-H) 6.676 (1 H d J 15.2 13-H) 6.65ndash;6.63 (2 H m 5- and 8-H) 6.443 (1 H d J 11.2 15-H) 6.231 (1 H d J 11.9 2-H) 5.881 (1 H d J 11.9 11-H) 3.436 (1 H s C CH) 3.054 (1 H dt J 11.3 and 1.3 Hb) 2.006 (3 H s Me) and 0.441 (1 H d J 11.3 Ha); dC 136.73 (t) 134.71 (t) 134.29 (t) 131.40 (t) 131.29 (t) 131.0 (t) 125.50 (t) 125.19 (t) 124.84 (t) 121.88 (q) 121.74 (q) 121.59 (q) 119.14 (t) 116.35 (q) 116.14 (t) 114.66 (q C N) 84.98 (t C CH) 82.55 (q C ) 32.56 (s) and 23.48 (p) (Found C 89.3; H 6.05; N 4.8).(3Z,5Z)-2-(4,9-Methanocycloundeca-2,4,6,8,10-pentaenylidene)- 6-methylocta-3,5-dien-7-ynal 9b To a stirred solution of the Z-isomer 8b of the cyanofulvene (104 mg 0.367 mmol) in dry toluene (56 cm3) at 210 8C was added dropwise a solution of DIBAH (1.5 mol dm23; 1.2 cm3 1.84 mmol) in toluene during 15 min by a syringe under argon and the solution was then stirred for 30 min at the same temperature. Then 5 sulfuric acid (13 cm3) was added dropwise to the mixture below 0 8C and the mixture was extracted with benzene. The combined extracts were washed with aq. NaHCO3 and dried. The product obtained after removal of solvent was chromatographed on silica gel (3.5 times; 10 cm). The fractions eluted with benzene afforded the Z-isomer 9b of the formylfulvene (32 mg 30) as orange needles mp 94ndash;96 8C (from hexanendash;benzene); m/z 286 (M1 100) (C21H18O requires M 286.3); nmax/cm21 3295 (C CH) 2923 2852 (CHO) 2092 (C C) 1659 (C O) 1596 (C C) and 741 (Z)-HC CH; lmax/ nm 246 (e 11 500) 332 (7200) and 421 (4900); dH 10.231 (1 H s CHO) 7.18ndash;7.10 (2 H m 6- and 7-H) 6.877 (1 H d J 12 10-H) 6.842 (1 H t J 11.4 14-H) 6.761 (1 H d J 11.9 3- H) 6.732 (1 H m 8-H) 6.694 (1 H m 5-H) 6.455 (1 H dd J 11.9 and 1.7 11-H) 6.225 (1 H d J 11.3 15-H) 6.067 (1 H d J 11.4 13-H) 5.822 (1 H dd J 11.8 and 1.4 2-H) 3.353 (1 H s C CH) 3.004 (1 H dt J 11.2 and 1.3 Hb) 1.895 (3 H s Me) and 0.265 (1 H d J 11.1 Ha); dC 191.84 (t CHO) 151.18 (q) 134.81 (t) 134.17 (q) 133.84 (t) 132.54 (t) 131.35 (t) 130.86 (t) 130.86 (t) 125.45 (t) 125.42 (t) 123.99 (t) 121.05 (q) 120.98 (q) 120.77 (q) 117.52 (t) 115.26 (t) 83.93 (t C CH) 82.71 (q C ) 32.15 (s) and 23.39 (p) (Found C 88.0; H 6.5.C21H18O requires C 88.1; H 6.3). (3E,5Z)-2-(4,9-Methanocycloundeca-2,4,6,8,10-pentaenylidene)- 6-methylocta-3,5-dien-7-ynal 9a The conversion of the cyanofulvene 8a into the formylfulvene 9a was carried out in the exactly same manner as that of 8b into 9b using substrate 8a (47 mg 0.17 mmol) in dry toluene (65 cm3) with DIBAH (0.91 mmol) in toluene. The product obtained after removal of solvent was chromatographed on silica gel (3.5 times; 10 cm). The fractions eluted with benzene afforded the E-isomer 9a of the formylfulvene (20 mg 41) as dark red needles mp 136ndash;140 8C (decomp.) (from hexanendash; benzene); m/z 286 (M1 96) and 115 (100) (C21H18O requires M 286.3); nmax/cm21 3285 (C CH) 2931 2851 (CHO) 2081 (C C) 1664 (C O) 1598 (C C) and 983 (E)-HC CH; lmax/nm 239 (e 13 100) 293 (8900) 338 (9300) and 431 (8200); dH 10.402 (1 H d J 1.3 CHO) 7.554 (1 H dd J 15.8 and 11.1 14-H) 7.18ndash;7.00 (2 H m 6- and 7-H) 6.841 (1 H d J 11.8 10-H) 6.816 (1 H d J 11.8 3-H) 6.75ndash;6.68 (2 H m 5- and 8-H) 6.577 (1 H d J 15.8 13-H) 6.430 (1 H d J 11.0 15-H) 6.288 (1 H d J 11.9 11-H) 5.979 (1 H d J 11.8 2-H) 3.385 (1 H s C CH) 2.990 (1 H dt J 11.2 and 1.3 Hb) 1.993 (3 H s Me) and 0.161 (1 H d J 11.5 Ha); dC 192.65 (t CHO) 149.74 (q) 138.98 (t) 133.27 (t) 132.46 (t) 132.46 (t) 131.19 (q) 130.68 (t) 130.64 (t) 125.52 (t) 125.33 (t) 125.33 (t) 121.03 (q) 120.91 (q) 120.16 (q) 115.97 (t) 114.59 (t) 83.67 (t C CH) 83.06 (q C ) 31.74 (s) and 23.25 (p) (Found C 88.0; H 6.3).Isomeric 7-(4,9-methanocycloundeca-2,4,6,8,10-pentaenylidene)- 3,11-dimethyltrideca-3,5,8,10-tetraene-1,12-diyne 10 To a stirred suspension of the salt 7 7 (2.37 g 5.60 mmol) in dry THF (70 cm3) at 250 8C was added dropwise a solution of butyllithium (1.6 mol dm23; 3.6 cm3 5.60 mmol) in hexane by a syringe during 20 min under argon. After the mixture had been stirred for 1 h at 250 8C a solution of a stereoisomeric mixture of the formylfulvene 9 (161 mg 0.560 mmol) in dry THF (110 cm3) was added dropwise during 1.5 h at 230 8C and the solution was stirred for further 2 h at the same temperature. After addition of ethyl acetate (15 cm3) the mixture was worked up as for the isolation of the nitrile 6. The product obtained after removal of solvent was passed through a short column of alumina (3.2 times; 5 cm).The fractions eluted with hexanendash;ether (4 1) afforded the acyclic diacetylene 10 (72 mg 37) as a dark brown semi-solid. Since compound 10 proved to be extremely unstable towards diffused light and air it was used for the following reaction without further purification. 13-(4,9-Methanocycloundeca-2,4,6,8,10-pentaenylidene)-4,9- dimethylcyclotrideca-1,3,9,11-tetraene-5,7-diyne 4 A solution of a stereoisomeric mixture of the acyclic diacetylene 10 (72 mg 0.21 mmol) in a mixture of pyridine (20 cm3) and ether (7 cm3) was added dropwise during 2.5 h to a stirred solution of anhydrous copper(II) acetate (262 mg 1.45 mmol) in a mixture of pyridine (43 cm3) and ether (14 cm3) at 50 8C and the mixture was stirred for further 1 h before being poured into water and extracted with benzene.The extracts were washed with 5 HCl until they turned acidic (to litmus) and then with aq. NaHCO3 and dried. The product obtained after removal of solvent was chromatographed on silica gel (3.8 times; 12 cm). The fractions eluted with 5 benzene in hexane afforded the 1113 fulvalene 4 (18 mg 25) as black-purple needles mp 182ndash;185 8C (decomp.) (from hexanendash;dichloromethane); m/z 346 (M1 36) and 28 (100) (C27H22 requires M 346.4); nmax/ cm21 2148 (C C) 970 (E)-HC CH and 756 (Z)-HC CH; lmax/nm 237 (e 28 300) 267 (26 200) 308 (26 800) and 452 (24 300) (Found C 93.8; H 6.5. C27H22 requires C 93.6; H 6.4). X-Ray crystallographic analysis of compound 4 Crystals of compound 4 were grown from hexanendash;dichloromethane.Intensity data were collected on a Rigaku AFC-7R diffractometer using graphite-monochromated Mo-Ka radiation (l = 0.710 73 Aring;) with w scan mode. Accurate unit-cell dimensions and crystal-orientated matrix were obtained from least-squares refinement of 25 strong reflections in the range 218 2q 258. The structure was solved by direct methods using SHELXS-869 and subsequent calculations were carried out by the SHELXL-9310 program. The positions of all hydrogen atoms were located by difference Fourier synthesis. The refinement was accomplished on Fo 2 by means of full-matrix least-squares methods anisotropically for all carbons and isotropically for all hydrogens. Final difference map peaks were in the range from 0.150 to 20.16 Aring;23 and the maximal D/s being 0.001.The crystal data and parameters for data collection, 3188 J. Chem. Soc. Perkin Trans. 1 1997 structure determination and refinement are summarized in Table 4.dagger; Acknowledgements Financial support by Grant-in-Aids for Scientific Research Nos. 07246111 and 08454199 from the Ministry of Education Table 4 Crystal data for compound 4 and parameters for data collection structure determination and refinement Empirical formula Relative molecular mass Crystal dimension (mm) Crystal system Space group a (Aring;) b (Aring;) c (Aring;) V (Aring;3) Z Dc (g cm23) F(000) m(Mo-Ka) (cm21) Temp. (8C) Scan width (8) 2qmax (8) No. of reflections measured Total With I 2s(I) No. of refinement variables Final R; Rw a C27H22 346.45 0.6 times; 0.3 times; 0.1 Orthorhombic P212121 (No. 19) 11.745(2) 26.259(4) 6.334(2) 1953.6(6) 4 1.178 736 0.066 20.0 0.997 plusmn; 0.30 tan q 55 2598 1062 332 0.050; 0.097 a R= S(verbar;Foverbar;2verbar;Fcverbar;)/Sverbar;Foverbar; Rw = Sw(Fo 2 2 Fc 2)2/Sw(Fo 2)2� �� w = s2(Fo 2) 1 (0.0422P)221 where P = (Fo 2 1 2Fc 2)/3.dagger; Atomic coordinates thermal parameters and bond lengths and angles have been deposited at the Cambridge Crystallographic Data Centre (CCDC). See Instructions for Authors J. Chem. Soc. Perkin Trans. 1 1997 Issue 1. Any request to the CCDC for this material should quote the full literature citation and the reference number 207/139. Science Sports and Culture (Japan) is gratefully acknowledged. References 1 T. Asao N. Morita J. Ojima and M. Fujiyoshi Tetrahedron Lett. 1978 2795; N. Morita T. Asao J. Ojima and K. Wada Chem. Lett. 1981 57; N. Morita T. Asao J. Ojima and S. Hamai Chem. Lett. 1983 1887; T.Asao N. Morita J. Ojima M. Fujiyoshi K. Wada and S. Hamai Bull. Chem. Soc. Jpn. 1986 59 1713; J. Ojima K. Itagawa and T. Nakada Tetrahedron Lett. 1983 24 5273; Bull. Chem. Soc. Jpn. 1986 59 1723. 2 P. D. Howes and F. Sondheimer J. Org. Chem. 1978 43 2158. 3 H. Higuchi K. Kitamura J. Ojima K. Yamamoto and G. Yamamoto Chem. Lett. 1992 257; J. Chem. Soc. Perkin Trans. 1 1992 1343. 4 W. K. Schenck R. Kyburg and M. Neuenschwander Helv. Chim. Acta 1975 58 1099; M. Neuenschwander Pure Appl. Chem. 1986 58 55. 5 M. Nakagawa Pure Appl. Chem. 1975 44 885; A. T. Balaban M. Banciu and V. Ciorba Annulenes Benzo- Hetero- Homo- Derivatives and their Valence Isomers CRC Press Florida 1987 vol. 1 p. 67; J. Ojima S. Fujita M. Masumoto E. Ejiri T. Kato S. Kuroda Y. Nozawa S. Hirooka and H. Tatemitsu J.Chem. Soc. Perkin Trans. 1 1988 385; H. Higuchi H. Yamamoto J. Ojima M. Iyoda M. Yoshida and G. Yamamoto J. Chem. Soc. Perkin Trans. 1 1993 983. 6 E. Vogel and J. Reisdorf unpublished results; J. Reisdorf Ph.D. Dissertation Kouml;ln 1970. 7 J. Ojima E. Ejiri T. Kato M. Nakamura S. Kuroda S. Hirooka and M. Shibutani J. Chem. Soc. Perkin Trans. 1 1987 831. 8 W. Grimme J. Reisdorf W. Junemann and E. Vogel J. Am. Chem. Soc. 1970 92 6355. 9 G. M. Sheldrick Acta Crystallogr. Sect. A 1990 46 467. 10 G. M. Sheldrick SHELXL-93 Program for Crystal Structure Refinement University of Gouml;ttingen Germany 1993. Paper 7/04071G Received 10th June 1997 Accepted 26th June 1997 J. Chem. Soc. Perkin Trans. 1 1997 3183 Synthesis structure and tropicity of an 1113fulvalene derivative Gaku Yamamoto,*,a Yasuhiro Mazaki,a Ryoji Kobayashi,b Hiroyuki Higuchi b and Ju�ro Ojima *,b a Department of Chemistry School of Science Kitasato University Kitasato Sagamihara Kanagawa 228 Japan b nt of Chemistry Faculty of Science Toyama University Gofuku Toyama 930 Japan An 1113fulvalene derivative 13-(4,9-methanocycloundeca-2,4,6,8,10-pentaenylidene)-4,9-dimethylcyclotrideca- 1,3,9,11-tetraene-5,7-diyne has been synthesized.Examination of 1H and 13C NMR spectra indicates that the compound shows no detectable ring-current effect in nonpolar solvents arising from 10�- and 14�-electron systems which is verified by X-ray crystallographic structural analysis. In a polar solvent 2H6dimethyl sulfoxide a small contribution of the dipolar resonance structure is suggested.Introduction An extension of our interests in ring-expanded fulvalenes led us to the preparation of fulvalene derivatives composed of two large-membered rings.1 The only known macrocyclic compound of this type was a tetra(cyclohexane)-annulated 1313- fulvalene derivative 1,2 which was prepared by Howes and Sondheimer in 1978 and was found to be thermally unstable and completely atropic. The fact that compound 1 carries two rings of the same size can be associated with the absence of any cross-conjugation of p-electrons or any contribution from a dipolar resonance structure. Then we considered that the 1315fulvalene 2,3 in which one ring is 13-membered and the other is 15-membered is potentially aromatic as is sesquifulvalene 3,4 since polarization of the pinch bond would make both rings 14p-electron aromatic systems as shown in a dipolar structure 2a.However although compound 2 was isolated as thermally relatively stable crystals unlike compound 1 the compound shows no ring-current effect but instead a polyolefinic character indicating the absence of any contribution from a dipolar structure. It is recognized 5 that tropicity of annulenes usually increases with a decrease in the ring size. We considered that the replacement of one ring in compound 2 by a smaller ring with larger tropicity would facilitate polarization of the pinch bond. Thus we chose a fulvalene derivative 4 with 11- and 13-membered rings. Polarization of the pinch bond of compound 4 would afford a 10p/14p aromatic system. Another expectation was that the compound would give thermally stable crystals that would be suitable for X-ray crystallographic study.Results and discussion Synthesis A successful preparation of compound 2 stimulated us to elaborate an acyclic exocyclic moiety leading to a 13-membered conjugated system upon the methano-bridged 11-membered ring of compound 5. Thus the synthesis of compound 4 was planned and performed according to the reaction sequence outlined in Scheme 1. Reduction of the dicyanofulvene 5 6 with diisobutylaluminium hydride (DIBAH) in toluene at 210 8C afforded the cyano(formyl)fulvene 6 in 40 yield. Treatment of 3-methylpent- 2-en-4-ynyltriphenylphosphonium bromide 7 7 in tetrahydrofuran (THF) with butyllithium led to the corresponding ylide which was allowed to react with the cyano(formyl)fulvene 6 to afford a mixture of the E-isomer 8a and the Z-isomer 8b of the newly formed double bond in a ratio of 5 3 which were separately isolated by chromatography on silica gel.Individual reduction of compounds 8a and 8b with DIBAH in toluene at 210 8C afforded the E-isomer 9a (40) and Zisomer 9b (30) of the ethynyl(formyl)fulvene respectively retaining the stereochemistry of the substrates 8. However the Z-isomer 9b proved to be less stable than the E-isomer 9a and gradually isomerized to the E-isomer during chromatography. The ylide derived from the salt 7 was treated with an isomeric mixture of compounds 9 to afford a stereoisomeric mixture of the acyclic diethynylfulvene 10 as a semi-solid in 37 yield which was too unstable to give satisfactory spectral and analytical data. The structure of a desirable isomer of com- 1 Me Me Me Me 2 2 3 4 12 13 11 Me Me Me Me + 2a ndash; 3 Me Me 14 15 13 3 5 6 2 4 7 8 10 11 24 23 b a 22 3184 J.Chem. Soc. Perkin Trans. 1 1997 Scheme 1 CN CN CHO CN 5 a b 2 3 5 6 7 8 10 11 6 CN Me Me CH2PPh3 Br b a 6 5 3 2 7 8 10 11 13 14 15 7 8a + CN Me a b 6 7 5 8 3 10 2 11 13 14 15 8b CHO Me CHO Me a b b a 14 15 13 2 3 5 6 7 8 10 11 15 13 2 3 6 8 10 5 7 14 11 9b 9a + Me Me 10 4 7 + ndash; pound 10 is shown in Scheme 1. An intramolecular oxidative coupling of compound 10 as a mixture with its stereoisomers using anhydrous copper(II) acetate in pyridinendash;diethyl ether at 50 8C under relatively dilute conditions afforded the desired 1113fulvalene 13-(4,9-methanocycloundeca-2,4,6,8,- 10-pentaenylidene)-4,9-dimethylcyclotrideca-1,3,9,11-tetraene- 5,7-diyne 4 in 25 yield as relatively stable blackndash;purple needles.NMR spectral studies The 1H NMR spectrum of compound 4 obtained in CDCl3 was analysed with the aid of homonuclear double resonance and nuclear Overhauser effect (NOE) experiments and the data are given in Table 1. The chemical shift data in CDCl3 indicate that no appreciable ring-current effect is detected judging from a comparison with the data for the precursors 8 and 9 and with those for the 1315fulvalene 23 and 1,6-methano11annulen- 9-one 11,8 both of which have been concluded to be atropic. Thus it should be concluded that compound 4 is atropic and the O 11 Table 1 1H NMR data of compound 4 a Proton CH3 CH2 a b 2 3 5 6 13 14 15 in CDCl3 1.915s 0.161d (11.1) 3.266d (11.1) 6.674d (11.8) 6.058d (11.8) 6.604m 7.031m 6.777d (15.9) 7.071dd (15.9 10.4) 6.757d (10.4) in 2H6DMSO 1.907s 0.041d (10.8) 3.082d (10.8) 6.774d (11.8) 6.168d (11.8) 6.730m 7.072m 6.889d (16.3) 6.788dd (16.3 9.7) 6.998d (9.7) Dd b/ppm 20.01 20.12 20.18 0.10 0.11 0.13 0.04 0.11 20.28 0.24 a Chemical shifts are given in d-values.Coupling constants (J/Hz) are given in parentheses. b Negative values mean upfield shifts upon going from CDCl3 to 2H6DMSO. contribution of the dipolar resonance structure 4a is negligibly small if any. The 13C chemical shifts of compound 4 were also thoroughly assigned on the basis of the CH-chemical shift correlation spectroscopy (CH-COSY) 1H-coupled and selectively 1Hdecoupled spectra and are compiled in Table 2. The chemical shift difference between the pinch bond carbons is 8.1 ppm in CDCl3 a similar value to that in sesquifulvalene 34 (7.9 ppm) but it would be dangerous to consider that the large chemical shift difference is an indication of the contribution of the dipolar structure.The contribution of the dipolar structure 4a was naturally expected to increase in more polar media and thus the 1H and 13C NMR spectra were examined in 2H6dimethyl sulfoxide (2H6DMSO) and the data are included in Tables 1 and 2. In the 1H spectrum the signals of the methylene protons shift upfield by ~0.15 ppm and those of the olefinic protons of the 11-membered ring shift downfield by ~0.1 ppm upon going from CDCl3 to 2H6DMSO. Similarly the signal of the inner olefinic protons of the 13-membered ring moves upfield and those of the outer olefinic protons downfield though the methyl proton signal shows no significant shift.These shifts Table 2 13C NMR data of compound 4a Carbon CH3 CH2 1 2 3 4 5 6 12 13 14 15 16 17 18 in CDCl3 19.84 31.11 142.23 130.84 118.51 121.10 124.53 130.04 134.15 125.71 131.56 142.19 120.35 100.72 85.30 in 2H6DMSO 19.16 30.83 143.52 131.04 118.21 119.93 124.56 130.10 132.93 125.94 130.44 142.86 119.25 100.96 84.55 Dd b/ppm 20.7 20.3 1.3 0.2 20.3 21.2 0.0 0.1 21.2 0.2 21.1 0.7 21.1 0.2 20.8 a Chemical shifts are given in d-values. b Negative values mean upfield shifts upon going from CDCl3 to 2H6DMSO. J. Chem. Soc. Perkin Trans. 1 1997 3185 clearly indicate the increase in diatropicity in a more polar solvent although the extent is very small. The solvent effect on the 13C chemical shifts seems compatible with the increased contribution of the dipolar structure 4a in 2H6DMSO.The arithmetic average of the shifts upon the solvent change is 20.38 ppm for the 13-membered ring carbons and 20.10 ppm for the 11-membered ring carbons. The larger upfield shifts for the 13-membered ring carbons presumably reflect the increase in the negative charge in this ring due to the increased contribution of the dipolar structure. The C-4 signal moves upfield by 1.2 ppm and we have no explanation for this. I