Studies of bridged benzo-heterocycles. Part II. Cycloaddition reactions of epoxy-bridged cyclic olefins with tropone and tropolone, and photochemical behaviour of the adducts

摘要

1972 1951Studies of Bridged Benzo-heterocycles. Part II. Cycloaddition Re-actions of Epoxy-bridged Cyclic Olefins with Tropone and Tropolone, andPhotochemical Behaviour of the AdductsBy Tadashi Sasaki,' Ken Kanematsu, and Kenji Hayakawa, Institute of Applied Organic Chemistry, Facultyof Engineering, Nagoya University, Chikusa, Nagoya, 464, JapanReactions of 1.4-epoxy-1.4-dihydronaphthalene ( I ) with tropone and tropolone gave rise to the 4 + 2xendo,exo-( I I I a ) , and exo,exo- (Vb) cycloadducts, respectively, in relatively high yield ; reactions of dimethyl 7-oxabicyclo-2,2,1 hepta-2,5-diene-2,3-dicarboxylate (11) with tropone and tropolone afforded the 4 + 2x endo,exo-(VIIa), and endo,exo- cycloadducts (VIIb), respectively, in comparatively low yields.Irradiations ofthe tropone adducts ( I I I a ) and (VIIa) in methanol gave exclusively the methyl 12-oxatetracyclo7,2,1 .02.s,0316 -dodecadien-4-ylacetates ( X I I a and b). Similar irradiations of the tropolone adducts (Vb) and ( V I I b ) give the14-oxotetracyclo9,2.1 ,02~10,03~7tetradecadien-6,9-diones ( X V ) and ( X V I I ) , respectively, each being theonly product. The photoproducts ( X I I a and b) are formed by addition of methanol to initially formed ketens, andthe photoproducts ( X V ) and ( X V I I ) by 1,3 sigmatropic rearrangements of (Vb) and (VIIb), respectively,followed by hydrogen shifts.NORBORXADIENYL compounds show a low reactivity to-wards dienes; thus cycloaddition reactions with thesecompounds as dienophiles are rare. However, 'I-oxa-norbornadienyl compounds, such as 1,4-epoxy-1,4-di-hydronaphthalene (I) and dimethyl 7-oxabicyclo2,2,1-hepta-2,5-diene-2,3-dicarboxylate (11) ,4, are effectivedienophiles.6 Their increased dienophilicity is presum-ably due to ring strain and to orbital participation of the72-electrons of the proximate oxygen atom.ly7 Thus,compounds (I) and (11) would be expected to react morereadily with electron-poor dienes, such as tropone andtropolone.We have characterized the products of the thermalcycloaddition reactions of compounds (I) and (11) withtropone and tropolone, and have investigated the photo-chemical behaviour of the adducts.0 0Reactions of the epoxide (I) with tropone in chloro-benzene at 130-140" gave an adduct in quantitativeyield.Elemental analysis and the mass spectrum(M+ 250) showed the product to be a 1 : 1 adduct, forwhich the four stereoisomeric structures (1IIa)-(VIa) areconceivable. The presence of the bicyclo3,2,2nona-3,6-dien-Z-one system was suggested by spectral data.The n.m.r. spectrum is very similar to those of Diels-Alder adducts from tropone and azo-dienophiles in theolefinic region. The structure of the adduct wast The former prefix refers to the configuration with respect tothe bicyclo3,2,2nonadienone system (substituents on the car-bony1 side are defined as exo) ; the latter refers to the configur-ation with respect to the oxanorbornene system.amp;jj} e x o1 Part I, T. Sasaki, K. Kanematsu, and M. Uchide, Tetrahedron2 M.P. Cava and F. M. Sceel, J . Org. Chem., 1967,82, 1304.Letters, 1971, 4855.eventually proved by a complete analysis of the n.m.r.spectrum.a ; R = Hb; R = O HAThe absence of appreciable coupling between H-1 andH-2 and between H-11 and H-12 indicated the bridge-head protons (H-2 and H-11) to be exo to the bicyclo-3,2,2nonadienone ~ystem,~ thus ruling out structures(Va) and (VIa). Furthermore, the oxygen bridgeheadprotons (H-3 and H-10) each give rise to a sharp singlet(Z 4-88 and 4.98, respectively) with no vicinal couplingto H-2 and H-11. Therefore, H-2 and H-11 must beendo to the oxabenzonorbornene s.ystem,l0 and structure(IVa) is ruled out. Thus the adduct was assignedstructure (IIIa), that of the 4 + 2x cycloadduct withendo ,exo-configuration.?G. R.Ziegler, J . Amer. Chem. SOC., 1969, 91, 446.H. Prinzbach, M. Arguell, and E. Druchrey, Angew. Chem.,P. Deslongchamps and J. Kallos, Canda. J . Chem., 1967,45,L. F. Fieser and M. J. Naddain, Canad. J . Chem., 1965, 43,R. N. Warrener, J . Amer. Chem. SOC., 1971, 93, 2346.8 T. Sasaki, K. Kanematsu, and K. Hayakawa, (a) J . Chem.SOC. (C), 1971, 2142; (b) J.C.S. PerkiN I, 1972, 783.9 S. Ito, K. Sakan, and Y . Fujise, Tetrahedron Letters, 1969,775.10 J. D. Slee and E. LeGoff, J . Org. Chem., 1970, 35, 3897.1966, 78, 1057.2235.15991952 J.C.S. Perkin IReaction of the diester (11) with tropone in benzene a t130" gave an adduct in 21 yield. Elemental analysisand the mass spectrum (M+ 316) showed it to be a 1 : 1adduct.The n.m.r. spectrum was very similar to thatof compound (IIIa) except that signals for two methoxy-groups replaced those of the benzene ring. Of thepossible Diels-Alder adduct structures (V1Ia)-( Xa),only structure (VIIa), accommodates the data, i.e. theproduct was the endo,exo 4 + 23x cycloadduct.?10 5 MeOzC/Me02C(YmIReaction of the epoxide (I) with tropolone in chloro-benzene at 130" gave an adduct in quantitative yield.Elemental analysis and the mass spectrum (M+ 266)showed it to be a 1 : 1 adduct. The n.m.r. spectrumexhibited signals a t T 2.90 (4H, m, ArH), 2.92 (lH, q,H-17), 4.32 (lH, d, H-lo), 4-90 (lH, s, OH, exchangeable),5.01 (lH, d, H-3), 6.42 (lH, m, H-1), 7-53 (lH, dd, H-2),and 7.91 (lH, d, H-11), and suggested the presence of thebicyclo 3,2,2 nona-3,6-diene-2-one system.The absenceof a signal due to H-12 and long-range coupling betweenH-12 and H-14 indicated that the hydroxy-group is a tthe bridgehead C-12 rather than at C-14. These datasuggest the four possible structures (1IIb)-(VIb).The presence of the coupling between H-1 and H-2( J 3.5 Hz) indicated the oxabenzonorbornadiene ring tobe exo to the bicyclo3,2,2nonadienone system, ruling outstructures (IIIb) and (IVb). The presence of long-rangecoupling between H-3 and H-10 ( J 2-0 Hz), and theabsence of vicinal couplings between H-2 and H-3 andbetween H-10 and H-11 were observed in double-resonance experiments; on irradiation at the frequencyof H-10, the signal of H-3 collapsed to a singlet but therewas no change in that of H-2.The bridgehead protons(H-2 and H-11) were therefore assigned as endo to theH-15), 3-62 (lH, 9, H-16), 3.79 (lH, d, H-14), 4.03 (lH, d,f See foofnote on page 1951.l1 L. M. Jackman and S. Sternkell, ' Applications of NuclearMagnetic Resonance Spectroscopy in Organic Chemistry,'Pergamon, Oxford, 1969,12 P. Kitahara. I. Murata. and T. Nitta. Tetrahedron Letters.1967, 3003.Tetrahedron Letters, 1968, 3215.13 S. Ito, H. Takeshita, Y. Shoji, Y. Toyooka, and T. Nozoe,oxabenzonorbornene system, and structure (VIb) wasruled out. Furthermore, H-14 was deshielded by theanisotropic effect of the bridge oxygen atom l1 in com-parison with H-14 in (IIIa). Thus, the product was con-cluded to be the exo,exo 4 + 2x cycloadduct (Vb).Reaction of the diester (11) with tropolone in chloro-benzene at 130" gave an adduct in 21 yield.Itselemental analysis and mass spectrum (M+ 332) showedit to be a 1 : 1 adduct. The n.m.r. spectrum was verysimilar to that of compound (Vb) except that the signalsof two methoxy-groups replaced those of the benzenering, and that there was no coupling between H-1 andH-2, and between H-2 and H-3 and also between H-6and H-7, which indicated the bridgehead protons (H-2and H-7) to be endo to the oxanorbornadiene system.Thus, the product was concluded to be the endo,exo4 + 2n cycloadduct (VIIb), and the other threepossible structures (VII1b)-(Xb) were ruled out.The cycloaddition reactions of tropolone with com-pounds (I) and (11) were in contrast to the reactions oftropolone with azodienophiles, giving ene-adducts.*,12Furthermore, the reaction of compound (I) with tro-polone afforded only the exo-adduct (Vb), although thereaction of maleic anhydride with tropolone givesboth endo- and e~0-adducts.l~Attempted reactions of compound (I) with cyclo-heptatriene and cyclo-octatetraene were unsuccessful evenunder more drastic conditions, although similar reactionsof these compounds with electron-deficient dienophileshave been reported.14J5 This seems to stem from thefact that compounds (I) and (11) are electron-rich dieno-philes and react preferably with more electron-deficientdienes in inverse Diels-Alder reactions.l6 The electrondensity at the reactive double bond of structure (I) isincreased by through-space interaction l7 with the elec-tron-rich benzene ring, whereas that of compound (11)is decreased by interaction with the electron-poor doublebond bearing two electron-attracting methoxycarbonylgroups; this might be the cause of the difference in thereactivity between compounds (I) and (11).Irradiations of the tropone adducts (IIIa) and (VIIa)in methanol a t room temperature for 3 h with a highpressure 100 W mercury lamp in a Pyrex vessel undernitrogen gave only one product in each case (XIIa),95; (XIIb), 94.Elemental analysis and the massspectrum (M+ 272) of compound (XIIa) showed it to be amethyl ester, presumably formed by addition of meth-anol to an initially formed keten (XIa).The n.m.r.spectrum was very similar to that of a photoproductformed from tropone and 2,3-dihydrophthalazine-l,4-dione.* The photoproduct (XIIb) was similarly shownto be a methyl ester, formed through the keten inter-mediate (XIb) .l4 R. C. Cookson, S. S. H. Gilani, and I. D. R. Stevens, J . Chern.1s A. B. Evnin, A. Y. Lam, J. J. Maher, and J. J. Blyskal,l6 R. Huisgen, R. Grashey, and J. Sauer, ' The Chemistry ofSOC. (C), 1967, 1906.Tetrahedron Letters, 1969, 4497.Alkenes,' ed. S. Patai, Interscience, New York, 1964, p. 923.R. Hoffmann, Accounts Chem. Res., 1971, 4, 11972 1953Irradiation of the adduct (Vb) in methanol undersimilar conditions gave compound (XV) in 73 yield.When acetonitrile was employed as solvent, the yield of0rsquo; CH=C=O -a; x =nCO 2Me2Meb; X =SCHEME 1compound (XV) was only 50.Elemental analysisand mass spectroscopy (M+ 266) showed the productto be an isomer of (Vb). The i.r. spectrum exhibitedabsorptions at 1745 and 1700 cm-l due to a carbonylgroup on a six-membered ring and an ap-unsaturated3,31( Y b)Fl C H=C=O0 amp;HbH cSCHEME 2carbonyl group on a five-membered ring; compound(Vb) showed a carbonyl band at about 1660 cm-l.18The n.m.r. spectrum of compound (XV) showed nosignals for olefinic or hydroxy-protons. The formationof compound (XV) could be explained in terms of anJ . Ciabattoni, J . E. Crowley, and A. S. Kende, J. Amer.Chern. SOC., 1967, 89, 2778.initial 1,3sigmatropic rearrangement of (Vb) to (XIII)followed by isomerization to the conjugated diene (XIV)and ultimate enol-keto tautomerization as shown inScheme 2.Analogously, irradiation of the adduct (VIIb) inmethanol under similar conditions afforded one product(XVII) in 80 yield.The structure was similarly con-firmed by elemental analysis and spectroscopy.Kende et aZ.19 have reported that the chemical be-haviour of the excited tropone-benzyne adduct (XVIII)involves two distinct and competitive primary processes ;the more rapid of these is stereospecific 3,3 rearrange-ment to a keten intermediate (XIX) which might betrapped by nucleophiles but otherwise reverts rapidly toL -(mu1SCHEME 3the ketone (XVIII) , and the minor pathway is a 1,3 acylmigration producing the labile ketone (XXI) which israpidly converted by weak bases to the ketone (XXII).In contrast, irradiations of compounds (Vb) and (VII),even in methanol, did not afford the 3,3 rearrangementproduct (XVI) which might be trapped as a methylester, but instead gave the 1,3 rearrangement productsonly. Thus, the hydroxy-group at C-12 (Vb) 5 - 8 in(VIIb) caused a marked variation in the photochemicalbehaviour of the bicyclo3,2,2nonadienone system.EXPERIMENTALM.p.s were measured with a Yanagimoto apparatus.Microanalyses were performed with a Perkin-Elmer 240elemental analyser.N.m.r. spectra were taken with aJEOL C-60-XL spectrometer and with a Varian A60recording spectrometer, with tetramethylsilane as internalstandard.1.r. spectra were taken with a JASCO-IR-Sspectrophotometer. Mass spectra were obtained with aHitachi RMU-D double-focusing spectrometer operatinga t an ionization potential of 70 eV. The solid samples wereionized by electron bombardment after sublimation directlyinto the electron beam a t 100-150deg;.18-Oxupentacyclu 10,3, 2,02, 11, 139 10,04*suctudeca-4, 6,8,14,16-pentuen-13-one (IIIa).-A solution of tropone (1.1 g) and theIs A. S. Kende, 2. Goldschmidt, and P. T. Izzo, J . Amev.Chem. SOC., 1969, 91, 68581954 J.C.S. Perkin Ioxabenzonorbornadiene (I) (1.4 g) in chlorobenzene (30 ml)was heated at 130-140" in a sealed tube for 10 h. Chroma-tography on silica gel, followed by recrystallization frombenzene-n-hexane gave the adduct (IIIa) (2.1 g) as prisms,m.p. 164-165" (Found: C, 81-4; H, 5.85.C,7H1,02 re-quires C, 81.6; H, 5.65), v,=. (KBr) 1655, 1635, and1460 cm-l, m/e 250 and 118 (base), 7 (CDCl,) 2.88 (4H, m,ArH), 2.92 (lH, q, H-15, J 12.0 and 7.9 Hz), 3.53 (lH, t,H-14, J 12.0 and 2.0 Hz), 4-88 (lH, s, H-3), 4-98 (lH, s,H-lo), 6.25 (lH, dd, H-12, J 7.5 and 2.0 Hz), 6.50 (lH, dd,H-1, J 7.9 and 7-5 Hz), 7.47 (lH, d, H-2, J 7.8 Hz), and265sh (1330), 272sh (990), and 350 nm (100).12-Hydroxo-18-oxa~entacycZo 10,3,2,029 11, 1 3 9 10,043 Qocta-deca-4,6,8,14,16-pentaen-13-one (Vb) .-A solution of tropol-one (0.6 g) and the dienophile (I) (0.7 g) in chlorobenzene(20 ml) was heated at 120-130deg; in a sealed tube for 10 h.Chromatography on silica gel followed by recrystallizationfrom acetone-ether gave the adduct (Vb) (1.25 g) as prisms,m.p.169172" (Found: C, 76-95; H, 5.05. Camp;1@, re-quires C, 76.65; H, 5-3), vmx. (KBr) 3460, 1660, and1460 cm-l, m/e 266 and 118 (base), A,= (EtOH) 230 (G5780), 263sh (1690), 272sh ( l l O O ) , and 342 nm (100).9-Oxo- 14-oxatetracyclo6,3,2, 02, 7, 13*stetradeca-4,10,12-triene-4,5-dicarboxyZute (VIIa) .-A solution of trop-one (1.2 g) and the oxanorbornadiene dimethyl ester (11)(2.02 g) in benzene (10 ml) was heated at 130" in a sealedtube for 15 h. Work-up as before gave the adduct (VIIa)(0-68 g) as prisms, m.p. 100-102" (Found: C, 64-45; H,5-2. Cl7HI6O6 requires C, 64.55; H, 5.1), vmx. (KBr)1730, 1700, 1660, and 1635 cm-l, m/e 316 and 184 (base),T (CDC1,) 2.87 (lH, q, H-11, J 10.5 and 8.7 Hz), 3.60 (lH,t, H-12, J 8.7 and 6.8 Hz), 3.95 (lH, t, H-13, J 7.5 and6.8 Hz), 4.35 (lH, dd, H-10, J 10.5 and 2.0 Hz), 5-03 (lH,s, H-3), 5.11 (lH, s, H-6), 6.22 (6H, s, 2 x OMe), 6-26 (lH,m, H-8), 6.56 (lH, t, H-1, J 8.7 Hz), 7.31 (lH, dd, H-2,J 8.3 and 1-5 Hz), and 7.53 (lH, d, H-7, J 8.7 Hz), A,=(EtOH) 226 (c 10,190) and 350 nm (92).Diaiethyl 8-Hydroxy-9-oxo-l4-oxatetracyclo6,3, 2,023 ,, 1,' *I-tetrudeca-4,10,12-triene-4,5-dicarboxylate (VIIb) .-A solu-tion of tropolone (0-66 g) and the diester (11) (1.0 g) inchlorobenzene (20 ml) was heated a t 130' in a sealed tube for13 h; similar work-up gave the adduct (VIIb) (0.35 g) asprisms, m.p.114115" (Found: C, 61-45; H, 4.85. C1,H,6-0, requires C, 61.4; H, 4.9), v,, (KBr) 3480, 1730, 1715,1665, and 1640 cm-l, m/e 332 and 184 (base), T (CDC1,)2.72 (lH, q, H-11, J 11.0 and 8-4 Hz), 3.69 (lH, t, H-12,J 8.4 and 7.0 Hz), 4.10 (lH, d, H-13, J 7.0 Hz), 4.12 (lH, d,H-6, J 2.0 Hz), 5-39 (lH, s, OH, exchangeable), 6.21 (6H,s, 2 x OMe), 6-50 (lH, t, H-1, J 8.4 Hz), 7.41 (lH, d, H-2,J 8-3 Hz), and 7.76 (lH, d, H-7, J 8.3 Hz), A,, (EtOH) 226(E 10,410) and 342 nm (115).H-16, J 7.5 Hz), 3.87 (lH, t, H-17, J 7.5 Hz), 4.41 (1H, dd,7.68 (lH, d, H-11, J 7.8 Hz), A,=. (EtOH) 224 (amp; 5580),DimethylH-10, J 11.0 Hz), 4.50 (lH, d, H-3, J 2.0 Hz), 5.11 (lH, d,Irradiation of Compound (IIIa) .-The adduct (IIIa) (0.15g) was irradiated in methanol (100 ml) for 3.5 h with a high-pressure 100 W mercury lamp in a Pyrex vessel undernitrogen.Evaporation to dryness at reduced pressure andrecrystallization from benzene-n-hexane gave methyl 16-oxu-pentacyclo7,6, 1,02*8,03, 6,010~15hexadeca-6, 10,12,14-tetraen-4-ylacetate (XIIa) (0.16 g) as prisms, m.p. 103-104" (Found:C , 76.55; H, 6.4. C18H1803 requires C, 76.55; H, 6.45),vmx. (KBr) 1730 and 1440 cm-l, m/e 282 and 118 (base),7 (CDCl,) 2-84 (4H, m, ArH), 4.05 (lH, dd, H-6, J 11.0 and3.9 Hz), 4.27 (lH, dd, H-7, J 11.0 and 2-0 Hz), 4-80 (lH, s,H-l or H-9), 5-07 (lH, s, H-9 or H-1), 6-42 (3H, s, OMe),7-77-8.03 (4H, m, H-2 and -8 and CH,), and 8.33-8-65(3H, m, H-3, -4, and -5).Irradiation of Compound (VIIa) .-The adduct (VIIa)(0.25 g) was irradiated in methanol (100 ml) under the sameconditions ; work-up as before gave methyb 10,l l-bismethoxy-carbonyl- 12-oxatetracycZo 7,2, l,Oa, 8,03s 6dodeca-6, 1 O-dien-4-ylacetate (XIIb) (0.26 g) as an oil, nD20 1.5294 (Found: C,62.2; H, 5.8.C18H2,07 requires C, 62.05; H, 5.8), vmx,(film) 1735, 1720, and 1645 cm-l, m/e 348 and 184 (base),7 (CDCl,) 4-05 (lH, dd, H-6, J 10.5 and 3.6 Hz), 4.34 (lH,dd, H-7, J 10.5 and 2-0 Hz), 4-96 (lH, s, H-1 or H-9),5.22 (lH, s, H-9 or H-1), 6.21 (6H, s, 2 x OMe), 6.37 (3H, s,OMe), 7.68-7-95 (4H, m, H-2 and -8 and CH,), and 8.38-8.70 (3H, m, H-3, -4, and -5).Theadduct (Vb) (0.25 g) was irradiated in methanol (100 ml)under the same conditions. Evaporation to dryness andchromatography on silica gel followed by recrystallizationfrom benzene-n-hexane gave lS-oxupentacycZo9,6, 1,02* lo,-03~7,012*17octadeca-3(7), 12,14,16-tetraene-6,9-dione (XV) (0.18g) as prisms, m.p. 186-188" (Found: C, 76-75; H, 5.5.C1,H1403 requires C, 76.65; H, 5.3), vmx. (KBr) 1745,1700, and 1465 cm-l, m/e 266 and 118 (base), 7 (CDCl,) 2-82(4H, m, ArH), 4.13 (lH, S, Hc), 4-66 (lH, S, Ha), 6-50 (lH,d, Ha, J 6.0 Hz), 7.34 (lH, d, H b , J 6.0 Hz), and 7-57-8.52(6H, complex m) .The adduct (Vb) (0.06 g) was irradi-ated in acetonitrile (50 ml) under the same conditions;work-up as before gave the photoproduct (XV) (0.03 g).Irradiation of Compound (VIIb) .-The adduct (VIIb) (0.20g) was irradiated in methanol (100 ml) under the same con-ditions ; similar work-up gave dimethyl 6,g-dioxo- 14-oxa-tetracycZo9,2,1, 0,' lo, 039 7tetradeca-3 (7), 12-diene- 12,13-dicarb-oxylate (XVII) (0-16 g) as prisms, m.p. 154-156" (Found:C, 61.65; H, 4-9. C1,H1,O7 requires C, 61-45; H, 4.86),vmx. (KBr) 1735, 1700, and 1640 cm-l, m/e 332 and 184(base), T (CDCl,) 4.36 (lH, s, H, or Hd), 4.81 (lH, s, Hd orHJ, 6.20 (3H, S, OMe), 6-22 (3H, S, OMe), 6.46 (lH, d, Ha,J 6-0 Hz), 7.25 (lH, d, Hb, J 6.0 Hz), and 7.43-8.55 (6H,complex m, 3 x CH,).Irradiation of Compound (Vb).-(a) I n methanol.(b) I n acetonitrile.2/381 Received, 21st February, 1972