Synthesis of alkyl and aryl substituted buta-1,2,3-trienes

摘要

J. CHEM. SOC. PERKIN TRANS. 1 1995 Synthesis of Alkyl and Aryl Substituted Buta-I ,2,3-trienes Hak-Fun Chow," Xiao-Ping Cao and Man-kit LeungDepartment of Chemistry, The Chinese University of Hong Kong. Shatin, N.T,, Hong Kong Reaction of the lithium or cerium(iii) anion of 3-alkyl or 3-aryl substituted 3-trimethylsilylprop- 1 -yne 1 with aldehydes or ketones afforded 1 -hydroxy-4-trimethylsilylbut-2-ynes 2 in good yields. Conversion of the silyl prop-2-ynylic alcohols 2 into the corresponding acetates 3 followed by tetrabutylammonium fluoride-induced, 1,4-eIimination gave alkyl and aryl substituted buta-l,2,3- trienes 4 in good yields. Butatrienes are an interesting class of compounds which have recently been shown to possess interesting non-linear optical and amphoteric multistage redox properties2 They have also been used as intermediates for the preparation of biologically active enediynes and have potential as ferromagnetic materials and as intermediates for two-dimensional carbon networks such as radialene~.~ Although there are several synthetic methods for the preparation of b~ta-l,2,3-trienes,~ there are only a handful of procedures for the preparation of alkyl substituted buta-l,2,3- trienes6 Most of the known butatrienes are aryl or tert-butyl substituted because of their greater stability towards oxygen and acids.In a preliminary comm~nication,~ we disclosed a facile synthetic method for the preparation of 1-alkyl-4-aryl-and 1,l-dialkyl-4-arylbuta-1,2,3-trienes.In this report, we extend this methodology to include the synthesis of 1,4-dialkyl- and 1,I ,4-trialkylbuta-1,2,3-trienesas well as the full details of their preparation^.^ Results and Discussion Synthesis.-Our methodology is based on the well docu- mented synthesis of alkenes by 1,2-elimination reactions of (3-acetoxy organosilanes (Scheme 1).We envisaged that by Scheme 1 1,2-(top) and 1,4-eliminations (bottom) insertion of an acetylenic functionality between the acetoxy and the trimethylsilyl groups, the analogous 1,4-elirnination should become plausible with the formation of the highly re- active buta- 1,2,3-triene. In fact, the base-catalysed elimination of 1-hydroxy-4-trimethylsilylbut-2-enesto give buta-l,3-dienes and the reaction stereochemistry had previously been disclosed in the literature.' 3-Phenyl-3-trimethylsilylprop-1-ynela (R = Ph) or 3-tri-methylsilylhex-1-yne lb (R = Pr), readily available lo in 100 g quantities, can be converted into the corresponding lithium acetylides on treatment with butyllithium (1 equiv.) at 0 "C (Scheme 2).The resulting anion can be trapped with aldehydes or ketones to give a diastereoisomeric mixture of silyl propynylic alcohol 2 in good yields (Table 1). There is little 1,4- asymmetric induction for the addition of the acetylide anion to the carbonyl compounds. Typical diastereoisomeric ratios of the alcohols are between 1 : 1 and 2:1. The ratio is higher for SiMe3 SiMe,I I I/Ii SiMe3 4 3 Scheme 2 Reagenrs: i, BuLi, THF or BuLi, CeCI,, THF; ii, RZR3C-O; iii, DMAP, Ac,O, NEt,, ether; iv, TBAF, ether Table 1 Yields of reactions i-iv () Entry R' RZ R' 2 3 4 Ph H Ph 75 84 83 Ph H Ph H C,H,,Pr' 90' 78* 91 78 70 89 Ph H Bu' 80 90 93 Ph Me Me 83* 79 71 Pr H Ph 72 14 89 Pr H Pr H C,H,, Bu' 84* 89 83 78 92 91 Pr Me Me 90* 92 83 * Addition of CeCI, sterically hindered aldehydes such as pivalaldehyde.For easily enolizable aldehydes such as heptanal (entries b and g), the yield of the prop-2-ynylic alcohol 2 from the reaction is poor. However, conversion of the organolithium into organocerium ' by the addition of CeCI, results in a very clean transformation. The alcohol 2 is then converted into the corresponding acetate 3 (dimethylaminopyridine, triethyl-amine, acetic anhydride), subsequent treatment of which with tetrabutylammonium fluoride results in a facile 1,Celimination to give the substituted butatriene 4.Upon quenching with aqueous sodium carbonate, extractive work up with hexane (degassed) under nitrogen and then flash chromatography on Florisil, the butatriene 4 can be isolated as a mixture of (E)-and (Z)-isomers with 90 purity. On contact with alumina or silica gel, the butatriene polymerizes rapidly to form a solid precipitate. Both the prop-2-ynylic alcohols 2 and the acetates 3 are pale yellow, light- and heat-sensitive oils. The stability of the buta- 194 1,2,3-trienes depends heavily on the nature of the substituent.Phenyl or tert-butyl substituted butatrienes are more stable and can be stored at -30 "C for days in hexane solutions. The alkyl analogues are less stable and tend to polymerize upon con- centration from hexane solutions. For example, 4-methyl- 1-phenylpenta-l,2,3-triene4e polymerizes at 25 "C during 13C NMR data acquisition. When subjected to mass spectrometric analysis, the butatrienes 4e and 4i produced many higher molecular weight peaks in addition to the parent ion signal, suggesting that the polymerization process may take place during sample injection. These butatrienes 4 exhibit interesting spectroscopic proper- ties. Thus, for 1,4-disubstituted butatrienes, the two protons (d 6.22-6.5) couple to each other with a long-range coupling constant of 'JHH 7 Hz.There is little difference (0.5 Hz) between the cis- and trans-coupling constants of the butatrienes and, therefore, it is difficult to assign the geometry of the triene system. The presence of the butatriene skeleton was also confirmed by the characteristic CH coupling constants ('JCH 158-165 Hz) of the terminal olefinic carbons in their 13C NMR spectra. In summary, we have developed a facile method for the synthesis of both the alkyl- and aryl-substituted buta-l,2,3- trienes. Our method also allows us to prepare 1 ,4-unsymmetri- cally substituted butatrienes. The yields of the reactions are high and the butatrienes can be prepared in gram quantities. Experimental General.-IR spectra were recorded on a Nicolet (205) FT-IR spectrophotometer for samples as neat films on KBr disks and reported in wavenumbers (cm-I).'H NMR spectra were recorded on a Bruker Cryospec WM 250 (250 MHz) spectrometer for samples in CDCI, solution with dichloro- methane (S 5.32) or residual CHCI, (6 7.24) as internal standards. Coupling constants (J) are reported in Hz. I3C NMR spectra were obtained for samples in CDCI, on a Bruker WM 250 spectrometer at 62.9 MHz. Mass spectra were obtained on a Finnegan MAT 95 instrument. Elemental analyses were carried out by Medac Ltd., Uxbridge, U.K. Deuteriated chloroform (CDC1,) was freshly distilled over sodium hydrogen carbonate before use. General Procedure for the Synthesis of Sly1 Prop-2-ynylic Alcohols 2.-Method A.To a stirred solution of the acetylene 1 (6.4 mmol) in dry THF (20 cm3) was added butyllithium (1.6 mol dm-, in hexane; 4.0 cm3, 6.4 mmol) dropwise at 0 "C under nitrogen. The resulting solution was stirred at 20 "C for 30 min and then cooled to -78 "C. A solution of the aldehyde or ketone (6.4 mmol) in dry THF (15 cm3) was then added to the mixture which was then stirred at -78 "C for 1 h and then gradually warmed up to 20 OC over a period of 2 h. The reaction mixture was then poured into ice-water and the aqueous phase extracted with ethyl acetate (2 x 50 cm3). The combined organic solvents were dried (MgSO,), filtered and evaporated under reduced pressure, and the residue purified by flash chromatography on silica gel with hexane- ethyl acetate (10: 1) as eluent to give the silyl prop-2-ynylic alcohol 2 as an oil.Method B. To a stirred solution of the acetylene 1lo (6.4 mmol) in dry THF (20 cm3)was added butyllithium (1.6 mol dm-, in hexane; 4.0 cm3, 6.4 mmol) dropwise at 0 "C under nitrogen. The resulting solution was stirred at 0 "C for 30 min and then transferred uiu a syringe to a stirred suspension of anhydrous cerium(rI1) chloride (6.4 mmol) in dry THF (20 cm3) at -78 "C. This was kept for 30 min at -78 "C,after which the aldehyde or ketone (6.4 mmol) in THF (10 cm3) was added to it and the whole stirred at this temperature for 1 h; it was then J. CHEM. SOC. PERKIN TRANS. I 1995 gradually warmed to 20 "C over a period of 2 h. The mixture was worked up following the same procedure as that described in Method A.The following silyl prop-2-ynylic alcohols were prepared. 1,4-Diphenyl-4-trimethylsilyibut-2-yn-l-ol2a (Method A, 75): v,,,/cm-' 3422 (OH); SH 0.09 + 0.10 (total 9 H, 2 s, SiMe,), 2.362.40 (1 H, br s, OH), 3.28 (1 H, d, J2.2,4-H), 5.62 (1 H, br s, 1-H) and 7.19-7.70 (10 H, m, ArH); 6, -3.2, 29.5, 65.0, 82.8, 87.5, 125.1, 126.5, 127.0, 128.0, 128.1, 128.4, 139.0 and 141.6 Found (HRMS): 294.1428. Calc. for C19H,,0Si: 294.14391. 1-Phenyl-1-trimethyIsilyldec-2-yn-4-01 2b (Method B, 90): v,a,/cm-l 3416 (OH); 6,O.lO (9 H, s, SiMe,), 0.94 (3 H, t, J6.9, 10-H), 1.30-1.50 (6 H, m), 1.51-1.57 (2 H, m), 1.73-1.80 (2 H, m), 2.25-2.45 (1 H, br s, OH), 3.20 (1 H, d, J2.0, I-H), 4.474.53 (1 H, m, 4-H) and 7.147.34 (5 H, m, ArH); Sc -3.3, 14.0, 22.5, 25.3,28.9,29.3,31.8,38.4,63.0,84.1,85.2,125.1,126.9,128.1and 139.2 Found (HRMS): 302.2058. Calc.for C,,H,,OSi: 302.20661. 2-Methyl-6-phenyl-6-trimethylsilylhex-4-yn-3-ol2c (Method B, 78): vmax/crr-' 3416 (OH); S, 0.07 (9 H, s, SiMe,), 1.02 (3 H, d, 56.9, Me), 1.05 (3 H, d, J6.9, Me), 1.63-1.77 (1 H, br s, OH), 1.85 (I H, octet, 56.9, 2-H), 3.19 (1 H, d, J 1.9, 6-H), 4.284.34 (1H,m,3-H)and7.13-7.36(5H,m,ArH);Sc-3.2,17.5,18.3, 29.5,34.8,68.4,82.5,86.2,125.2, 127.0, 128.2 and 139.3 Found (HRMS): 260.1593. Calc. for C,,H,,OSi: 260.15961. 2,2-Dimethyl-6-phenyl-6-trimethylsilylhex-4-yn-3-ol 24J (Method A, 80): v,,,/cm-l 3466 (OH); SH0.10 (9 H, s, SiMe,), 1.07 (9 H, s, Bu'), 2.55-2.70 (1 H, br s, OH), 3.21 (1 H, d, J2,6-H),4.13 +4.15(total 1 H,2d,J2,3-H)and7.10-7.33 (SH,m,ArH);S, -3.2,25.5,29.5, 35.9,71.8, 82.5, 86.0, 125.1, 127.0, 128.1 and 139.3 Found (HRMS): 274.1746.Calc. for C,,H,,OSi: 274.17531. 2-Methyl-5-pheny1-5-trimethylsilylpent-3-yn-2-ol2e(Method B, 83): v,,,/cm-' 3395 (OH); 6,O. 10 (9 H, s, SiMe,), 1.62 (3 H, s,Me),1.63(3H,s,Me),3.18(lH,s,5-H),3.30-3.60(1H,brs,OH)and7.12-7.37(5H,m,ArH);Sc-3.3,28.8,31.8,31.9,65.6, 82.5, 88.0, 125.1, 126.9, 127.8 and 139.2 Found (HRMS): 246.1438. Calc. for CISH,,OSi: 246.14401. 1-Phenyl-4-trimethylsilylhept-2-yn-l-ol2f(Method A, 72): v,,,/cm-l 3437 (OH); 8H 0.09 + 0.10 (total 9 H, 2 S, SiMe,), 0.95(3H,t,J6.8,7-H), 1.3amp;1.50(3H,m), 1.53-1.70(2H,m), 2.37-2.47(1 H,brs,OH),5.47(1 H,brs, l-H)and7.28-7.60(5 H,m,ArH);G, -3.2,13.7,19.8,22.8,31.3,65.0,80.8,89.8,126.6, 127.9, 128.3 and 141.9 Found (HRMS): 260.1602. Calc.for Cl,H,,OSi: 260.1 5961. 4-Trimethylsilyltridec-5-yn-7-ol2g (Method B, 84): v,,,/cm-' 3460 (OH); 6" 0.09 (9 H, s, SiMe,), 0.80-0.97 (6 H, m, 1-H and 13-H), 1.22-1.71 (16 H, m) and4.314.44(1 H, m, 7-H); dC-3.2, 13.7, 14.0, 19.6, 22.5, 22.7, 25.2, 29.0, 31.3, 31.8, 38.6, 63.1, 82.0 and 87.5 Found (HRMS): 268.2216. Calc. for C,,H,,OSi: 268.22221. 2,2-Dimethyl-6-trimethylsilylnon-4-yn-3-ol2h (Method A, 89): v,,,/cm-' 3459 (OH); SH0.06 (9 H, s, SiMe,), 0.88 (3 H, t, J6.4,9-H), 0.93 (9 H, s, Bu'), 1.32-1.36 (3 H, m), 1.60-1.68 (2 H, m), 1.71-1.78 (1 H, br s, OH) and 3.99 (1 H, d, J 2.1, 3-H); 6, -3.1, 13.7, 19.6, 22.8, 25.4, 31.5, 35.9, 71.9, 80.5 and 88.2 Found (HRMS): 240.1905.Calc. for C,,H,,OSi: 240.19091. 2-Methyl-5-trimethylsilyloct-3-yn-2-ol2i (Method B, 90): vmaX/cm-' 3381 (OH); SH0.04 (9 H, s, SiMe,), 0.87 (3 H, t, J6.9, 8-H),1.29-1.36(3H,m),1.46(6H,s,2x Me),1.5amp;1.62(2H, m)and 1.85-1.93(1 H,brs,OH);6, -3.2, 13.7, 19.4,22.7,31.4, 32.0, 65.5, 84.6 and 85.9 Found (HRMS): 240.1582. Calc. for C,,H,,OSi 212.15961. General Procedure for the Synthesis of Silyl Prop-2-ynylic Acetates 3.-A mixture of the prop-2-ynylic alcohol 2 (4.0 mmol), triethylamine (14.0 mmol), acetic anhydride (14.0 (79): v,,,/cm-' 1736 (C=O); 6, 0.12 (9 H, S, SiMe,), 1.72 (3 H, (Z)-isomers, 6.37 + 6.39 total 1 H, 2 dd, J 7 and 2, I-H of s,Me),1.74(3H,s,Me),2.11(3H,s,CH3CO),3.18(1H,s,5-H)(E)-and (Z)-isomers and 7.16-7.49 (5 H, m, ArH); 6, 22.0 + and 7.12-7.33 (5H, m, ArH);6, -3.4,21.9,29.3,29.4,72.8,84.5, 22.9, 32.0 + 32.1, 106.6 + 106.7 ('JCH 164, 443, 118.5 ('JCH 84.6, 125.0, 127.0, 128.4, 139.3 and 169.3 Found (HRMS): 164, I-C), 127.4, 127.5, 128.6, 137.0 + 137.2, 157.3 and 160.8; 288.1540.Calc. for C1,Hz,OzSi: 288.15461. mjz 170 (M', 44). 1-Phenyl-4-trimethylsilylhept-2-ynylacetate 3f (74): v,,,/ 5,5-Dimethyl- 1 -phenylhexa- 1,2,3-triene 4d (93): v,,,/cm-' cm-' 1743 (GO); 6,O. 14 + 0.15 (total 9 H, 2 s, SiMe,), 0.98 (3 2968, 2909, 1940, 1679, 1478, 1366, 835, 788, 755 and 696; 6, H,t,J7.5.7-H), 1.40-1.80(5H,m),2.14(3H,s,CH3CO),6.561.19 + 1.25 (total 9 H, intensity l:l.5, 2 s, Bur), 5.75 + 5.83 total 1 H, 2 d, J 7.7, 4-H of (E)-and (Z)-isomers, 6.39 + J.CHEM. SOC. PERKIN TRANS. I 1995 mmol) and dimethylaminopyridine (100 mg, 0.08 mmol) in dry ether (30 cm3) was stirred at 0 "C for 16 h and then poured into ice-water and extracted with diethyl ether (2 x 50 cm3). The organic extracts were washed with saturated brine, dried (MgSO,), filtered and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel with hexane-ethyl acetate (20: 1) as eluent to give the acetate 3 as a pale yellow oil. The following silyl prop-2-ynylic acetates were prepared. 1,4-Diphenyl-4-trimethylsilylbut-2-ynylacetate 3a (84): v,,,/cm ' 1744 (M);S, 0.1 1 (9 H, S, SiMe,), 2.16 (3 H, S, CH,CO), 3.30 + 3.31 (total 1 H, 2 d, J 1.7, 4-H), 6.64 + 6.65 (total 1 H, 2 d, J 1.8, 1-H) and 7.20-7.70 (10 H, m, ArH); 6, -3.4, 20.8, 29.3, 66.3, 79.5, 88.3, 125.1, 126.8, 127.5, 128.3, 128.5, 128.7, 137.7, 138.5 and 169.8 Found(HRMS): 336.1546.Calc. for CZlH2,O2Si: 336.15463. I-Phenyl-1-trimethylsilyldec-2-yn-4-ylacetate 3b (91): v,,,/ cm-' 1736 (C=O); 6,0.08 (9 H, s, SiMe,), 0.92 (3 H, t, 37, 10-H), 1.23-1.60 (8 H, m), 1.77-1.88 (2 H, m), 2.10 (3 H, s, CH,CO), 3.18 +3.19(totalIH,2d,J2, l-H),5.45-5.53(1H,m,4-H) and 7.09-7.33 (5 H, m, ArH);S, -3.3,14.0,21.0,22.5,25.1,28.8, 29.4, 31.7, 35.3, 65.0, 80.8, 86.0, 125.1, 127.0, 128.1, 139.0and 170.0 Found (HRMS): 344.2166. Calc. for C,,H,,O,Si: 344.2 1721.2-Methyl-6-phenyl-6-trimethylsilylhex-4-yn-3-ylacetate 3c (78): vmax/cm-' 1741 (GO);S, 0.11 (9 H, s, SiMe,), 1.09 (3 H, d, J7,Me), 1.12(3H,d, J7,Me),2.03-2.23(1 H,m,2-H),2.15(3 H, s, CH,CO), 3.24 (1 H, d, J2, 6-H), 5.35-5.41 (1 H, m, 3-H) and7.167.40(5H,m,ArH);Sc-3.2,17.7,18.4,21.0,29.5,32.6, 69.8, 79.0, 86.6, 125.1, 127.0, 128.2, 139.1 and 170.2 Found (HRMS): 302.1688. Calc. for C18H,,02Si: 302.17021. 2,2-Dimethyl-6-phenyl-6-trimethylsilylhex-4-yn-3-ylacetate 3d (90): v,,,/cm-' I744 (GO);6, 0.08 (9 H, S, SiMe,), 1.08 (9 H, S, Bu'), 2.12 (3 H, S, CH,CO), 3.21 (1 H, d, J2, 6-H), 5.24 + 5.25 (total 1 H, 2 d, J2, 3-H) and 7.12-7.35 (5 H, m, ArH); 6, -3.2, 20.9, 25.7, 29.5, 35.2,72.8, 79.3, 86.4, 125.1, 127.0, 128.1, 139.1 and 170.2 Found (HRMS): 316.1850.Calc. for C, 9H2802Si: 316.18591. 2-Methyl-5-phenyl-5-trimethylsilylpent-3-yn-2-ylacetate 3e 195 2 x Me) and 1.95 (3 H, s, CH,CO); 6, -3.3, 13.7, 19.5, 22.0, 22.6,29.5,29.6,31.2,72.9,82.1,86.6and169.1 Found(HRMS): 254.1709. Calc. for C1,H,,OzSi: 254.17021. General Procedure for the Synthesis of Buta-l,2,3-trienes 4.-Tetrabutylammonium fluoride (1.0 mol dm-3 in THF; 1.O cm3, 1.0 mmol) was added dropwise to a stirred solution of the acetate 3 (1.O mmol) in diethyl ether (20 cm3) under nitrogen at -10deg;C. After 5 min, the reaction mixture was poured into saturated aqueous sodium carbonate and extracted with hexane (degassed; 2 x 50 cm3) under nitrogen. The combined extracts were washed with saturated aqueous sodium carbonate, dried (K2C03), filtered and evaporated under reduced pressure to give a yellow oil.This oily residue was chromatographed on Florid under nitrogen with hexane (degassed) as eluent to give the butatriene 4 as an oil. Unfortunately, owing to the instability of the butatrienes, we were unable to obtain satisfactory high resolution mass data or elemental analysis data of these compounds. The following butatrienes were prepared. 1,4-Diphenylbuta-l,2,3-triene4a (83): vmax/cm-' 3022, 1945, 1672, 1494, 836, 784, 761 and 696; 6, 6.53 + 6.61 total 2 H, intensity 1 :1, 2 s, I-H and 4-H of (E)-and (Z)-isomers and 7.24-7.60 (10 H, m, ArH); 6c 109.6 ('JCH164, 1-C and 4-C), 127.9, 128.0 + 128.1, 128.7 + 128.8, 137.0 + 137.2 and 155.7 + 155.8; m/z204 (M', 47).I-Phenyldeca-l,2,3-triene4b (70): v,,,/cm-l 2956, 2928, 1947,1680,1448,1314,836,788, 764and699;SH0.85-1.00(3 H, m), 1.20-1.73 (8 H, m), 2.28-2.41 (2 H, m), 5.73 + 5.79 total 1 H,intensity 1 : 1, 2 q, J 7.4, 4-H of (E)-and (Z)-isomers, 6.36 f6.37 total 1 H, 2 dt, J 7.4 and 1.6, 1-H of (E)-and (Z)-isomers and 7.18-7.44 (5 H, m, ArH); 6, 14.0, 22.6, 28.8, 31.7, 33.0, 33.5, 106.6 + 106.7 ('.ICH163, 4-C), 111.7 ('JCH158, 1-C), 127.4, 127.5, 128.6, 137.1, 158.8 and 159.8; m/z 212 (M', 41). 5-Methyl-1-phenylhexa-l,2,3-triene4c (89): v,,,/cm-' 2962, 2929, 1920, 1647, 1450, 1314,835,751 and 699; 6, 1.14 + 1.21 (total 6 H, intensity 1 :1.2,2 d, J6.7, CMe,), 2.5g2.72 (1 H, m, 5-H), 5.76 + 5.81 total 1 H, 2 dd, J 7 and 6, 4-H of (E)-and (1 H, br s, I -H) and 7.40-7.62 (5H, m, ArH); Sc -3.2,13.7,19.9, 21.0, 22.8, 31.2, 66.5, 77.2, 90.8, 127.6, 128.4, 128.5, 138.3 and 169.8 Found (HRMS): 302.1704.Calc. for C,,H,,O,Si: 302.17021, 4-Trimethylsilyltridec-5-yn-7-ylacetate 3g (83): v,,,km-' 1746(GO);6,0.04(9H,s,SiMe3),0.80-0.90(6H,m,I-Hand 13-H), 1.20-1.45 (11 H, m), 1.541.74 (4 H, m), 2.06 (3 H, s, CH3CO)and5.28-5.37(1H,m,7-H);6,-3.3,13.7,14.0,19.6, 21.1, 22.5, 22.7, 25.1, 28.8, 31.2, 31.7, 35.3, 65.1, 78.3 + 78.4, 88.2 + 88.3 and 170.1 Found (HRMS): 310.2333. Calc. for C18H,,02Si: 3 10.23283. 2.2-Dimethyl-6-trimethylsilylnon-4-yn-3-ylacetate 3h (78): v,,,lcm-' 1744 (C--O);dH0.03 (9 H, s, SiMe,), 0.85 (3 H, t, J7.2, 9-H), 0.96 (9 H, s, Bu'), 1.31-1.38 (3 H, m), 1.55-1.65 (2 H, m), 2.04(3H,s.CH3CO)and5.06 + 5.07(total.I H,2d,J2.6,3-H); 6c -3.1, 13.7, 19.6, 20.9, 22.7, 25.7, 31.2, 35.1, 72.8, 76.9, 88.4 and 170.2 Found (HRMS): 282.2020.Calc. for C16H3002Si: 282.20151. 2-Methyl-5-trimethylsilyloct-3-yn-2-ylacetate 3i (92): v,,,/cm-' 1747(C--O);SH0.03 (9 H, s, Me3), 0.82 (3 H, t, J 6.7, 8-H), 1.25-1.35 (3 H, m), 1.50-1.65 (2 H, m), 1.55 (6 H, s, 6.43 total 1 H, 2 d, J 7.7, I-H of (E)-and (Z)-isomers and 7.20-7.50(5H,m,ArH);SC29.7+ 29.9, 35.5 + 35.7, 106.5 + 106.6 ('JCH165, 447, 122.7 + 122.7 ('J,, 165, 1-C), 127.4, 128.6, 128.7, 137.0 + 137.3, 156.0 + 156.2 and 161.3; m/z 184 (M', 52).4-Methyl-l-phenylpentu-l,2,3-triene4e(71):S, 2.05 (3 H, s, Me), 2.12 (3 H, s, Me), 6.20 (1 H, s, I-H) and 7.167.43 (5 H, m, ArH).l-Phenylhepta-l,2,3-triene4f (89): v,,,/crn-' 2990, 2920, 1956, 1423, 1357, 825, 795, 764 and 699; 6, 1.11 + 1.16 (total 3 H,t,J7.3,7-H),1.53-1.90(2H,m),2.33-2.51(2H,m),5.85+ 5.92 total 1 H, intensity 1 : 1, 2 q, J 7.4, 4-H of (E)-and (2)- isomers, 6.51 + 6.52 total 1 H, 2 dt, J7.5 and 1.5, 1-H of (E)-and (Z)-isomers and 7.25-7.59 (5 H, m, ArH); 6, 13.6,22.0 + 22.1, 35.0 + 35.4, 106.6 + 106.7 ('JCH 162, 4-C), 111.3 ('JCH 161, I-C), 127.3, 127.4, 128.5, 137.0, 158.9 and 159.7; m/z 170 (M+, 33). Trideca-4,5,6-triene 4g (92): v,,,/cm-' 2966, 2938, 2059, 1744, 1475, 1378 and 842;6,0.8amp;0.98 (6 H, m), 1.22-1.38 (6 H, m), 1.42-1.60(4 H,m), 2.12-2.25(4H, m)and 5.48 + 5.50 total 2 H, intensity 1 :1, 2 q, J 7.4, 4-H and 7-H of (E)-and (2)-isomers;S, 13.6, 14.0, 22.0,22.2, 22.6,28.7 + 28.8, 31.7, 32.8, 34.8 + 34.9, 107.3 + 107.4 (d, lJCH163), 107.6 + 107.8 (d, 'JCH163), 161.0 and 161.2; m/z 178 (M', 12).2,2-DimethyInona-3,4,5-triene4h (91): v,,,/cm-' 2959,2938, 2000, 1744, 1475, 1378 and 842; SH 0.93 + 0.94 (total 3 H, intensity 1 :2, J 7.1,9-H), 1.09 + 1.10 (total 9 H, 2 s, Bu'), 1.45-1.62(2H,m),2.11-2.23(2H,m)and5.4~5.592H,m,3-Hand 6-H of (E)-and (Z)-isomers; S, 13.8, 21.9, 22.2, 29.8, 34.8 + 34.9, 107.0 (d, lJCH165), 118.6 + 118.7 (d, lJCH168), 158.4 and 162.8; m/z 150 (M', 6). 2-Methylocta-2,3,4-triene 4i (83): v,,,/cm-' 296 1, 2924, 2062, 1644, 1464, 1375 and 857;SH0.93 (3 H, t, J7.3, 8-H), 1.50 J.CHEM. soc. PERKIN TRANS. I 1995 J. Org. Chem., 1990,55,2983; I. Saito, K. Yamaguchi, R. Nagataand E. Murahashi, Tetrahedron Lett., 1990,31,7469. 4 H. Hopf and G. Mass, Angew. Chem., In?. Ed. Engl., 1992,31,931; F. Diederich and Y. Rubin, Angew. Chem., Inr. Ed. Engl., 1992,31, 1101. 5 H.-F. Chow, X.-P. Cao and M.-K. Leung, J. Chem. Soc., Chem. Commun., 1994,2121 and references cited therein. 6 C. B. Ziegler, Jr., Tetrahedron Lett., 1988, 29, 411; E.-i. Negishi, T. Yoshida, A. Abramovitch, G. Lew and R. M. Williams, Tetrahedron, 1991,47, 343; J. A. Marshall and W. J. DuBay, J. Org. Chem.,1991,56,1685; K. Fujiwara,H. SakaiandM. Hirama,J. Ore. Chem., 1991,56, 1688. 7 During the preparation of this manuscript, a conference abstract employing a similar synthetic strategy appeared.The authors made use of a sulfonate ester as the leaving group for the fluoride-induced (2H,sextet,J7.4,7-H),1.88(3H,s,Me),1.90(3H,s,Me),2.13 (2H,q, J7.4,6-H)and5.28(1 H,t,sextet,J7.2and 1.3,5-H);SC 13.6,22.2,23.9,24.4, 34.6, 103.0(d, 'JCH 159, 543, 112.2, 156.0 and 157.8. Acknowledgements We thank the Research Grant Council (CM-O18D/10/92), Hong Kong, for financial support. References 1 S.Enner, S. Lovejoy, D. Leung, R. Spitzer, G. Hansen and R.Stone, Proceedings of The International Society of Optical Engineering, Vol. 1560, Nonlinear Optical Properties of Organic Marerials IV, ed. K. D. Singer, SPIE, Washington, 1991, p. 120. 2 T. Kawase, S. Muro, H. Kurata and M. Oda, J. Chem. SOC., Chem. Commun., 1992,778. 3 A. G. Myers, Tetrahedron Lett., 1987, 28, 4493; C. B. Ziegler, Jr., 1,4-elirnination, see K. K. Wang, B. Liu and Y.-d. Lu, Abstract of Paper Program Number 213, American Chemical Society, Division of Organic Chemistry, 208th ACS National Meeting, Washington, D.C., 1994. 8 E. Colvin, Silicon in Organic Synthesis, Butterworths and Co, London, 1981, p. 141. 9 A. G.AngohandD. L. J. Clive,J. Chem. SOC.,Chem. Commun., 1984, 534; I. Fleming, I. T. Morgan and A. K. Sarkar, J. Chem. Soc., Chem. Commun., 1990, 1575. 10 L. Brandsma and H. D. Verkruijsse, Synthesis of Acetylenes, Allenes and Cumulenes, a Laboratory Manual, Elsevier Scientific Publishing Company, Amsterdam, 1981; H. Hommes, H. D. Verkruijsse and L. Brandsma, Rec. Trau. Chim. Pays-Bas, 1980,99, 113. 11 T. Immamoto, Y. Sugiura and N. Takiyama, Tetrahedron Lett., 1984,25,4233. 12 P. J. Bauer, 0. Exner, R. Ruzziconi, T. D. An, C. Tarchini and M. Schlosser, Tetrahedron, 1994,50, 1707. Paper 4105777E Received 22nd September 1994 Accepted 18th October 1994