Organozinc reagents in synthesis: the facile generation of 2-(trialkylsilyl)prop-2-enylzinc from 2-bromo-1-trimethylsilylprop-2-ene

摘要

Organozinc reagents in synthesis: the facile generation of 2-Q m(trialkylsilyl)prop-2-enylzinc from 2-brorno-l-trimethylsilylprop-2-nII ene 7T-xJames J. Eshelby,a7b Philip J. Parsons *,f,' and Patrick J. Crowley a Department of Chemistry, University of Reading, Whiteknights, Reading, Berkshire RG6 2A D, UK Zeneca Agrochemicals, Jealotts Hill Research Station, Bracknell, Berkshire RGI2 6E Y, UK A range of electrophiles react with 2-(trimethylsilyl)prop-2-enylzincchloride, which is prepared by sequentially treating 2-bromo-1-trimethylsilylprop-2-enewith Bu'Li and then zinc chloride. The addition of transition metal catalysts can alter the reactivity of the organometallic compound from prop-Zenylation to prop- 1-en-2-ylation. The generation of carbon-carbon bonds by nucleophilic reaction of organometallic reagents with electrophiles is a well established method.' Organometallic reagents are sometimes difficult to use because they can (i) react as a base instead of as a nucleophile,2 (ii) be difficult to make,3 (iii) have poor regi~-~~hemo-,~ or stereo-selectivity. These problems have resulted in a constant investigation of organometallic reagents and their varying reactivities. The formation of 2-(trialkylsilyl)prop-2-enylcupratesby the silylcupration of allene(prop-l,2-diene) and their use has been described by Fleming and Overman.' The use of 2-(trimethyl-silyl)prop-2-enylmagnesium bromide is also well documen- ted.','' Trost and co-workers have described many elegant uses for this reagent including the generation and trapping of trimethylenemethanepalladium complexes.We now report in full, our that 2- (trimethyl- silyl)prop-2-enylzinc chloride 1 13' can be generated in one pot from 2-bromo-3-trimethylsilylprop-1 -ene 2 and that the organo- zinc reagent 1 is a useful reagent that can be trapped with a range of electrophiles. TMSyBr___c hCl TMS 2 1 Scheme 1 This work complements that of Fleming and Overman but adds a further dimension since under certain catalysed conditions the organozinc reagent 1 can be trapped as its prop- 1 -en-2-yI isomer 3.' TMS=Ycl 3 The development of organozinc chemistry has recently wit- nessed a revival, mainly due to the extensive work by Knochel.Knochel usually transmetallates the organozinc reagent to a more reactive species such as a copper organometallic which can react more efficiently with electrophiles. ' Results and discussion Our studies have been concerned with the construction of the allylic alcohol 4 and its use in the total synthesis of galbonolide B 5 l4 (Scheme 2). t Current address: The School of Chemistry and Molecular Sciences, University of Sussex, Falmer, Brighton BNI 9QJ. HO ~ TMS 4 5 Scheme 2 The alcohols 4a and 4b were formed in good yield when 3-(trimethylsily1)prop- 1 -en-2-ylmagnesium bromide 6 was added to the homochiral epoxide 7 (Scheme 3). X-Ray analysis l5 of 0 7 TMS TMS TMS 6 4a 4b Scheme 3 the nitrobenzoate ester of 4b confirmed a 5 :6 diastereoselection in favour of the syn product 4b.It was interesting to note that no Payne rearrangement product l6 was observed during the preparation of 4. In order to optimise the diastereoisomeric ratio of 4 in favour of 4b we investigated the use of other organometallic reagents. To our surprise, when 2-bromo- 1-trimethylsilylprop-2-ene was treated with Bu'Li followed by ethereal zinc chloride, an 'apparent' equilibration (or isomerisation) of the initially formed zinc species 3 to another reagent, presumed to be 1, was observed.$ The apparent equilibration (or isomerisation) of the prop- 1 -en-Zylzinc 3 to the prop-2-enylzinc 1 is aided by raising the temperature, as demonstrated in Table 1. However, when the reagent is re-cooled to -70 "C, after storage at ambient temperature, there were no products from prop-1 -en-2-yl attack on 7 to give 4.Transmetallation of the prop-1-en-2-yllithium to give the prop-2-enylzinc reagent 1 could be slow at low J It should be noted that the reaction of the Grignard reagent 6 resulted in a ~2contamination with the products of prop-2-enyl attack, 8. A brief investigation of other metals indicated that the correspond- ing organoaluminium reagents formed by the reaction of 2-( I-trimethylsilylprop-2-enyl)lithiumwith diethylaluminium chloride also exhibited a similar 'equilibration' although reactions with this reagent were generally poor. J. Chem. SOC.,Perkin Trans. I 191 Table 1 The reaction of propenylzinc with the aldehyde 7 HO TMS €10 TMSyBr 2 8 Temp.(trC)for organozinc formation Yields of isomers () ~ 4a 4b 8a 8b -70 to 0 0 (anti) 0 (syn) 48 17 -70 to 20 to -70 0 0 58 19 -70 to -50 25 13 7 5 -100 10 50 10 6 temperature explaining why no prop- 1 -en-2-yl attack is observed when the anion stored at ambient temperature is re-cooled to -70 "C. The prop-2-enylzinc reagent 1 was treated with a variety of other electrophiles including epoxides and alkyl halides. Our results are summarised in Table 2. The prop-2-enylzinc reagent 1 added smoothly to a wide range of aldehydes resulting in the formation of the homoallylic alcohols 8-10. With cyclohexanone, the reaction with 1 proceeded less well; the desired homoallylic alcohol 11 was isolated along with the unsaturated ketone 12 which arises from an aldol condensation of cyclohexanone with itself.Clearly the organozinc reagent 1can act as a base/Lewis acid system as well as being nucleophdic in character. This duality of Lewis acidity and nucleophilicity is apparent from Table 1 when the organozinc reagent 1 promotes rearrangement of styrene oxide to phenylacetaldehyde as well as acting as a nucleophile 14-15. It is interesting to note that when iodine is added to the prop-2-enylzinc reagent 1 the product of formal prop-1 -en-2-yl anion attack is isolated in 73 yield.$ We next investigated the reaction of 1 with a range of electrophiles in the presence of Lewis acids and selected transition-metal catalysts.Our results are summarised in Table 3. The prop-2-enylzinc reagent 1 failed to react with cyclohexenone. Thus, we attempted a nickel acetylacetonate- assisted conjugate addition to cyclohexenone and, to our surprise, the product of the reaction, 19, resulted exclusively from prop-1-en-2-yl attack. The addition of a nickel catalyst apparently caused the organozinc 1 to react as if it were 3. In contrast, when boron trifluoride was used as a Lewis acid in this reaction, the product of prop-2-enyl attack, 18, was obtained as the sole product albeit in a low yield; this demonstrated a complete switch in the chemical reactivity of the organozinc species. Palladium-mediated coupling of I -iodo-4-isopropyl-benzene with the organozinc reagent gave the prop- I -en-2-yl product 22 as the exclusive product.Treatment of cyclohexa- diene oxide with the organozinc reagent under catalysed and uncatalysed reaction conditions led exclusively to the products of prop-2-enyl attack in all cases. In our research towards the total synthesis of the galbonolides we required the synthesis of the alcohols 28 which contain the much bulkier tert-butyldiphenylsilyl group in place 9 Reaction of iodine, with 2-dimethyl(phenyl)silylprop-2-enylcuprate gave a similar result for which the following explanation was proposed by Fleming:7a 1 192 J. Chern. Soc., Perkin Trans. 1 Table 2 Reaction of the prop-2-enylzinc reagent 1 with electrophiles Electrophile Products Yield () 0 TMS HO 65 (3:1 ratio of'k', 8 diastereoisomers) pp 90aCHOBr Br 9 76 (1:l sydmfi) OHCr 10 n 50.20 11 12 86 130""' + HO 14 15 OH 27WS16 I 73I2 yms17 of the trimethylsilyl group of alcohol 4.Fleming has found that reaction of tert-butyl(dipheny1)silyl cuprates with propa- 1,2- diene followed by quenching with electrophiles gives formal prop-1-en-2-yl attack at low temperatures, 7b whereas phenyl- (dimethy1)silyl cuprates leads to prop-2-enyl attack. He has further suggested that these reactions may be re~ersible.~ We were thus interested to see if switching to the more bulky, 2- bromo-1 -(tert-butyldiphenylsilyl)prop-2-enewould affect the ratio of prop-1 -en-2-yl to prop-2-enyl adduct of the organozinc reagent.The results are shown in Table 4. At temperatures above 0 "C the major product 29 results from prop-2-enyl attack although a small amount of prop- l-en- 2-yl attack is always observed. Re-cooling the organozinc reagent did not result in a reversion back to prop-1-en-2-yl attack. It was interesting to note that the products of prop-l-en- 2-yl attack, 28, can be formed exclusively if the transmetallation/ reaction sequence is carried out at low temperature. This could be due to slower transmetallation or a shift in equilibrium. Further work will determine the mechanism of this intriguing reaction and we are currently investigating this by NMR spectroscopy. Interesting comparisons can be made with the regiochemical variations observed in the silylcupration of allene and the 1,2-silyl migration and destannylation observed Table 3 Reaction of the zinc reagent 1with electrophiles and a catalyst Substrate + catalyst Product(s) and yields 8 18 19 None 0 0 BFpO 34 0 Ni(acac)z 11 12 None 50 20 BFpO 66 0 Ni(acach 0 >95 b 20 21 37 21 21 16 2-7 14 kI 22 TMS 88 23 24 25 26 in the Lewis acid-mediated reactions of 2-stannyl-3-trimethylsilylprop-2-ene with acid chlorides. It may be that the rearrangement occurs via the intermediacy of the prop-1,2-diene followed by a silylzincation process to yield the prop-Zenylzinc 1(Scheme 4).Alternatively, a new cyclopropyl organozinc species 30 may form, and this can react by different mechanisms depending on the reaction (Scheme 5).A further possibility arises if, prior to nucleophilic attack, coordination of the electrophile to zinc could occur. This may then allow an interaction of the chloride with silicon allowing a sequential alkylation/silicon shift (Scheme 6). In the palladium-mediated coupling, prior coordination of I II (+ ZnICl) 1 Scheme 7 Table 4 The reaction of propenylzinc with the aldehyde 7 €10 TBDPS I10 Temp. (t/"C)for organozinc formation Yield s () of isomers 28a 28b 29a 29b -70 to 20 c2 c2 38 16 -70 to 20 to -70 c2 c2 27 13 -70 to 0 2 3 37 9 -70 20 25 0 0 the zinc species could occur. It is conceivable that iodide coordination with zinc would disfavour chloride association with silicon in the transition state and hence coupling at the prop-1 -en-2-yl carbon of the organozinc reagent occurs (Scheme 7).Whether the presence of iodide anion will affect product ratios remains to be seen. Experimental General methods All reactions were conducted under an atmosphere of nitrogen. Reaction solvents were purified/dried by standard procedures; ether refers to diethyl ether. Vacuum liquid chromatography (VLC) was performed on silica gel 60 (Merck 7729, particle size J. Chem. Soc., Perkin Trans. I 193 less than 0.063 mm). Gas chromatographic (GC) analyses were performed on a Hewlett-Packard 5890A equipped with a 25 m Chrompack fused-silica capillary column, (coating CP-SIL 5CB, film thickness 0.12 pm, i.d.0.25 mm) using helium as the carrier gas, and a FID detector. Gas chromatographic-mass spectra (GC-MS) were obtained on a Fisons Trio 1. Fast atom bombardment-mass spectra (FAB-MS) and probe mass spectra were obtained on a JEOL DX303. Exact mass measurements were made by high-resolution mass spectrometry (HRMS) using a VG Autospec Q instrument. All mps are uncorrected. Optical rotations alD values are given in 10-1 deg cm2 g' and were measured on an Optical Activity AA-100 polarimeter. Elemental analyses were carried out on a Perkin- Elmer 240G. IR spectra were recorded on a Perkin-Elmer 298 or a Nicolet FT-IR 205 spectrophotometer. NMR spectra were obtained on either a JEOL GX400 FTNMR ('H 400 MHz, ' 100 MHz, ''F 376 MHz) or a JEOL GSX270 ('H 270 MHz, 13C 67.8 MHz, "F 254 MHz) spectrometer.Chemical shift 6 values are referenced to tetramethylsilane. J Values are given in Hz. 2-Bromo-1-trimethylsilylprop-2-ene 2.-This compound was used either as supplied by Fluka or prepared according to the procedure of Itoh.' 2,3-Epoxy-2-methylpentan-1-a1 7.-This compound was prepared according to literature procedure. 2o 4,5-Epoxy-4-methyl-2-(trimethylsilylmethyl)hept-l-en-3-ol4 To a suspension of magnesium (0.62 g, 0.026 mol) and 1,2- dibromoethane (110 mm3, 1.3 mmol) in THF (10 cm3) was added compound 2 (4.44 cm3, 26 mmol) dropwise over 30 min, the mixture being held at gentle reflux after initiation had occurred.Upon cooling of the mixture to 0 "C an opaque olive- coloured solution containing a gelatinous precipitate was obtained. The aldehyde (2.74 cm3, 24 mmol) 7 in THF (5 cm3) was added dropwise to the Grignard solution over 20 min and the reaction mixture allowed to warm to room temperature over 30 min. A solution of saturated aqueous ammonium chloride was added carefully with stirring to the mixture until no precipitate remained. The mixture was then filtered and the aqueous layer separated and extracted with ether. The combined organic layer and extracts were dried (MgSO,), filtered through a silica plug and dried in uacuo. Chromato-graphy with 20 ether-pentane yielded the two product diastereomers. 4a: RF 0.33 (1.15 mg, 2073, clear colourless oil (Found: C, 62.6; H, 10.6.Calc. for C,,H,,O,Si: C, 63.1; H, 10.6); v,,,(thin film)/cm-' 3480br s (OH), 2970s (CH), 1640w (C=C), 1250s and 850s; 6,(270 MHz; CDCI,; Me,Si) 4.95 (1 H, s, CSHH), 4.80 (1 H, S, C=CHH), 3.93 l H, S, C(H)OH, 3.09 (1 H, t, J6.5, CHCH,), 2.14 (1 H, br s, OH), 1.75-1.48 (4 H, m, 2 x CH,), 1.25 (3 H, s, CH,), 1.05 (3 H, t, J7.5, CH,CH,) and 0.06 (9 H, s, TMS); 6,-(100 MHz; CDCI,; Me,Si) 145.77 (C), 110.56 (CH,), 77.22 (CH), 62.24 (C), 61.03 (CH), 23.12 (CH,), 21.59 (CH,), 14.25 (CH,), 10.53 (CH,) and -1.16 (3 x CH,); m/z (EI) 210 (M+ -H,O, l), 195 (M' -H,O -Me, l), 170 (18), 155 (22) and 73 (TMS+, 100); m/z (HRMS) 228.1546 (Calc.: 228.1546). 4b: RF 0.27 (1.121 g, 25), clear colourless oil (Found: C, 62.8; H, 10.6.Calc. for C,,H,,O,Si: C, 63.1; H, 10.6); v,,,(thin film)/cm-' 3470br s (OH), 2975s (CH), 1640w, 1250s and 850s; 6,(270 MHz; CDCI,; Me,Si) 5.08 (1 H, s, C=CHH), 4.78 (1 H, s, C=CHH), 3.63 l H, d, J 4, C(H)OH, 2.94 (1 H, t, J 6.5, CHCH,), 2.25 (1 H, d, J4, OH), 1.69 (1 H, dpent, J 14 and 7, CHHCH,), 1.65 (1 H, d, J 14, CHHTMS), 1.54 (1 H, dpent, J 14 and 7, CHHCH,), 1.34 (1 H, d, J 14, CHHTMS), 1.20 (3 H, s, CH,), 1.05 (3 H, t, J 7, CH,CH,) and 0.04 (9 H, s, TMS); 6,(100 MHz; CDCI,; Me,Si) 144.85 (C), 109.03 (CH,), 79.19 (CH), 63.86 (CH), 63.19 (C), 23.03 (CH,), 21.47 (CH,), 11.31 (CH,), 10.42 (CH,) and -1.25 (3 x CH,); m/z (EI) 210 (M' -H,O, l), 195 (M' -H,O -Me, 2), 170 (8), 155 194 J. Chem. SOC., Perkin Trans.I (33) and 73 (TMSf, 100); m/z (HRMS) 228.1546 (Calc.: 228.1 546). 2-TrimethylsiIylprop-2-enylzinc reagent 1. A solution of compound 2 (2.05 cm', 12 mmol) in ether (7 cm3) at -80 "C was treated with Bu'Li (1.7 mol dmP3 in pentane solution; 14.1 cm3, 24 mmol) over 10 min (exotherm to -52 "C),and stirred a further 5 min (re-cooled to -80 "C). To the pale yellow solution was added a solution of zinc dichloride (1.0 mol dm-, in ether solution; 12.6 cm3, 12.6 mmol) over 5 min. The mixture was then allowed to warm to room temperature and stirred for 2 h at that temperature. Further ether was commonly added to make solutions of convenient concentration. Measured aliquots were then added to various electrophiles. Uncatalysed reactions 5,6-Epoxy-5-methy1-2-trimethylsilyloct-l-en-4-018.A solu- tion of compound 2 (4.74 cm3, 27.8 mmol) in ether (20 cm3) at -70 "C was treated with Bu'Li (1.0 mol dm in pentane solution; 55.5 cm3, 55.5 mmol) over 20 min. The pale yellow solution was allowed to warm to 0 "C after which it was stirred for 1 h and then re-cooled to -70 "C. A solution of zinc chloride (1.0 mol dm-, in ether solution; 27.8 cm3, 27.8 mmol) was added over 5 min to the mixture which was then warmed to 0 "C and stirred for 1 h before being re-cooled to -70 "C. The resulting solution of vinylzinc chloride was added via a cannula over 1 h to a solution of the aldehyde 7 (2.11 g, 18.5 mmol) in ether (20 cm3) at -70 "C. The cooling bath was removed and the mixture allowed to reach 0 "C when it was quenched with saturated aqueous ammonium chloride.The aqueous layer was separated and extracted with ether and the combined organic layer and extracts were dried (MgSO,), filtered and concentrated under reduced pressure. Chromatography of the residue in 20 ether-hexane yielded two diastereoisomeric products. 8a: R, 0.31 (2.01g, 48), clear colourless oil (Found: C, 63.0; H, 10.6. Calc. for C,,H,,O,Si: C, 63.1; H, 10.6); v,,,(thin film)/cm-' 3470br s (OH), 2950s (CH), 1245s and 835s; 6,(270 MHz; CDC1,; Me,Si) 5.70 (1 H, br s, C=CHH), 5.46 (1 H, d, J 3, C=CHH), 3.60 l H, dd, J 10 and 2.5, C(H)OH, 2.94 (1 H, t, J6.5,CHCH2),2.50(1 H,dd, J14and2.5,C=CCHH),2.15(1 H, dd, J 14 and 10, CSCHH), 2.07 (1 H, s, OH), 1.63 (1 H, dpent, J 14 and 7, CHHCH,), 1.52 (1 H, dpent, J 14 and 7, CHHCH,), 1.28 (3 H, s, CH,), 1.02 (3 H, t, J 7, CH,CH,) and 0.10 (9 H, s, TMS); 6,(67.8 MHz; CDCI,; Me,) 148.75 (C), 127.35 (CH,), 72.03 (CH), 62.61 (C), 61.40 (CH), 39.87 (CH,), 21.47 (CH,), 13.88 (CH,), 10.47 (CH,) and -1.33 (CH, x 3); m/z (GC-MS, EI) 155 (M+ -TMS, 70) and 73 (TMS', 100); m/z (CI) 246 (M + NH4+, lo), 229 (MH', 8), 211 (68), 171 (73), 155 (84) and 58 (100); m/z (HRMS) 228.1550 (Calc.: 228.1546).8b: RF 0.15 (0.715 g, 17), clear colourless oil (Found: C, 62.8; H, 10.6. Calc. for C,,H,,O,Si: C, 63.1; H, 10.6); v,,,(thin film)/cm-' 3440br s (OH), 2955s (CH), 1245s and 833s; 6,(270 MHz; CDCI,; Me,Si) 5.69 (1 H, br s, C=CHH),5.49 (1 H, d, J 2, WHH), 3.38 I H, dt, J9.5 and3.5, C(H)OH, 2.84(1 H, t, J6.5, CHCH,), 2.45 (1 H, dd, J 14 and 3.5, MCHH), 2.28 (1 H, dd, J 14 and 9.5, WCHH), 1.84 (1 H, br s, OH), 1.62 (1 H, dpent, J 14 and 7, CHHCH,), 1.51 (1 H, dpent, J 14 and 7, CHHCH,), 1.29 (3 H, s, CH,), 1.02 (3 H, t, J 7, CH,CH,) and 0.10 (9 H, s, TMS); 6,(67.8 MHz; CDCI,; Me,Si) 148.30 (C), 127.81 (CH2),74.82(CH), 63.40(C), 62.94(CH), 39.93 (CH,), 21.40 (CH,), 11.68 (CH,), 10.46 (CH,) and -1.33 (3 x CH,); m/z (GC-MS, EI) 155 (M' -TMS, 80),73 (TMS', 100); m/z (CI) 246 (M + NH,', lo), 229 (MH', 4), 211 (28), 195 (49, 171 (69), 155 (72) and 58 (100); m/z (HRMS) 228.1550 (Calc.: 228.1546).1-(2-Bromophenyl)-3-timethylsilylbut-3-en-l-o19.To a solu- tion of 2-bromobenzaldehyde (1 17 mm3, 1 mmol) in ether (2 cm3) at room temperature was added a solution of the pre- formed allylzinc reagent 1 2 mmol in ether (5.5 cm3) over 1 h.After complete addition the mixture was treated with saturated aqueous ammonium chloride to quench the reaction and the aqueous layer extracted with ether. The combined extracts were dried (MgSO,) and concentrated under reduced pressure. Chromatography in 20 ether-hexane (RF0.35) yielded a clear colourless oil (269 mg, 90); v,,,(thin film)/cm-' 3450br m (OH), 2960m (CH), 1570w, 1468m, 1440m, 1245s and 840s; S,(270 MHz; CDC1,; Me,Si) 7.63 (1 H, dd, J 7 and 1, ArH), 7.52 (1 H, d, J7, ArH), 7.35 (1 H, t, J7, ArH), 7.13 (1 H, td, J7 and 1, ArH), 5.81 (I H, s, C=CHH), 5.62 (1 H, d, J 1, C=CHH), 5.09 l H, dd, J9 and 1, C(H)OH, 4.75 (1 H, br s, OH), 2.85 l H, br d, J 12, C(H)OHCHH, 2.20 l H, dd, J 12 and 9, C(H)OHCHW and 0.20 (9 H, s, TMS); 6,(67.8 MHz; CDCl,; Me,Si) 149.20 (C), 143.13 (C), 132.53 (CH), 128.92 (CH,), 128.66 (CH), 127.71 (CH), 127.35 (CH), 121.65 (C), 70.75 (CH), 45.34 (CH,) and -1.29 (3 x CH,); m/z (EI) (consistent with one bromine) 298/300 (M', l/l), 283/285 (M' -Me, 8/9), 257/259 (12/13), 185/187 (100/83) and 73 (TMS', 48); m/z (HRMS) 298.0390 (Calc.: 298.0389).5-Methyl-2-trimethylsilylhept-l-en-4-ol 10.To a solution of 2-methylbutanal (86 mg, 1 mmol) in ether (2 cm3) at 0 "C was added a solution of the pre-formed allylzinc reagent 1 2 mmol in ether (8 cm') over 5 min. After the mixture had been stirred for 1 h it was treated with saturated aqueous ammonium chloride to quench the reaction.The aqueous layer was separated and extracted with ether and the combined extracts were dried (MgSO,), filtered and concentrated under reduced pressure. Chromatography in 20 ether-pentane (R, 0.50)yielded a pale yellow oil (1 58 mg, 76) as a I :1 mix of diastereoisomers A and B (Found: C, 65.8; H, 12.1. Calc. for C, ,H,,OSi: C, 65.9; H, 12.1); v,,,(thin film)/cm-' 3480br m (OH), 2960s (CH), 1461w, 1250s and 839s; 6,(400 MHz; CDCl,; Me,Si) 5.67 (1 H, m, MHH, A and B), 5.50 (1 H, d, J3, C=CHH, A or B), 5.49 (1 H,d,J3,AorB),3.56(1H,ddd,JlO.Oand3.5and3.5,AorB), 3.47 (1 H, ddd, J 10.5 and 5.5 and 2.5, A or B), 2.51-2.46 (1 H, m, CHHC-C, A or B), 2.45-2.40 (1 H, m, CHHC=C, A or B), 2.14 (1 H, dd, J 14 and 10, CHHW, A or B), 2.05 (1 H, dd, J 13.5 and 10.5, CHHW, A or B), 1.77-1.39 (3 H, m, A and B), 1.27-1.11 (1 H, m, A and B), 0.91 (6 H, m, CH,CH and CH,CH,, A and B), 0.102 (9 H, s, TMS, A or B) and 0.103 (9 H, s, TMS, A or B); 6,( 100 MHz; CDC1,; Me,Si) (diastereoisomer 1): 150.02 (C), 127.93 (CH,), 72.71 (CH), 40.90 (CH,), 40.09 (CH), 25.06 (CH,), 14.47 (CH,), 11.63 (CH,) and -1.28 (3 x CHJ; (diastereoisomer 2): 149.92 (C), 127.64 (CH,), 72.28 (CH), 41.79 (CH,), 39.85 (CH), 25.74 (CH,), 13.71 (CH,), 11.84 (CH,) and -1.28 (3 x CH,); m/z (EI) 185 (M' -Me, 773,159 (30), 99 (loo), 75 (97), 73 (TMS', 75); m/z (CI) 218 (M + NH4+, 27) and 90 (100); m/z (HRMS) 200.1597 (Calc.: 200.1597).1-(2-Trimethylsilylprop-2-enyl)cyclohexanoll1.To a solution of cyclohexanone (104 mm3, 1 mmol) in ether (2 cm') at room temperature was added a solution of the pre-formed allylzinc reagent 1 2 mmol in ether (8 cm') over 5 min.After the mixture had been stirred for 30 min it was treated with saturated aqueous ammonium chloride to quench the reaction. The aqueous layer was extracted with ether and the combined extracts were dried (MgSO,), filtered and concentrated under reduced pressure. Chromatography of the residue in 10 ether- pentane (RF 0.41) yielded the title compound as a clear colourless oil (106 mg, 50) (Found: C, 67.8; H, 11.3. Calc. for C,,H,,OSi: C, 67.9; H, 11.4); v,,,(thin film)/cm 3478br m (OH), 2930m (CH), 2855m (CH), 1447s, 1246m and 838s; 6,(270 MHz; CDC1,; Me,Si) 5.72 (1 H, d, J2, MHH), 5.57 (1 H, d, J2, C=CHH), 2.30 2 H, s, CH,C(TMS)=CH,, 2.67-1.14 (1 1 H, m, Cy -H + OH) and 0.1 1 (9 H, s, TMS); 6,(67.8 MHz; CDCl,; Me,Si) 148.79 (C), 129.91 (CH,), 71.15 (C), 48.55 (CH,), 37.98 (2 x CH,), 25.80 (CH,), 22.16 (2 x CH,) and -0.62 (3 x CH,); m/z (EI) (M+ -H,O, 194, llx), (M' -H,O -Me, 179, 22), 120 (36) and 73 (TMS, 100); m/z (HRMS) 212.1597. (Calc.: 212.1597).Also obtained was 2-cyclohexylidenecyclohexanone 12:(R, 0.33) (18 mg, 20); v,,,(thin film)/cm-' 2930s (CH), 2860s (CH), 1682s (C=C), 1620m (GC), 1448m, 1285m, 1212m and 1130m; 6,(270 MHz; CDCl,; Me,Si) 2.40 (2 H, m), 2.31 (4 H, m), 2.10 (2 H, m), 1.78 (2 H, m), 1.64 (2 H, m) and 1.48 (6 H, m); 6,(100 MHz; CDC1,; Me,) 207.02 (C), 147.14 (C), 131.43 (C), 44.13 (CH,), 32.40 (CH,), 31.40 (CH,), 30.34 (CH,), 29.31 (CH,), 28.88 (CH,), 27.25 (CH,), 26.19 (CH,) and 26.12 (CH,); m/z (EI) 178 (M', 8673, 149 (100) and 79 (74); m/z (HRMS) 178.1358 (Calc.: 178.1359).4-Phenyl-2-trimethylsilylbut-l-ene13. To a solution of benzyl bromide (1 19 mm3, 1 mmol) in ether (2 cm') at room temper- ature was added a solution of the pre-formed allylzinc reagent 1 2 mmol in ether (8 cm') in one portion. The reaction was stirred for 3 days and then further allylzinc reagent 2 mmol in ether (8 cm') was added and the reaction stirred for a further 3 days. The reaction was quenched with saturated aqueous ammonium chloride and the aqueous layer was separated and extracted with ether.The combined extracts were dried (MgSO,), filtered and concentrated under reduced pressure. Chromatography of the residue in pentane (R,0.49) yielded a clear colourless oil (1 75 mg, 86) (Found: C,76.3; H, 9.9. Calc. for C,,H,,Si: C, 76.4; H, 9.9); v,,,(thin film)/cm 3030m (ArH), 2957s (CH), 1603w, 1495w, 1451w, 1249s and 835s; 6,(270 MHz; CDC1,; Me,Si) 7.33-7.1 1 (5 H, m, ArH), 5.61 (1 H, br s, C=CHH), 5.37 (1 H, d, J 1, C=CHH), 2.71 (2 H, m, ArCH,), 2.41 (2 H, m, CH,C=C) and 0.1 1 (9 H, s, TMS); 6,( 100 MHz; CDCl,; Me,) 151.77 (C), 142.48 (C), 128.30 (2 x CH), 128.36 (2 x CH), 125.75 (CH), 124.05 (CH,), 37.69 (CH,), 35.57 (C'H,) and -1SO (3 x CH,); m/z (EI) 204 (M+, 573,189 (M+ -Me, 55), 130 (47), 91 (PhCH,', 37) and 73 (TMS', 100); m/z 204.1339 (Calc.for C,,H,,Si: 204.1334). 2-Phenyl-4-trimethylsilylpent-4-en-1-0114 and l-phenyl-4-trimethylsilylpent-4-en-2-01 15. To a solution of styrene oxide (1 14 mm3, 1 mmol) in ether (2 cm3) at 0 "C was added a solution of the pre-formed allylzinc reagent 1 2 mmol in ether (8 cm3) over 10 min. The mixture was stirred overnight at room temperature after which it was treated with saturated aqueous ammonium chloride to quench the reaction. The aqueous layer was extracted with ether and the combined extracts were dried (MgSO,) and concentrated under reduced pressure. Chromato- graphy in 20 ether-pentane yielded two regioisomeric compounds 14and 15. 14:R, 0.21 (115 mg, 49), clear colourless oil (Found: C, 71.6; H, 9.5.Calc. for C,,H,,OSi: C, 71.7; H, 9.5); v,,,(thin fi1m)lcrn-l 3380br m (OH), 3030w (ArH), 2955m (CH), 1249s, 839s and 700s; 6,(400 MHz; CDC1,; Me,) 7.33-7.18 (5 H, m, PhH), 5.50 (1 H, dt, J 3 and I, C=CHH), 5.34 (1 H, dt, J 3 and 1, C=CHH), 3.77 (1 H, dd, J 1 1 and 5.5, CHHOH), 3.68 (1 H, dd, J 11 and 7.5, CHHOH), 2.98 (1 H, dddd, J 7.5 and 7 and 7 and 5.5, PhCH), 2.53 (I H, ddt, J 14 and 7 and 1, CHHGCH,), 2.47 (1 H, ddt, J 14 and 7 and 1, CHHGCH,), 1.49 (1 H, s, OH) and 0.08 (9 H, s, TMS); 6,(300 MHz; CDCl,; Me,Si) 149.55 (C), 142.37 (C), 128.54 (2 x CH), 128.06 (2 x CH), 126.66 (CH), 126.31 (CH,), 66.99 (CH,), 47.15 (CH), 38.69 (CH,) and -1.40 (3 x CH,); m/z(EI) 203 (M' -CH,OH), 201 (M+ -H,O -Me), 73 (TMS+); m/z (CI), 252 (M + NH,'); m/z (HRMS) 234.1439 (Calc.: 234.1440).15: R, 0.32 (47 mg, 2073, clear colourless oil (Found: C, 71.6; H, 9.4. Calc. for C1,H,,OSi: C, 71.7; H, 9.5); vma,(thin film)/cm-' 3440br m (OH), 3035w (PhH), 2958m (CH), 1249s, 838s and 701s; 6,(400 MHz; CDC1,; Me,Si) 7.33-7.20 (5 H, m, PhH), 5.69 (1 H, dt, J3 and 1.5, C=CHH), 5.50 (1 H, d, J3, C=CHH), 3.89 l H, dddd, J9 and 7.5 and 5.5 and 4, C(H)OH, 2.79(lH,dd7J14and5.5,PhCHH),2.75(1H,dd,J14and7.5, PhCHH), 2.44 l H, ddd, J 14 and 4 and 1.5, C(H)OHCHH, 2.25 1 H, dd, J 14 and 9, C(H)OHCHHJ, 1.76 (1 H, s, OH) and 0.08 (9 H, s, TMS); 6,(100 MHz; CDC1,; Me,Si) 149.28 (C), 138.62 (C), 129.36 (2 x CH), 128.44 (2 x CH), 127.76 (CH,), 126.37 (CH), 70.81 (CH), 44.17 (CH,), 43.50 (CH,), -1.38 J.Chem. Suc., Perkin Trans. 1 195 (3 x CH,); m/z(EI) 216 (M' -H,O, 773,201 (M' -H,O -Me, 12), 142 (38), 129 (51), 73 (TMS', 100);m/z(CI) 252 (M + NH,', 70), 234 (M + NH,' -H,O, 7) and 217 (MH+ -H,O, 22); m/z (HRMS) 234.1439 (Calc.: 234.1440). (E)-2-Methyl-6-trimethylsilylhepta-2,6-dien-l-ol16. To a solution of 2-methyl-2-vinyloxirane (98 mm3, 1 mmol) in ether (2 cm3) at 0 "C was added a solution of the pre-formed allylzinc reagent 1 2 mmol in ether (8 cm3) over 10 min. The mixture was stirred at 0°C for 2 h after which it was treated with saturated aqueous ammonium chloride to quench the reaction. The aqueous layer was extracted with ether and the combined extracts were dried (MgSO,) and concentrated under reduced pressure.Chromatography of the residue in 20 ether-pentane (RF0.23) yielded a clear colourless oil (92 by GC analysis), with 8 of a single unidentified impurity (59 mg, 27); v,,,(thin film)/cmp' 3350br s (OH), 2960s (CH), 1250s and 840s; 6,(270 MHz; CDCl,; Me,Si) 5.55 (1 H, br s, WHH),5.40-5.26 (2 H, includes 1 H, d, J 2 at 5.34,2MH), 4.1 1 (2 H, br s, CH,OH), 2.21-2.10 (4 H, m, CH,CH,), 1.80 (3 H, s, CH,) and 0.08 (9 H, s, TMS); 6,(100 MHz; CDC1,; Me,Si) 151.76 (C), 134.43 (C), 128.05 (CH), 124.06 (CH,), 61.48 (CH,), 35.81 (CH,), 27.1 1 (CH,), 21.20 (CH,) and -1.58 (3 x CH,); m/z (EI) 180 (M' -H,O, 673, 165 (M' -H,O -Me, 3), 106 (15), 91 (22), 73 (TMS', 100); m/z(CI) 216 (M + NH,', l), 198 (M + NH4+ -H,O, 4), 181 (MH' -H,O, 50) and 90 (100).2-Iodo-3-trimethylsilylprop-1-ene17. To a solution of iodine (3.81 g, 15 mmol) in ether (50 cm3) was added a solution of the pre-formed allylzinc reagent 1 (1 6.5 mmol in 55 cm3 ether) over 10 min. The mixture was stirred for 20 min after which it was treated with saturated aqueous ammonium chloride to quench the reaction. The aqueous layer was extracted with ether and the combined extracts were dried (MgSO,) and concentrated under reduced pressure to yield a brown liquid (2.61 g, 73); v,,,(thin film)/cm-' 2963m (CH), 1609m (CS), 1250s, 1189m, 1069m, 938m and 852s; 6,(270 MHz; CDCl,; Me,Si) 5.74 (1 H, s, CXHH), 5.53 (1 H, s, WHH), 2.28 (2 H, s, C==CCH,) and 0.13 (9 H, s, TMS); 6,(100 MHz; CDCl,; Me,) 123.21 (CH,), 105.60 (C), 37.76 (CH,) and -1.41 (3 x CH,); m/z (HRMS) 239.9825 (Calc.for C,H,,TSi: 239.9830). Catalysed reactions 3-(2-Trimethylsilylprop-2-enyl)cyclohexanone 18. To a solu- tion of cyclohex-2-enone (580 mm3, 6 mmolj and boron trifluoride-diethyl ether (812 mm3, 6.6 mmol) in ether (20 cm3) at -15 "C was added a solution of the pre-formed prop-2- enylzinc reagent 1 C6.6 mmol in ether (22 cm') over 10 min. The mixture was stirred for 5 rnin after which it was treated with saturated aqueous ammonium chloride to quench the reaction. The aqueous layer was extracted with ether and the combined organic layer and extracts were dried (MgSO,) and concentrated under reduced pressure. Chromatography of the residue in 20 ether-hexane (R, 0.29) yielded the title compound as a clear colourless oil (515 mg, 37) (Found: C, 68.7; H, 10.5.Calc. for C12HZ20Si: C, 68.5; H, 10.5); v,,,(thin film)/cmpl 2960s (CH), 1715s (M),1249s and 834s; 6,(270 MHz; CDCl,; Me,Si) 5.53 (1 H, d, J 1,=CHH),5.40 (1 H, d, J 1, =CHH), 2.48-1.78 (9 H, m), 1.2-1.50 (1 H, m), 1.35-1.16 (1 H, m) and 0.08 (9 H, s, TMS); 6,(100 MHz; CDC1,; Me,Si) 21 1.78 (C), 149.33 (C), 126.40 (CH,), 48.1 1 (CH,), 43.92 (CH,), 41.44 (CH,), 37.96 (CH), 31.16 (CH,), 25.07 (CH,) and -1.38 (3 x CH,); m/z (EI) 210 (M', l), 195 (M' -Me, loo), 167 (M' -Me -CO, 21) and 73 (TMS, 70); m/z (CI) 228 (M + NH,+, 100); m/z (HRMS) 210.1443 (Calc. for C,,H,,OSi: 2 10.1443). 3-(1-Trimethylsilylprop-2-en-2-yl)cyclohexanone 19. To a solution of cyclohex-2-enone (290 mm3, 3 mmol) and nickel acetylacetonate (16 mg, 0.06 mmol) in ether (10 cm3) at -15 "C was added a solution of the pre-formed prop-2-enylzinc reagent 1 C3.3 mmol in ether (1 1 cm3)f over 10 min.After the mixture had been stirred for 5 rnin at -15 "C it was treated with 196 J. Chem. Soc., Perkin Trans. I saturated aqueous ammonium chloride to quench the reaction. The aqueous layer was extracted with ether and the combined organic layer and extracts were dried (MgSO,) and concentrated under reduced pressure. Chromatography in 20 ether-pentane (RF0.30) yielded the title compound as a clear colourless oil (504 mg, 80) (Found: C, 68.2; H, 10.6. Calc. for C,,H,,OSi: C, 68.5; H, 10.5); v,,,(thin film)/cm-' 2960s (CH), 1715s (W),1632m (M),1250s and 850s; 6,(270 MHz; CDC1,; Me,Si) 4.64 (1 H, s, C=CHH), 4.62 (1 H, s, CXHH), 2.51-1.90 (7 H, m), 1.70-1.45 (4 H, m) and 0.00 (9 H, s, TMS); 6J67.8 MHz; CDCl,; Me,Si) 211.59 (Cj, 149.71 (C), 106.39 (CH,), 47.06 (CH,), 45.64 (CH), 41.19 (CH,), 30.40 (CH,), 25.60 (CH,), 25.09 (CH,) and -1.43 (3 x CH,); m/z (EI) 210 (M', 1273, 195 (M+ -Me, loo), 167 (M+ -Me -CO, 93) and 73 (TMS', 96); m/z (HRMS) 210.1443 (Calc. for C, ,H,,OSi: 210.1443).l-(2-Trimethylsilylprop2-enyl)cyclohexanoIll. To a solution of cyclohexanone (310 mm3, 3 mmol) and boron trifluoride- diethyl ether (406 mm3, 3.3 mmol) in ether (10 cm3) at -15 "C was added a solution of the pre-formed allylzinc reagent 1 C3.3 mmol in ether (1 1 cm') over 10 min. After the mixture had been stirred for 1.5 h it was treated with saturated aqueous ammonium chloride to quench the reaction.The aqueous layer was extracted with ether and the combined organic layer and extracts were dried (MgSO,) and concentrated under reduced pressure. Chromatography in 10 ether-pentane (RF0.41) yielded the title compound as a clear colourless oil (417 mg, 66) (Found: C, 67.8; H, 11.3. Calc. for C,,H,,OSi: C, 67.9; H, 11.4.); v,,,(thin film)/cm-' 3478br m (OH), 2930m (CH), 2855m (CH), 1447s, 1246m and 838s; 6,(270 MHz; CDC1,; Me,Si) 5.72 (1 H, d, J2, CSHH), 5.57 (1 H, d, J2, CXHH), 2.30 2 H, s, CH,C(TMS)=CH,, 2.67-1.14 (1 1 H, m, Cy -H + OH) and 0.1 1 (9 H, s, TMS); 6,(67.8 MHz; CDCl,; Me,Si) 148.79 (C), 129.91 (CH,), 71.15 (C), 48.55 (CH,), 37.98 (2 x CH,), 25.80 (CH,), 22.16 (2 x CH,) and -0.62 (3 x CH,); m/z(EI) 194 (M' -H,O, llx), 179 (M' -H,O -Me, 22), 120 (36) and 73 (TMS, 100); m/z 212.1597 (Calc.: 212.1597).2-Cyclohexylidenecyclohexanone 12. To a solution of cyclohexanone (310 mm3, 3 mmol) and nickel acetylacetonate (16 mg, 0.06 mmolj in ether (10 cm3) at -15 "C was added a solution of the pre-formed allylzinc reagent 1C3.3 mmol in ether (1 1 cm') over 10 min. After the mixture had been stirred for 0.5 h at -15 "C and then 18 h at room temperature, it was treated with saturated aqueous ammonium chloride to quench the reaction. The aqueous layer was extracted with ether and the combined organic layer and extracts were dried (MgSO,) and concentrated under reduced pressure.Chromatography of the residue in 10 ether-pentane (R, 0.33) yielded the title compound as a clear colourless oil (267 mg, 100); v,,,(thin film)/cm-' 2930s (CH), 2860s (CH), 1682s (W),1620m (M),1448m, 1285m, 1212m and 1130m; 6,(270 MHz; CDCl,; Me,Si) 2.40 (2 H, m), 2.31 (4 H, m), 2.10 (2 H, m), 1.78 (2 H, m), 1.64 (2 H, m) and 1.48 (6 H, m); S,( 100 MHz; CDCl,; Me,Si) 207.02 (C), 147.14 (C), 131.43 (C), 44.13 (CH,), 32.40 (CH,), 31.40 (CH,), 30.34 (CH,), 29.31 (CH,), 28.88 (CH,), 27.25 (CH,), 26.19 (CH,) and 26.12 (CH,); m/z (EI) 178 (M+) and 149; m/z (HRMS) 178.1358 (Calc.: 178.1359). 2-(2-Trimethylsilylprop2-enyl)cyclohex-3-enol 20 and 4-(2 trimethylsilylprop-2-enyl)cyclohex-2-enol 21. To a solution of 3,4-epoxycyclohexene (480 mg, 5 mmol) in ether (15 cm3) at -15 "C was added a solution of the pre-formed allylzinc 1 C5.5 mmol in ether (18.5 cm3)3 over 10 min. After 5 rnin the mixture was treated with saturated aqueous ammonium chloride to quench the reaction.The aqueous layer was extracted with ether and the combined organic layer and extracts were dried (MgS0,) and concentrated under reduced pressure. Chromato- graphy in 30 ether-pentane followed by chromatography in 20 ethyl acetate-hexane yielded the regioisomeric title compounds as clear colourless oils. 20:(389 mg, 37), R, 0.32 (in 30 ether-hexane) (Found: C, 68.1; H, 10.5. Calc. for C,,H,,OSi: C, 68.5; H, 10.5); v,,,(thin film)/cm-'; 3350br s (OH), 3025m (WH), 2958s (CH), 1437m, 1410m, 1251s, 1046m, 930m, 837s, 760m and 692m; 6,(270 MHz; CDCl,; Me,Si) 5.66 (1 H, dt, J 3 and 1.5, C=CHH), 5.66- 5.58 (1 H, m, HGCH), 5.51-5.45 (I H, m, HCSH), 5.45 (1 H, dt, J 3 and 1, WHH), 3.59 l H, ddd, J 10 and 7 and 3, C(H)OH, 2.51 (1 H, ddt, J 14 and 6 and 1, CHHC=C), 2.30- 1.98 (4 H, m), 1.97-1.80 (1 H, m), 1.65 l H, dddd, J 12.5 and 9.5 and 8.5 and 6, HHCC(H)OH and 0.12 (9 H, s, TMS); 6,-(100 MHz; CDCl,; Me,) 151.03 (C), 128.42 (CH), 126.28 (CH), 126.14 (CH,), 71.95 (CH), 42.53 (CH), 40.90 (CH,), 29.56 (CH,), 23.64 (CH,) and -1.30 (3 x CH,); m/z (EI) 195 (M' -Me, 379, 119 (39, 96 (loo), 73 (TMS', 95), 45 (52); m/z (CI) 228 (M + NH,', 13), 211 (MH', lo), 193 (45), 121 (85) and 90 (100); m/z(HRMS) 210.1443 (Calc.for C12H,,0Si: 2 10.1443).21:(193 mg, 18), R, 0.20 (in 30 ether-hexane) 3.5: 1 ratio of diastereoisomers, by GC analysis (Found: C, 68.2; H, 10.4. Calc. for C,,H,,OSi: C, 68.5; H, 10.5); v,,,(thin film)/cm-' 3345br s (OH), 3025m (=CH2), 2940s (CH), 1408m, 1248m and 860m; 6,(270 MHz; CDCl,; Me,Si) 5.8g5.70 (2 H, m, CH=CH), 5.58 (1 H, d, J 1, =CHH),5.42 (1 H, d, J 1, =CHH), 4.24-4.1 1 l H, m, CH(OH), 2.31-1.99 (3 H, m, HCCH,C==C), 1.90-1.10 (5 H, m) and 0.08 (9 H, s, TMS); 6,( 100 MHz; CDC1,; Me,Si) 149.92 (C), 135.23 (CH), 128.74 (CH), 125.91 (CH,), 66.82 (CH), 42.37 (CH,), 34.06 (CH), 30.1 7 (CH,), 24.06 (CH,) and -1.37 (3 x CH,); m/z (EI) 192 (M+ -H,O, 16), 177 (M' -H,O -Me, 6), 118 (22), 79 (66) and 73 (TMS', 100); m/z (CI) 228 (M + NH4+, 7), 211 (MH+, 17), 210 (83), 193 (100) and 90 (99); m/z 210.1443 (Calc.for C,,H,,OSi: 2 10.1443). 2-(4-Isopropylphenyl)-l-trimethylsilylprop-2-ene 22. To 4-iodoisopropylbenzene (984 mg, 4 mmol) and tetrakistri-phenylphosphinepalladium (1 16 mg, 0.1 mmol) in ether (5 cm3) at -15 "C was added a solution of the pre-formed allylzinc reagent 1 C4.4 mmol in ether (15 cm') over 10 min. The mixture was stirred for 10 min after which it was treated with saturated aqueous ammonium chloride to quench the reaction. The layers were separated and the aqueous layer extracted with ether. The combined organic layer and extracts were washed with brine, dried (MgSO,) and concentrated. Chromatography of the residue with hexane (RF 0.39) yielded a clear colourless oil (817 mg, 88), and recovered starting material (46 mg, 5) (Found: C, 77.2; H, 10.3.Calc. for C,,H,,Si: C, 77.5; H, 10.4); v,,,(thin film)/cm-l 3085w (ArH), 2963m (CH), 1616m (W),1249s,855s and 839s; 6,(270 MHz; CDC1,; Me,Si) 7.32 (2 H, d, J 7, ArH), 7.14 (2 H, d, J 7, ArH), 5.11 (1 H, s,SHH),4.81 (1 H, s,=CHH), 2.88 (1 H, hept, J7, CHMe,), 1.99 (2 H, s, CH,TMS), 1.24 6 H, d, J7, CH(CH,), and 0.10 9 H, s, Si(CH,),; 6,(100 MHz; CDCl,; Me,Si) 147.87 (C), 146.34 (C), 140.15 (C), 126.19 (2 x CH), 126.05 (2 x CH), 109.27 (CH,), 33.72 (CH), 26.02 (CH,), 23.97 (2 x CH,) and -1.37 (3 x CH,); m/z (EI) 232 (M+, 8), 217 (M' -Me, 9), 189 (M' -Pr, 51) and 73 (TMS+, 100); m/z 232.1648(24) (Calc. for C, ,H,,Si: 232.1647).2,3-Bis(trimethylsilylmethyl)buta-1,3-diene 26. To benzyl bromide (594 mm3, 5 mmol) and tetrakistriphenylphosphine-palladium (173 mg, 0.15 mmol) in ether (15 cm3) at -15 "C was added a solution of the pre-formed prop-2- enylzinc reagent 1 C5.5 mmol in ether (18.5 cm3) over 10 min. The mixture was stirred for 15 min after which it was treated with saturated aqueous ammonium chloride to quench the reaction. The layers were separated and the aqueous layer was extracted with ether. The combined organic layer and extracts were washed with brine, dried (MgSO,) and concentrated. Chromatography of the residue with pentane yielded three com- ponents. 26:(315 mg, 51, based on allylzinc), RF'0.62 (Found: C, 63.6; H, 11.6. Calc. for C,,H,,Si,: C, 63.6; H, 11.6); v,,,(thin film)/cm-' 3098w (=CH,), 2955, 2900s (CH), 1588m (C=C), 1414m, 1249s, 1162m, 840s and 697s; 6,(270 MHz; CDCl,; Me,) 4.92 2 H, s, (WHH),, 4.73 2 H, s, (C=CHH),, 1.75 4 H, s, (CH,TMS), and 0.00 lS H, s, Si(CH,),; 6,(67.8 MHz; CDCl,; Me,Si) 145.81 (2 x C), 110.98 (2 x CH,), 24.08 (2 x CH,) and -1.07 (6 x CH,); m/z (EI) 226 (M', 2073, 21 1 (M' -Me, 1l), 123 (32) and 73 (TMS, 100); m/z (HRMS) 226.1572 (CalC.for C12H26Si2: 226.1573). 24: (134 mg, 13), R, 0.48; v,,,(thin film)/cm-' 3065w (ArH), 3030w (=CH), 2958 and 2900s (CH), 1633m (W),1248s, 850s and 699s; 6,(270 MHz; CDCl,; Me,Si) 7.40-7.18 (5 H, m, ArH), 4.69 (1 H, s, =CHH), 4.62 (1 H, s, =CHH), 3.32 (2 H, s, ArCH,), 1.55 (2 H, s, CH,TMS) and 0.10 9 H, s, Si(CH,),; 6,(67.8 MHz; CDCl,; Me,Si) 146.75 (C), 139.85 (C), 129.10 (2 x CH), 128.22 (2 x CH), 126.01 (CH); 109.44 (CH,), 45.04 (CH,), 26.1 1 (CH,) and -1.25 (3 x CH,); m/z (EI) 204 (M', 20) and 73 (TMS, 100); m/z (HRMS) 204.1339 (Calc.for C1 ,H,,Si: 204.1334). Benzyl bromide (446 mg, 75). 2-Benzyl-3-trimethylsilylpropene 24, 1,Zdiphenylethane 25 and 2,3-bis(trimethylsilylmethyl)buta-l,3-diene 26. To benzyl bromide (238 mm3, 2 mmol) and nickel acetylacetonate (14 mg, 0.05 mmol) in ether (5 cm3) at -15 "C was added a solution of the pre-formed prop-2-enylzinc reagent 1 C2.2 mmol in ether (7.7 cm') over 10min. The mixture was stirred for 36 h at room temperature after which it was treated with saturated aqueous ammonium chloride to quench the reaction.The layers were separated and the aqueous layer was extracted with ether. The combined organic layer and extracts were washed with brine, dried (MgSO,) and concentrated. Chromatography of the residue with pentane yielded three components. 26:(25 mg, lo, based on allylzinc), R, 0.62 (Found: C, 63.6; H, 11.6. Calc. for C,,H,,Si,: C, 63.6; H, 11.6); v,,,(thin film)/cm-I 3098w (SH,), 2955, 2900s (CH), 1588m (C=C), 1414m, 1249s, 1162m, 840s and 697s; 6,(270 MHz; CDCl,; Me,Si) 4.92 2 H, s, (C==CHH),, 4.73 2 H, s, (CSHH),, 1.75 4 H, s, CH,TMS), and 0.00 18 H, s, Si(CH,),; 6,(67.8 MHz; CDC1,; Me,) 145.81 (2 x C), 110.98 (2 x CH,), 24.08 (2 x CH,) and -1.07 (6 x CH,); m/z(EI) 226 (M +,2079,211 (M' -Me, ll), 123 (32) and 73 (TMS, 100); m/z (HRMS) 226.1572 (Calc. for C, ,H,,Si,: 226.1573).24:(56 mg, 14), R, 0.48; v,,,(thin film)/cm-' 3065w (ArH), 3030w (=CH), 2958, 2900s (C-H), 1633m (W),1248s, 850s and 699s; 6,(270 MHz; CDCl,; Me,) 7.40-7.18 (5 H, rn, ArH), 4.69 (1 H, s, CXHH), 4.62 (1 H, s, GCHH), 3.32 (2 H, s, ArCH,), 1.55 (2 H, s, CH,TMS) and 0.10 9 H, s, Si(CH,),; 6,(67.8 MHz; CDCl,; Me,Si) 146.75 (C), 139.85 (C), 129.10 (2 x CH), 128.22 (2 x CH), 126.01 (CH), 109.44 (CH,), 45.04 (CH,), 26.1 1 (CH,) and -1.25 (3 x CH,); m/z (EI) 204 (M', 20) and 73 (TMS, 100); m/z (HRMS) 204.1339 (Calc. for C, ,H,,Si: 204.1334). 25:(99 mg, 54, based on benzyl bromide), R, 0.29; 6,(270 MHz; CDCl,; Me,Si) 7.467.23 (10 H, m, ArH) and 3.03 (4 H, s, ArCH,); m/z (EI) 182 (M+, 42) and 91 (PhCH,', 100).3-tert-Butyl(diphenyl)silyl-2-bromopropl-ene27. tert-Butyl-(dipheny1)silyl chloride (7.7 cm3, 30 mmol) was added to a stirred suspension of lithium wire (2 sodium) (1.26 g, 180 mmol) in THF (30 cm3)at 0 "C. The colour began to darken after 10 min. The mixture was stirred for 4 h to yield a dark- brown solution which was titrated against butylated hydroxy- toluene with fluorene as indicator. The titre indicated the solution was 0.82 mol dm-,. To copper(r) cyanide (1.16 g, 13 mmol) in THF (20 cm3) at 0 "C was added the tert-butyl(dipheny1)silyllithium (3 1.7 cm3, 26 mmol) over 5 min. The colour initially became mauve and then rapidly darkened. The resulting black solution was stirred for 30 min and then cooled to -78 "C.2,3-Dibromopropene (2.7 cm3, 26 mmol) which had been freshly distilled (64-65 "C at 49 mmHg) in THF (10 cm3) was added over 10 min to the mixture which was then stirred at -70 to -78 "C for 10 min. It was then allowed to warm to room temperature over 2 h before being diluted by the J. Chem. Soc., Perkin Trans. I 197 slow addition of saturated aqueous ammonium chloride to quench the reaction. The mixture was extracted with ether and the combined extracts were washed with brine, dried (MgSO,) and concentrated under reduced pressure. Chromatography of the residue in hexane (RF 0.22) yielded the title compound in 91 purity by GC analysis (6.05 g, 59); v,,,(thin film)/cm ' 3052w (ArH), 2930, 2858m (CH), 1618m, 1427s, 1104s and 696s; 6,(270 MHz; CDCl,; Me,Si) 7.72-7.60 (4 H, m, ArH), 7.47-7.30 (6 H, m, ArH), 5.16 (2 H, s, CXH,), 2.73 (2 H, s, SiCH,) and 1.05 (9 H, s, Bu'); (lo0 MHz; CDCl,; Me,Si) 136.17 (4 x CH), 133.22 (2 x C), 130.00 (C), 129.39 (2 x CH), 127.56(4 x CH), 117.73(CH2),27.66(3 x CH3),26.78(CH2) and 18.51 (C); m/z (El) (consistent with 1 bromine) 303/301 (M+ -Bu, 18/15), 263/261 (Ph,Si+Br, 100/96), 239 (16), 197 (28), 181 (31), 135 (73) and 105 (29); m/z (CI) 361/359 (MH+, < l/< 1) and 256 (100); m/z 301.0073 (Calc.for M+ -Bu: CISH,,BrSi 301.0048). 2-tert-Butyl(diphenyl)silylmethyl-4,5-epoxy-4-methylhept-l-en-3-01 28.To a suspension of magnesium (0.60 g, 25 mmol) and 1,Zdibromoethane (43 cm3, 0.5 mmol) in THF (20 cm3) was added the prop-2-enylsilane 27 (4.44 cm', 26 mmol) dropwise over 30 min, a gentle reflux being maintained after initiation had occurred. Upon cooling to 0 "C the reaction mixture, an opaque olive solution, provided a gelatinous precipitate.The aldehyde (1.14 cm3, 0.01 mol) in THF (5 cm3) was added dropwise to the Grignard solution over 20 rnin and the reaction mixture allowed to warm to room temperature over 1 h. Saturated aqueous ammonium chloride was added carefully with stirring to the mixture until no precipitate remained after which it was filtered and the aqueous layer separated and extracted with ether. The combined organic layer and extracts were dried (MgSO,), fil-tered through a silica plug, evaporated and the residue dried in vacua Chromatography of the residue with 20 ether-hexane as the eluent yielded the two diastereoisomeric products.28a:(0.48 g, 12), R, 0.30; v,,,(thin film)/cmp' 3462br m (OH), 3073m (ArH), 2966,2935,2861s (CH), 1958,1898,1821~ (ArH), 164Ow (C=C), 1468m, 1428m, 1106s, 738s and 701s; 6,(270 MHz; CDCI,; Me,) 7.73-7.61 (4 H, m, ArH), 7.45- 7.29 (6 H, m, ArH), 4.87 (1 H, s, C=CHH), 4.73 (1 H, s, C=CHH), 3.63 l H, s, C(H)OH, 2.98 (1 H, t, J 7, CHCH,), 2.33 (1 H, d, J 15, CHHTBDPS), 2.08 (1 H, d, J 15, CHHTBDPS), 1.77 (1 H, s, OH), 1.64 (1 H, dpent, J 14 and 7, CHCHHCH,), 1.51 (1 H, dpent, J 14 and 7, CHCHHCH,) and 1.09-0.97 (15 H, m, 5 x CH,); 6,(100 MHz; CDCl,; Me,Si) 144.31 (C), 136.30 (2 x CH), 136.18 (2 x CH), 134.47 (C), 134.05 (C), 129.19 (2 x CH), 127.50 (2 x CH), 127.48 (2 x CH), 114.02 (CH,), 77.39 (CH), 61.74 (C), 61.13 (CH), 27.74 (3 x CH,), 21.58 (CH,), 18.45 (C), 14.84 (CH,), 13.74 (CH,) and 10.55 (CH,); m/z (EI) 337 (M' -Bu, 479, 319 (2), 279 (loo), 199 (94) and 135 (79); m/z (CT) 412 (M + NH,', loo), 395 (MH', 9), 337 (100) and 317 (80); m/z (HRMS) 394.2336 (Calc.for C2,H3,02Si: 394.2328). 28b:(1.79 g, 45), R, 0.21 (Found: C, 75.8; H, 8.75. Calc. for C,,H,,OSi: C, 75.7; H, 8.5); v,,,(thin film)/cm-' 3462br m (OH), 3072 (m, ArH), 2965, 2930, 2857s (CH), 1957, 1887, 1823w (ArH), 1641w (C=C), 1464m, 1428m, 1107s, 736s and 702s; 6,(270 MHz; CDCI,; Me,Si) 7.72-7.55 (4 H, m, ArH), 7.45-7.28 (6 H, m, ArH), 5.00 (1 H, s, C=CHH), 4.79 (1 H, s, WHH), 3.24 l H, d, J 4, C(H)OH, 2.64 (1 H, t, J 7, CHCH,), 2.32 (1 H, d, J 15, CHHTBDPS), 1.89 (1 H, d, J 15, CHHTBDPS), 1.58 (1 H, d, J4, OH), 1.61 (1 H, dpent, J 14 and 7, CHCHHCH,), 1.47 (1 H, dpent, J 14 and 7, CHCHHCH,), 1.10 (3 H, s, CH,), 1.02 9 H, s, C(CH,), and 1.00 (3 H, t, J 7, CHCH,CH,); 6,(100 MHz; CDCI,; Me,Si) 143.88 (C), 136.23 (2 x CH), 136.16 (2 x CH), 134.20 (C), 134.10 (C), 129.32 (CH), 129.26 (CH), 127.55 (2 x CH), 127.52 (2 x CH), 112.25 (CH,), 79.17 (CH), 63.14 (CH), 62.59 (C), 27.74 (3 x CH,), 21.43 (CH,), 18.44 (C), 15.89 (CH,), 11.63 (CH,) and 10.48 (CH,); m/z (EI) 337 (M' -Bu, 2), 319 (2), 279 (93), 199 (100) and 135 (92); m/z (CT) 412 (M + NH4+, loo), 395 198 J.Chem. SOC.,Perkin Trans. I (MH', 9), 337 (62) and 317 (51); m/z (HRMS) 394.2336 (Calc.for C,,H,,O,Si: 394.2328). 2-tert-Butyl(diphenyI)silyl-5,6-epoxy-5-methyloct-1 -en-4-ol 29. A solution of 2-(bromoprop-2-enyl)-tert-butyl(diphenyl)-silane (3.6 g, 10 mmol) in ether (10 cm3) at -70 "C was treated with Bu'Li (1.5 mol dmp3 in pentane solution; 13.5 cm3, 20 mmol) over 10 rnin (exotherm to -50 "C). The pale yellow solution was stirred for 5 rnin at -70 "C after which it was treated with a solution of zinc dichloride (1 .O mol dm-, in ether solution; 10.5 cm3, 10.5 mmol), added over 10 rnin (exotherm to -50 "C). The mixture was stirred for 10 rnin at -70 "C after which it was made up to 30 cm3 with ether (aliquots of this solution were added to different reactions). For example, the organozinc reagent was stirred at ambient temperature for 2.5 h before being added (1.5 mmol) to the aldehyde 6 (116 g, 1 mmol) in ether (5 cm3) (pre-dried with molecular sieves).The mixture was stirred for 10 min and treated with saturated aqueous ammonium chloride to quench the reaction. The aqueous layer was separated andextracted with ether and thecom- bined organic layer and extracts were dried (MgSO,) and concen- trated under reduced pressure. Chromatography of the residue in 20 ether-hexane yielded two diastereoisomeric products. 29a:A clear colourless oil (149 mg, 38), R, 0.29; v,,,(thin film)/cm-' 3491br s (OH), 3070w (ArH), 2967, 2859s (CH), 1469m, 1426s, 1104s, 909s, 734s and 702s; 6,(270 MHz; CDC1,; Me,) 7.70-7.57 (4 H, m, Ph), 7.45-7.29 (6 H, m, Ph), 6.17 (1 H, d, J0.5, C=CHH), 5.83 (1 H, d, J 1, C=CHH), 3.38 (1 H, br d, J 10, CHOH), 2.82 (1 H, t, J7, CHCH,), 2.43 (1 H, br d, J 14, HHCCHOH), 2.08 (1 H, dd, J 14 and 10, HHCCHOH), 1.99 (1 H, br s, OH), 1.53 (1 H, dpent, J 14 and 7, CHHCH,), 1.40(1H,dpent,J14and7,CHHCH3),1.15(9H,s,But),0.93 (3 H, t, J 7, CH,CH,) and 0.84 (3 H, s, CH,); 6,(67.8 MHz; CDCl,; Me,Si) 142.56 (C), 136.42 (2 x CH), 136.24 (2 x CH), 134.43 (C), 134.28 (C), 132.49 (CH,), 129.19 (CH), 129.18 (CH), 127.71 (2 x CH), 127.64 (2 x CH), 70.78 (CH), 62.47 (C), 60.58 (CH), 41.01 (CH,), 28.64 (3 x CH,), 21.29 (CH,), 18.54 (C), 13.53 (CH,) and 10.37 (CH,); GC-MS m/z (ET) 337 (M+ -Bu, I), 319 (5), 279 (72), 251 (48), 201 (IOO), 199 (554, 183 (37) and 173 (36); m/z (CI) 412 (M + NH,+, l), 361 (48), 354 (IOO), 259 (97) and 256 (73); m/z (HRMS) 3 19.I523 (Calc. for Mf -Bu -H,O: 319.1518). 29b:A clear colourless oil (64 mg, 16), RF 0.15; v,,,(thin film)/cm-' 3460br s (OH), 3070w (ArH), 2967, 2859s (CH), 14m, 1426s, 1104s, 1054m, 909s, 734s and 702s; 6,(270 MHz; CDCI,; Me,Si) 7.72-7.55 (4H, m, Ph), 7.45-7.29 (6 H, m, Ph), 6.15(1H,d,J0.5,C=CHH),5.86(1H,d,Jl,C=CHH),2.88(1 H, br d, J 10, CHOH), 2.36 (1 H, br d, J 14, HHCCHOH), 2.23 (1 H, dd, J 14 and 10, HHCCHOH), 2.08 (I H, t, J 7, CHCH,), 1.78(1 H, brs,OH), 1.51-1.20(2H,m,CH2CH3), 1.12(9H,s, Bu'), 1.03 (3 H, s, CH,) and 0.84 (3 H, t, J7, CH,CH,); 6,(67.8 MHz; CDCl,; Me,) 142.43 (C), 136.37 (2 x CH), 136.24 (2 x CH), 134.41 (C), 134.09 (C), 132.87 (CH,), 129.32 (CH), 129.25 (CH), 127.78 (2 x CH), 127.76 (2 x CH), 74.46 (CH), 63.30 (C), 62.42 (CH), 41.70 (CH,), 28.61 (3 x CH,), 21.23 (CH,), 18.66 (C), 11.24 (CH,) and 10.35 (CH,); GC-MS m/z (El) 319 (573,279 (loo), 251 (45), 201 (loo), 199 (70), 183 (30), 181 (38) and 173 (36); m/z (Cl) 412 (M + NH4+, 1), 361 (22), 354 (31), 259 (100) and 256 (38); m/z (HRMS) 319.1523 (Calc.for M+ -Bu -H,O: 319.1518). 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Sturmer, Liebigs Ann. Chem., 1991, 31 1; (c) B. E. Rossiter, T. Katsuki and K. B. Sharpless, J. Am. Chem. Soc., 198I, 103,464. Paper 5/040321 Received 22nd June 1995 Accepted 6th September 1995 J. Chem. SOC.,Perkin Trans. 1 199