ORGANOMETALLIC COMPOUNDS 351 (c) The desired product is a secondary alkyl bromide. a reasonable synthesis would be to first prepare the analogous secondary alcohol by reaction of phenylmagnesium bromide with benz- aldehyde, followed by a conversion of the alcohol to the bromide Retrosynthetically this can C6HSCH-C6Hs CHCH.H3□> C6HSMgX+cHCH I diethyl ether HBr or PBrs MgBr t hc- CH一 Phenylmagnesium Benzaldehyde (d) The target molecule is a tertiary alcohol, which requires that phenylmagnesium bromide react with a ketone By mentally disconnecting the phenyl group from the carbon that bears the hydroxyl group, we see that the appropriate ketone is 4-heptanone. CH CH,CH,CCH, CH, CH3 CH,,CH, CCH, CH, CH3 4-Phenyl-4-heptanol 4-Heptanone The synthesis is therefore OH t CHaCH,CH,CCH,CH,CH 1. diethyl ether CHaCH,CH,CCH, CH, CH Phenylmagnesium 4-Heptanone 4-Phenyl-4-heptanol (e) Reaction of phenylmagnesium bromide with cyclooctanone will give the desired tertiary alcohol 1. diethyl ether 2.H3O (f) The 1-phenylcyclooctanol prepared in part (e) of this problem can be subjected to acid- catalyzed dehydration to give l-phenylcyclooctene. Hydroboration-oxidation of 1-phenyl cyclooctene gives trans-2-phenylcyclooctanol H, SO, he 1.B2H6 l-Phenylcyclooctanol I-Phenylcyclooctene trans-2-Phenylcyclooctanol Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website(c) The desired product is a secondary alkyl bromide. A reasonable synthesis would be to first prepare the analogous secondary alcohol by reaction of phenylmagnesium bromide with benz￾aldehyde, followed by a conversion of the alcohol to the bromide. Retrosynthetically this can be seen as (d) The target molecule is a tertiary alcohol, which requires that phenylmagnesium bromide react with a ketone. By mentally disconnecting the phenyl group from the carbon that bears the hydroxyl group, we see that the appropriate ketone is 4-heptanone. The synthesis is therefore (e) Reaction of phenylmagnesium bromide with cyclooctanone will give the desired tertiary alcohol. ( f) The 1-phenylcyclooctanol prepared in part (e) of this problem can be subjected to acid￾catalyzed dehydration to give 1-phenylcyclooctene. Hydroboration–oxidation of 1-phenyl￾cyclooctene gives trans-2-phenylcyclooctanol. H2SO4, heat 1. B2H6 2. H2O2, HO OH 1-Phenylcyclooctanol 1-Phenylcyclooctene H trans-2-Phenylcyclooctanol H H OH O OH 1. diethyl ether 2. H3O Cyclooctanone 1-Phenylcyclooctanol MgBr Phenylmagnesium bromide 1. diethyl ether 2. H3O 4-Heptanone 4-Phenyl-4-heptanol MgBr OH Phenylmagnesium bromide CH3CH2CH2CCH2CH2CH3 CH3CH2CH2CCH2CH2CH3 O 4-Heptanone O CH3CH2CH2CCH2CH2CH3 4-Phenyl-4-heptanol OH CH3CH2CH2CCH2CH2CH3 1. diethyl ether 2. H3O Benzaldehyde Diphenylmethanol CH OH MgBr Bromodiphenylmethane CH Br Phenylmagnesium bromide HC O HBr or PBr3 Br O C6H5CH C6H5 OH C6H5CH C C6H5 6H5MgX C6H5CH ORGANOMETALLIC COMPOUNDS 351 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website