Reactivity of the secondary benzylic Grignard reagent from 1-phenylethyl chloride with aldehydes and ketones. More evidence for the rearrangement mechanism in benzyl Grignard reactions

Article abstract of DOI:10.1016/0022-328X(89)87200-6

Additional evidence for the mechanism proposed previously to account for diol formation in the reaction of the Grignard reagent from benzyl chloride with aldehydes has been obtained from a study of the interaction of the Grignard reagent from 1-phenylethyl chloride with carbonyl compounds.This Grignard reagent reacts with ketones (except non-enolisable ketones) to give normal alcohols in low yields, and with aldehydes to give diols.However, in contrast to that formed in the reaction of benzylmagnesium chloride, an unstable trienic alcohol formed from the rearrangement of the corresponding alkoxide could be isolated in some case as the major product, providing confirmatory evidence for the existence of an initial reversible rearrangement in the reaction of the benzylic Grignard reagents with carbonyl compounds.