Diastereoselective Alkylation of 8-Phenylmenthyl Phenylacetate: Aggregated Lithium Enolate versus "Naked" Enolate

Article abstract of DOI:10.1021/jo00097a041

It is shown that monoalkylation of 8-phenylmenthyl phenylacetate using lithiated bases leads to poor or no diastereoselectivities (50/50 to 69/31) and high yields (75 to 98percent) while alkylation using tBu-P4 (a strong and cation free base, known to provide "naked" anion) leads to high diastereoselectivities (92/8 to 98/2) and high yields (65 to 95percent).It is postulated that, in the case of phenylacetates, the degree of aggregation of the lithium enolate is responsible of the poor diastereoselectivities.