Catalytic Asymmetric Homologation of Ketones with α-Alkyl α-Diazo Esters

The homologation of ketones with diazo compounds is a useful strategy to synthesize one-carbon chain-extended acyclic ketones or ring-expanded cyclic ketones. However, the asymmetric homologation of acyclic ketones with alpha-diazo esters remains a challenge due to the lower reactivity and complicated selectivity. Herein, we report the enantioselective catalytic homologation of acetophenone and related derivatives with alpha-alkyl alpha-diazo esters utilizing a chiral scandium(III) N,N'-dioxide as the Lewis acid catalyst. This reaction supplies a highly chemo-, regio-, and enantioselective pathway for the synthesis of optically active beta-keto esters with an all-carbon quaternary center through highly selective alkyl-group migration of the ketones. Moreover, the ring expansion of cyclic ketones was accomplished under slightly modified conditions, affording a series of enantioenriched cyclic beta-keto esters. Density functional theory calculations have been carried out to elucidate the reaction pathway and possible working models that can explain the observed regio- and enantioselectivity.

Automated summary

This study describes an enantioselective homologation of ketones with alpha-alkyl alpha-diazo esters using a chiral scandium(III) N,N'-dioxide catalyst to produce a series of optically active beta-keto esters with an all-carbon quaternary center. This method provides a highly selective and synthetically efficient strategy for the synthesis of enantioenriched compounds.