C–O cleavage via InIII alkoxide intermediates: In situ 13C NMR analysis of the mechanism of an enantioselective in-mediated cyclopropanation reaction

Abstract The mechanism of asymmetric cyclopropanation dibenzylideneacetone and benzylideneacetone by in situ generated allyl indium reagents the presence methyl mandelate as a chiral modifier has been studied 13C{1H} NMR conjunction with 13C/2H labelling mass spectrometry. Two alkoxides were identified, first arising from mediated allylation ketone, second reaction an liberated homoallylic via LiI excess reagent. On acidification, protonation at oxygen induces C–O rather than In–O cleavage incipient tertiary allylic cation is stereoselectivly allylated approximately 90% si selectivity, what assumed to be mandelate-chelated