Rhodium-catalyzed hydroaroylation of α,β-unsaturated esters using aroyl chlorides and Et2MeSiH

Hydroaroylation of methyl acrylate 2a to give the α-aroyl esters 4 took place in the three-component reaction of 2a, aroyl chlorides 1, and Et2MeSiH in the presence of 1 mol % of [Rh(cod)(PR3)2]OTf (cod = 1,5-cyclooctadiene, OTf = OSO2CF3, R = Ph (3a), OPh (3b)) in CH2Cl2. GC and 1H NMR investigation revealed that the rhodium-catalyzed hydroaroylation proceeds via two successive transformations, that is, hydrosilylation of 2a to afford silyl enol ether 5a followed by C-C bond formation between 5a and 1a.