Carbene-Catalyzed Activation of C−Si Bonds for Chemo- and Enantioselective Cross Brook–Benzoin Reaction

The first carbene-catalyzed asymmetric chemoselective cross silyl benzoin (Brook–Benzoin) reaction has been developed. Key steps of this reaction involve activation of the carbon–silicon bond of an acylsilane by a chiral N-heterocyclic carbene (NHC) catalyst to form a silyl acyl anion intermediate. These acyl anions then undergo an addition reaction with indole aldehydes in a highly chemo- and enantioselective manner to afford α-silyloxy ketones with excellent optical purities. The reaction mechanism of this cross Brook–Benzoin reaction was investigated through both experimental and computational methods. The chiral α-hydroxy ketone derivatives obtained by this approach show promising, agrochemically interesting activity against harmful plant bacteria.