Cross Silyl Benzoin Additions Catalyzed by Lanthanum Tricyanide

摘要

From a screen of (cyanide)metal complexes,an improved catalyst for the cross silyl benzoin addition was discovered.Several M(CN)s complexes (M=Ce,Er,Sm,Y,Yb,La) were evaluated and lanthanum tricyanide was identified as the optimal catalyst.The catalyst,prepared in situ from LaCl_3,effects the selective coupling of aryl and alkyl acylsilanes with aryl,heteroaryl,alpha,beta-unsaturated,and aliphatic aldehydes.The reactions occur at ambient temperature in less than 5 min to provide,depending on the workup,a-hydroxy or alpha-silyloxy ketones in 48-93% isolated yield.