Enantioselective allylation of aldehydes with allyltrichlorosilane promoted by chiral sulfoxides: a kinetic study

The allylation of aldehydes is one of the most important methods for C-C bond formation because the obtained homoallylic alcohols are useful building blocks for the synthesis of complex molecules and natural products.1 Particular attention has been devoted to the development of enantioselective versions utilizing chiral allylating reagents, chiral Lewis acids as catalysts and, more recently, chiral Lewis base organocatalysts in the presence of allyltrichlorosilane.1 In the latter case, a wide variety of chiral Lewis bases derived from phosphoramides, N-oxides, sulfoxides, formamides, phosphine oxides, amines and ureas, has been demonstrated to be effective in enantioselective allylation.1 In this context, on the basis of our studies about the use readily available chiral sulfoxides in the allylation of aldehydes with allyltrichlorosilane,2 the peculiarities of this Lewis base have been analyzed from a mechanistic point of view. In this presentation we report a kinetic study in which we have determined kinetic orders with respect to benzaldehyde, silane and (R)-methyl p-tolyl sulfoxide. Moreover conductivity experiments gave us important insights about the species formed during the reaction.