Recent developments in synthetic strategies with allylsilanes: from tetracoordinate to pentacoordinate allylsilanes

Abstract

Abstract Allylsilanes are one of the most versatile reagents in organic synthesis and there are numerous examples of their applications. However, these reagents fall largely into the class of tetracoordinate allylsilanes. Currently, a new field of pentacoordinate allylsilanes is rapidly developing. Pentacoordinate allylsilicates react with aldehydes and ketones to give homoallyl alcohols with exceptionally high regio- and diastereoselectivity. The high reactivity of the allylsilicates is attributed to the significantly high Lewis acidity of the silicon centre to give hexacoordinate silicates (which allows for a six-membered cyclic transition state) as well as to the enhanced nucleophilicity of the -y-carbon of the allylsilicates arising from cr-1r conjugation. The stereochemical outcome of the reaction with pentacoordinate allylsilanes, which is completely different from that with tetracoordinate allylsilanes, should also find widespread use in organic synthesis. Reactions of pentacoordinate allylsilicates, which are remarkably different from those of the well established tetracoordinate allyltri methylsilanes, are described.