Further studies on silatropic carbonyl ene cyclisations: β-crotyl(diphenyl)silyloxy aldehyde substrates; synthesis of 2-deoxy-2-C-phenylhexoses

Abstract

Silatropic carbonyl ene cyclisations of β-(allylsilyloxy)- and β-(crotylsilyloxy)butyraldehydes are shown to proceed with high stereoselectivity but at a much reduced rate in comparison to the cyclisation of analogous α-substrates. In the second section, olefin cross-metathesis is explored as a route to substituted α-(allylsilyloxy)aldehydes and the method applied to the synthesis of diastereomeric 2-deoxy- and 2-deoxy-2-C-phenyl hexose derivatives from butanediacetal-protected D-glyceraldehyde.