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 beta-(allylsilyloxy)- and beta-(crotylsilyloxy)butyraldehydes are shown to proceed with high stereoselectivity but at a much reduced rate in comparison to the cyclisation of analogous alpha-substrates. In the second section, olefin cross-metathesis is explored as a route to substituted alpha-(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.

Nickel-Catalyzed Radical Migratory Coupling Enables C-2 Arylation of Carbohydrates

“…It is noteworthy that catalytic C-2 arylation of readily available sugar precursors for the preparation of saturated, fully oxygenated 2-aryl-2-deoxy sugars has not been reported . The existing approaches to this class of sugar derivatives involve either the construction of carbon skeletons by homologation of chiral aldehydes using the carbonyl ene cyclization strategy or epoxide ring opening of 2,3-epoxy sugars with arylmagnesium iodides or lithium diarylcuprates . However, these methods require the multistep synthesis of advanced intermediates, involve harsh reaction conditions, and have limited substrate and reaction scopes.…”