Diastereoselective palladium-catalyzed formate reduction of allylic carbonates en route to polypropionate systems.

Diastereoselective palladium-catalyzed formate reduction of allylic carbonates presents unique opportunities for applications in target-oriented organic synthesis provided that selectivity, in particular stereoselectivity, in the course of this metal-catalyzed reaction can be controlled. This article describes our recent developments on new and efficient metal-catalyzed processes exploiting resident stereocenters on the substrates as a means to control stereoselectivity en route to preparing propionate units containing an array of stereochemical patterns. In particular, the effect of the protecting group, the stereochemistry of the aldol adduct, neighboring substituents, and the olefin geometry were examined. Strategic choice of the above parameters provides entry into three of the four possible diastereomeric triads, namely syn-syn, anti-syn, and anti-anti. Preliminary results indicate that construction of the syn-anti triad is possible, albeit in moderate diastereoselectivity.