Development of Enantioselective Processes Catalysed by Novel Asymmetric Bifunctional Phase-Transfer Organocatalysts

Abstract

A new family of chiral bifunctional phase-transfer catalysts were developed to promote an enantioselective SN2 reaction for the construction of malleable oxindoles with all-carbon quaternary stereocenters in high yield and excellent enantioselectivity (up to 97% ee). The utility of this methodology was demonstrated through the concise and highly enantioselective synthesis of (-)-debromoflustramine B and (-)-flustramine B. The newly developed family of chiral bifunctional phase-transfer catalysts, in conjunction with catalytic amounts of fluoride, were also utilised in a hitherto, unprecedented method of enantiocontrolled desymmetrisation. A selection of meso-anhydrides were converted to their corresponding hemiesters with reasonable levels of enantiocontrol. Reaction scope was demonstrated with the promotion of a nucleophilic catalysis-mediated rearrangement of O-acylated enolates as well as a nucleophilic catalysis-mediated Curtius rearrangement to form synthetically useful products