Highly Selective Primary Alkoxycarboxylation and Esterification of Unprotected Pyranose Derivatives Mediated by Scandium(III) Triflate Catalysis

A highly selective method for the alkoxycarboxylation and acylation of primary alcohols of pyranose derivatives is described. The reaction is high yielding and proceeds under mild conditions with 0.151 mol-% Sc(OTf)3 used in combination with anhydrides or pyrocarbonates at 4050 degrees C. Selectivities observed for alkoxycarboxylation of unprotected pyranose derivatives are > 95?%, and this constitutes a significant advantage over existing methods. Mechanistic implications, including the role of steric demand and metalheteroatom coordination are also discussed.