Rhenium(V)-Catalyzed Synthesis of 2-Deoxy-α-glycosides

A mild method for the synthesis of 2-deoxysugars from the coupling of glycals with a range of nucleophiles is described. The method employs 1 mol % of an air- and moisture-tolerant rhenium-oxo complex [ReOCl3(SMe2)(Ph3PO)] as a catalyst for the formation of O-, N-, and S-alpha-glycosides. The catalytic system tolerates a number of commonly employed protecting groups, including isopropylidene acetals, alkyl and silyl ethers, acetates, and benzoates. Furthermore, the high-oxidation-state complex selectively catalyzes the coupling with the glycal acceptor in preference to oxidation of the glycals, alcohols, and even thiols.