Desymmetrization of (R,R)-hexa-1,5-diene-3,4-diol via monofunctionalization and rhodium-catalyzed allylic substitution.

A sequence of selective monoprotection and Rh-catalyzed enantioconservative allylic substitution is established as a desymmetrization strategy for C(2)-symmetric hexa-1,5-diene-3,4-diol. A benzyl protecting group and ethyl carbonate as a leaving group emerged as the most useful combination with respect to reproducibility, stereoselectivity, and yield. A remarkable deviation from the normally observed regiospecificity of Rh-catalyzed allylic alkylations was observed for unprotected carbonates. In this case, a linear, rather than a branched alkylation product was obtained exclusively.