Cleavage of Unsaturated α-Ketols to ω-Oxo-α,β-unsaturated Acids

Sodium periodate is a better reagent than sodium bismuthate, manganese dioxide, or lead tetraacetate for the cleavage of unsaturated α-ketols and affords ω-oxo-α,β-unsaturated acids in good yield. The combination of this cleavage reaction and a rhodium(I)-mediated decarbonylation of ω-oxo-α,β-unsaturated esters derived from polycyclic systems provided an enantioselective synthesis of cyclic systems bearing contiguous quaternary centers where one of the centers possessed gem-dimethyl groups.