Enantioselective N-Heterocyclic Carbene-Catalyzed Michael Addition to α,β-Unsaturated Aldehydes by Redox Oxidation

Enantioselective N-heterocyclic carbene-catalyzed Michael addition reactions to alpha,beta-unsaturated aldehydes by redox oxidation were realized. With 10 mol % of camphor-derived triazolium salt D, 15 mol % of DBU, 5 mol % of NaBF4, and 100 mol % of quinone oxidant, the reactions of various dicarbonyl compounds with alpha,beta-unsaturated aldehydes led to 3,4-dihydro-alpha-pyrones in good yields and excellent ee's.