Catalytic Desymmetrizing Baeyer-Villiger Oxidation of Quaternary Carbon-Containing Cyclobutane-1,3-diones.

The first highly enantioselective Baeyer-Villiger oxidation of quaternary carbon-containing cyclobutane-1,3-diones using chiral phosphoric acid catalysis and commercially available oxidants was reported. According to the structure of the substrates, two optimized reaction conditions were developed to afford the corresponding chiral tetronic acid products in ≤93% and ≤95% ee values. This reaction offers the first catalytic asymmetric approach to chiral 5,5-disubstituted tetronic acid derivatives. The synthetic potential of this method has been demonstrated by the formal asymmetric synthesis of (-)-vertinolide and the first catalytic asymmetric total synthesis of plakinidone B.

Catalytic Enantioselective Desymmetrization of Cyclobutane-1,3-diones by Carbonyl-Amine Condensation.

A chiral phosphoric acid-catalyzed enantioselective condensation of 2,2-disubstituted cyclobutane-1,3-diones with a primary amine is described. This reaction offered a mild and efficient protocol for constructing quaternary carbon-containing cyclobutanes in good to high yields and enantioselectivities. This reaction is the first catalytic desymmetrizing carbonyl-amine condensation reaction and also represents the first catalytic desymmetrizing reaction of prochiral cyclobutane-1,3-dione.