Bismuth(III) Triflate-Based Catalytic Direct Opening of Oleanolic Hydroxy-γ-lactones to Afford 12-Oxo-28-carboxylic Acids

The bismuth(III) triflate-based catalytic direct opening of oleanolic hydroxy-gamma-lactones affords the corresponding 12-oxo-28-carboxylic acid derivatives, in both acetonitrile and dichloromethane, at reflux, in high yields. Participation of an in situ generated Bronsted acid species from bismuth-(III) triflate is most likely involved in the reaction mechanism. Full structural elucidation of the products obtained has been performed by 1D and 2D NMR techniques.