Trifluoroacetic Anhydride Promoted Tandem Conjugate Addition of Boronic Acids/Acetal Ring Opening

A new stereoselective tandem reaction consisting of the metal-free conjugate addition of boronic acids followed by an intramolecular ring opening of a cyclic acetal has been disclosed. Optically pure polysubstituted tetrahydropyrans have been synthesized diastereoselectively by this new reaction. Two new C C bonds and up to three stereocenters are formed in a single step, allowing the generation of quaternary stereocenters.