Gold(I)-catalyzed [2 + 2 + 2] cycloaddition of allenamides, alkenes and aldehydes: a straightforward approach to tetrahydropyrans

Abstract

Allenamides participate as two-carbon components in an intermolecular [2 + 2 + 2] cycloaddition with alkenes and aldehydes when treated with catalytic amounts of a phosphite gold complex. The reaction is highly regio- and chemoselective, and works with different types of alkenes, including styrenes, enolethers or enamides, as well as with aromatic and aliphatic aldehydes. Accordingly, different types of 2,6- disubstituted tetrahydropyrans can be stereoselectively assembled in a single step from commercial or very accessible starting materials