Chemodivergent annulations of allenyl imides and β,γ-enones switched by nucleophilic phosphine and amine catalysts

Abstract

Nucleophilic phosphine and amine catalyst-switched chemodivergent [4 + 1] and [3 + 3] annulations of allenyl imides and β,γ-enones have been developed, furnishing highly substituted 2-cyclopentenone and 2-pyranone derivatives in moderate to excellent yields. Two plausible reaction mechanisms involving two different ketene intermediates have been proposed to explain the observed chemoselectivity. Moreover, by virtue of the α,β-enone substructure of the [4 + 1] adducts, 1,3-dipolar cycloaddition of nitrile imines has been studied in one-pot to provide various fused pyrazoline derivatives.