Diels–Alder reaction of highly substituted 2H-pyran-2-ones with alkynes: reactivity and regioselectivity

Abstract

The Diels–Alder reactions of a variety of electron-rich 2H-pyran-2-ones 4 with alkynes 2 yielding aniline derivatives 6 under thermal conditions as well as at high pressures are presented. The effects of the substituents at the positions 3 and 5 in the 2H-pyran-2-one ring on the reactivity and the regioselectivity with different alkynes were qualitatively explained on the basis of electron demand and also by the formation of zwitterionic intermediates.