A tetrazine-driven photocatalytic system suitable for the synthesis of unstable 2,3-dihydroisoxazoles

Abstract

A novel visible-light-driven [3 + 2] cycloaddition reaction of nitrones with alkynyl esters, catalyzed by 3,6-di(pyridin-2-yl)-1,2,4,5-tetrazine (pytz), has been investigated. This reaction effectively synthesizes unstable 2,3-dihydroisoxazole derivatives with yields reaching up to 97%, attaining high selectivity under mild conditions and within a short reaction time. Furthermore, the methodology demonstrates a broad substrate scope, accommodating a wide variety of aromatic and aliphatic nitrones, thereby presenting a novel strategy for the efficient construction of multi - substituted five - membered heterocyclic structures. Based on a series of validation experiments, this paper proposes a plausible hybrid mechanism involving free radicals and synergistic reactions.