Evidence for the reaction of nitrosocarbonyl compounds as heterodienes in the Diels–Alder reaction

Abstract

Evidence is given that a nitrosocarbonyl compound can react with a cyclic diene to give a 5,6-dihydro-1,4,2-dioxazine, not only by isomerisation of an initially formed 2-acyl-3,6-dihydro-1,2-oxazine, but also by reacting as a heterodiene directly with a π-bond in the cyclic diene; the role of the ring oxygen in retarding the isomerisation of an oxazine to a dioxazine is discussed.