Studies on heterocyclic chemistry. Part X. Synthesis of aziridin-2-ylphosphonates by the thermally induced isomerization of isoxazoles in trialkyl phosphites. A related reaction of 2H-azirine

Abstract

The reactions of isoxazoles and of 2H-azirines with trialkyl phosphite have been studied. 5-Amino-3-arylisoxazoles and 3-aryl-2H-azirine-2-carboxamides afford aziridin-2-ylphosphonates whereas 5-methoxy-3-phenylisoxazole gives an aziridine dimer which has a phosphonyl group at C-2. 5-Amino-3,4-diphenylisoxazole, 2,3-diphenyl-2H-azirine-2-carboxamide, and related compounds produce Δ⁴-oxazolin-2-ylphosphonates via aziridin-2-ylphosphonates. The mechanism of these reactions is accounted for in terms of the nucleophilic attack on the CN bond of 2H-azirine by trialkyl phosphite.