Studies on heterocyclic chemistry. Part XII. Tautomerism of α-(5-oxo-Δ3-isoxazolin-4-yl)benzylphosphonates

Abstract

α-(5-Oxo-Δ³-isoxazolin-4-yl)benzylphosphonates (2) mostly exist in the NH form in the solid state, and in the OH form in non-polar solvents, owing to chelation with the phosphonyl group. The tautomeric equilibrium in solution is influenced by the nature of the 3-substituent in the isoxazole ring; the 3-methyl compounds exist partially in the NH form. A modified synthesis of these compounds is described.