1,3-Dipolar cycloaddition route to oxygen heterocyclic triones
Abstract
1,3-Dipolar cycloadditon of nitrile oxides, formed in situ by dehydration of primary nitro compounds, with pyrrolidine enamines of protected γ-hydroxy-β-keto esters affords isoxazole-4-carboxylates; these are subjected to N–O bond cleavage and lactonisation to afford 3-acyltetronic acids and 3-acyl-4-hydroxytetrahydropyran-2-ones.