An alternative isoxazole route to α-alkoxycarbonyl-β-diketones

Abstract

Cycloaddition of oxygen-functionalized nitrite oxides to the enamine from ethyl acetoacetate produces 4-ethoxycarbonyl-5-methylisoxazoles carrying a 3-tetrahydropyranyloxymethyl, 3-diethoxymethyl or 3-ethoxycarbonyl substituent; the 3-formylisoxazole is prepared from the former two and condensed in situ with phosphoranes to give 3-alkenylisoxazoles that are cleaved by hexacarbonylmolybdenum or hydrogenolysis to afford α-alkoxycarbonyl-β-diketones.