Stereoselectivity of cycloadditions of arylnitrile oxides to 5-alkoxy-2(5H)-furanone

Abstract

1,3-Dipolar cycloaddition of arylnitrile oxides to 5-alkoxy-2(5H)-furanones (II) and 5-hydroxy-2(5H)-furanone leads regiospecifically to 4-oxo-3a,4,6,6a-tetrahydrofuro[3,4-d]isoxazole derivatives IIIa-IIIj. The alkoxy derivatives give exclusively products of exo-configuration (III), whereas the hydroxy compound affords a 52 : 48 mixture of both diastereoisomers IIIj and IVj. Reaction of III with ammonia furnished diastereoisomeric tetrahydropyrrolo[3,4-d]isoxazoles V and VI, reaction with hydrazines led to hexahydroisoxazolo[4,5-d]pyridazin-7-one derivatives VII.