Formation of Benzofuro[2, 3-c]tetrahydropyran-3, 4-dione 4-Oximes from 4-Substituted 5-Hydroxymethyl-3-methoxycarbonyl-2-isoxazoline 2-Oxides

Abstract

4-Substituted 5-hydroxymethyl-3-methoxycarbonyl-2-isoxazoline 2-oxides (1) reacted with an excess of titanium tetrachloride in dichloromethane to yield a new type of functionalized heterocycle, benzofuro[2, 3-c]tetrahydropyran-3, 4-dione 4-oximes (2). The structure of the 7-chloro derivative (2a) was determined by single crystal X-ray analysis and a mechanism is proposed for the formation of 2 from 1.