Isoxazoles. XXII. A New Synthesis of 4-Isoxazolines and Their Thermal Conversion into Pyrroles

Thirteen N-substituted 4-isoxazoline derivatives were obtained by reaction of 3-unsubstituted and 3, 5-disubstituted isoxazolium salts with Grignard reagents. Similarly, 3-benzyl-2-methyl-2, 3, 4, 5-tetrahydronaphth [2, 1-d] isoxazoles and 3-benzyl-2-ethyl-2, 3-dihydrobenzisoxazole were produced by reaction of the corresponding quaternary salts with benzylmagnesium chloride. Thermal reactions of some 4-isoxazoline derivatives and 3-benzyl-2, 3, 4, 5-tetrahydronaphth [2, 1-d] isoxazole derivatives leading to substituted pyrrole derivatives and 3H-benz [e] indole derivatives were investigated. A tentative mechanism for the formation of pyrrole from 4-isoxazoline is also presented.