Intramolecular nitrone-quinone cycloaddition. Formation of isomeric isoxazolidines by kinetic and thermodynamic control

AG Schultz, WG McMahon…

Index: Schultz, Arthur G.; McMahon, Wayne G.; Kullnig, Rudolph K. Journal of Organic Chemistry, 1987 , vol. 52, # 17 p. 3905 - 3909

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Citation Number: 9

Abstract

Cyclization of nitrone 5a occum at 25" C to give isoxazolidine 6a; 6a is unstable at higher reaction temperatures and rearranges to isoxazolidine 7a presumably via a 1, 3-dipolar cycloreversion to regenerate 5a. Structural assignments for 6a and 7a were made by X-ray diffraction analyses. Only the linearly fused isoxazolidine 7b was obtained by cyclization of nitrone 5b. Isoxazolidine 7b is stable in refluxing benzene but in refluxing methanol ...