Experimental and Theoretical DFT Study on Synthesis of Sterically Crowded 2,3,3,(4) 5-Tetrasubstituted-4-nitroisoxazolidines via 1,3-Dipolar Cycloaddition Reactions Between Ketonitrones and Conjugated Nitroalkenes

摘要

1,3-Dipolar cycloaddition reactions between ketonitrones (1a-e) and beta-substituted nitroalkenes (2a-d) proceed under mild conditions, with complete regioselectivity, and lead with high yields to sterically crowded 2,3,3,5-tetrasubstituted-4-nitroisoxazolidines (3a-f). Reaction course may be interpreted on the basis of nature of local, nucleophile-electrophile interactions. Moreover, density functional theory (DFT) simulations of reaction paths suggest that these reactions should be considered as polar, "one-step two-stage" cycloadditions. Subsequently, it has been found that similar reactions between ketonitrones and a-substituted nitroalkenes do not allow to obtain the expected 2,3,3,4-tetrasubstituted-4-nitroisoxazolidines.