Synthesis of some novel nitrones and their applications in organic syntheses

Nitrones are reactive 1,3-dipoles which readily form isoxazolidines and isoxazolines with olefinic and acetylenic dipolarophiles. In this study, a novel nitrones (56,57) were prepared in two steps in good yields. In the first step, N-phenylhydroxylamine was prepared then followed by a condensation reaction with some selected aldehydes. All nitrones were obtained in good yield (60-93%). In the second stage of the study, due to the importance of isoxazolidines in biologically active compounds, we aimed to extend our project by employing 3+2-cycloaddition reactions by using nitrones. After the success in the preparation of nitrones (9, 53-57), we investigated the synthesis of some novel isoxazolidine derivatives by 3+2 cycloaddition reaction. As a result of the reaction of nitrones with styrene, the desired isoxazolidine derivatives (58-63) were obtained in good yield and regioselectivity. All nitrones and cycloadducts were characterized by 1H, 13C, and other NMR techniques (DEPT, HETCOR, COSY). The stereochemistry of the major cycloadduct 61 was determined by X-ray crystallography.