Studies on new radical precursors, benzoselenohydroximates and N-alkoxyphthalimides

Abstract

New types of alkyl, aminyl and alkoxy radical precursors were developed. Se-Phenyl benzoselenohydroximate(BSH) was prepared from the reaction of benzohydroxamoyl chloride and sodium salt of benzeneselenol in high yields. Acyl, carbamate, ether and carbonate derivatives of BSH were prepared as alkyl, aminyl, alkoxy and alkoxycarbonyloxy radical precursors, respectively. All the above derivatives were thermally stable. i) Acyl derivatives were prepared in quantitative yield by the reaction of BSH either with an acid chloride or with a carboxylic acid. The reaction of the acyl derivatives with Bu3SnH/AIBN gave the decarboxylated product in quantitative yield. The relative reactivity of the precursors toward tin radical was in the following order; iodide > bromide > BSH ester > vinyl bromide > xanthate > selenide. ii) Carbamate derivatives of BSH were prepared by two methods such as phosgene/amine method and isocyanate method in high yield. When the carbamate was subjected to the standard radical conditions the corresponding amines were obtained in high yields as a tosyl amide after the tosylation. iii) Ether derivatives of BSH were also prepared in high yield by the reaction of BSH with alkyl bromides and cesium carbonate. Alkoxy radicals were cleanly generated from the precursors under the standard radical conditions. iv) Carbonate derivatives of BSH were prepared in resonable yields by the reaction of BSH with triphosgene and alcohols. Various five and six-membered cyclic carbonate products were performed in moderate yields through the intramolecular cyclization of alkenyloxycarbonyloxy radicals. N-Alkoxyphthalimides were prepared as an alkoxy radical precursor in high yields by the reaction of N-hydroxyphthalimide either with an alkyl halide or with an alcohol and DEAD/PPh3. Alkoxy radicals were generated in high yields from N-alkoxyphthalimides under the standard radical conditions. The relative reactivity of the N-alkoxyphthalimides and the known alkyl r...