Synthesis of five-membered cyclic nitrones based on the Lewis acid-catalysed [3+2]-annulation reaction of donor–acceptor cyclopropanes with 1,4,2-dioxazoles
作者:Zhe-Hao Wang、Huan-Huan Zhang、Peng-Fei Xu、Yong-Chun Luo
DOI:10.1039/c8cc04656e
日期:——
A novel synthesis of five-membered cyclic nitrones has been developed based on the Lewis acid-catalysed [3+2]-annulation reaction of D–A cyclopropanes with 1,4,2-dioxazoles. Broad substrate scope and generally good yield make this reaction useful in the preparation of nitrones. When a suitable 1,4,2-dioxazole was used, nitrone and tetrahydrofuran could be prepared in one pot with high atom economy
2, 2, 5-Tri-substituted-1, 3, 4-dioxazoles have been prepared by the reactions of benzhydroxamic acids with the diethylketals of such ketones as acetone, cyclohexanone, acetophenone and benzophenone. These dioxazoles decompose at elevated temperatures (above 150°C) into phenylisocyanates and ketones. A kinetic study of the decomposition reaction in nitrobenzene has been attempted, and the first-order rate constants have been obtained.