Isoxazoles substituted with an electron-withdrawing group at the 4-position undergo electrochemical and yeast-catalysed N–O bond cleavage. The electrolysis is much more efficient and, with acyl- and alkoxycarbonyl-substituted isoxazoles, it affords the enolised dicarbonylimine functionality characteristic of the herbicide Grasp®. Regioisomeric 4- and 5-substituted isoxazoles are accessible through nitrile oxide cycloaddition chemistry, using halogen as a steric auxiliary to control the regiochemistry of reaction. Crystal data for compounds 11 and 19b are presented.
4位带有吸电子基团的
异恶唑在电
化学和酵母催化下发生N–O键断裂。电解过程更为高效,并且对于酰基和烷氧羰基取代的
异恶唑,它能生成草剂Grasp®所特有的烯醇化双羰基
亚胺结构功能。通过使用卤素作为立体辅助控制反应区域
化学的
氰氧基团环加成反应,可以获得4位和5位取代的
异恶唑的区域异构体。化合物11和19b的晶体数据已给出。