N-Heterocyclic Carbenes of Indazole: Ring Enlargement Reactions by α-Halo Ketones and Dehalogenations of Vicinal Dihalides
作者:Andreas Schmidt、Bohdan Snovydovych、Mimoza Gjikaj
DOI:10.1055/s-2008-1067215
日期:2008.9
ring enlargement to cinnolines. Reaction with 2-bromo-2,3-dihydro-1Η-inden-1-one gives a 4-hydroxyspiro[cinnoline-3,2'-inden]-1'-one by ring enlargement reaction (X-ray crystal structure analysis). Vicinal dibromides undergo debromination under these conditions to give alkenes, and substrates with 1,2-dibromoethene partial structure give acetylenes. As 3-bromoindazole is found as the second product of
在脱羧时,1,2-二甲基吲唑鎓-3-羧酸盐形成 N-杂环卡宾 (l,2-dimethylindazol-3-ylidene),使 α-卤代酮去质子化。所得的吲唑盐和相应的烯醇化物形成 1:1 的加合物,其环扩大为 cinnolines。与 2-bromo-2,3-dihydro-1H-inden-1-one 反应通过扩环反应得到 4-羟基螺[cinnoline-3,2'-inden]-1'-one(X 射线晶体结构分析) )。邻二溴化物在这些条件下脱溴生成烯烃,而具有 1,2-二溴乙烯部分结构的底物生成乙炔。由于发现3-溴吲唑是该反应的第二个产物,因此提出了由吲唑的N-杂环卡宾夺取Br + 引发的E 1cb 机制。