Construction of pyrazolo[3,4-b]pyridines and pyrazolo[4,3-c]pyridines by ring closure of 3-acylpyridine N-oxide tosylhydrazones
作者:William J. Lominac、Megan L. D’Angelo、Mark D. Smith、Darius A. Ollison、James M. Hanna
DOI:10.1016/j.tetlet.2011.12.055
日期:2012.2
3-Acylpyridine N-oxide tosylhydrazones give good overall yields of a mixture of pyrazolo[3,4-b]pyridines and pyrazolo[4,3-c]pyridines when treated with an electrophilic additive and an amine base. (Z)-Hydrazones cyclize readily, while (E)-hydrazones fail to react under the reported conditions. The reaction takes place at room temperature, and moderate regiocontrol over the cyclization can be achieved
当用亲电子添加剂和胺碱处理时,3-酰基吡啶N-氧化物甲苯磺酰腙产生良好的吡唑并[3,4- b ]吡啶和吡唑并[4,3- c ]吡啶混合物的总产率。( Z )-腙容易环化,而 ( E )-腙在报道的条件下不能反应。该反应在室温下进行,通过改变亲电子试剂/溶剂组合可以实现对环化的适度区域控制。