Lewis Acid-Promoted Ring-Contraction of 2,4,6,8-Tetrasubstituted 1,5-Diazacyclooctatetraenes to 2,4,6-Trisubstituted Pyridines
作者:Zhe Huang、Wen-Xiong Zhang、Zhenfeng Xi
DOI:10.1021/acs.orglett.7b03917
日期:2018.1.19
Ring-contraction of 2,4,6,8-tetrasubstituted 1,5-diazacyclooctatetraenes was highly efficiently promoted by Lewis acid such as TiCl4, affording 2,4,6-trisubstituted pyridines in excellent yields, along with release of a nitrile. A reaction mechanism involving a 6π electrocyclic ring-closing followed by a retro [2 + 2] cyclization of an 1-azetine moiety was supported by both experimental observations
2,4,6,8-四取代的1,5-二氮杂环辛酸酯的环缩合被路易斯酸如TiCl 4高效地促进,以优异的产率得到2,4,6-三取代的吡啶,并释放出腈。实验观察和密度泛函理论计算均支持了涉及6π电动环闭环,然后对1-azetine部分进行逆向[2 + 2]环化的反应机理。