Base treatment of the pyridinium bromides 11a-e gives rise to the formation of the dihydropyridoazepines 14a-e as the only monomolecular products. The reaction takes place by initial deprotonation to the ylides 12, which undergo 8pi-electrocyclization affording the seven-membered-ring systems; no products of a dipolar 6pi-cyclization were detected. On the basis of quantum mechanical calculations a
溴化
吡啶鎓11a-e的碱处理引起
二氢吡啶并氮杂卓14a-e的形成,这是唯一的单分子产物。该反应通过最初的去质子化反应产生的酰基化物12进行8π电环化,得到七元环系统。没有检测到偶极6pi环化的产物。在量子力学计算的基础上,合理化了电环化过程的周选择性。