<i>N</i>-Mesityl-<i>C</i>-acylketenimines: 1,5-Sigmatropic Shifts and Electrocyclization to Quinolines
作者:V. V. Ramana Rao、Belinda E. Fulloon、Paul V. Bernhardt、Rainer Koch、Curt Wentrup
DOI:10.1021/jo9722562
日期:1998.8.1
undergo a 1,5-H shift to o-quinoid imines 12/13, followed by electrocyclization to dihydroquinolines 14 (unobserved) and 15 (observed by NMR). The latter are easily oxidized to alkylquinoline-3-carboxylates or quinoline-3-carboxamides 16 by atmospheric oxygen. Ab initio calculations on model compounds 18-23 predict an energy barrier of ca. 38 kcal mol(-)(1) (161 kJ mol(-)(1)) for the 1,5-H shift in N-(o-
三唑6a-c的快速真空热解(FVT)产生α-氧杂环丁酮10,酯10a是可分离的。吡咯二酮8的FVT产生异构的酰亚胺基亚油基烯9a。在适度的FVT条件下(约350-400摄氏度),Ketenes 9和ketenimines 10通过甲氧基和二甲基氨基的1,3-移位进行热转化。9和10均可通过红外光谱在77 K或在12 K的Ar基质隔离下直接观察到。在400℃下,酮亚胺10经历1,5-H转变为邻喹啉亚胺12/13,然后电环化为二氢喹啉14(未观察到)和15(通过NMR观察)。后者容易被大气氧氧化为烷基喹啉-3-羧酸盐或喹啉-3-羧酰胺16。从头开始对模型化合物18-23进行的计算预测约有4.8的能垒。38 kcal mol(-)(1)(161 kJ mol(-)(1))通过过渡态TS19在N-(邻甲基苯基)酮亚胺中的1,5-H转移,随后是对二氢喹啉23a的电环化势垒通过ca的TS22a 16 kcal