Quinoline synthesis: scope and regiochemistry of photocyclisation of substituted benzylidenecyclopentanone O-alkyl and O-acetyloximes
作者:Mark Austin、Oliver J. Egan、Raymond Tully、Albert C. Pratt
DOI:10.1039/b711620a
日期:——
resulting in 7-substituted products. 2-Furylmethylene and 2-thienylmethylene analogues yield annulated furo- and thieno-[2,3e]pyridines respectively. Sequential E- to Z-benzylidene group isomerisation and six pi-electron cyclisation steps result in formation of a short-lived dihydroquinoline intermediate which spontaneously aromatises by elimination of an alcohol or acetic acid. For 2-benzylidenecyclopentanone
在甲醇中辐照取代的2-亚苄基环戊酮的O-烷基和O-乙酰肟,可以方便地合成烷基,烷氧基,羟基,乙酰氧基,氨基,二甲基氨基和苯并取代的环喹啉。对位取代基可生成6位取代的2,3-二氢-1H-环戊基[b]喹啉,其中8位取代的产物可从邻位取代的起始原料中获得。间位取代的前体的反应是高度区域选择性的,烷基取代基导致5-取代的2,3-二氢-1H-环戊[b]喹啉和更强的供电子取代基,通常产生7-取代的产物。2-呋喃基亚甲基和2-噻吩基亚甲基类似物分别产生环呋喃基和噻吩并[2,3e]吡啶。依次的E-到Z-亚苄基异构化和六个π电子环化步骤导致形成短寿命的二氢喹啉中间体,该中间体通过消除醇或乙酸而自发芳香化。对于2-亚苄基环戊酮O-烯丙基肟,两个步骤均涉及单重态激发态。