Photochemical Elimination of Leaving Groups from Zwitterionic Intermediates Generated via Electrocyclic Ring Closure of α,β-Unsaturated Anilides
作者:Jinli Jia、Majher Sarker、Mark G. Steinmetz、Ruchi Shukla、Rajendra Rathore
DOI:10.1021/jo8017445
日期:2008.11.21
PhCO2(-), PhCH2CO2(-), PhO(-)) undergo photochemical electrocyclic ring closure to produce a zwitterionic intermediate. Further reaction of the intermediate results in expulsion of the leaving group to give an alpha-methylene lactam as the major product. In addition, a lactam product that retains the leaving group is formed via a 1,5-H shift in the intermediate. Elimination of the leaving group is generally
甲基丙烯酰苯胺,ArN(CH3)COC(CH2LG)= CH2,具有烯丙基离去基团(LG(-)= BocAla,PhCO2(-),PhCH2CO2(-),PhO(-))经历光化学电环闭合以产生两性离子中间体。中间体的进一步反应导致离去基团的排出,从而得到α-亚甲基内酰胺为主要产物。另外,通过中间体中的1,5-H移位形成保留离去基团的内酰胺产物。即使在LG(-)= PhO(-)的情况下,通常也优选消除离去基团,尽管在作为溶剂的苯中,保留酚盐基团的内酰胺成为唯一的光产物。电环闭环在对位COPh取代的苯胺衍生物的单线激发态下发生,并且不会被0.15 M的戊二烯或0淬灭。01 M 2-萘磺酸钠(2-NPS)作为三重态猝灭剂。根据激光闪光光解实验,可比较浓度的2-NPS强烈淬灭了在450-700 nm处观察到的三重激发态的瞬态吸收。在水性介质中,总产物的量子产率对离开基团的能力不敏感,并且在310
Photochemical electrocyclization of α,β-unsaturated anilides to give zwitterionic intermediates which eliminate carboxylate and phenolate leaving groups
作者:Jinli Jia、Mark G. Steinmetz、Ruchi Shukla、Rajendra Rathore
DOI:10.1016/j.tetlet.2008.05.079
日期:2008.7
alpha, beta-Unsatu rated anilides bearing allylic leaving groups undergo photochemical electrocyclic ring closure to produce zwitterionic intermediates which eliminate carboxylate and phenolate leaving groups. (c) 2008 Elsevier Ltd. All rights reserved.