Photochemical Cleavage and Release of Para-Substituted Phenols from α-Keto Amides
作者:Chicheng Ma、Yugang Chen、Mark G. Steinmetz
DOI:10.1021/jo060338x
日期:2006.5.1
= Me) with para-substituted phenolic substituents (Y = CN, CF3, H) undergo photocleavage and release of 4-YC6H4OH with formation of 5-methyleneoxazolidin-4-ones 7a,b. For both 5a,b quantum yields range from 0.2 to 0.3. The proposed mechanism involves transfer of hydrogen from an N-alkyl group to the keto oxygen to produce zwitterionic intermediates 8a−c that eliminate the para-substituted phenolate
在水性介质中,α-酮酰胺4-YC 6 H 4 OCH 2 COCON(R)CH(R')CH 3(5a,R = Et,R'= H; 5b,R = i具有对位取代的酚取代基(Y = CN,CF 3,H)的Pr,R'= Me)发生光裂解并释放4-YC 6 H 4 OH,并形成5-亚甲基恶唑烷-4-酮7a,b。对于两个5a,b的量子产率都在0.2到0.3之间。所提出的机理涉及将氢从N-烷基转移至酮氧以产生两性离子中间体8a - c,其消除对位取代的酚盐离去基团。生成的亚硝酸根离子H 2 C C(OH)CON +(R)C(R')CH 3 9a,b在分子内环化得到7a,b。在CH对于photoelimination降低量子产率3 CN,CH 2氯2,或C 6 H ^ 6由于竞争环化8A,b,得到恶唑烷-4-酮,其保留的离去基团的产品4-YC 6 ħ 4 ö -(Y = H,CN)。被观察到,以进行环化反应在非水介质更大的倾向Ñ,ñ