Type II photoreaction of benzoyl- and (benzoylmethyl)cyclohexanones: cyclohexanone ring inversion and other factors determining their photoreactivities
作者:Tadashi Hasegawa、Yiming Yang、Shuichi Kikuchi、Takayuki Nakamura、Yutaka Maeda
DOI:10.1002/poc.1008
日期:2006.2
intramolecular hydrogen bonding in the 1,4-biradical intermediate. When 6 is irradiated on a dry silica gel surface, the Type II reaction occurs to give 7, 8 and 9 in 38, 38 and 43% yield, respectively. The cyclization in the photoreaction of (benzoylmethyl)cyclohexane also increases from 68% in benzene to 81% on a dry silica gel surface. Restriction of conformational change in the 1,4-biradical is an important
X射线晶体结构分析表明,在溶液中经历有效的II型反应但未处于结晶状态的2-苯甲酰基环己酮(2)分子为具有赤道苯甲酰基的酮和椅子形式。3-2-苯甲酰(照射3)给出7- phenylhepten -4,7-二酮(4,61%)和环化产物的混合物5(25%)。2和3的高光反应性是由有效的环己酮环转化引起的。辐射后,2-(苯甲酰基甲基)环己酮(6)得到苯乙酮(7),2-环己烯酮(8)和环丁醇9分别以59、59和35%的产率,和1-苯基-3-丙基戊烷-1,4-二酮(10)分别以73和4%的产率得到7和环丁醇11。6和10消失的量子产率分别为0.68和0.67。照射2-(苯甲酰基甲基)-2-乙氧基羰基环己酮(12),分别以46%和51%的产率得到7和环丁醇13。消失12的量子产率为1.00,因此反向氢转移被1,4-双自由基中间体中的分子内氢键抑制。当6是在干燥硅胶表面照射,发生II型反应,得到7,8和9