[2+2]Photocycloaddition of 2-(dibenzylamino)ethyl 3-benzoylacrylate in a crystalline state: weak intermolecular interactions as important factors determining efficiency of the solid-state photoreaction
作者:Tadashi Hasegawa、Kaori Ikeda、Yuko Yamazaki
DOI:10.1039/b105970j
日期:2001.11.15
Upon UV irradiation 2-(dibenzylamino)ethyl 3-benzoylacrylate in a crystalline state undergoes efficient [2+2]photocycloaddition to give a head-to-tail dimer, bis[2-(dibenzylamino)ethyl] c-2,t-4-dibenzoylcyclobutane-r-1,t-3-dicarboxylate, quantitatively. The X-ray structure analysis shows CH/π interactions between aliphatic and aromatic C–H bonds and benzene rings make the orientation of the benzoylacrylate molecules in a crystalline state suitable for the [2+2]photocycloaddition. The aliphatic CH/π interaction is responsible for formation of the cis-configuration between the 2-(dibenzylamino)ethoxycarbonyl and benzoyl groups in the cyclobutanedicarboxylate. The cyclobutanedicarboxylate is hydrolyzed quantitatively to 2,4-dibenzoylcyclobutane-1,3-dicarboxylic acid, which is not
directly produced from irradiation of crystals of 3-benzoylacrylic acid.
在紫外线照射下,2-(二苄基氨基)乙基3-苯甲酰基丙烯酸酯在结晶状态下发生有效的[2+2]光环加成反应,生成头对尾二聚体,即双[2-(二苄基氨基)乙基]c-2,t-4-二苯甲酰基环丁烷-r-1,t-3-二羧酸酯,且反应是定量进行的。X射线结构分析显示,脂肪族和芳香族C-H键与苯环之间的CH/π相互作用使得苯甲酰丙烯酸酯分子在结晶状态下的取向适合进行[2+2]光环加成反应。脂肪族CH/π相互作用导致环丁烷二羧酸酯中的2-(二苄基氨基)乙氧基羰基和苯甲酰基之间形成顺式构象。环丁烷二羧酸酯被定量水解为2,4-二苯甲酰基环丁烷-1,3-二羧酸,而后者并非由3-苯甲酰基丙烯酸晶体照射直接产生的。