苯乙烯基氮氧杂芳烃间的交叉光二聚反应

用中压汞灯(λ > 300 nm)照射4-苯乙烯基吡啶、2-苯乙烯基苯并噁唑和5-苯基-2-苯乙烯基噁唑三种杂芳基乙烯单体中任意两种的硫酸水溶液，得到三种交叉二聚体.用高效液相色谱跟踪研究了交叉光二聚反应，发现每组反应生成三种光二聚体，其中二种为单体自身的光二聚体，而另外一种是两种不同单体的交叉光二聚体.交叉二聚体通过柱色谱分离得到，其顺式头对尾结构经紫外、红外、氢谱、碳谱和元素分析确定.用紫外光谱和高效液相色谱跟踪研究了交叉光二聚体的稀溶液在低压汞灯（λmax=254 nm）照射下的光解反应.研究发现交叉二聚体能够彻底发生光解，首先生成原来的反式单体，所生成的反式单体容易发生异构化而生成顺式单体，最终建立起反顺异构化平衡.

Cross- photodimerization of 4- (2- phenylethenyl)pyridine,2- (2- phenylethenyl)benzoxazole and 5- phenyl- 2- (2- phenyl- ethenyl) oxazole

Three cross- photodimers were synthesized by irradiation of each two monomers of 4- (2- phenylethenyl)pyridine,2- (2- phenylethenyl)benzoxazole and 5- phenyl- 2- (2- phenylethenyl)oxazole in H2SO4 solution using medium- pressure Mercury lamp (λ > 300 nm) as light source.The cross- photodimerization was monitored by HPLC titration.The results showed that three photodimers were produced in each reaction,two of them were the self- photodimers and the other one was the cross- photodimer.The cross- photodimers were isolated by column chromatography and their structures with syn- head- to- tail configurations were determined by UV,IR,1H NMR,13C NMR and MS.The photolysis of the cross- photodimer was performed in dilute methanol solution upon the irradiation of low- pressure Mercury lamp (λ =254 nm) and monitored by HPLC and UV titration.It was found that the cross- photodimer was photolyzed into trans- monomers at first,and then the new formed trans- monomers were converted into cis- ones by the trans- cis isomerization.