Abstract: Four cyclobutane derivatives, rctt-1-(2-benzoxazolyl)-2-(4-chlorophenyl)-3-(4-pyridinyl) -4-phenylcyclobutane, rctt-1-(2-benzoxazolyl)-2-phenyl-3-(4-pyridinyl)-4-(4-chlorophenyl)cyclo-butane, rctt-1-(2-benzoxazolyl)-2-(4-chlorophenyl)-3-[2-(5-phenyloxazolyl)]-4-phenylcyclobutane and rctt-1-(2-benzoxazolyl)-2-phenyl-3-[2-(5-phenyloxazolyl)]-4-(4-chlorophenyl)cyclobutane, containing four different aryl groups, were synthesized by the cross-photodimerization reactions of different heteroarylethene monomers in sulfuric acid solution upon the irradiation of medium-pressure mercury lamp. Three photodimers were detected in the reaction, two of them were the photodimer of the monomer itself and the other was the cross-photodimer. The photolysis of the cross-photodimer upon the irradiation of low-pressure mercury lamp was carried out in dilute methanol solution and the reactions were traced by UV and HPLC. It was found that the cross-photodimer photolysized into trans-monomers at first, which were then converted to cis-monomers by trans-cis isomerization.

Key words: Cyclobutane, Heteroarylethene, Cross-photodimerization, Photolysis, Benzoxazole