The title compound (C28H21ClN2O, Mr = 436.92) was synthesized by the cross- photodimerization of (E)-2-(2-phenylethenyl)benzoxazole and (E)-4-[2-(4-chlorophenyl)ethenyl]- pyridine in sulfuric acid solution. Its molecular structure has been unequivocally determined by X-ray crystallography. The title compound belongs to triclinic system, space group P?with cell parameters: a = 9.648(3), b = 10.458(4), c = 12.106(4) , a = 89.089(7), b = 75.644(6), g = 68.441(7)? V = 1096.7(7) 3, Z = 2, Dc = 1.323 g/cm3, F(000) = 456 and m(MoKa) = 0.198 mm-1. The final R and wR are 0.0627 and 0.1285, respectively for 1737 observed reflections with I > 2s(I). S = 0.921 and (/s)max = 0.001. The cyclobutane ring has a puckered conformation with four different aryl groups substituted on each carbon atom. The dihedral angles of the cyclobutane ring are 20.2 and 20.6? The bond distances of the cyclobutane ring are 1.541, 1.555, 1.560 and 1.563 ? respectively, which are slightly longer than that of the normal CC single bond. The title compound is the only cross-dimer and its two heteroaryl groups are situated at the trans-1,3 position of the cyclobutane ring, revealing that the cross-photodimerization proceeds in a head-to-tail pattern with high stereo-selectivity. The title compound (C28H21ClN2O, Mr = 436.92) was synthesized by the cross photodimerization of (E) -2- (2- phenylethenyl) benzoxazole and (E) -4- [2- (4- chlorophenyl) ethenyl] The title compound belongs to triclinic system, space group P? with cell parameters: a = 9.648 (3), b = 10.458 (4), c = 12.106 (4) a = 89.089 (7) b = 75.644 (6) g = 68.441 (7) V = 1096.7 (7) 3 Z = 2 Dc = 1.323 g / cm3 F (000) = 456 and m (MoKa) = 0.198 mm-1. The final R and wR are 0.0627 and 0.1285, respectively for 1737 observed reflections with I> 2s (I). S = 0.921 and (/ s) max = 0.001. The cyclobutane ring has The dihedral angles of the cyclobutane rings are 20.2 and 20.6? The bond distances of the cyclobutane rings are 1.541, 1.555, 1.560 and 1.563? respectively, which are slightly longer than that of the normal CC single title. The title compound is the only cross-dimer and its two heteroaryl groups are situated at the trans-1,3 position of the cyclobutane ring, revealing the cross-photodimerization proceeds in a head-to-tail pattern with high stereo -selectivity.