Mizuki Yamada

Copper-catalyzed [3 + 2] cycloaddition of (phenylethynyl)di-p-tolylstibane with organic azides

Summary Trisubstituted 5-stibano-1H-1,2,3-triazoles were synthesized in moderate to excellent yields by the Cu-catalyzed [3 + 2] cycloaddition of a ethynylstibane with organic azides in the presence of CuBr (5 mol %) under aerobic conditions. The reaction of 5-stibanotriazole with HCl, I2, and NOBF4 afforded 1-benzyl-4-phenyltriazole, 1-benzyl-5-iodo-4-phenyltriazole, and a pentavalent organoantimony compound, respectively.

Synthesis, antitumor activity, and cytotoxicity of 4-substituted 1-benzyl-5-diphenylstibano-1H-1,2,3-triazoles

Trisubstituted 5-organostibano-1H-1,2,3-triazoles (3a-f) were synthesized by the Cu-catalyzed azide-alkyne cycloaddition of various ethynylstibanes (1) with benzylazide (2) in the presence of CuBr (5 mol%) under aerobic conditions. The reaction of 5-stibanotriazoles with HCl afforded C5-unsubstituted 1,2,3-triazoles (4a-f). The antitumor activity of trisubstituted 5-organostibano-1H-1,2,3-triazoles (3a-f) and their 5-unsubstituted 1,2,3-triazoles (4a-f) were evaluated in several tumor cell lines. All 5-stibanotriazoles (3a-f) exerted an excellent antitumor activity. On the contrary, 5-unsubstituted 1,2,3-triazoles (4a-f) without a diphenylantimony group in the molecule exhibited very low antitumor activity compared with 5-stibanotriazoles (3a-f). In compounds of both the series, the substituted 4-butyl group appeared to decrease antitumor activity. However, results suggested that organometal (antimony) in the molecule was required for greater antitumor activity. In addition, all 5-stibanotriazoles (3a-f), but not all 5-unsubstituted 1,2,3-triazoles (4a-f), exhibited cytotoxicity in normal vascular endothelial cells derived from bovine aorta. Among the compounds (3b-e) that exhibited excellent antitumor activity, those with 4-methylphenyl (3b) and 1-cyclohexenyl (3e) showed relatively low cytotoxicity to vascular endothelial cells. Together, these results suggest that trisubstituted 5-organostibano-1H-1,2,3-triazoles, including compounds 3b and 3e, may serve as potential anticancer therapeutic drugs in the future.

Synthesis and photophysical properties of novel benzophospholo[3,2-b]indole derivatives

The parent benzophospholo[3,2-b]indole was prepared by the reaction of dichlorophenylphosphine with a dilithium intermediate, which was prepared in two steps from 2-ethynyl-N,N-dimethylaniline. Using the obtained benzophosphole-fused indole as a common starting material, simple modifications were carried out at the phosphorus center of the phosphole, synthesizing various functionalized analogs. The X-ray structure analysis of trivalent phosphole and phosphine oxide showed that the fused tetracyclic moieties are planar. The benzophosphole-fused indoles, such as phosphine oxide, phospholium salt, and borane complex, exhibited strong photoluminescence in dichloromethane (Φ = 67–75%).