The dicopper-substituted ﾎｳ-Keggin silicotungstate TBA4[ﾎｳ-H2SiW10O36Cu2(ﾎｼ-1,1-N3)2] (I, TBA = tetra-n-butylammonium) could act as an efficient precatalyst for the regioselective 1,3-dipolar cycloaddn. of org. azides to alkynes. Various combinations of substrates (four azides and eight alkynes) were efficiently converted to the corresponding 1,2,3-triazole derivs. in excellent yields without any additives. The present system was applicable to a larger-scale cycloaddn. of benzyl azide to phenylacetylene under solvent-free conditions (100 mmol scale) in which 21.5 g of the anal. pure corresponding triazole could be isolated. In this case, the turnover frequency and the turnover no. reached up to 14 800 h-1 and 91 500, resp., and these values were the highest among those reported for the copper-mediated systems so far. In addn., I could be applied to the one-pot synthesis of 1-benzyl-4-phenyl-1H-1,2,3-triazole from benzyl chloride, sodium azide, and phenylacetylene. The catalyst effect, kinetic, mechanistic, and computational studies show that the reduced dicopper core plays an important role in the present 1,3-dipolar cycloaddn. [on SciFinder(R)]
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