A dinuclear copper(i) thiodiacetate complex as an efficient and reusable 'click' catalyst for the synthesis of glycoconjugates.

We report herein the facile synthesis and structural characterization of a highly stable dinuclear Cu(i) complex, [(PPh3)2Cu(μ-tda)Cu(PPh3)2]·6H2O 1 (tda = thiodiacetate anion), in which the Cu-Cu distance is 7.197 Å. This "pre-formed" complex serves as an extremely efficient and recyclable homogeneous catalyst (2 mol%, 30 min) for CuAAC in dichloromethane solvent. The synthesis of a variety of glycoconjugates under ambient conditions is successfully achieved using 1 as a catalyst. The products are obtained in high yields and very short reaction times while complying with the "click protocols". A simpler procedure solely involving the mixing of substrates with 1 (i.e. base free and solvent free) gave the corresponding glycoconjugate in 10 min using 2 mol% of the catalyst.