(Iminophosphorane)copper(I) Complexes as Highly Efficient Catalysts for 1,3-Dipolar Cycloaddition of Azides with Terminal and 1-Iodoalkynes in Water: One-Pot Multi-Component Reaction from Alkynes and in situ Generated Azides

Treatment of water-soluble phosphanes PTA (1) and DAPTA (2) with an equimolecular amount of azides (RO)(2)P(=S)N-3 (R = Et, Ph) leads to high-yield formation of the N-thiophosphorylated iminophosphorane derivatives 3b and 4a,b, respectively. The reaction of these new iminophosphorane ligands with [Cu(NCCH3)(4)][PF6] (in a 2:1 molar ratio) has been investigated. The resulting (iminophosphorane)copper(I) complexes 5b and 6a,b are efficient catalysts for the three-component cycloaddition reaction (organic halide, NaN3 and terminal alkynes) in aqueous media to afford regioselectively, under mild and aerobic conditions according to click laws, 1,4-disubstituted triazoles with a broad substrate scope and functional compatibility. The unprecedented application of the analogous (iminophosphorane)copper(I) catalyst 5a to a one-pot three-component reaction with 1-iodoalkynes as an internal alkyne in aqueous medium is also reported. ESI-MS analysis of 5a in water and DFT theoretical calculations [B3LYP/6-31G(d)] have been carried out providing valuable insight into the actual active species responsible for catalytic activity in water.