Novel cyano-activated Cu() complexes of arylhydrazones of active methylene nitriles and their catalytic application for azide-alkyne cycloaddition in water and glycerol

The reaction of 2-(2-(dicyanomethylene)hydrazineyl)benzoic acid (H 2 L 1 ) with copper( ii ) acetate in the absence or presence of imidazole (im), 4,4′-bipyridine (4,4′-bipy) or pyridine (py) leads to the new complexes [Cu 2 (CH 3 OH) 2 (μ-L 1a ) 2 ] ( 1 ), [Cu(L 1a )(im)] ( 2 ), [Cu(L 1a )(H 2 O)(4,4′-bipy)]·H 2 O ( 3 ) or [Cu(L 1a )(py)] n ( 4 ), respectively, where (L 1a ) 2− = ( Z )-1-(2-carboxylatophenyl)-2-(1-cyano-2-imino-2-methoxyethylidene)hydrazin-1-ide. A one-pot activation of nitrile groups in the reaction of copper( ii ) acetate monohydrate with 2-(2-(dicyanomethylene)hydrazineyl)terephthalic acid (H 3 L 2 ) in the presence of pyridine in methanol affords the trinuclear Cu( ii ) complex [Cu(py) 2 {Cu(py)(μ-L 2a )} 2 ] ( 5 ), where (L 2a ) 3− = ( Z )-2-((1-cyano-2-imino-2-methoxyethylidene)-1-(2,5-dicarboxylatophenyl)hydrazin-1-ide). Both arylhydrazone ligands and the auxiliary ligands were used to modulate the nuclearity and design of the supramolecular arrangements of the obtained Cu( ii ) complexes. The complexes were characterized by elemental analyses, electrospray ionization mass spectrometry (ESI-MS), and FT-IR spectroscopy. Their molecular structures were established using single crystal X-ray diffraction (SCXRD) analysis. The catalytic activity of the complexes was investigated for the microwave assisted 1,3-dipolar azide-alkyne cycloaddition reaction using a mixture of water and glycerol as reaction medium. Pre-catalyst 1 was found to be the most efficient one by affording a quantitative conversion to 1,4-disubstituted-1,2,3-triazoles after 30 minutes at 125 °C. The catalytic system proceeds with a broad scope of substrates according to "Click" rules. Synthesis of five novel copper-arylhydrazone complexes and their catalytic activity for microwave-assisted click reaction in water and glycerol.