An efficient 2-(2-Pyridyl)imidazole based copper catalyst for N-Arylation of N-heterocycles

An earth-abundant copper based 2-(2-pyridyl)imidazole (L) complex of the type [CuL2(NO3)](NO3), (1) has been characterized spectroscopically, structurally and electrochemically. The copper(II) in 1 is present in a distorted trigonal-bipyramidal coordination environment and has structural similarity with the well-known 1,10-phenan-throline (L') coordinated copper catalytic system used in Ullmann-type N-arylation reactions. Complex 1 is more electronically rich than the corresponding 1,10-phenanthroline-based complex, [CuL'(2)(NO3)](NO3), (2) and shows excellent catalytic activity towards N-arylation of nitrogen heterocycles like pyrazole, imidazole, benz-imidazole and less reactive indole with aryl-iodides and-bromides. Electronically deficient aryl-chlorides are also successful as a coupling agent for N-arylation with good yields. Wide spectrums of common organic functional groups are also tolerated in our catalytic conditions. A possible mechanistic route for this N-arylation reaction has been proposed by considering several experimental and spectroscopic results along with computational details.