Copper(I)-mediated preparation of new pyrano[3′,4′:4,5]imidazo[1,2-a]pyridin-1-one compounds under mild palladium-free conditions

A general and efficient Cu(I)-mediated cross-coupling and heterocyclization reaction of 3-iodoimidazo[1,2-a]pyridine-2-carboxylic acid, and terminal alkynes was developed under very mild conditions. This method allows the introduction in one pot of a third ring fused in positions 2 and 3 of the imidazo[1,2-a]pyridine core with reasonable yields and total regioselectivity. This procedure does not require the use of any expensive supplementary additives, and is palladium-free.