Synthesis and functionalization of 2-iodoimidazo[1,2-a]pyridines in palladium-catalysed amino-, aryloxy- and alkoxycarbonylations

Imidazo[1,2-a]pyridines possessing carboxamido and ester functionalities in 2- and 6-positions were synthesised in palladium-catalysed amino- and alkoxy/aryloxycarbonylation using a great variety of amines and alcohols/phenols as N- and O-nucleophiles, respectively. The corresponding iodoheteroaromatics, used as substrates, were synthesised from the substituted 2-aminopyridines, terminal alkynes and iodine in copper-catalysed oxidative ring-closure─iodination reaction sequence. Mono- and dinuclear copper-2-aminopyridine complexes, used as pre-formed catalysts, were characterised by X-ray crystallography. The amides and esters were obtained in moderate to high yields mainly depending on the nucleophile and not on the structure of the 2-iodo[1,2-a]pyridine substrates.