Synthesis of 3-aryl-2-phosphinoimidazo[1,2-]pyridine ligands for use in palladium-catalyzed cross-coupling reactions.

3-Aryl-2-phosphinoimidazo[1,2-]pyridine ligands were synthesized from 2-aminopyridine two complementary routes. The first synthetic route involves the copper-catalyzed iodine-mediated cyclizations of 2-aminopyridine with arylacetylenes followed by palladium-catalyzed cross-coupling reactions with phosphines. The second synthetic route requires the preparation of 2,3-diiodoimidazo[1,2-]pyridine or 2-iodo-3-bromoimidazo[1,2-]pyridine from 2-aminopyridine followed by palladium-catalyzed Suzuki/phosphination or a phosphination/Suzuki cross-coupling reactions sequence, respectively.