New catalytic systems for coupling of dihalogenopyridines and 5,5″-dibromo-2,2′:6′,2″-terpyridine with 5-bromo-2-trialkylstannylpyridines and 2-trialkylstannylthiophenes

Catalytic activity of a number of systems consisting of a stable palladium precursor ([Pd(acac)2], [PdCl2(1,5-COD)], …) and a ligand (phosphines, AsPh3, SbPh3, P(OPh)3, …) in Stille coupling reactions of 2,6-dihalogenopirydines with 5-bromo-2-trialkylstannylpyridines, forming 5,5″-dibromo-2,2′:6′,2″-terpyridine. A new, active, selective and convenient catalytic system for this reaction, consisting of [Pd(acac)2] and triphenyl phosphite was found. A new, four membered library of thienyl-substituted pyridine and terpyridine ligands has been synthesized at the same conditions, by coupling of 2-tributylstannyl-3,4-ethylenedioxythiophene or 5-tributylstannyl-2,2′-bithiophene with 5,5″-dibromo-2,2′:6′,2″-terpyridine or 3,5-dibromopyridine.