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

摘要

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-trialkylstannylpyri-dines,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-ethylencdioxythiophene or 5-tributylstannyl-2,2'-bithi-ophene with 5,5"-dibromo-2,2':6',2"-terpyridine or 3,5-dibromopyridine.