Palladium-catalyzed highly regioselective 2-alkynylation of 2,x-dihalopyridines

2,4-Dibromopyridines reacted with arylacetylenes, catalyzed by Pd(CF3COO)2/CuI/PPh3 in the presence of i-Pr2NH in CH3CN at reflux for 24 h, to afford 2-alkynylpyridines in good to high yields, while 2,3- and 2,5-dihalopyridines reacted with arylacetylenes, catalyzed by Pd(OAc)2/CuI/PPh3 in the presence of i-Pr2NH in CH3CN at reflux for 24 h, to afford 2-alkynylpyridines in good to high yields.