Access to 2,3-bis(buta-1,3-diynyl)pyridines
. Mendeleev Commun. 2011
The selectivity of halogen substitution in Pd/Cu-catalyzed cross-coupling of 2-chloro-3-iodopyridines and 2-bromo-3-iodopyridines with 1,3-diynes was investigated. Significant difference in the rate of substitution of chlorine versus iodine atom in 2-chloro-3-iodopyridines led to selective carbon-carbon bond formation only at iodine position. Sonogashira cross-coupling of 2-bromo-3-iodopyrydine with terminal diacetylenes, on the other hand, produces either 3-(buta-1,3-diynyl) or 2,3-bis(buta-1,3-diynyl)pyridine depending on reaction conditions.