Catalytic synthesis and asymmetric reduction of pyridylglyoxylic amides and esters

The preparation of 2-pyridyl- and 4-pyridylglyoxylic esters and amides in m oderate to high yields via palladium-catalyzed double carbonylation of 2-io do- and 4-iodopyridines is reported. The effect of temperature, CO pressure , solvent, nature and concentration of nucleophile, nature of catalyst prec ursor, and substituents on iodopyridines has been investigated. The reducti on of 4-pyridylglyoxylate esters into the corresponding alpha -hydroxy este rs via ruthenium-catalyzed asymmetric hydrogenation or using alpine-borane proceeded in high yields but poor enantioselectivity. The results for the c arbonylation and the hydrogenation catalytic processes are discussed in ter ms of electronic effects induced by the pyridyl ring.