Synthesis of Pyridine and Dihydropyridine Derivatives by Regio- and Stereoselective Addition to N-Activated Pyridines

A study was conducted to demonstrate the synthesis of pyridine and dihydropyridine derivatives by regio- and stereoselective addition to N-activated pyridines. The study examined the functionalization of N-activated pyridinium species by the addition of nucleophiles and electrophiles, along with transition metal-mediated functionalization. The investigations emphasized on the bimolecular addition of nucleophilic and electrophilic reagents directly to the ring of N-activated pyridinium species. It was observed that mixtures of substituted 1,2- and 1,4-dihydropyridines were frequently obtained upon the addition of an organometallic nucleophile in place of the addition at the 1-acyl carbon. The regioselectivity of addition to pyridines activated by methyl chloroformate was also investigated by other researchers who compared the nature of the nucleophile.