Regio- and stereoselective synthesis of 1,4-dihydropyridines by way of an intramolecular interaction of a thiocarbonyl or carbonyl with a pyridinium nucleus
Chiral 1,4-dihydropyridines were prepared by the regio- and stereoselective addition of ketenesilylacetals and organometallic reagents to pyridinium salts. In the addition reaction, an intramolecular interaction between the thiocarbonyl or carbonyl with the pyridinium nucleus plays an important role in bringing about the selectivities. The absolute configuration of the newly produced stereogenic