Regio- and stereoselective synthesis of 1,4-dihydropyridines by way of an intramolecular interaction of a thiocarbonyl or carbonyl with a pyridinium nucleus
S. Yamada et al., Regio- and stereoselective synthesis of 1,4-dihydropyridines by way of an intramolecular interaction of a thiocarbonyl or carbonyl with a pyridinium nucleus, TETRAHEDRON, 57(43), 2001, pp. 8939-8949
Chiral 1,4-dihydropyridines were prepared by the regio- and stereoselective
addition of ketene silyl acetals 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 ro
le in bringing about the selectivities. The absolute configuration of the n
ewly produced stereogenic center of the 1,4-dihydropyridines was determined
by X-ray analysis and CD Cotton effects after conversion into the appropri
ate derivatives. The working model for the stereoselectivity was proposed b
ased on the ab initio calculations at the RHF/3-21G* level. (C) 2001 Elsevi
er Science Ltd. All rights reserved.