PROCESS FOR THE PREPARATION OF ACETAL DERIVATIVES OF 1,4-DIHYDROPYRIDINES

摘要

A process for the preparation of 1,4-dihydropyridine acetal derivatives of formula (II) wherein R<1> each, independently, represents H, Cl or CF3; R<2> represents H, C1-C5 alkyl, C3-C6 cycloalkyl or aralkyl; R<3> and R<4> which may be the same or different, represent C1-C5 alkyl, C3-C6 cycloalkyl, aralkyl or together represent -(CH2)m-, wherein m is 2 or 3, and n is 1 or 2, wherein the 1,4-dihydropyridine ring structure is formed by a Hantzsch synthesis carried out in one or more steps using a compound containing a group of formula (a); wherein R<3> and R<4> have the same meanings as defined above, as one of the reactants in the Hantzsch condensation, is described. The Hantzsch synthesis, or at least one step thereof, is carried out in a solvent, which is capable of forming an azeotrope with water, under azeotropic removal of water of reaction. The compounds of formula (II) are useful as intermediates for the preparation of pharmaceutically active 1,4-dihydropyridines and other intermediates of use for such purpose.