Stereochemical Course of the Reduction

Abstract

As mentioned above, it is reasonable to consider that the reduction by a 1,4-dihydropyridine derivative catalyzed by metal ions proceeds via a ternary complex as shown in Fig. 3. In the reduction by PNPH, the factor which determines the stereochemistry of the product is the mode of approach of the substrate to PNPH. Namely, the relative orientation between the 1,4-dihydropyridine ring and the substrate in the ternary complex is important. There are many possibilities for the molecular arrangement in the ternary complex as well as for the fashion of the coordination of Mg(II) to PNPH. Here we will discuss what kind of complexation and approach should be considered in order to understand the magnitude and direction of the induced chirality, or the mechanism of chirality induction.