Rationalization of the stereochemistry of an addition of dialkyl phosphites to certain chiral aldimines: The experimental and theoretical approach

The absolute configuration of an alpha-P stereogenic center in two diastereomeric O,O-dialkyl alpha-aminophosphonates (3), arising from an induced 1,3-asymmetric phosphite addition to the C=N bond of furfural-derived Schiff bases (1), was established from single product H-1 NMR data. Such spectra were interpreted with anisotropic shielding in relation to the AMI and MNDO/d structures of 3; the former ones turned out to be closer to the obtained experimental results (H-1 NMR spectra of 3, crystallographic database study). Since favored 3-21G geometries of starting imines 1 were modeled as well, it was in-ferred that a stereochemical outcome of this reaction is governed by Cram selectivity. (C) 2002 Wiley Periodicals, Inc.