Kevin E. Gilbert

Diastereo- and Enantioselective Three-Component Coupling Approach to Highly Substituted Pyrrolidines

The enantioselective synthesis of substituted pyrrolidines through a mild Lewis-acid catalyzed three-component coupling reaction between picolinaldehyde, amino acids, and activated olefins is reported. The reaction uses low catalyst loadings of commercially available chiral diamines and copper triflate proposed to self-assemble in conjunction with the chelating aldehydes, 4-substituted-2-picolinaldehydes or 4-methylthiazole-2-carboxaldehyde, to generate a catalyst complex. A model is provided to explain how this complex directs enantioselectivity. This work represents a significant advance in the ease, scope, and cost of producing highly substituted, enantioenriched pyrrolidines.

General molecular mechanics approach to transition metal complexes

Transition metal complexes have been treated by a molecular mechanics approach using an MM2‐like valence force field for the ligands and a Urey–Bradley force field about the metal. Metal–ligand atom bonds are parameterized with dependence on the metal covalent radius. The current metal–ligand distances and covalent radii were determined by a Simplex minimization and visual optimization of the deviations in bond distance between 230 structures from the Cambridge Crystallographic Structure Database and the force field calculated values. Moderately good reproducibility of structures is obtained with a variety of metal types with different oxidation states, and degree of unsaturation and with square‐planar compounds. The current model also includes coordination of π ligands to the metal center with a 1/r6 attractive term whose minimum is 25 kcal/mol per p orbital at a distance dependent on the covalent radius of the metal and an angular attentuation factor. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1167–1178, 1998

Numerical methods: An implementation of difsub on an ibm-pc

Abstract An implementation of the Gear program for numerical integration, DIFSUB, has been done on an IBM-PC microcomputer. A Simplex optimization subroutine has been added and the program is parameterized for six species reacting by first order reversible processes. The accuracy and speed of the program, SMPLXKS, is compared to that of the Runge-Kutta programs that have previously been used in studies of hydrocarbon isomerizations. Two examples of the use of SMPLXKS in the study of the Cope rearrangement are given.