Interpretation of the diastereoselectivity of the cyclopropane formation involving pi-allyl palladium complexes based on molecular mechanics calculations

The diastereoselectivity of the base-induced cyclization of 2-amino-4-chlor obutyronitrile derivatives and of the palladium (0) catalyzed tandem alkyla tion and cyclization of (E)- and (Z)-1,4-dichlorobut-2-enes, providing suit able precursors of asymmetric 2,3-methanoamino acids, was interpreted by me ans of molecular mechanics calculations based on the MM2 force field. The d ummy atom concept for the construction of eta (3)-allyl palladium complexes and a new parameter set for the calculation have been used. The observed d iastereoselectivity which resulted from simple kinetic or thermodynamic con trol, can be however altered in some cases by the palladium-induced reversi bility of the three-membered ring formation. (C) 2000 Elsevier Science Ltd. All rights reserved.