The potential energy surfaces of acetaldoxime carbanion and its ion pairs formed with lithium and sodium cations ions have been explored with ab initio methods to model and study the regiochemistry of metalated oxime ethers. Planar structures of the carbanions produced by deprotonating acetaldoxime are minima on the potential energy surface. The syn-isomer is 2.6 Kcal/mole more stable than the anti. This difference is not a manifestation of cyclic conjugation but more likely is a result of electrostatic effects. Two chiral and almost isoenergetic minima have been located for the ion pairs formed by either of the isomeric carbanions with Li+ or Na+. The gegenion engages either in face coordination or bridges the NO-bond in a n2-fashion. In oxime ethers face coordination is expected to become dominant for steric reasons. LiC-contacts are surprisingly long in all of the ion pairs. Bonding to the metals in the ion pairs is predominantly ionic. Ion pair formation increases the syn preference energy compared to the free anions, and the syn preference energy is greater for Na+ than for Li+. Reactions with electrophiles via the syn-coordinated metal permits prior coordination and ion pair formation in the product.
R. Glaser and A. J. Streitwieser, "Theoretical Study of Structure and Reactions of Metalated Oximes and Oxime Ethers," Pure and Applied Chemistry, vol. 60, no. 2, pp. 195-204, Walter de Gruyter, Aug 1988.
The definitive version is available at https://doi.org/10.1351/pac198860020195
World Congress of Theoretical Organic Chemists (1988: Aug. 12-19, Budapest, Hungary)
International Standard Serial Number (ISSN)
Article - Conference proceedings
© 1988 Walter de Gruyter, All rights reserved.