AB-INITIO INVESTIGATIONS OF THE GEOMETRIC CONFORMATION OF GLYCIDIC METHYL-ESTERS AND THE RELATED COMPLEXES WITH A LITHIUM CATION - A CONTRIBUTION TO THE UNDERSTANDING OF REGIOSELECTIVE OPENINGS OF THESE ESTERSWITH LITHIUM REAGENTS

In order to contribute to the understanding of the regioselective epox ide ring opening by lithium organometallic reagents, ab initio calcula tions have been performed on the methyl glycidate, the methyl trans-3- methyl-glycidate, the methyl cis-3-methyl-glycidate and their complexe s with a lithium cation. All structural parameters were optimized at t he RHF/6-31G level for the six compounds. The effects of methyl subst itution at C-3, and/or chelation with Li+, on geometry and net atomic charges are discussed. The present results suggest that the steric fac tor might contribute to explain the regioselective epoxide ring openin g by lithium organometallic reagents such as cuprates. (C) 1998 Elsevi er Science B.V.