Computational Study of the Stereochemistry of Intramolecular Carbolithiation of an Alkene by a Secondary Alkyllithium:  Stereochemistry Change Caused by a Single THF Molecule of Solvation

Theoretical calculations reveal that the 40:1 ratio of trans- to cis-2-methylcyclopentylmethyllithium formed in the cyclization of 6-lithio-1-heptene by intramolecular carbolithiation is due to steric crowding in the transition state for the cis-cyclization pathway when a single THF molecule complexes the lithium cation. In the absence of this specific solvation, the cis-cyclization pathway is predicted to be slightly favored.