MECHANISMS OF AROMATIC LITHIATION INFLUENCE OF AGGREGATION AND DIRECTING GROUPS

Journal article


Publication Details

Author(s): van Eikema Hommes N, Schleyer P
Journal: Tetrahedron
Publisher: Elsevier
Publication year: 1994
Volume: 50
Journal issue: 20
Pages range: 5903-5916
ISSN: 0040-4020


Abstract


High level ab initio calculations (MP2(fc)/6-31+G(*)//MP2(fc)/6-31G(*)+Delta ZPE//6-31G(*) show that the reaction of aromatic compounds with methyllithium is not an electrophilic substitution, but a hydrogen transfer along an almost linear path, with the (coordinatively highly unsaturated) ''active'' lithium cation bridging the methyl carbanion and the carbon atom being lithiated. Aggregation (modelled with lithium hydride) does not change the mechanism. However, intra-aggregate bonding stabilizes the ''active'' lithium (i.e., the one directly undergoing transfer). The mixed dimer of methyllithium and lithium hydride is predicted to be more reactive than methyllithium monomer in the lithiation of benzene, due to interaction of the ''passive'' lithium with the aromatic pi-system and the carbon atom being lithiated. The accelerating and ortho-directing effect of Lewis base substituents is due to stabilization of the ''active'' lithium in the transition state by intramolecular coordination and favorable electrostatic interactions. These stabilizing effects are strongest for reaction of a monomer, but are also significant in the reaction of anisole with the mixed dimer of methyllithium and lithium hydride.



FAU Authors / FAU Editors

Schleyer, Paul Prof. Dr.
Naturwissenschaftliche Fakultät
van Eikema Hommes, Nico Dr.
Computer-Chemie-Centrum


How to cite

APA:
van Eikema Hommes, N., & Schleyer, P. (1994). MECHANISMS OF AROMATIC LITHIATION INFLUENCE OF AGGREGATION AND DIRECTING GROUPS. Tetrahedron, 50(20), 5903-5916.

MLA:
van Eikema Hommes, Nico, and Paul Schleyer. "MECHANISMS OF AROMATIC LITHIATION INFLUENCE OF AGGREGATION AND DIRECTING GROUPS." Tetrahedron 50.20 (1994): 5903-5916.

BibTeX: 

Last updated on 2018-19-04 at 03:17