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Updated: Feb 27, 2026

A Protocol for Safe Lithiation Reactions Using Organolithium Reagents
Published on: November 12, 2016
"Conducted Tour" Migration of Li+ during the cis/trans Stereoinversion of α-Arylvinyllithiums
Rudolf Knorr1, Claudia Behringer1, Jakob Ruhdorfer1
1Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13 (Haus F), 81377, München, Germany.
Abstract:
A "conducted tour" migration keeps a mobile client on a profitable route even though an occasional side-step may seem attractive. A stereochemical manifestation of such a migration had been suggested by Donald J. Cram (1964), and we present now a different example that concerns the cis/trans stereoinversion of monomeric H2 C=C(Li)-aryl compounds: Upon tetrahydrofuran (THF)-assisted heterolysis of the Li-C bond with formation of a solvent-separated ion pair (SSIP), the unchained "mobile client" Li+ (THF)4 is proposed to surmount the rim of the electronically fixed aryl group and to disdain the less encumbered pathways across the H2 C=C region. This interpretation is based on knowledge from a previously published series of monomeric α-arylalkenyllithiums in combination with two new members: 4-(α-lithiovinyl)-2,2-dimethylbenz[f]indane (1) revealed both a barrier against α-aryl rotation and a route-distinguishing retardation as compared with the corresponding migration-dependent cis/trans stereoinversion rate constant of 1-(α-lithiovinyl)naphthalene (2). Monomeric and dimeric ground states of 1 and 2 and their microsolvation numbers were determined by using the recently developed primary and secondary NMR criteria.
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