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“Conducted Tour” Migration of Li + during the cis / trans Stereoinversion of α‐Arylvinyllithiums
Author(s) -
Knorr Rudolf,
Behringer Claudia,
Ruhdorfer Jakob,
von Roman Ulrich,
Lattke Ernst,
Böhrer Petra
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201702353
Subject(s) - chemistry , aryl , monomer , stereochemistry , indane , naphthalene , tetrahydrofuran , steric effects , heterolysis , solvent , crystallography , alkyl , organic chemistry , catalysis , polymer
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 H 2 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 H 2 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.