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Capricious Stereoselectivities of Alkenylpotassium Formation under Kinetic and Thermodynamic Control Oxygen‐Triggered Configurational Equilibration of an Allyl Type Organometallic Compound
Author(s) -
Stähle Manfred,
Hartmann Jürgen,
Schlosser Manfred
Publication year - 1977
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19770600527
Subject(s) - chemistry , allylic rearrangement , kinetic control , oxygen , tetrahydrofuran , group 2 organometallic chemistry , computational chemistry , medicinal chemistry , stereochemistry , organic chemistry , catalysis , molecule , solvent
( Z )‐1‐Alkylated propenes undergo metallation at an allylic site more rapidly than do their ( E )‐isomers, no matter in which configuration the resulting organometallic is thermodynamically more stable. A striking illustration is given by ( Z )‐4,4‐dimethyl‐2‐pentenyl potassium which is formed 15 times faster than its ( E )‐isomer, although the latter is clearly favored under equilibrium conditions. The configurational reorganization of alkenylpotassium compounds in tetrahydrofuran solution is very slow. At least in one case, however, traces of oxygen efficiently catalyse the Z / E equilibration.