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Additive‐Free Isomerization of Allylic Alcohols to Ketones with a Cobalt PNP Pincer Catalyst
Author(s) -
Spiegelberg Brian,
Dell'Acqua Andrea,
Xia Tian,
Spannenberg Anke,
Tin Sergey,
Hinze Sandra,
de Vries Johannes G.
Publication year - 2019
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.201901148
Subject(s) - isomerization , dehydrogenation , cobalt , pincer movement , allylic rearrangement , chemistry , catalysis , alkene , photochemistry , medicinal chemistry , double bond , hydride , solvent , organic chemistry , hydrogen
Catalytic isomerization of allylic alcohols in ethanol as a green solvent was achieved by using air and moisture stable cobalt (II) complexes in the absence of any additives. Under mild conditions, the cobalt PNP pincer complex substituted with phenyl groups on the phosphorus atoms appeared to be the most active. High rates were obtained at 120 °C, even though the addition of one equivalent of base increases the speed of the reaction drastically. Although some evidence was obtained supporting a dehydrogenation–hydrogenation mechanism, it was proven that this is not the major mechanism. Instead, the cobalt hydride complex formed by dehydrogenation of ethanol is capable of double‐bond isomerization through alkene insertion–elimination.