Synlett 2006(13): 2127-2129  
DOI: 10.1055/s-2006-948180
LETTER
© Georg Thieme Verlag Stuttgart · New York

Transposition of Allylic Alcohols into Carbonyl Compounds Catalyzed by Rhodium-Phosphinine Complexes

Manfred T. Reetz*, Hongchao Guo
Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim/Ruhr, Germany
Fax: +49(208)3062985; e-Mail: reetz@mpi-muelheim.mpg.de;
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Publikationsverlauf

Received 3 May 2006
Publikationsdatum:
09. August 2006 (online)

Abstract

The isomerization of a variety of allylic alcohols with formation of the corresponding saturated carbonyl compounds is readily accomplished by a new catalyst system comprising rhodium and a trisubstituted phosphinine (phosphabenzene derivative), especially when the Rh complex is activated by hydrogen prior to the transposition reaction.

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General Procedure for the Isomerization of Allylic Alcohol.
A dry 5-mL Schlenk flask under an atmosphere of argon was charged with a 5.4 mM solution of P-ligand (0.5 mL) in dry CH2Cl2 and a 5.4 mM solution of [Rh(NBD)2]BF4 (0.25 mL) in CH2Cl2. The mixture was stirred for 30 min at r.t., then stirred for an additional 30 min under 1.3 bar H2. The CH2Cl2 and H2 were removed by Ar displacement under reduced pressure, then 0.5 mL of CH2Cl2 and a 67.5 mM solution of an allylic alcohol in CH2Cl2 (1 mL) were added. The isomerization was carried out for the periods given. The reaction solution was passed through a small amount of silica gel and selectivity and conversion were determined by gas chromatography (GC and GC-MS).