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

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.

Key words

green chemistry - homogeneous catalysis - isomerization - phosphorus - rhodium

References and Notes

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• Reviews:
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7

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).