[5590-56-7] · C54H45O4Si3V · Tris(triphenylsilyl) Vanadate · (MW 893.20)
Alternate Name: oxotris(triphenylsilanolato)vanadium
Physical Data: mp 225-227 °C.
Solubility: sol xylene, benzene, mineral oil.
Form Supplied in: not commercially available.
Preparative Methods: from vanadium pentoxide and triphenylsilanol.1
Purification: recrystallize from xylene, benzene, or mesitylene and wash with hexane.
Handling, Storage, and Precautions: hydrolyzes in moist air.
Propargylic alcohols are converted into a,b-unsaturated aldehydes or ketones by treatment with the title reagent (1) in mineral oil at 150 °C (eq 1).1,3 Yields in this reaction are typically greater than 85%. The reaction proceeds via a mechanism involving a [3,3]-sigmatropic rearrangement and thus the reaction proceeds with complete allylic inversion after protonolysis of the oxyallene intermediate.
Treatment of allylic alcohols with (1) in mineral oil at 150 °C effects clean allylic inversion (eq 2).2 Since this is an equilibrium process, the reaction is probably limited to cases where the starting allylic alcohol is considerably less stable than its allylic rearrangement product. As in the above case with propargylic alcohols, the reaction proceeds via a [3,3]-sigmatropic rearrangement. In some cases, minor amounts of alcohol oxidation products were also observed. Yields for this process are typically greater than 80%.
James W. Herndon
University of Maryland, College Park, MD, USA