Tetrapropylammonium Perruthenate (TPAP)
Tetrapropylammonium perruthenate, TPAP, is a readily soluble, nonvolatile, air stable oxidant for alcohols. The commercially available reagent can be used in catalytic amounts in the presence of a stoichiometric oxidant, operates at room temperature and is devoid of obnoxious or explosive side products. Suitable co-oxidants are hydroperoxides or N-methylmorpholine N-oxide (NMO), which seems to be the most effective. In oxidations of primary alcohols, TPAP/NMO gives aldehydes rather than carboxylic acids in nonaqueous solutions in the presence of molecular sieves. The presence of water fosters an equilibrium concentration of the aldehyde hydrate, which can undergo further oxidation to the carboxylic acid. (Review: S. Ley, J. Norman, W. P. Griffith, S. P. Marsden, Synthesis, 1994, 639. Abstract)
Recent Literature
Tetrapropylammonium perruthenate enables oxidations of a wide range of molecules
including examples of both double oxidations and selective oxidations.
Mechanistic studies and general experimental procedures are reported. In
addition several interesting developments in the chemistry of this reagent are
outlined: heteroatom oxidation, cleavage reactions and use in sequential
reaction processes.
S. B. Ley, J. Norman, W. P. Griffith, S. P. Marsden, Synthesis, 1994,
639-666.
he mild instability of the Ley-Griffith catalyst (TPAP) creates preparation,
storage, and reaction reproducibility issues, due to unpreventable slow
decomposition. A set of readily synthesized, bench stable, phosphonium
perruthenates (ATP3 and MTP3) mirror the reactivity of TPAP, but avoid storage
decomposition issues.
P. W. Moore, C. D. G. Read, P. V. Bernhardt, C. M. Williams, Chem. Eur. J., 2018, 24, 4556-4561.
In a simple, mild, and highly effective method for the direct conversion of
primary alcohols to carboxylic acids, TPAP serves as the catalyst, and NMO • H2O
plays a dual role, acting as the co-oxidant and as a reagent for aldehyde
hydrate stabilization. This previously unknown stabilizing effect of geminal
diols by N-oxides is the key for the efficiency of the overall
transformation.
A.-K. C. Schmidt, C. B. W. Stark, Org. Lett., 2011,
13, 4164-4167.
An efficient method for the oxidation of an olefin to the less
substituted carbonyl compound is described. This one pot conversion
includes hydroboration with borane dimethyl sulfide (BDMS), followed by
oxidation of the resulting alkylboranes with tetrapropylammonium
perruthenate (TPAP) and NMO.
M. H. Yates, Tetrahedron Lett., 1997, 38, 2813-2816.
