TPAP

Tetrapropylammonium perruthenate is the chemical compound described by the formula N(C₃H₇)₄RuO₄. Sometimes known as the Ley-Griffith reagent, this ruthenium compound is used in organic synthesis. This salt consists of the tetrapropylammonium] cation and the perruthenate, RuO₄^- anion. Ruthenium tetroxide is a highly aggressive oxidant, but its one-electron reduced derivative is a mild oxidizing agent for the conversion of alcohols to aldehydes.[2] This oxidizing agent can also be used to oxidize primary alcohols all the way to the carboxylic acid through a higher catalyst and co-oxidant loading along with the addition of two equivalents of water. The mechanism works by a normal oxidation of the alcohol to the aldehyde followed by hydration, and a final oxidation.[3]

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The oxidation generates water that can be removed by adding molecular sieves. TPAP is expensive but it can be used in catalytic amounts. The catalytic cycle is maintained by adding a stoichiometric amount of a co-oxidant such as N-methylmorpholine N-oxide or an oxygen.[4]

References

1. ^  A High-Yielding Synthesis of the Naturally Occurring Antitumour Agent Irisquinone John A. Hadfield, Alan T. McGown1 and John Butler Molecules 2000, 5, 82-88 Online Article

[2] Review: Steven V. Ley, Joanne Norman, William P. Griffith, Stephen P. Marsden, "Tetrapropylammonium Perruthenate, Pr4N+RuO4-, TPAP: A Catalytic Oxidant for Organic Synthesis" Synthesis, 1994, 639. doi:10.1055/s-1994-25538

[3] "Applications of Zr-Catalyzed Carbomagnesation and Mo-Catalyzed Macrocyclic Ring Closing Metathesis in Asymmetric Synthesis. Enantioselective Total Synthesis of Sch 38516 (Fluvirucin B1)" Z. Xu, C. W. Johannes, A. F. Houri, D. S. La, D. A. Cogan, G. E. Hofilena, A. H. Hoveyda, J. Am. Chem. Soc., 1997, 119, 10302

[4] "Tetra-n-propylammonium perruthenate (TPAP)-catalysed oxidations of alcohols using molecular oxygen as a co-oxidant" Roman Lenz and Steven V. Ley. J. Chem. Soc., Perkin Trans. 1, 1997, 3291.