Tetra-N-propylammonium Perruthenate (TPAP)

Abstract

The crystalline, non-volatile and air-stable material tetra-N-propylammonium perruthenate (TPAP) is an important commercial catalytic oxidant, mostly used in natural products synthesis due to its ease of use, excellent performance and versatility. [1] In 1987, Ley and co-workers first introduced TPAP as a readily soluble, nonvolatile, air-stable oxidant for alcohols. [1] [2] It behaves as an overall three-electron oxidant for a wide range of multifunctional species. The full potential of TPAP was revealed when its catalytic behavior with N-methylmorpholine N-oxide (NMO) as terminal oxidant was uncovered. [3] It is stable at room temperature and may be stored for long periods under low-temperature condition. The TPAP-O2 oxidizing system meets several principles of Green Chemistry [4] and raises the prospect for industrial oxidations because of (i) its applicability in oxidation of a wide range of alcohols, (ii) its potential as terminal oxidant with air, (iii) the simple separation of the catalyst from the products, and (iv) its chemoselectivity and tolerance against many functional groups. The catalyst is inert towards double bonds, polyenes, enones, halides, cyclopropanes, epoxides, acetals, esters, amides, lactones, amines, peroxides, and catechols. Clean oxidation of alcohols occurs with TPAP in systems where competitive β-elimination poses a problem with other oxidants. [5] In addition to that, oxidation with TPAP can be achieved without racemization of the adjacent stereogenic α-centers and without double-bond migration. [4]