Tetra-n-propylammonium perruthenate

Form Supplied in dark green solid commercially available. Analysis of Reagent Purity microanalysis. 

Handling, Storage, and Precautions stable at room temperature and may be stored for long periods of time without significant decomposition, especially if kept refrigerated in the dark. The reagent should not be heated neat, as small quantities decompose with flame at 150-160 °C in air. 

Oxidation of Primary Alcohols. Primary alcohols can be oxidized in the presence of a variety of functional groups, including tetrahydropyranyl ethers (eq 1), epoxides (eq 2), acetals (eq 3), silyl ethers, peroxides, lactones, alkenes, alkynes, esters, amides, sulfones, and indoles. Oxidation of substrates with labile a-centers proceeds without epimerization.  

Oxidation of Secondary Alcohols. In a similar fashion, multifunctional secondary alcohols are oxidized to ketones (eqs 4 and 5) in good yields.  

A particularly hindered secondary alcohol (an intermediate in the latter stages of the synthesis of tetronolide) resisted oxidation with activated DMSO, Pyridinium Chlorochromate, and ac-tivatedMaji onese Dioxide, yet stoichiometric TPAP afforded the ketone in 81% yield.  

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Tetra-n-propylammonium perruthenate (TPAP, tetrapropyl tetraoxoruthenate) [114615-82-6] M 351.4, m 160"(dec). It is a strong oxidant and may explode on heating. It can be washed with aq n-propanol, then H2O and dried over KOH in a vac. It is stable at room temp but best stored in a refrigerator. It is sol in CH2CI2 and MeCN. [Dengel et al. Transition Met Chem 10 98 1985 Griffith et al. J Chem Soc, Chem Commun 1625 1987.] Polymer supported reagent is available commercially. 

Tetramethylpiperidine tetra-n-Propylammonium perruthenate Tolyl Trityl... 

R. Ciriminna and M. Pagliaro, Tailoring the Catalytic Performance of Sol-Gel-Encapsulated Tetra-n-propylammonium Perruthenate (TPAP) in Aerobic Oxidation of Alcohols, Chem. Eur. J., 2003, 9, 5067. 

Tetra-n-propylammonium perruthenate also oxidizes sulphides to sulphones [45]. Yields are generally high for dialkyl sulphides and alkyl aryl sulphides, but lower for diaryl sulphides. 

Secondary nitro compounds are oxidized to the corresponding ketones in moderate yields by a catalytic amount of tetra-n-propylammonium perruthenate in the presence of N-methyImorpholine-A-oxide and a silver salt [46]. Oxidation with a stoichiometric amount of the ammonium perruthenate has also been reported [47]. 

Reductive y-lactone ring opening, with concomitant desilylation at the tertiary position by LiAlH4, gave triol 17 in 80% yield. Finally, acetonide formation followed by oxidation with tetra-n-propylammonium perruthenate/A-methylmorpholine / /-oxide oxidation, led to the target aldehyde 19 in 80% overall yield. 

After desilylation with tetra-n-butylammonium fluoride and oxidation with tetra-n-propylammonium perruthenate the dialdehyde 23 was obtained in 32% overall yield. 

Unambigous structural confirmation was obtained by converting 53a to diol carbonate 56, which was independently synthesised from baccatin III. Selective deprotection of 53a with TBAF gave alcohol 54, which was oxidised with tetra-n-propylammonium perruthenate/)V-methylmorpholine A -oxide (CH2CI2, molecular sieves, 25 °C, 1.5 h) to ketone 55 in 86% overall yield from 53a. Deprotection (HF, pyridine, CH3CN, 96%) of gave diol carbonate 56, identical to the compound prepared from baccatin III. 

TPAP Tetra-n-Propylammonium Perruthenate Pr4N+Ru04 ... 

Tetra-n-propylammonium Perruthenate (TPAP, nPr4N+ RUO4)... 

The oxidation to the enone was realized with catalytic amounts of tetra-n-propylammonium perruthenate (TPAP)21 (46), which is a mild oxidant for conversion of multifunctionalized alcohols to aldehydes or ketones. Catalytic TPAP oxidations are carried out in the presence of stoichiometric or excess A-methylmorpholine-A-oxide (NMO)22 (47) as cooxidant. Other common reagents for oxidation of alcohols are e.g. DMS0/C202C1223, Dess-Martin periodinane24, PCC25, PDC26 or the Jones reagent27. 

W. P. Griffith, S. V Ley, TPAP Tetra-n-Propylammonium Perruthenate, a Mild and Convenient Oxidant for Alcohols, Aldrichimica Acta 1990, 23, 13-19. 

The seven-step flow synthesis of ( )-oxomaritidine included the oxidation of benzylic alcohol 25 to aldehyde 26 (Scheme 4.67) using polymer-supported tetra-N-propylammonium perruthenate (TPAP) 27. Although this reaction is stoichiometric in ruthenium, the Ru(VII) species can be readily regenerated by flowing a solution of NMO through the spent reagent cartridge [89]. 

Modern variations include the in situ, and thus catalytic, use of this high-valent selective reagent, not only for alcohols but also for ethers (see later). Ru(VII) (perruthenate) in the compounds tetra-n-butylammonium perruthenate (TBAP) and tetra-n-propylammonium perruthenate (TPAP) has found wide application in alcohol oxidation. Ru-oxo complexes with valence states of IV to VI are key intermediates in, for example, the selective oxygen transfer to alkenes, leading to epoxides. On the other hand 16-electron Ru(II) complexes can be used to catalyse hydrogen transfer thus these are excellent catalysts for oxidative dehydrogenation of alcohols. A separate section is included to describe the different mechanisms in more detail. 

Some very mild oxidizing agents are being more and more widely used for the synthesis of very sensitive aldehydes. One of these is known as TPAP (tetra-n-propylammonium perruthen-ate, pronounced tee-pap ). 

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