Perruthenates, TPAP and

Although perruthenates contains no peroxo ligands (like permanganates and perrhenates) the name is a well-established one and will be used here. 

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R)-isomer in a reaction where chirality was transferred from a (R)-ct-phenyl methyl substituent at N-4 <2004TA687>. The imine double bond of a l,4-diazepin-5-one can be introduced by oxidation of the saturated amine using tetra- -propylam-monium perruthenate (TPAP) and A -mcthyl morpholine /V-oxide (NMO), as the co-oxidant <1997T3223>. 

Scheme 15). Treatment of 42 with DDQ in CH2CI2/H2O (19/1) afforded diol 43 in 81% yield. Subsequent oxidation was carried out with a catalytic amount of tetrapropylammonium perruthenate (TPAP) and N-methylmorpholine-Y-oxide to furnish lactone 44 in 82% yield.In the H NMR spectrum of 44, the coupling constants of Jl,l-trans, and... 

Microflow systems are also effective for the oxidation of henzyl alcohol to benzaldehyde using a catalytic amount of tetrapropylammmonium perruthenate (TPAP) and a stoichiometric amount of N-methylmorpholine-N-oxide (NMO) [6]. At a reaction time of 2 min, the conversion of benzyl alcohol in the microreactor is higher than that in the flask (Scheme 7.2). 

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. 

A very mild oxidative transformation of nitro compounds into ketones using tetrapropylam-monium perruthenate (TPAP) has been developed. A stoichiometric amount of TPAP in the presence of A-methylmorpholine A-oxide (NMO) and 4 A molecular sieves (MS).18a As the reaction conditions are neutral and mild, this method is compatible with the presence of other sensitive functionalities (Eq. 6.11). This transformation can be carried out with 10 mol% of TPAP and 1.5 equiv of NMO in the presence of potassium carbonate, 4 A MS, and silver acetate (Eq. 6.12).18b... 

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. 

Hydroboration occurred from the less hindered top face of rac-29 and resulted in the formation of alcohol rac-30. After a three-step sequence which included oxidation with tetrapropylammonium perruthenate (TPAP), methyl lithium addition and repeated oxidation with TPAP, ketone rac-31 was isolated. Finally, epimerization of the stereogenic center at C-7 to the correct configuration and methylenation with the Lombardo reagent led to the formation of racemic kelsoene (rac-1). 

From the study of a microbially mediated oxidation of arteether 28b, sufficient quantities of 7a-hydroxy 180 and 15-hydroxy derivatives 182 were obtained to employ them as intermediates for the preparation of fluorinated compounds. The hydroxyl groups were oxidized to the corresponding aldehyde 187, or ketone 188, with catalytic quantities of tetra- -propylammonium perruthenate (TPAP) in the presence of excess iV-methylmorpholine A -oxide. On reaction with DAST, 187 and 188 were converted into the corresponding geminal difluoro derivatives, 189 (63%) and 190 (42%). In addition to 190, a monofluoro olefin 191 was obtained in 25% yield from 188 on reaction with DAST <1995JME4120>. 

A milestone in the routine employment of perruthenate in the oxidation of alcohols was established with the publication by Griffith, Ley et al. in 1987 on the catalytic use of tetra- -propylammonium perruthenate (TPAP).11 The presence of the tetra- -propylammonium cation renders this compound soluble in apolar media and allows the existence of a high concentration of perruthenate ion in organic solvents. The tetra- -propylammonium perruthenate is easily prepared and can be employed catalytically in CH2CI2 solution in the oxidation of alcohols to ketones and aldehydes, using /V-methyl morpholine A-oxide (NMO) as the secondary oxidant. 

Reductive alkylation of -caprolactone (1 equiv) with a 2 0.25 mixture of Grignard reagent and Zn(BH4)2 affords monoalkylated diols, which can be further selectively oxidized with tetrapropylammonium perruthenate (TPAP) into the expected monoalkylated lactones <2002CR571>. 

P. Langer, Tetra-n-propyl Ammonium Perruthenate (TPAP) - An Efficient and Selective Reagent for Oxidation Reactions in Solution and on the Solid Phase, J. Prakt. Chem. 2000, 342, 728-730. 

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. 

A catalytic method which promises to find wide application in view of its mildness and ease of execution uses a catalytic amount of tetra-n-propylammonium perruthenate (TPAP) with A7-methylmorpholine -oxide (NMO) as the cooxidant. ° l4imary (and secondary) alcohols which contain a range of ftinc-tional groups (alkenes, tetrahydropyran ethers, epoxides, lactones, silyl ethers and indoles inter alia) can be oxidized without interference by the other functional group (equations 21-23). The performance of the reagent is improved further by including molecular sieves in the reaction mixture. ... 

Griffith, W. P., Ley, S. V., Whitcombe, G. P., White, A. D. Preparation and use of tetrabutylammonium perruthenate (TBAP reagent) and tetrapropylammonium perruthenate (TPAP reagent) as new catalytic oxidants for alcohols. J. Chem. Soc., Chem. Common. 1987,1625-1627. 

Discovered in 1987, the tetra-n-propylammonium perruthenate (TPAP) oxidation is straightforward to run. The reagent is expensive and thus it is used in catalytic amounts and becomes re-oxidized by A-methyl morpholine-A-oxide. For a review see Ley, S. V. Norman, J. Griffith, W. P Marsden, S. P. Synthesis 1994, 639-666. 

Tetrapropylammonium perruthenate (TPAP 63 mg) was added in 1 portion to a stirred mixture of A -Boc-4-fra .y-hydroxy-L-proline (1 g, 3.47 mmol), A-methyl-morpholine A-oxide (0.62 g, 15.6 mmol), and powdered molecular sieves (4 A, 1.78 g) in CH2CI2 (7 mL) at room temperature under argon. The mixture was stirred for 3 h, filtered, and evaporated in vacuo to give a black residue. The product was purified by... 

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