Ruthenium Tetroxide and Perruthenate Chemistry. Recent Advances and Related Transformations Mediated by Other Transition Metal Oxo-species

Abstract

Abstract:In the last years ruthenium tetroxide is increasingly being used in organic synthesis. Thanks to the fine tuning of the reaction conditions, including pH control of the medium and the use of a wider range of co-oxidants, this species has proven to be a reagent able to catalyse useful synthetic transformations which are either a valuable alternative to established methods or even, in some cases, the method of choice. Protocols for oxidation of hydrocarbons, oxidative cleavage of C-C double bonds, even stopping the process at the aldehyde stage, oxidative cleavage of terminal and internal alkynes, oxidation of alcohols to carboxylic acids, dihydroxylation of alkenes, oxidative degradation of phenyl and other heteroaromatic nuclei, oxidative cyclization of dienes, have now reached a good level of improvement and are more and more included into complex synthetic sequences. The perruthenate ion is a ruthenium (VII) oxo-species. Since its introduction in the mid-eighties, tetrapropylammonium perruthenate (TPAP) has reached a great popularity among organic chemists and it is mostly employed in catalytic amounts in conjunction with N-methylmorpholine N-oxide (NMO) for the mild oxidation of primary and secondary alcohols to carbonyl compounds. Its use in the oxidation of other functionalities is known and recently, its utility in new synthetic transformations has been demonstrated. New processes, synthetic applications, theoretical studies and unusual transformations, published in the last eight years (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013), in the chemistry of these two oxo-species, will be covered in this review with the aim of offering a clear picture of their reactivity. When appropriate, related oxidative transformations mediated by other metal oxo-species will be presented to highlight similarities and differences. An historical overview of some aspects of the ruthenium tetroxide chemistry will be presented as well.

Pyridinium chlorochromate chemistry. New insight into oxidation of tetrahydrofurans

“…1,2 Though the most popular process mediated by PCC is the oxidation of primary and secondary alcohols to aldehyde and ketones, respectively, many other functional groups undergo PCC oxidation. As a continuation of our interest in oxidative processes mediated by transition metal oxo-species [3][4][5][6][7][8][9][10][11] as well as in the synthesis and derivatization of new THF-containing compounds, [12][13][14][15][16][17][18][19][20][21] we recently focused on oxidation processes mediated by PCC. These studies led to the discovery of new interesting transformations including oxidative spiroketalization, 22 oxidative cleavage of trisubstituted mono-THF compounds 23 and synthesis of bis--acyloxy-1,4-and 1,5-diketones from THF and THP-diols, respectively.…”

Ultrasonic-assisted ruthenium-catalyzed oxidation of some organic compounds in aqueous medium

“…Therefore, K 2 S 2 O 8 is considered the best co-oxidant and HCO 4 − is the worst one, since it is formed with t 1/2 ≈ 5 min [10,11]. However, when the reaction is also conducted at 60°C, benzonitrile was obtained in 80% yield and benzamide in 19% yield ( [1][2][3][4] were smoothly converted to their respective nitriles in better yields than those containing electron-withdrawing groups ( Table 1, entries 5-7). In all reactions, yield and turnover frequency (TOF) were calculated and the produced nitriles were identified by measuring their melting point and recording their IR and 1 H NMR spectra where appropriate.…”

“…Melting points were measured on a Buchi Melting Point B-540 instrument. 1 then filtered and evaporated to give the product. Similarly, nitriles were hydrated to their respective amides at 100°C.…”

“…Many organic transformations which involve ruthenium species as catalyst are known and well documented [1,2]. Ruthenium(III) complexes are also well known to catalyze a variety of organic transformations [3][4][5][6][7].…”

A Novel PCC-Catalyzed Process Involving the Oxidative Cleavage of an α-Bromomethyl-tetrahydrofuran Bond. Synthesis of (2S,3R)-2-{(R)-Bromo[(2R,3R,5S,6R)-3,5-dibromo-6-ethyltetrahydro-2H-pyran-2-yl]methyl}-5-oxotetrahydrofuran-3-yl Benzoate

“…Oxidation methods, mediated or catalyzed by transition metal oxo-species, are a class of processes of pivotal importance in organic synthesis [1][2][3][4]. Pyridinium chlorochroamte (PCC) is a well known oxidizing reagent.…”