Alkynes to a-diketones

In conjunction with several ruthenium catalysts, C6HsIO oxidizes internal alkynes to a-diketones in 65-85% yield and terminal alkynes to carboxylic acids (70-80% yield).2... 

IOB in the presence of catalytic (1%) amounts of the ruthenium compound RuCl2(Ph3P)3 becomes a very effective oxidant. Among various substrates, it oxidized internal alkynes to a-diketones and cleaved terminal alkynes to acids. 

ZnIMnO,), effects several known oxidations such as oxidation of alkynes to a-diketones, cyclic ethers to lactones, and cycloalkanones to dicarboxylic acids. The paper reports one novel transformation Oxidation of a cyclohexcne to a ketol in moderate yield (36%), equation (1). 

I2 DMSO, " MeRe03/H202, " as well as by electrooxida-A ruthenium complex with a small amount of trifluoroacetic acid converts internal alkynes to the a-diketone. Ozone generally oxidizes triple-bond compounds to carboxyhc acids (19-9), but a-diketones are sometimes obtained instead. Selenium dioxide (Se02) with a small amount of H2SO4 oxidizes alkynes to a-diketones as well as arylacetylenes to a-keto acids (ArC=CH ArCOCOOH). " ... 

The oxidation of alkynes to a-diketones with potassium permanganate is a well-known reaction, but the early examples gave carboxylate salts that are soluble in aqueous permanganate. What conditions would you choose to oxidize 1-phenyl-1-pentyne to 1-phenyl-1, 2-pentanedione [86]... 

Internal alkynes have been oxidized to a-diketones by several oxidizing... 

Dialkyl- and diaryl-acetylenes are selectively converted to a-diketones (equation 121), whereas terminal alkynes give the corresponding carboxylic acid with loss of one carbon atom.337... 

The MTO/H202 system has been used to oxidize several other classes of substrates. Internal alkynes may be oxidized to a-diketones and/or carboxylic acids, whereas terminal alkynes are oxidized to mixtures of carboxylic acids, -ketoacids, and (in alcoholic solvents) esters.49 These conversions are proposed to proceed through an oxirene intermediate by analogy to the alkene epoxidations discussed earlier. 

A ruthenium-catalysed, three-component addition of alkyne to a,)5-unsaturated ketones to produce 1,5-diketones has been developed (Scheme 32). "... 

Dlsubstltuted alkynes are oxidized to a-diketones by NaOCl (or NaI04) with a catalytic amount of Ru04. Symmetrically dlsubstltuted acyclic olefins or large ring allcyclic olefins are directly converted to a-dlketones by KMn04 Ac20 In the cold. 

Diketones. The Sharpless procedure for oxidation of alkenes with NaIO catalyzed by Ru02 (11,462-463) is equally efficient for oxidation of alkynes to 1,2-diones. In fact, alkenes and alkynes react at a similar rate, but ether, epoxide, and ester groups are stable to the reagent. A 1-silylacetylene is oxidized to an acylsilane. Yields are moderate to high.1... 

The meso-ionic 1,3-oxazol-S-ones show an incredible array of cycloaddition reactions. Reference has already been made to the cycloaddition reactions of the derivative 50, which are interpreted as involving cycloaddition to the valence tautomer 51. In addition, an extremely comprehensive study of the 1,3-dipolar cycloaddition reactions of meso-ionic l,3-oxazol-5-ones (66) has been undertaken by Huisgen and his co-workers. The 1,3-dipolarophiles that have been examined include alkenes, alkynes, aldehydes, a-keto esters, a-diketones, thiobenzophenone, thiono esters, carbon oxysulfide, carbon disulfide, nitriles, nitro-, nitroso-, and azo-compounds, and cyclopropane and cyclobutene derivatives. In these reactions the l,3-oxazol-5-ones (66)... 

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