Cyclohexane-1,3-dione, oxidation

Within the cubane synthesis the initially produced cyclobutadiene moiety (see p. 329) is only stable as an iron(O) complex (M. Avram, 1964 G.F. Emerson, 1965 M.P. Cava, 1967). When this complex is destroyed by oxidation with cerium(lV) in the presence of a dienophilic quinone derivative, the cycloaddition takes place immediately. Irradiation leads to a further cyclobutane ring closure. The cubane synthesis also exemplifies another general approach to cyclobutane derivatives. This starts with cyclopentanone or cyclohexane-dione derivatives which are brominated and treated with strong base. A Favorskii rearrangement then leads to ring contraction (J.C. Barborak, 1966). 

Farage and Janjic (1982-1 and 2) observed oscillations in the concentrations of bromide and redox potentials during the uncatalyzed oxidation of 1,4-cyclohexane-dione by bromate in sulfuric, nitric (1982-1), perchloric and orthophosphoric (1982-2) acid solutions. The system does not require a catalyst such as the redox couple Ce(IV)/Ce(III) or Mn(III)/Mn(II) of the B-Z reaction. Experimenting with this system Farage and Janjic (1982-3) observed that temperature, stirring and oxygen affect the frequency or amplitude of oscillations. 

Figure 16.5-21. Baeyer-Villiger oxidation of 2,2,5,5-tetramethyl-l,4-cyclohexane-dione by Curvularia lunata.

In a route by Hoffman—La Roche workers [35] ring contraction of the cyclohexane dione (24) with sodium carbonate in mesitylene gave the cyclopentenone (25) which was elaborated to the lactone (26a) by 1,4 addition of nitromethanc, oxidative cleavage of the allyl side chain, ketone reduction and lactonisation. 

In 2003, Wudl and coworkers [109] reported the preparation of 2,3,9,10-tetramethylpentacene (113) from 4,5-dime-thylphthalyl alcohol (110) [114] in three steps, which involved a Swern oxidation [115], an aldol-condensation of the resulting phthalaldehyde 111 with 1,4-cyclohexane-dione (105), and a Meerwein-Ponndorf reduction of the final... 

Selenium dioxide may be used for the oxidation of reactive methylene groups to carbonyl groups. An example is the oxidation of cyclohexanone to cyclohexane-1,2-dione (27). In the procedure, the reaction is carried out on camphor to give camphor... 

Wiberg and Koch 167) also disagreed with Littler s results, and found that the major product (75%) obtained on treatment of cyclohexanone with aqueous thallium(III) perchlorate was cyclopentanecarboxylic acid (XL). 2-Hydroxycyclohexanone was isolated in only 3 % yield unchanged starting material accounted for the remainder of the product. Wiberg and Koch were unable to detect any cyclohexane-1,2-dione in the product mixture, but did prove that 2-hydroxycyclohexanone did not function as the precursor to the ring-contracted acid. From the results obtained from a study of the oxidation of 2,2,6,6-[Pg.196]

The chromic acid oxidation of cyclohexanone to adipic acid via 2-hydroxy-cyclohexanone and cyclohexane-l,2-dione is third order , viz. 

The ultimate product of Hg(II) oxidation is cyclohexane-1,2-dione which is probably produced from 2-hydroxycyclohexanone. The oxidation by thallic perchlorate produces cyclopentanecarboxylic acid in 75 % yield this contrasts with the production of 2-acetoxycyclohexanone by thallic acetate . The mechanism favoured for the production of the carboxylic acid is... 

When nitric acid was added to cyclohexanol when preparing cyclohexane-1,2-dione, the reactor detonated, probably because of the exothermicity of the oxidation reaction, which was complete instead of partial (reaction (2)). 

When cyclohexane-1,4-dione reacted with 3-aminocarbazole, the presumed initial double condensation product was dehydrogenated and 212 was actually isolated. Dichromate oxidation of this diamine gave the quinone... 

Disilyl ethers of bicyclo[2.2.0]hexane-l,4-diols were transformed to cyclohexane-1,4-diones by oxidation after hydrolysis in methanol to the diols, which can be isolated.100 Sodium periodate101-103 and molecular oxygen100,101,104 were used as oxidants. 

Oxidation of cyclohexane-1,4-dione with MCPBA in dichloromethane (DCM) affords oxepane-2,5-dione, which the authors claim as a precursor of a novel class of versatile semicrystalline biodegradable (co)polyesters <2002MM7857, 2003MM2609>. 

With alkyl methyl ketones (R-CH2,CO,Me) the reaction is complicated by the presence of two alternative sites of oxidation in practice the methyl group appears to be oxidised in preference to the methylene group for reasons which have not been adequately clarified, but in any case the yields are usually poor. Unsubstituted, or symmetrically substituted cyclic ketones possessing of course an a-methylene group, are similarly converted into 1,2-diketones (e.g. the formation of cyclohexane-l,2-dione from cyclohexanone, Expt 5.99, cognate preparation) unsymmetrically substituted cyclic ketones would normally give rise to regioisomers. 

Photosensitized oxygenation of the enolic forms of cyclohexane-1,2-diones in methanol gives 5-oxoalkanoic acids and methyl 5-carboxy-1-hydroxypentanoates with evolution of CO. The product distribution shows a marked temperature dependence which suggests that endoperoxides (16) and (17), present as unstable intermediates, are trapped by the solvent. a-Oxocarboxylic esters undergo direct photo-oxidation in polar and non-polar... 

Treatment of enamino ketones 3, obtained from cyclohexane-1,3-dione and 2-nitroaniline, with base gives quinoxaline Af-oxides 4 in good yields. 

Benzofuroxan (benzofurazan 1-oxide, 1) reacts with readily enolizable cyclohexane-1,2-dione in the presence of a secondary or tertiary amine to give a mixture of phenazine-l-ol mono- and di-jV-oxides. In order to improve the yield of the dioxides, the mixture obtained can be treated without further separation with 3-chloroperoxybenzoic acid in benzene. ... 

Phenazine 5-Oxide A solution of the benzofuroxan 1 (0.032 mol) in Et NH (100 mL) or EtjN was added dropwise to cyclohexane-1,2-dione (1.79 g, 0.016 mol) in a 250-mL 3-necked round-bottom flask equipped with a mechanical stirrer. After the addition of the benzofuroxan solution was complete, the mixture was stirred for A h (see table above). The mixture was diluted with crushed ice and acidified with HOAc. The red-brown solid was collected, washed with HjO and dried. TLC showed the presence of red and olive-green products. 

R2CHOH—>J 2C=0. In a preliminary experiment Berkowitz and Rylander oxidized tra/ -cyclohexane-12-Uiol in water as solvent and isolated in 15% yield a product characterized as probably cyclohexane-l -dione. Nakata oxidized several steroid secondary alcohols to ketones in very high yield. For example a... 

Of a number of syntheses of cyclohexane-1,2-dione investigated the method preferred is oxidation of 2-hydroxycyclohexanone with ferric chloride in acid solution.""... 

Cyclic 1,3-diketones. Wolfrom and Bobbitt found that severai cyclic 1,3-di-ketones reduce sodium periodate in aqueous solution and are oxidized to dibasic acids. Thus cyclohexane-1,3-dione, in which the diketo form (1) is practically nonexistent, on oxidation with excess periodate (5.7 equiv.) afforded pure glutaric acid in 86.5% yield. The reaction is regarded as involving intermediates (3)-(5),... 

The total neutral essential oil from M. oleifera leaves is composed of 44 constituents and include toluene, 5-ter/-butyl-l,3-cyclopentadiene, benzaldehyde, 5-methyl-2-furaldehyde, benzeneacetaldehyde, linaloloxide, 2-ethyl-3,6-dimethylpyrazine, undecane, a-isophorone, benzylnitrile, 2,6,6-trimethyl-2-cyclohexane-l, 4-dione, 2,2,4-trimethyl-pentadiol, 2,3 -epoxycarane, p-menth-1 -en-8-ol, 2,6,6-trimethylcyclohexa-1,3 -dienecarbaldehyde, indole, tridecane, a-ionone, l,l,6-trimethyl-l,2-dihydronaphthalene, a-ionene, (1-damascenone, 3-ionone, ledene oxide, 2-ter/-butyl-l,4-dimethoxybenzene, ( )-6,10-dimethylundeca-5,9-dien-2-one, 4,6-dimethyl-dodecane, 3,3,5,6-... 

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