Cyclohexane-1,2-diones

Degradatiou. Heating of succinic acid or anhydride yields y-ketopimehc ddactone, cyclohexane-1,4-dione, and a mixture of decomposition products that include acetic acid, propionic acid, acryUc acid, acetaldeide, acrolein, oxaUc acid, cyclopentanone, and furane. In argon atmosphere, thermal degradation of succinic anhydride takes place at 340°C (123). Electrolysis of succinic acid produces ethylene and acetylene. 

The first series of soluble oligo(/ ara-phenylene)s OPVs 24 were generated by Kern and Wirth [48] and shortly after by Heitz and Ulrich [49]. They introduced alkyl substituents (methyls) in each repeat unit and synthesized oligomers 24 up to the hexamer. Various synthetic methods, like the copper-catalyzed Ullmann coupling, the copper-catalyzed condensation of lithium aryls, and the twofold addition of organomelallic species to cyclohexane-1,4-dione, have been thereby investigated. 

The authors developed two general concepts for the synthesis of these mono-disperse, defined oligomers. The oligomers can be built up in a stepwise fashion, e.g. via addition of organomelallic species to cyclohexane-1,4-dione followed by aromatization to the oligo(arylene) (e.g. for 25). 

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... 

The Fischer sequence applied to the bisphenylhydrazone of cyclohexane-1,4-dione by warming in acetic acid-sulfuric acid gave the 3-phenylhydra-zinocarbazole 242 as well as the indolocarbazole 243. ° In alcoholic sulfuric acid, 3-hydroxycarbazole, 3-aminocarbazole, and the pentacycle 243 were formed along the helicene 244. ... 

The dioxime of cyclohexane-1,4-dione reacts with acetylene in an autoclave in the presence of KOH/dimethyl sulfoxide (DMSO) (Trofimov reaction) to give l,5-divinyl-4,8-dihydropyrrolo[2,32f]indole by sequential [1,3]- and [3,3]-rearrangements in poor yield (Equation 91) <2004TL3789>. 

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. 

In contrast, cyclohexane-1,4-dione affords, in addition to other products, small quantities of the bisapiroepoxidos shown in Eq. (277), with diaaometbane1 and diaaocyclohmane76 respectively. 

We now discuss y-diketones. Pilcher and coworkers131 show cyclohexane-1,4-dione (57) to have a gas-phase enthalpy of formation of —332.6 1.2 kJmol-1, i.e. 3.0 ... 

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>. 

Cyclohexane-1,4-dione (0.27 mmol), 2,2-diethylpropane-l,3-diol (0.27 mmol) and p-toluenesulfonic acid (0.36 g) were dissolved in 200 ml toluene and heated on a water bath. After the mixture had cooled to ambient temperature, water was removed, the organic phase was washed with aqueous NaHC03, dried and the solvent removed. The residue was purified by flash chromatography using EtOAc/petroleum ether, 1 4, and the product isolated in 47% yield. 

Spiroepoxide derivatives of cyclohexane-1,4-dione ethylene monoketal have been prepared (1,2,3) as illustrated below in Eq. 2 ... 

Dioximes of hexane-2,5-dione (81) and cyclohexane-1,4-dione (82) reacted with acetylene under pressure to give dipyrrole 83 and 1,5-divinyl-4,8-dihydropyrrolo[2,3-/]indole (84) in 12% and 6% yields, respectively, thus exemplifying a very simple, straightforward route to inaccessible or unknown pyrrolic assemblies (Equation (22)) (04TL3789). 

Until recently knowledge of twist conformation of simple cyclohexanes could be said to be limited to certain di-f-butylcyclohexanes which if they existed as chair conformations would have an axial f-butyl group, to cyclohexane-1,4-dione and to certain highly substituted cyclohexanes. Undoubtedly twist conformations are quite common, it is unfortunate that reasonably direct evidence is often not available. 

With 1,4-diketones the distribution of the reduction products is dependent on the stereochemical situation of the two carbonyl functions. In acyclic derivatives, with no stereochemical interaction between the two carbonyl functions, the ketone groups are independently reduced to give methylene products in the usual manner. On the other hand, cyclic 1,4-diketones react differently. For example, cyclohexane-1,4-dione (22) suffers ring opening to give hexane-2,5-dione and hex-5-en-2-one derivatives, and products of further reduction are also detectable (equation 11). A 1,4-diketone (23) in which the two carbonyls are stereochemically close, gave the diketone (24) under relatively mild conditions (Zn/AcOH, 25 C), formed by the same C—C bond cleavage as seen in cyclohexane-1,4-dione. Under Clemmensen conditions this derivative was then converted to cyclobutane-1,4-diol (25 equation 12) in 98% yield, which is closely related to the aforementioned cyclopropanediol intermediate. ... 

Out of several conceivable probes, a cyclohexane derivative was selected initially because twofold allylation of cyclohexane-1,4-dione offered a ready entry and led to an easily separable mixture of the corresponding cis-(47) and trans- (45) tertiary alcohols. In each case ozonolysis resulted in the forma-... 

Hydrolysis-decarboxylation. The Organic Syntheses procedure4 for the conversion of diethyl 2,5-diketocyclohexane-l,4-dicarboxylate (1) to cyclohexane-1,4-dione (2) calls for treatment with water in a steel autoclave at 185-195° for 10-15 min. (yield 72-80%). The reaction can be carried out more conveniently and in higher yield by refluxing in aqueous ethylene glycol containing some p-toluenesulfonic acid.5... 

A. The chair conformation is shown in 74. One consequence of a chair conformation is that a pronounced l,3-diaxial interaction exists between a /-butyl group and a hydroxyl group. This can be avoided if the ring adopts a twist-boat conformation 75. The number of molecules that exist to any extent in the twist-boat conformation is small, and 75 has the benefit of a hydrogen-bonded interaction between the two hydroxyl groups. The twist-boat conformation is ca, 6 kJ mol 1 more stable than the boat conformation. In this work, Stolow8 claims an equilibrium between 74 and 75. Another molecule known to exist in a twist-boat conformation is cyclohexane-1,4-dione (76) (see Hoffmann and Hursthouse9). 

Mol. wt. 204.18, m.p. 296°. The reagent was prepared by condensation of cyclohexane-1,4-dione with malononitrile, bromination, and dehydrobromination with pyridine. The compound has properties similar to those of tetracyanoethylene and is a TT-acid of comparable strength. The equilibrium constant for ir-complex formation with pyrene is 78.4 as compared to 29.5 for the tetracyanoethylene-pyreno complex. 

The biradical formed on photolysis of 2,3-epoxy-cyclohexane-1,4-dione... 

Three chemical steps convert cyclohexane-1,4-dione into a compound which is used for the synthesis of the anti-migraine drug frovatriptan. Suggest how this transformation is carried out. 

As with the similar formation of catechol and resorcinol, cyclohexane-1,4-dione can be converted into 1,4-dihydroxybenzene in high yield by treatment with acetic anhydride and inorganic acids (ref49). 

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