5,5 -Dimethylcyclohexane-1,3-dione

Hexa hydro-3,4-d ioxobenzo[b] fura n 85 was obtained by intramolecular nucleophilic heterocyclization of 2-chloroacetyl-5,5-dimethylcyclohexane-1,3-dione 84 (85KGS1130). Cyclization was also achieved in the presence of sodium nitrite, sodium methoxide, sodium acetate, or silver acetate. The nucleophiles acted as basic deprotonating agents and did not interact with the chloroacetyl group (89ZOR1882). 

C7H1HN2O, cis-N-Cyclohexyl-N -methyldiimide N-oxide, 43B, 175 C7Hii,N20, cis-N-Methyl-N -cyclohexyldiimide N-oxide, 43B, 175 CsH,1CI3O, 2,2,3-Trichloro-4,4-dimethylcyclohexanone, 44B, 126 CgH,lOsRbS, Rubidium 5,5-dimethylcyclohexan-1,3-dione-2-sulphonate, 40B, 1078... 

In the following examples, pinacol is oxidised to acetone, which is identified as its semicarba2one and its 2,4 dinitrophenylhydra2one, and glycerol is oxidised to formaldehyde and formic acid. The formaldehy de is readily detected by the condensation product which it gives with dimedone, 5,5-dimethylcyclohexan-i,3-dione (p, 277). 

Dipping solution Dissolve 0.3 g dimedone (S,S-dimethylcyclohexane-1.3-dione) in... 

Amines, thiols, eOH (p. 226), etc., will also add to the 0-carbon atom of 0-unsaturated carbonyl compounds and esters, but the most important reactions of C=C—C=0 systems are in Michael reactions with carbanions reactions in which carbon-carbon bonds are formed. A good example is the synthesis of l,l-dimethylcyclohexan-3,5-dione (dimedone, 100) starting from 2-methylpent-2-ene-4-one (mesityl oxide, 101) and the carbanion 0CH(CO2Et)2 ... 

Mercapto-4-amino[l,2,4]triazole can also be transformed to derivatives of the title ring system by 1,3-dioxo reagents. These transformations are summarized in Table 6. In most of these cases, 5,5-dimethylcyclohexane-l,3-dione was used, and, accordingly, this procedure can lead to some cyclohexenyl-fused derivatives. 

The diacylation of isopropenyl acetate with anhydrides of dicarboxylic acids is applicable for the synthesis of several other cyclic jS-triketones in moderate yield. - It has been used for the synthesis of 2-acetylcyclohexane-l,3-dione (40% yield), 2-acetyl-4-methylcyclopentane-l,3-dione (10% yield), 2-acetyl-4,4-dimethylcyclopentane-l,3-dione (10% yield), 2-acetyl-5,5-dimethylcyclohexane-l,3-dione (10% yield), 2-acetylcyclo-heptane-l,3-dione (12% yield) and 2-acetylindane-l,3-dione (26% yield). Maleic anhydrides under more drastic conditions give acetylcyclopent-4-ene-l,3-diones in yields from 5% to 12%. The corresponding acylation of the enol acetate of 2-butanone with succinic anhydride has been used to prepare 2-methylcyclopentane-l,3-dione, an important intermediate in steroid synthesis. - ... 

Microbial reduction of prochiral cyclopentane- and cyclohexane-1,3-diones was extensively studied during the 1960 s in connection with steroid total synthesis. Kieslich, Djerassi, and their coworkers reported the reduction of 2,2-dimethylcyclohexane-l,3-dione with Kloeokera magna ATCC 20109, and obtained (S)-3-hydroxy-2,2-dimethylcyclohexanone. We found that the reduction of the 1,3-diketone can also be effected with conventional baker s yeast, and secured the hydroxy ketone of 98-99% ee as determined by an HPLC analysis of the corresponding (S)-a-methoxy-a-trifluoromethylphenylacetate (MTPA ester).(S)-3-Hydroxy-2,2-dimethy1cyc1ohexanone has been proved to be a versatile chiral non-racemic building block in terpene synthesis as shown in Figure 1. 

Reaction of 31d-f or 154 with a cyclic active methylene compound such as 5,5-dimethylcyclohexane-l,3-dione (dimedone) gave 299a-d (47-85%), which by subsequent cyclization led to the substituted 1,2,3,4,5,6,7,8-octahy-droxanthenes 300a-d (72-90%) <1999CCC1135>. 

When an a-chloroaldehyde or an a-chloroketone is condensed with a /3-ketoester, in the presence of aqueous base, a furan is produced bearing an ester substituent at the /3-position. It is thought that the reaction is of the aldol type intermediate dihydrofurans (256) have been isolated in certain cases (Scheme 70) (74BSF519). The condensation of ethyl bromopyru-vate and sodium oxaloacetate follows a similar mechanism (54JOC1671). The one-pot synthesis of 2,4,5-trisubstituted furans (257) from ketones and ethyl 3,4-dibromo-2-butenoate is a useful addition to a well known route (80S52). The analogous reaction of cyclic /3-diketones, i.e. cyclohexane-1,3-dione and 5,5-dimethylcyclohexane-l,3-dione, results in the formation of the condensed furans (258) and (259). These reactions are preformed either in ethanol with sodium ethoxide or in DMF with potassium carbonate. 

Dimedone (5,5-dimethylcyclohexane-l,3-dione) in saturated aqueous solution or in 10 per cent alcohol solution gives crystalline derivatives (2) with aldehydes, but not with ketones. The reaction is ... 

You can buy dimedone (5,5-dimethylcyclohexane-l,3-dione) from chemical suppliers. If, as is wise when you buy any compound, you run an NMR spectrum of the compound to check on its purity, you might be inclined to send the compound back. In CDCI3 solution it is clearly a mixture of two compounds. Overleaf you can see lH and l3C NMR spectra of the mixture with the peaks of the dione in red. 

These forms are in equilibrium and cannot be separated at room temperature. The equilibrium is nothing to do with the two methyl groups at C5. And yet the 2,2-dimethyl compound is a perfectly normal diketone with all the expected peaks in the NMR. You will see later that it is only the relative position (1,3) of the carbonyl groups and the presence of at least one hydrogen at 2,2-dimethylcyclohexane-l,3-dione... 

S)-3-Hydroxy-2,2-dimethylcyclohexanone as a Building Block. Reduction of 2,2-dimethylcyclohexane-l,3-dione (24) with baker s yeast gives (S)-3-hydroxy-2,2-dimethylcyclohexanone (25) of 98-99% e.e. 21). This hydroxy ketone 25 was proved to be a versatile chiral building block in terpene synthesis (3). 

The IR, Raman and XH-NMR spectra and the X-ray crystallographic study of 2,2-diacetylethenamines (63) and 2-aminomethylene-5,5-dimethylcyclohexane-l,3-diones (64) show that these substances exist exclusively in the chelated enamino-diketone form, and that the conjugated system contained in them is essentially planar. The open-chain enamino-diketones 63, exist either in the solid state or in solution in the (E,Z,E) conformation (65). A similar conjugated core, having the fixed (Z,Z, ) conformation (66),... 

The reaction of dibenzoylacetylene and enol systems, such as acetylacetone, 5,5-dimethylcyclohexane-l,3-dione, 1-naphthol, 2-naphthol, 2,7-dihydroxynaphthalene, or 8-hydroxyquinoline in the presence of triphenylphosphine, leads to tetrasubstituted furans in 65-83% yield (Equation 115) <2002TL4503>. DABCO-catalyzed reaction of a-bromocarbonyl compounds with DMAD also yields highly substituted furans <2005JOC8204>. 

The fluorination of 1,3-diketones, for example 5.5-dimethylcyclohexane-l,3-dione, with xenon difluoride results in a complex mixture of products however, when the fluorination is carried out with two equivalents of xenon difluoride in the presence of insoluble cross-linked polystyrene-4-vinylpyridine only 2.2-difluoro-5,5-dirncthylcyclohexane-l,3-dione (4) is form-... 

Knoevenagel condensation of aldehydes with malononitrile under mechanochemi-cal mixing in the presence of MgO resulted in adducts of general structure 138 (Scheme 27), which were further treated with either ethylacetoacetate or 5,5-dimethylcyclohexane-l,3-dione to provide products 139 and 140 [63]. The transformation of 138 and 139 or 140 proceeded via a Michael-type nucleophilic addition of the enolizable ketoester or dione, followed by intramolecular cyclization. 

Dimethylcyclohexane-l,3-dione (dimedone) and Ai,Ai-dimethylbarbituric acid are relatively acidic (3-dicarbonyl compounds 5.3 and 4.7, respectively). The deprotection reaction involves (Scheme 16) a prototropic equihbrium between the P-dicarbonyl compounds and the deprotected carbamate species (shifted further to right by the formation of carbon dioxide and the respective amine). 

The Dde-protected amino acids are readily synthesized by acylation of dimedone (5,5-dimethylcyclohexane-l,3-dione) with acetic acid (DCCyDMAP activation), followed by condensation with the primary amine, e.g. Fmoc-Lys-OH, in refluxing ethanol for 60 hours, affording the orthogonally protected amino acid 24 (Scheme 9). 

In the case of derivatives carrying two carbonyl functions stereochemically close to each other, Clem-mensen reduction affords an interesting product distribution, passing through characteristic intermediates. o In the case of 1,3-diketones, a cyclopropanediol is involved, similar to the cyclopropanes formed from conjugated carbonyl systems. For instance, 5,5-dimethylcyclohexane-l,3-dione (16) is converted into 2,4,4-trimethylcyclopentanone (17) as the major product (equation 10). ... 

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