5.5- Dimethylcyclohexane-l ,3-dione

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. - ... 

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. 

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). ... 

Beckmann rearrangement of cyclohexane-1,3-dione. Methyl (50, R = Me, R1 = H) and dimethyl 50 (R = R1 = Me) derivatives were also prepared from 5-methyl- and 5,5-dimethylcyclohexane-l,3-dione, respec-... 

Dimedon, 5,5-dimethylcyclohexane-l,3-dione, is prepared by an interesting process discovered by Vorlander. The reaction of 1 mole each of diethyl malonate, mesityl oxide, and sodium ethoxide in absolute ethanol probably involves a Michael addition followed by an intramolecular ester condensation to close the ring to give the diketo ester formulated (procedure of Shriner and Todd. Aqueous potassium... 

Dimethyl-2-phenylspiro[2.5]nonane-4,8-dione (17) was obtained with high enantioselectiv-ity from styrene and 2-diazo-5,5-dimethylcyclohexane-l,3-dione (diazodimedone) in the presence of a copper complex bearing chiral 1,3-dioxo ligands derived from 3-trifluoroacetyl-( + )-camphor. The catalysts retain their activity even if linked to a polymeric support. Despite the impressive optical induction for this transformation, no other successful applications of these catalysts have so far been reported with a trisubstituted alkene, only very low enan-tioselectivity was observed. ... 

The carbenoid reaction between a-diazo ketones and simple alkenes or styrenes leads to acylcyclopropanes. (For the enantioselective cyclopropanation of styrene with 2-diazo-5,5-dimethylcyclohexane-l,3-dione, see Section 1.2.1.2.4.2.6.3.2.). With ketene acetals, 2,3-dihyd-rofurans are obtained. In contrast, l-acyl-2-oxycyclopropanes or 2-oxy-2,3-dihydrofurans can be formed in reactions with enol ethers and enol acetates the result depends strongly on the substitution pattern of both reaction partners.Whereas simple diazo ketones usually lead to cyclopropanes (Table 15), 3-diazo-2-oxopropanoates and 2-diazo-l,3-dicarbonyl compounds, such as 2-diazoacetoacetates, 3-diazopentane-2,4-dione, and 2-diazo-5,5-dimethylcy-clohexane-1,3-dione, yield 2,3-dihydrofurans and occasionally acyclic structural isomers thereof when reacted with these electron-rich oxy-substituted alkenes. 

Diphenylcyclopropenone (2.06 g, 10 mmol) was dissolved in anhyd 1,2-dichloroethane (20 mL) and alkylated with triethyloxonium tetrafluoroborate (1.90 g, 10 mmol). After 15 min, a solution of 5,5-dimethylcyclohexane-l,3-dione (1.40 g, 10 mmol) in 1,2-dichloroethane (20 mL) was added then a solution of i-PfjNEt (1.30 g, 10 mmol) in 1,2-dichloroethane (20 mL) was added dropwise over a 90-min period with efficient stirring. Then, the resulting solution was stirred for a further 3 min and the solvent was evaporated in vacuo. The residue was triturated with benzene (40 mL) and the precipitated amine hydro-tetrafluoroborate salt was filtered off. Evaporation of the benzene solution yielded the main portion of crude product a second (minor) crop was obtained as insoluble material when the hydrotetrafluoroborate salt was dissolved in HjO. Both fractions were combined and recrystallized (EtOH) yield 2.10 g (64%) mpl98-199=C. 

To a THF suspension (2 ml) of sodium enolate, generated from sodium hydride (ca. 80 mg) and 5,5-dimethylcyclohexane-l,3-dione (140 mg, 1.0 mmol), was added triphenylbismuth dichloride (511 mg, 1.0 mmol) at —20°C under nitrogen. The colorless suspension turned yellow and after 1 h a clear solution was obtained. Removal of the solvent followed by chromatographic purification of the product on a short silica gel column, using methanol-dichloromethane as the eluent, gave the bismuthonium ylide in 52% yield (m.p. 75°C) [89CC1749]. 

Diazo-5,5-dimethylcyclohexan-l,3-dione (140) with an excess of acrylate esters serving as both reactant and solvent in the presence of rhodium acetate afforded benzofuran 141 (98SC865). The formation of the dihydrofurans probably proceeded via a 1,3-dipolar cycloaddition of a metal carbenoid to the x,/)-unsa titrated ester (98SC865). Similarly, the reaction can take place with dihydrofuran, furan, and 1-acetyl indole to give 109,142, and 143, respectively (91JOC6269) (Scheme 24). 

Cyclocondensation of 3-amino-5-methylpyrazole with 2-arylmethyli-dene-5,5-dimethylcyclohexane-l,3-diones or 9-aryl-3,3,6,6-tetramethyl-2,3,4,5,6,7,8,9-octahydro-lH-xanthene-l,8-diones, in DMF or methanol gave 4-aryl-3,7,7-trimethyl-l,4,6,7,8,9-hexahydropyrazolo[3,4- 7]quinolin-5-ones 323 whose structure was proved by the X-ray diffraction data (06RJOC1015). 

Dimedone was treated with two equivalents of bromine in glacial acetic acid to yield 2,2-dibromo-5,5-dimethylcyclohexane-l,3-dione. The dibromo compound was subjected to reaction with substituted 2-aminothiophenols, 2-aminophenol, thiocarbohydrazones, and triazoles to furnish spiro-(2, 6 -dioxo-4, 4 -dimethylcyclohexane)-6-substituted-l,... 

---