2.2- Dimethyl-1,3-cyclohexanedione

This reaction has been applied to a great number of carbonyl compounds, e.g., cyclopentanone, 1,3-cyclohexanedione, 5,5-dimethyl-l,3-cyclohexanedione, 1-acenaphthenone, 1,3-indane-dione, 1,3-phenalanedione, sodium salts of 3-aryl-3-oxo-propanals, 2,3-dihydrobenzo[6]thiophen-3-one, sodium benzoyl-acetate, benzoylacetonitrile, ethyl cyanoacetate, cyano-acetanilide, barbituric acid, rhodanine, iV-phenylrhodanine, and iV-methylenebenzothi azoline. ... 

From the aldehyde and methone (dimedone 5,5-dimethyl-1,3-cyclohexanedione dimethyl dihydroresorcinol) in aqueous ethanol or methanol. 

Acetaldehyde can be isolated and identified by the characteristic melting points of the crystalline compounds formed with hydrazines, semicarbazides, etc these derivatives of aldehydes can be separated by paper and column chromatography (104,113). Acetaldehyde has been separated quantitatively from other carbonyl compounds on an ion-exchange resin in the bisulfite form the aldehyde is then eluted from the column with a solution of sodium chloride (114). In larger quantities, acetaldehyde may be isolated by passing the vapor into ether, then saturating with dry ammonia acetaldehyde—ammonia crystallizes from the solution. Reactions with bisulfite, hydrazines, oximes, semicarb azides, and 5,5-dimethyl-1,3-cyclohexanedione [126-81 -8] (dimedone) have also been used to isolate acetaldehyde from various solutions. 

ALKYLATION OF DIMEDONE WITH A TRICARBONYL(DIENE)IRON COMPLEX TRlCARBONYL[2-[(2,3,4,5-t))-4-METHOXY 2,4 CYCLOHEXADUEN-l-YLJ-5,5-DIMETHYL-l,3-CYCLOHEXANEDIONE]IRON... 

On the other hand y-pyrones or 1,3-diketones could be obtained from the reactions of ketone derived enamines with diketene 423-426). The addition of dimethyl ketene dimer to aldehyde or ketone derived enamines produced cyclohexanediones 425,426). 

Mesityl oxide (Section 111,79) (I) condenses with ethyl malonate in the presence of sodium ethoxide to give the sodium derivative of (II) this upon hydrolysis with aqueous potassium hydroxide, followed by acidification, gives the cyclic diketone 5 5-dimethyl-1 3-cyclohexanedione (III), of which the enolic form is 5 5-dimethyldihydroresorcinol (IV) ... 

The assay for formaldehyde is today mainly performed by either of two general methods. The one most widely used depends on the reaction of 5,5-dimethyl-1,3-cyclohexanedione (Dimedon) with formaldehyde when applied after the destruction of excess periodate, it proceeds quantitatively,... 

When 2-4-0-ethylidene-D-glucofuranurono-6,3-lactone [obtained by the hydrolysis of thioacetal 61 (Ph = Et)] was treated with 5,5-dimethyl-l,3-cyclohexanedione (dimedone), 6-deoxy-6,6-bis(4,4-di-methyl-2,6-dioxocyclohexyl)-3,5-0-ethylidene-L-gulono-1,4-lactone (73) was formed in 71% yield.99... 

Lehn, which was obtained from a dynamic library of hydrogen-bonding building blocks [101]. This system involved the equilibration between different products resulting from the condensation of 5,5-dimethyl-1,3-cyclohexanedione (74) and 2-hydrazinopyridine (75) (see Scheme 38). 

Yoshida and coworkers [63, 64] studied the oxidative cycloaddition of cyclic 1,3-dione (1,3-cyclopentanedione and some 1,3-cyclohexanediones) and olefins in various solvents and electrolytes. The best results were obtained in acetonitrile containing tetraethylammonium tosylate as electrolyte (97% yield with 5,5-dimethyl-l,3-cyclohexadione and styrene) (Scheme 45). 

Cycloaddition Reactions with Other Nucleophiles The anodic two-electron oxidation of catechol affords o-quinone that may react with the enolates of 4-hydroxycoumarine or 5,5-dimethyl-1,3-cyclohexanedione (dimedone). The resulting adducts undergo a second anodic oxidation leading to benzofuran derivatives in good yields (90-95%) (Scheme 53) [75, 76]. 

Crystal structures of compounds of the conformation shown in [27] and [28] have been reported 2-phenylmalondialdehyde (Semmingsen, 1977) and 5,5-dimethyl-l,3-cyclohexanedione, i.e. dimedone (Semmingsen, 1974 Singh... 

Several 1,4-disubstituted derivatives of the dication, 63, were successfully prepared. The 1,4-diphenyl, 1,4-dimethyl, 1,4-dicyclopropyl-substituted derivatives of carbodication 63 (65, 66, and 67) are exceptionally stable. The 1,4-dimethyl-1,4-cyclohexyl dication, devoid of the adjacent cyclopropyl groups, could not be prepared. The carbocationic center in all these dications are somewhat shielded as compared to their monocations. The C NMR chemical shifts of the carbocationic centers for the dications 65, 66, and 67 are 235.4, 293.4, and 260.8 ppm, respectively. The diprotonated ann -tricyclo(5.1.0.0 )octa-2,6-dione, 68, may be treated as a dicarboxonium ion, instead of dihydroxy dicarbenium ion, since the cabronyl carbon is shielded by only 25.2 ppm, much smaller than that observed for the protonated cyclohexanedione (34 ppm). The para carbons of the phenyl substituents in carbodication 65 are relatively shielded by about 5 ppm from that of the parent l,4-diphenylcyclohexane-l,4-diyl dication showing relatively less delocalization of the charge into the aromatic rings. 

The mixed hydrazones (667), prepared from diacetyl monobenzoyl hydrazone and arylhydrazines, undergo oxidative cyclization to 2-aryl-jV-benzoyl-4,5-dimethyl-l,2,3-triazol-l-ylimines (668) in 32-76% yield upon treatment with lead tetraacetate in acetonitrile (Scheme 132) <92JOC2252>. The cychzation of bishydrazones to 1,2,3-triazoles can also occur in acidic or basic media. For instance, the tetrahydrobenzo[ /]triazol-4-one (669) is prepared by the base-catalyzed cyclization of the corresponding a-hydrazono oxime (Equation (53)) <85HCA1748>. 3-Methyl-1,2-cyclohexanedione reacts... 

ALKYLATION OF DIMEDONE WITH A TRICAEBONYL(DIENE)IEON COMPLEX TRICAEB0NYL[2-[(2,8,4,5-7,)-4-METH0XY-2,4-CYCL0HEXADIEN-1-YLJ-5,5-DIMETHYL-I,3-CYCLOHEXANEDIONE]IEON... 

Nitro-5,5-dimethyl-l, 3 cyclohexanedione or 4-Nitro-l,l-dimethyl-3,5-cyclohexanodione,... 

Cyclizations involving cyclic 1,3-diones are very effective. Thus 5,5-dimethyl-l,3-cyclohexanedione (dimedone) and 5-phenyl-1,3-cyclohexane-dione react with aldehydes R2CHO to give condensed 4//-pyrans 86a,2,132 86b,63133 86d,63 and 86e.2... 

IPA (Pr IR ivDde-OH 2-propanol isopropyl infrared 2-(3-methylbutyryl)-5,5-dimethyl-l,3-cyclohexanedione... 

The reaction of 2,2-disubstituted 1,3-cyclohexanediones 1 with dimethyl methanephosphonate in THF in the presence of LDA gives 3-substituted 2-cyclohexenones 2 in moderate to very good yields. 

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