1.3- Cyclohexanediones, reaction with

Cyclohexanedione, reaction with guanidinium groups, 126 Cyclophilin 488 human 488s D-Cycloserine 739s Cyclosporin 488, 488s p Cylinders 65, 66, 686 Cystathionine, 746s formation 746 Cystathionine p lyase 742 Cystathionine p-synthase 744 Cystathionine y-synthase 743, 746 Cystatins 622, 629... 

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. 

Enamines of cyclic ketones react similarly (68,131). Thus the enamine (28) gave a goodyield of the monophenylhydrazone of 1,2-cyclohexanedione (193) on reaction with phenyldiazonium fluoborate and subsequent hydrolysis (6S). The products (193) have been cyclized to the corresponding... 

Another procedure relies on a domino Michael-O-alkylation reaction sequence to yield a variety of dihydrofurans. Combination of cyclohexanedione (30) with vinyl bromide 50 in the presence of l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) provides dihydrofuran 51 in 83% yield. Numerous 1,3-dicarbonyls and vinyl bromides are amenable to this methodology, and thus a wide range of products like 51 are available via this strategy. 

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,... 

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]. 

There are some methods that are specific to HCHO. For example, the Hantzsch reaction of HCHO, collected with a diffusion scrubber, with ammonium acetate, acetic acid, and acetylacetone to form diacetyldihydrolutidine, which is measured using its fluorescence at 470 nm, has been applied to air measurements (Dasgupta et al., 1988, 1990 Kleindienst et al., 1988a,b Lawson et al., 1990 Khare et al., 1997). Reaction with 1,3-cyclohexanedione and ammonium acetate to form a dihydropyridine derivative that is measured by fluorescence has been used in conjunction with a diffusion scrubber (Fan and Dasgupta, 1994). Enzymatic methods have been used in which formaldehyde dehydrogenase catalyzes the oxidation of HCHO to HCOOH in the presence of -nicotinamide adenine dinucleotide, NAD+, which is reduced to NADH. The latter is measured by fluorescence at 450 nm (Lazrus et al., 1988 Ho and Richards, 1990). 

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. 

The structure of the 1,2-cyclohexanedione dioxime (niox) complex, [Fe(niox)2(imid)2] (54), which is more soluble than the analogous DMG complex, has also been determined,604 but because of disorder in the cyclohexyl rings some of the important structural parameters were ill defined. However, the Mossbauer spectra of [Fe(niox)2L2] (L = py, imid, NH3, BuNH2) and related complexes have been studied in detail and are consistent with considerable tetragonal distortion.605,606 [Fe(niox)2(imid)2] reacts with CN to give [Fe(niox)2(CN)2]2, and by using only one equivalent of CN" [Fe(niox)2(CN)(imid)] can be obtained.605 Reaction with CO affords [Fe(niox)2(imid)(CO)] as in Scheme 13. 

Hence, the first clearcut evidence for the involvement of enol radical cations in ketone oxidation reactions was provided by Henry [109] and Littler [110,112]. From kinetic results and product studies it was concluded that in the oxidation of cyclohexanone using the outer-sphere one-electron oxidants, tris-substituted 2,2 -bipyridyl or 1,10-phenanthroline complexes of iron(III) and ruthenium(III) or sodium hexachloroiridate(IV) (IrCI), the cyclohexenol radical cation (65" ) is formed, which rapidly deprotonates to the a-carbonyl radical 66. An upper limit for the deuterium isotope effect in the oxidation step (k /kjy < 2) suggests that electron transfer from the enol to the metal complex occurs prior to the loss of the proton [109]. In the reaction with the ruthenium(III) salt, four main products were formed 2-hydroxycyclohexanone (67), cyclohexenone, cyclopen tanecarboxylic acid and 1,2-cyclohexanedione, whereas oxidation with IrCl afforded 2-chlorocyclohexanone in almost quantitative yield. Similarly, enol radical cations can be invoked in the oxidation reactions of aliphatic ketones with the substitution inert dodecatungstocobaltate(III), CoW,20 o complex [169]. Unfortunately, these results have never been linked to the general concept of inversion of stability order of enol/ketone systems (Sect. 2) and thus have never received wide attention. 

The de Mayo reaction with cyclohexa-l,3-diones is a method which still attracts interest as a synthetic approach to natural products. Typical of this is the short route to hirsutene (88). This involves photoaddition of the cyclohexanedione (89) to... 

Chemical modification of arginine.4 A new a-amino acid prepared by the reaction of 1,2-cyclohexanedione (1) with L-arginine (2) in aqueous 0.2 N NaOH was shown to be yV5-(-4-oxo-l,3-diazaspiro[4.4]non-2-ylidene-L-ornithine (3) by an independent synthesis. It is concluded that, in a tryptic digestion, 1,2-cyclohexanedione reacts... 

It was characterized by chemical analysis, ozonolysis to form formaldehyde, hydrogenation, bromination and by its infrared and 1H-NMR spectra. The diene has also been prepared by pyrolysis of l,4-bis-(acetoxymethyl)cyclohexane (13,14), from cyclohexanedione by the Wittig reaction (11,15) or by reaction with diazomethane (16), and by the electrochemical or metal reduction of 1,4-dihalo-bicyclo-[2,2,2-]octanes (17,18) or of l,l,2,2-tetrakis-(bromo-methyl)-cyclobutane (19). It is very stable if stored in ammonia rinsed, dry flasks. 

Pentaerythritol was chosen since it forms spiro compounds very readily and gives high enough yields to be used in a polymerization reaction with dialdehydes (, 1 )). Thus it was reasoned that a similar reaction with a cyclic diketone should produce a polyspiroketal. Thus, when 1,4-cyclohexanedione was heated in benzene with pentaerythritol plus a trace of -toluenesulfonic acid (PTSA) and the resulting water (93%) was removed by distillation, a white polymer precipitated. The spiro polymer I was shown by X-ray analysis to be highly crystalline and decomposed at 350°C without melting. It was almost completely insoluble in most solvents but was completely soluble in hot hexafluoroisopropanol. 

Cyclic ketones are converted smoothly to diazo ketones in the presence of HMPA. 4-Nitrophenyl azide (128) exhibits a diazo transfer reaction with malonates and cyclic 1,3-cyclohexanedione (128) in some cases diazo compound 129 further leads to fused triazole derivative (130) formation.52... 

A variety of monoterpenes take part in a hetero Diels-Alder reaction with the oxabutadiene derivative formed from 1,3-cyclohexanedione and formaldehyde, giving polyketide terpene frameworks by a one-pot regio-, chemo- and stereoselective reaction. Amongst the products accessible by this route is the oxapropellane (4) (94H661). 

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