Diketones hydrolytic

Tetramethylisoindolenine (50) is obtained as an unstable, crystalline solid from the reaction of 2,5-hexanedione with 2,5-dimethylpyrrole in the presence of sulfuric acid. Treatment of the same diketone with ammonium sulfate also affords this isoindolenine. NMR measurements in deuteriochloroform indicate that a small amount of 1,3,4,7-tetramethylisoindole (51) is present in equilibrium with the isoindolenine. This same isoindole was postulated as an intermediate in the reductive self-condensation of 2,5-dimethyl-pyrrole (52) which affords a mixture of cis- and lwMs-l,3,4,7-tetra-methylisoindolines (53 and 54). Hydrolytic opening of the... 

After the first hydrolytic step, secondary alcohols seem to continue biodegradation through ketone, hydroxyketone, and diketone. Diketones then produce a fatty acid and a linear aldehyde which is further oxidized to fatty acid. Finally, these two fatty acids continue biodegradation by enzymatic 3 oxidation [410],... 

The functionalized [4]radialene 86 offers opportunities for further transformations by hydrolytic cleavage of the O-silylenol moieties and by oxidative desilylation (Scheme 16). Base- and acid-catalyzed hydrolyses lead to different products (130 and 131, respectively)60. By analogy with the formation of 1,4-diketones by oxidative coupling of two siloxyalkene molecules, treatment of 86 with the iodonium salt Phl+—O—+I—Ph BF4 in dichloromethane leads to 132 which is immediately... 

Both D-[l- C]xylose and D-[5- C]arabinose were exposed to a concentrated phosphate buffer solution (pH 6.7). 1-Hydroxy-2-propanone (ace-tol) was distilled from the heated solution. Radioassay indicated that similar labeling [3- C] occurred in the acetol from both pentoses, with loss of the configurational difference thus, a 3-ketopentose or its enediol was suggested as an intermediate. Further work with 3-0- and 6-0-methyl-D-glucose and with 1-0-methyl-D-fructose indicated that /3-elimination from a 3-ketose or, in the case of a hexose, from a 3-ketose or a 4-ketose, or both, tautomerization of the resulting a-diketone to a /3-diketone, and hydrolytic cleavage are essential steps in the formation of acetol. 

Simple a-diimines are hydrolytically unstable, but can be stabilized as metal complexes by virtue of the formation of stable five-membered chelate rings.68 69 a-Diketones and glyoxal undergo metal template reactions with amines to yield complexes of multidentate ligands such as (34),70 (35)71 and (36).72>73 In the last case, the metal exerts its stabilizing influence on the a-diimine partner in an equilibrium process (Scheme 5). The same phenomenon occurs with amino alcohols74 75 in addition to amino thiols. The thiolate complexes (37) can be converted to macrocyclic complexes by alkylation in a kinetic template reaction (Scheme 5).76 77... 

The synthesis of 1,5-diketones 521 from 3,4-dihydropyranones 519 has been reported and is shown in Scheme 95 <1999T9333>. Organolithium reagents were used to open the lactone reagents, and best results were achieved when the reactions were quenched with trimethylsilyl chloride prior to hydrolytic workup. 

CH3 to Br to N02. The product / -diketones (largely enolic) were susceptible to hydrolytic retroaldol cleavage, a result which affected the UV spectrum of the reacting solutions. Only when this process occurred at a rate similar to that of the enamine hydrolysis, was the first-order behavior of the time course compromised, and in these cases correction for loss of dione was made. 

In contrast to intermolecular photoaldols, which can be manipulated with facility, intramolecular cycloadducts undergo retro-[2 + 2] cycloaddition when subjected to hydrolytic conditions. In an alternative protocol, oxymercuration of (229) afforded a-mercurio ketone (230 42%) which was acetylated under standard conditions to provide 1,4-diketone (231) quantitatively. Similarly, epoxidation of (229) provided functionalized photoaldol (232), which was hydrolyzed and acetylated to form a-acetoxy derivative (233). Finally, hydrolysis of (234) (4 1 THF/0.1 N HCl) gave lactol (235) in nearly quantitative yield, illustrating the utility of the intramolecular furan carbonyl photocycloaddition in spirocycle formation. 

Diraethyldihydroresorcinol (dimedone) is converted into 3,3-di-methylglutaric acid on treatment with sodium hypochlorite or sodium hy-pobromite. As a p-diketone, it suffers alkaline hydrolysis to 3,3-dimethyl-5-ketohexanoic acid, which undergoes regular hypohalite degradation of the methyl ketone end (equation 429) [735. Both the hydrolytic opening of the ring and the hypohalite reaction are accomplished in one step [699],... 

Dieckmann-condensation of the tetraester (104b) followed by hydrolytic decarboxylation yielded the diketone (107), which could be converted into the compounds 108. Treatment of 108b or 108c with potassium t-butoxide in toluene gave a dihydrodiazapyraceheptylene... 

Alkylation of lithiated l-(l-ethoxyprop-2-enyl)benzotriazole leads to enones after hydrolytic removal of the heterocycle addition of the lithiated species to cyclohexenone then hydrolytic cleavage of the heterocycle prodnces an nnsaturated l,4-diketone. ° Addition of the same anion to methyl but-2-enoate generates an anion in which the benzotriazole is displaced intramolecularly and a cyclopropane resnlts. ... 

Acrylonitrile (2) has also been used for heterocycle formation from p-diketone substrates. Conjugate addition of 185 to acrylonitrile produced 186 with previously reported conditions,2 and cyclization under hydrolytic conditions generated the corresponding lactam 187 (Scheme 15).65 Dissolving metal reduction provided the trans ring fused product 188, which was subsequently converted to 189. Reduction of 189 completed the synthesis of the Lycopodium alkaloid ( )-Na-methyl-A p-acetylphlegmarine (190) as a mixture of 4 diastereomers. 

The reaction is applicable to almost all aromatic diketones, but in the aliphatic series it is restricte4 to isolated cases.164 When carrying out the benzilic acid rearrangement it is necessary to ensure that the diketone is free from cyanide, because Dilthey and Scheidt165 have shown that in the presence of cyanide ions benzil is cleaved hydrolytically to benzaldehyde and benzoic acid. 

The specific diketones and method of preparation used for the chelates are given in Table VIII. In general, the tetrakis species are white to pale yellow in color, whereas the halosubstituted species are yellow and yield yellow solutions. In many instances there are discrepancies in the melting points reported by different authors. Although the possibility of different crystalline forms cannot be dismissed, the presence of hydrolytic impurities is the most likely explanation. The data given by Fay are considered the most reliable. 

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