Ketones aliphatic diketones

The latter method can also be applied to aliphatic or ,/Tunsaturated ketones, to diketones and to aromatic or acetylenic aldehydes. Furthermore, it tolerates a variety of functional groups present in the substrate, as demonstrated by the efficient formation of allenes 174 and 175, which bear an additional nitro and ester group, respectively (Scheme 2.55) [89]. 

The following tables are intended to include all the reductions with aluminum alkoxides which were reported prior to February, 1943, although some examples doubtless have been overlooked. Table I lists the reduction of aldehydes, which have been subdivided into (a) aliphatic aldehydes and (b) alicyclic and aromatic aldehydes. Table II lists the reduction of ketones, which have been classified as (a)-satu-rated and unsaturated aliphatic ketones, (b) aromatic ketones, (c) alicyclic ketones, (d) unsaturated alicyclic and aromatic ketones, (e) a- — halogen substituted ketones, (f) diketones, (g) protected diketones, (h) alcoholic and phenolic ketones (and ethers or esters of these), and (i) keto esters. 

Benzil and its derivatives condense with aliphatic ketones to give 4-hydroxycyclopentenones in good yield (equation 37). Although this reaction is not usually observed with aliphatic diketones, a recent example has been reported. A special version of this reaction involves the use of dibenzyl ketone. In such cases the initial 4-hydroxycyclopentenone dehydrates to form the tetraphenylcyclopentadienone ( tetracyclone equation 38). ... 

Waxes in general can contain a wide range of different compounds, including aliphatic diols, free alcohols, hydrocarbons (especially squalene), aldehydes, ketones, hydroxy-ketones, p-diketones and sesquiterpenes. The composition and biochemistry of waxes in nature, and methods for their analysis, have been reviewed in a comprehensive monograph [491],... 

One of the most actively investigated aspects of enamine chemistry has been the acylation process (i). Initial intensive studies by Hiinig (373-375) showed the ease of preparing a variety of 9-diketones and particularly the synthetic potential of acylated cyclic ketones as intermediates in the preparation of aliphatic keto acids, keto dicarboxylic acids and diketo dicarboxylic acids (376-378). 

The preparative importance of the acyloins depends on the fact that they are intermediate products, from which many 1 2-diketones can be obtained. The simplest aromatic member of this group is benzil (anisil and furil are analogous) like its aliphatic prototype diacetyl CH3.CO.CO.CH3 (and like anhydrous glyoxal) it is yellow in colour. Diacetyl is obtained from methyl-ethyl ketone via the monoxime of the former compound (von Pechmann). It is remarkable that diacetyl condenses to p-xyloquinone. (Formulate). 

Irradiation of mixtures of 1,3-diketones and aliphatic or aromatic primary or secondary amines absorbed over montmorillonite clay or silica in a microwave oven affords enamino ketones, e.g. equation 99311. 

The preferred route for reducing the molecular weight of PVA involves chain scission at the 1,3-diketone site (see Fig. 6). As the diketone element is chemically not very stable, a spontaneous degradation of oxidised PVA was also discussed [80]. Nevertheless, the preferred degradation pathway is most likely the biochemical process because enzymes were identified that showed high activity with diketone substrates [81], especially with oxidised PVA. The p-diketone hydrolase (BDH EC 3.7.1.7) hydrolyses aliphatic p-diketones to form methyl ketones and carboxylic acids in equimolar amounts [82]. The enzymatic cleavage of C-C bonds in p-diketones is not well studied [83]. BDH enzymes could be isolated from different PVA-degrading strains, purified, characterised and cloned [84]. 

The Acylation of Methyl Ketones with Aliphatic Esters to -Diketones... 

The lower members of the homologous series of 1. Alcohols 2. Aldehydes 3. Ketones 4. Acids 5. Esters 6. Phenols 7. Anhydrides 8. Amines 9. Nitriles 10. Polyhydroxy phenols 1. Polybasic acids and hydro-oxy acids. 2. Glycols, poly-hydric alcohols, polyhydroxy aldehydes and ketones (sugars) 3. Some amides, ammo acids, di-and polyamino compounds, amino alcohols 4. Sulphonic acids 5. Sulphinic acids 6. Salts 1. Acids 2. Phenols 3. Imides 4. Some primary and secondary nitro compounds oximes 5. Mercaptans and thiophenols 6. Sulphonic acids, sulphinic acids, sulphuric acids, and sul-phonamides 7. Some diketones and (3-keto esters 1. Primary amines 2. Secondary aliphatic and aryl-alkyl amines 3. Aliphatic and some aryl-alkyl tertiary amines 4. Hydrazines 1. Unsaturated hydrocarbons 2. Some poly-alkylated aromatic hydrocarbons 3. Alcohols 4. Aldehydes 5. Ketones 6. Esters 7. Anhydrides 8. Ethers and acetals 9. Lactones 10. Acyl halides 1. Saturated aliphatic hydrocarbons Cyclic paraffin hydrocarbons 3. Aromatic hydrocarbons 4. Halogen derivatives of 1, 2 and 3 5. Diaryl ethers 1. Nitro compounds (tertiary) 2. Amides and derivatives of aldehydes and ketones 3. Nitriles 4. Negatively substituted amines 5. Nitroso, azo, hy-drazo, and other intermediate reduction products of nitro com-pounds 6. Sulphones, sul-phonamides of secondary amines, sulphides, sulphates and other Sulphur compounds... 

A 2,2-disubstituted chromanone results from the condensation of o-hydroxyacetophenone with diethyl oxalate. The initially formed 1,3-diketone cyclizes spontaneously to ethyl 2-hydroxy-4-oxochroman-2-carboxylate (77LA1707). The enolate also reacts with aliphatic ketones to give 2,2-disubstituted chroman-4-ones via the diol (79TL3685). 

Table 8.6 shows that the equilibrium mixture consists of almost entirely keto form in the case of simple aliphatic and aromatic ketones, whereas significant amounts of enol tautomer are present in /J-diketones and /J-ketoesters. In these latter cases, the enol contains a conjugated tt electron system and an intramolecular hydrogen bond (30). Phenol exists entirely in the enol form, as the alter-... 

Pentanedione. 2,4-Pentanedione [123-54-6] (acetylacetone) is the lowest member of the aliphatic 1,3-diketones and is a colorless liquid with a mild ketone-like odor. It is completely miscible with organic solvents other physical properties are shown in Table 1. 

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