Ketone condensation

Other Uses. More than 70 thousand metric tons of acetone is used in smaU volume appHcations some of which are to make functional compounds such as antioxidants, herbicides, higher ketones, condensates with formaldehyde or diphenylamine, and vitamin intermediates. 

The long known catalyses of some ketone condensation reactions by secondary amines, can be postulated to have their basis in the reactions of enamine intermediates with ketones. The unsuitability of methyl ketones for azeotropic enamine formation is based on this phenomenon. Recent studies in cyclization reactions have added further support to this concept (354). 

The product resulting from this reaction is dissolved in ether, the latter is evaporated and the residue subjected to the fractional distillation in vacuo. The fraction distilling under a pressure of 12 mm. at a temperature of from 125° to 135° C. is collected. This product may be still further purified by converting it by means of phenylhydrazine or other substituted ammonias into a ketone condensation product decomposable under the action of dilute acids. 

The process for the production of the ionone referred to in the second claim, consisting in treating the pseudo-ionone referred to in the first claim or its ketone condensation products with phenylhydrazine or other ammonia derivatives, finally with acids, substantially as described. 

Intramolecular phosphonate-ketone condensation (Homer-Wadsworth-Emmons)... 

Methyl vinyl ketone, condensation with 2-methyl-l,3-cyclohexanedione, 41, 38... 

Reaction between Two Molecules of the Same Ketone. In this case, the equilibrium lies well to the left and the reaction is feasible only if the equilibrium can be shifted. This can often be done by allowing the reaction to proceed in a Soxhiet extractor (e.g., see OS I, 199). Two molecules of the same ketone can also be condensed without a Soxhiet extractor, by treatment with basic Al203. Unsymmetrical ketones condense on the side that has more hydrogens. (An exception is butanone, which reacts at the CH2 group with acid catalysts, though with basic catalysts, it too reacts at the CH3 group.)... 

Aldehydes and ketones condense with a-halo esters in the presence of bases to give ot,p-epoxy esters, called glycidic esters. This is called the Darzens condensation. The reaction consists of an initial Knoevenagel-type reaction (16-41), followed by an internal Sn2 reaction (10-13) ° ... 

Condensation between carboxylic esters and aldehydes or ketones Condensation between active-hydrogen compounds and aldehydes or ketones (Knoevenagel)... 

Basazol dyes, 9 489-490 Base-catalyzed coupling, 10 356 Base-catalyzed ketone condensation,... 

The intermediate product undergoes an aldol condensation with a second molecule of phenol, of which the p-position is involved along with the 0=0 group in exactly the same way as Michler s ketone condenses with dimethylaniline, as described above. 

Aliphatic and alicyclic ketones condense with primary nitroalkanes under the influence of A,A-dimethylethylenediamine to yield ally lie nitro compounds as mixtures of geometrical isomers, e.g. equation 125408. 

The conditions were found to be similar to those applied to phenol-ketone condensations. With hydrochloric acid and sulphuric acid high yields were obtained, while 85% phosphoric acid gave only poor yields of the condensation products. 

Problem 17.35 In the Knoevenagel reaction, aldehydes or ketones condense with compounds having a reactive CHj between two C=0 groups. The cocatalysts are both a weak base (RCOO ) and a weak acid (R,NH,). Outline the reaction between C<,H,CH==0 and H2C(COOEt)2. d... 

Soxhlet extractor,505 by treatment with basic Al203.506 Unsymmetrical ketones condense on the side that has more hydrogens. (An exception is butanone, which reacts at the CH2 group with acid catalysts, though with basic catalysts, it too reacts at the CH3 group.)... 

Aldol reactions are often used to close five- and six-membered rings. Because of the favorable entropy (p. 211), such ring closures generally take place with ease, even where a ketone condenses with a ketone. An important example is the Robinson annulation reaction which has often been used in the synthesis of steroids and terpenes. In this reaction a cyclic ketone is converted to another cyclic ketone, with one additional six-membered ring containing a double bond. The substrate is treated with methyl vinyl ketone (or a simple derivative of methyl vinyl ketone) and a base.551 The enolate ion of the substrate adds to the methyl vinyl ketone in a Michael reaction (5-17) to give a diketone that undergoes or... 

In this procedure acyclic methyl ketones condense almost exclusively at the methyl group. Rnoli/ablc a,/ -enals also undergo efficient cross condensation with methyl kcloncs.1... 

This condensation is undergone by all compounds containing the group—CH2—CO—. It follows the same lines as the other ester-ketone condensations (see pp. 142 et seq.). 

A spontaneous cyclization occurs by effect of the Hiinig s base, added during the decomposition of the activated alcohols. This is a rare case in which a ketone condenses in situ with a stabilized phosphonate anion after a Swern oxidation. The condensation is facilitated by the formation of a six-membered ring, and by the relatively high reactivity of a ketone, possessing two activating oxygens at the a-position. 

P-Keto esters. Enolates of aliphatic ketones condense selectively at the more substituted site with CS2 /5-keto dithioesters are obtained on methylation (CH3I). These products are converted into P-keto esters by HgO-BF3 and CH3OH in THF.2 Examples ... 

Condensation of aldehydes with a-mereurio ketones. In the presence of BF3 elhcrate, a-mercurio ketones condense with aldehydes with moderate to high erylhro-sclection. 

The starting materials for this quinoline synthesis are o-aminoaryl aldehydes or ketones and a ketone possessing an a-methylene group. After an initial amino-ketone condensation, the intermediate undergoes base- or acid-catalyzed cyclocondensation to produce a quinoline derivative. 

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