Claisen condensation, with acetone and

Chromium trioxide, 21, 6 24, 39, 76 Cinnamic acid, 20, 77 22, 26 24, 21 Cinnamoyl chloride, 20, 77 24, 21 Citral, bisulfite compound, 23, 78 purification of, 23, 78 Claisen condensation, with acetone and ethyl formate, 27, 92 with ethyl oxalate and ethyl succinate, 26,42... 

Claisen, in the following year, used 10 per cent, aqueous sodium hydroxide to condense furfurol with acetone and thus obtained mono-fnrfurylidene acetone S1... 

Aldol and related condensation reactions such as Knoevenagel and Claisen-Schmidt condensations are also widely used in the fine chemicals and specialty chemicals, e.g. flavors and fragrances, industries. Activated hydrotalcites have been employed as solid bases in many of these syntheses. Pertinent examples include the aldol condensation of acetone and citral [107, 108], the first step in the synthesis of ionones, and the Claisen-Schmidt condensation of substituted 2-hydroxyacetophenones with substituted benzaldehydes [109], the synthetic... 

Other reports deal with a pyrrolidine-catalysed homo-aldol condensation of aliphatic aldehydes (further accelerated by benzoic acid), a diastereoselective aldol-type addition of chiral boron azaenolates to ketones,the use of TMS chloride as a catalyst for TiCU-mediated aldol and Claisen condensations, a boron-mediated double aldol reaction of carboxylic esters, gas-phase condensation of acetone and formaldehyde to give methyl vinyl ketone, and ab initio calculations on the borane-catalysed reaction between formaldehyde and silyl ketene acetal [H2C=C(OH)OSiH3]. ... 

For the liberation of N-methylethylamine, a 1-1. Claisen flask is equipped with a 250-ml. separatory funnel and an efficient condenser for distillation. The receiver is cooled with a mixture of acetone and dry ice (Note 7). A solution of 100 g. (2.5 moles) of sodium hydroxide in 100 ml. of water is added to the flask and kept at about 100° by heating on a steam bath. The aqueous solution of N-methylethylamine hydriodide is added to this solution through the separatory funnel in the course of 1.5 hours. After the addition is complete, the final solution is heated for an additional 30 minutes. Crude N-methylethylamine, b.p. 30-70°, collects in the cooled receiver. It is purified by distillation from 25 g. of solid potassium hydroxide in a 250-ml. modified Claisen flask fitted with a 25-cm. Fenske column and a receiver cooled by dry ice and acetone. N-Methylethylamine is collected at 34-35° weight 49-55 g. (83-93%) 2 3 4 5d 1.3830. 

The method described is that of Hampton, Harris, and Hauser6 and is an improvement over the benzyne method, which gives poor yields.6,7 This /J-diketone has been prepared by Claisen condensation of ethyl phenylacetate with acetone,8 but the yield is poorer and the product has been shown by gas chromatography to be impure.6 The j8-diketone has also been prepared by the hydrolysis of 4-methoxy-5-phenyl-3-penten-2-one and by hydrolysis and decarboxylation of ethyl a-acetyl-/3-oxo-y-phenylbutyrate10 but these compounds are more difficult to obtain than the starting materials used in the present synthesis. 

The acylation of ketones with esters an example of the Claisen condensation is generally effected with a basic reagent, such as sodium ethoxide, sodium, sodamide or sodium hy dride. Thus acetone and ethyl acetate condense in the presence of sodium ethoxide to yield acetylacetone ... 

The reaction of an aldehyde with a ketone employing sodium hydroxide as the base is an example of a mixed aldol condensation reaction, the Claisen-Schmidt reaction. Dibenzalacetone is readily prepared by condensation of acetone with two equivalents of benzaldehyde. The aldehyde carbonyl is more reactive than that of the ketone and therefore reacts rapidly with the anion of the ketone to give a /3-hydroxyketone, which easily undergoes base-catalyzed dehydration. Depending on the relative quantities of the reactants, the reaction can give either mono- or dibenzalacetone. 

Two moles of this ketone (K) were then condensed by Claisen reaction in 5% ethanolic potassium hydroxide with crocetindial (ref.52) and the terminal ketal groups in the product then removed by refluxing with acetone containing 4-toluenesulphonic acid. The resultant... 

Claisen-Schmidt condensation, i.e., the condensation of benzaldehyde and acetone to a,(3-unsaturated ketones, has been performed to a high degree at 0°C with rehydrated oxides from LDH precursors by Rao et al. (532). 

There have been many other investigations of the applications of LDO catalysts to Claisen-Schmidt condensation (540). For example, with activated MgAl-COs-LDH as catalyst, benezaldehyde and 2-hydroxylacetophenone react at 50°C to give the desired compounds (2-hydroxychalcone and flavanone) at 80% conversion and 78% selectivity (541). As another example, the condensation of citral and acetone produces an intermediate that can be finally transformed to chemically useful ionones (542,543). The use of calcined LDH results in 70% selectivity at about 95% conversion. In addition, Dumitriu et al. (544) and Suzuki... 

In 1967 Shimizu, Sakamoto and Fukushima [13] prepared 2-methyl-4-oxopyrano[2,3-b]pyridine (XIX, R = Me, R = R = H) in 27 per cent yield by condensing ethyl 2-methoxynicotinate with acetone followed by ring closure by heating under reflux with hydroiodic acid. When benzal-dehyde was used instead of acetone, 4-oxo-2-styryl[2,3-b]pyridine (XIX, R = CH CHPh, R = H) was obtained. Spectroscopic data (u.v., i.r. and n.m.r.) are also given for the products [13]. In the same year, Bonsall and Hill [14] reported a number of derivatives of (XIX, R = Me, Ph, C02Et, or CO2H R = R = Me) which they had prepared by the usual Claisen condensation of 3-acetyl-4,6-dimethylpyridine-2-one with appropriate dicarbonyl compounds followed by acid-cyclisations. Overall yields for these compounds were above 30 per cent. Sliwa [15] recently reported the synthesis of (XIX, R = Ph, R = R = H) from ethyl 2-ethoxy-nicotinate. 

Dilute sodium hydroxide was used as a condensing ent by J. G. Schmidt and the method was applied by Claisen and collaborators to the s3mthesis (Claisen reaction) of aromatic ketonic esters, e.g. benzylidene acetone and di-benzylidene acetone from benzaldehyde and acetone. An alternative method was the use of an aromatic aldehyde or ketone with acetoacetic ester in presence of hydrogen chloride. Benzoylacetic ester, CgHgCO CHe-COOCoHs, was obtained by condensing benzoic and acetic esters in presence of sodium ethoxide, and j8-diketones by condensing ketones and acid esters, e.g. acetyl-acetone CHaCO-CHaCOCHg."... 

The Claisen condensation of ethyl acetate yields ethyl acetoacetate. This readily available compound and other P-keto esters formed by Claisen condensations are used as intermediates on the synthesis of alkyl derivatives of ketones. For example, ethyl acetoacetate is like an acetone molecule with an appended ester group. 

The condensation of aliphatic aldehydes with acetone to give methyl vinyl ketone derivatives is rather common. The reaction can be carried out to the ketol stage (equations 39 and 40),or under conditions that lead to the a,3-unsaturated ketone (equations 41 and 42). 42 3y adjusting the stoichiometry, bis-condensation products can often be obtained in excellent yield (equations 43 and 44). 44 Similar transformations can be obtained in the reactions of acetone with aromatic aldehydes, the classic Claisen-Schmidt reaction. These reactions invariably give the a,p-unsaturated ketone products. Either the mono- or bis-condensation product may be obtained by suitable adjustment of the reaction conditions (equation 45 and 46). 46... 

Registry No 99-93-4 100-06-1 <Claisen condensation of. with benzoate>. 106-89-8 reactions with phenols>. 120-47-8 . 1676-63-7 <Claisen condensation of. with benzoate>. 19152-55-7 hydration acetalization of. with acetone>. 26537-19-9 <Claisen condensation of. with acetophenone>. 50625-94-0 hydration acetalization of. with acetone>. 

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