Benzoylacetone

The preparation of benzoylacctone Is another example of the acylation of a ketone (acetophenone) by ethyl acetate to a p diketone (Claisen condensation compare preceding Section)  

Oxidation of acetophenone with selenium dioxide iu the presence of dioxan or ethyl alcohol as solvent affords phenylglyoxal  

CgHjCOCH, + SeO — CgHjCOCHO + Se + H O This is one example of the oxidation by selenium dioxide of compounds containing a methylene group adjacent to a carbonyl group to the corresponding a-ketoaldehyde or a-diketone (see also Section VII,23). 

After some hours the blue-green compound of copper and acetylacetone is separated by filtration with suction, washed twice with water, transferred directly from the filter funnel to a separating funnel, and, after being covered with ether, decomposed by continuous shaking with 50 c.c. of 42V-sulphuric acid. The ethereal solution is separated and the acid layer is extracted with ether the extract is then combined with the ethereal solution, which is now dried over calcium chloride. After the ether has been removed by distillation the diketone is likewise distilled. The bulk of the material passes over at 125°-140° and, on repeating the distillation, at 135°-140°. The boiling point of the completely pure substance is 139°. Yield 15-20 g. 

If the distillation is carried out under reduced pressure (about 50 mm. reduction), a purer and also more stable product is obtained. 

Experiment.—One drop of ferric chloride solution is added to a few drops of an aqueous solution of acetylacetone. The reaction characteristic of enols takes place. If now the solution is cooled in ice and dilute bromine water is rather quickly added, the red colour of the iron enolate disappears for a short time and then returns rapidly. 

Benzoylacetone. — C6H5.CO.CH2.CO.CH3 is prepared in an analogous way from acetophenone and ethyl acetate according to the procedure of Claisen, Ber., 1905, 38, 695. The yield may be as much as 75 per cent of the theoretical. The cheaper converse method—action of sodamide on ethyl benzoate and acetone—also succeeds in this case, although it fails when sodium or sodium ethoxide is used as condensing agent. In general the use of sodamide is to be preferred in the synthesis of 1 3-diketones. 

Diethyl Ethylmalonate.—Sodium (4-6 g.) is dissolved, in a small flask fitted with an efficient reflux condenser, in 75 c.c. of absolute alcohol and to the cooled solution 33 g. of diethyl malonate are added (precipitation of diethyl sodio-malonate). To the mixture thus obtained, ethyl bromide (25 g.) or ethyl iodide (35 g.) is added in small portions with shaking and the flask is then heated on the water bath until, after one to two hours, the contents are no longer alkaline. The alcohol is removed by distillation in a vacuum from the water 

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Adducts of BF and some organic compounds having labile hydrogen atoms in the vicinity of the atom bonding to the boron atom of BF may form a derivative of BF by splitting out HF. For example, P-diketones such as acetylacetone or benzoylacetone react with BF in benzene (38) ... 

Benzoylacetone (l-pbenyl-l,3-butanedione) [93-91-4] Et20 or MeOH and dried under vacuum at 40 . 

The reaction of 3,6-diphenyl-1,2,4-triazine 4-oxide 58 with benzoylacetone under basic conditions affords substituted 1,2,4-triazine 74 in low yield (96MC116). 

Cyclocondenzation of 2-amino-3-hydroxypyridinium perchlorate with benzoylacetone in boiling EtOH afforded 2-methyl-4-phenylpyrido[l,2-n]pyrimidinium perchlorate in 23% yield (94KFZ(10)23). 

Benzene-1,2-diamine (2.0 g. 18.5 mmol) and benzoylacetone (4.0 g. 24.6 mmol) in warm EtOH (8 mL) and HOAc (3 mL) were kept at 40 C for 30 min, cooled, diluted with EtzO (20 mL) then treated with coned H2S04 (2.5 ntL) in H,0 (5 mL) and kept overnight. The precipitated violet product was collected and washed with Et20 yield 4.9 g (75%) mp 173-175 C. 

Aryl-substituted biguanides (c.g. 1) can be condensed with 1-benzoylacetone to provide 1,3,5-triazocine derivatives,13 Two isomers of product 2 can be isolated upon recrystallization from ethanol. The isomers, probably tautomers 2A and 2B, exhibit the same melting point and rapidly interconvert in solution, thereby giving identical NMR spectra in deuteriochloroform at room temperature. 

To a solution of l-(4-methoxyphenyl)-biguanide (2.07 g, 10 mmol) and l-(4-methoxyphenyl)-biguanide hydrochloride (0.2 g, 1 mmol) in EtOH (50 mL) was added 1-benzoylacetone (1.62 g, 10 mmol) and the solution was heated under reflux for 10 h. After the solution was concentrated, the oily residue was poured into H20 and repeatedly washed with H20. The resulting solidified mass was collected by filtration and dissolved in EtOH by heating. After standing overnight at rt, a mixture of needles and prisms was isolated yield 1.5 g (45%). The mixture was dissolved in a suitable amount of EtOH by heating and, after 2 h at rt, the deposited, needles were collected by filtration mp 166 C. The needles were dissolved in a suitable amount of EtOH and the solution was left to stand at rt for a couple of days. The deposited prisms were collected by filtration mp 166°C. 

OS 52[ [OS 53[ [OS 54[ [OS 55[ [R 4b[ [P 38[ In a two-micro-mixing tee chip reactor, substrates with diketone moieties of known different reactivity, such as 2,4-pentanedione, benzoylacetone and diethyl malonate, were processed, each with the same acceptor ethyl propiolate [8]. Also, a reaction with the less alkynic Michael acceptor methyl vinyl ketone was carried out. 

The conversions observed followed the sequence of reactivity known from batch experiments carried out in advance. For example, only 15% conversion was found for the less reactive reagent benzoylacetone in the micro reactor experiment, while 56% was determined when using the more reactive 2,4-pentanedione (batch syntheses 78% and 89%, respectively) [8]. Using the stopped-flow technique (2.5 s with field applied 5.0 s with field turned off) to enhance mixing, the conversions for both syntheses were increased to 34 and 95%, respectively. Using a further improved stopped-flow technique (5.0 s with field applied 10.0 s with field turned off), the conversion could be further enhanced to 100% for the benzoylacetone case. For the other two substrates, diethyl malonate and methyl vinyl ketone, similar trends were observed. 

In the presence of a very strong base, such as an alkyllithium, sodium or potassium hydride, sodium or potassium amide, or LDA, 1,3-dicarbonyl compounds can be converted to their dianions by two sequential deprotonations.79 For example, reaction of benzoylacetone with sodium amide leads first to the enolate generated by deprotonation at the more acidic methylene group between the two carbonyl groups. A second equivalent of base deprotonates the benzyl methylene group to give a dienediolate. 

Benzoylacetone was studied using both X-ray and neutron diffraction. Four X-ray data sets at four different temperatures were collected, namely at room temperature, 160, 20 and 8 K. Furthermore a neutron data set was collected at 20 K. 

Nitromalonamide (C3H,N304, Ri = R3 = NH2, R2 = N02) was chosen as a further example of a very short intramolecular keto-enol 0- H 0 hydrogen bond. It has one of the shortest known 0- H 0 distances at 2.38 A[5]. Both low-temperature X-ray (10 K) and neutron data sets (15 K) have been collected to examine whether our results from benzoylacetone are of a general nature. 

The charge density study of benzoylacetone [8] revealed that the Laplacian at the bond critical points between the enol hydrogen and the oxygens has a negative value. This means that the bonds between that hydrogen and both the oxygens have covalent character. Furthermore the populations of the spherical valence parts of the multipole... 

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