Acetophenones, addition

Phenyl-2-butanol has a methyl group, an ethyl group, and a phenyl group (—Cgl ) attached to the alcohol carbon atom. Thus, the possibilities arc addition of ethylmagnesium bromide to acetophenone, addition of methylmagnesium bromide to propiophenone, and addition of phenylmagnesimn bromide to 2-butanone. 

Vinyl thiophene reacts with singlet oxygen giving the corresponding [4 +2] adduct (75TL4471). 1 1 Adducts were obtained from the photosensitized (benzophenone and acetophenone) addition of cis or transA, 2-dichloroethylene to benzo[b]thiophene (Scheme 11) (70JOC1582). 

The student should note that ketones in class (1), t.c., those having the >CO group in the side chain, will form additive compounds with sodium bisulphite only if this >CO group is not directly joined to the benzene ring acetophenone therefore will not form such compounds, whereas benzyl methyl ketone, CaHsCHjCOCH, will do so. Many quinones, particularly ortho quinones such as phenanthraquinone, form additive compounds with sodium bisulphite. 

Aldehydes and ketones may frequently be identified by their semicarbazones, obtained by direct condensation with semicarbazide (or amino-urea), NH,NHCONH a compound which is a monacidic base and usually available as its monohydrochloride, NHjCONHNH, HCl. Semicarbazones are particularly useful for identification of con jounds (such as acetophenone) of which the oxime is too soluble to be readily isolated and the phenylhydrazone is unstable moreover, the high nitrogen content of semicarbazones enables very small quantities to be accurately analysed and so identified. The general conditions for the formation of semicarbazones are very similar to those for oximes and phenylhydrazones (pp. 93, 229) the free base must of course be liberated from its salts by the addition of sodium acetate. 

Bisulphite addition compound. Shake 1 ml. of acetone with 0 5 ml. of a saturated solution of NaHS03. A white precipitate is formed, the mixture becoming warm and then, on cooling, almost solid. Acetophenone and benzophenone, having the >CO group directly joined to tlie benzene ring, do not respond to the test (p- 257). 

Acetophenone can react with formaldehyde to yield light-resistant resins which are used as additives in nitrocellulose paints. It is also used as a photoinitiator, and in the pharmaceuticals, perfumery, and pesticide industries (344). It can be hydrogenated to 1-phenylethanol which is used for the production of aromatic ester fragrances (345). Technical-grade acetophenone is available at 2.29/kg perfume-grade acetophenone was 6.50/kg in October 1994. 

The distillate is extracted with five 50-cc. portions of benzene, and the benzene solution is dried thoroughly with powdered sodium hydroxide and distilled (Note 5). Most of the amine distfls at 184-186°, but the fraction distilling at 180-190° is sufficiently pure for most purposes (Note 6). The yield of this fraction is 80-88 g. By combining the benzene fore-run with the distillation residue, extracting with dilute acid, and recovering the amine as above, an additional 10-12 g. of material can be obtained (Note 7), making the total yield po-ioo g. (60-66 per cent of the theoretical amount based on the acetophenone taken) (Note 8). 

Reductions by NaBKt are characterized by low enthalpies of activation (8-13kcal/mol) and large negative entropies of activation (—28 to —40eu). Aldehydes are substantially more reactive than ketones, as can be seen by comparison of the rate data for benzaldehyde and acetophenone. This relative reactivity is characteristic of nearly all carbonyl addition reactions. The reduced reactivity of ketones is attributed primarily to steric effects. Not only does the additional substituent increase the steric restrictions to approach of the nucleophile, but it also causes larger steric interaction in the tetrahedral product as the hybridization changes from trigonal to tetrahedral. 

Acetophenone.—The Fnedel-Crafts reaction, of which this pieparation is a type, consists in the use of anhydious aluminium chlonde for effecting combination between an aromatic hydrocarbon or its deiivative on the one hand, and a halogen i,Cl 01 Bi) compound on the othei. The leaction 13 always accompanied by the evolution of hydiochloiic or hydio-bromic acid, and the product is a compound with AlCl-j, which decomposes and yields the new substance on the addition of watei. This reaction has been utilised, as in the present case, (r) for the prepaiation of ketones, in which an acid chloiide (aliphatic or aromatic) is employed,... 

As will be discussed in the next section, 1,5-pentanediones are obtained by Michael addition of acetophenones to chalcones. The addition and cyclization may be merged in one step (see Section II,C,2,g). When acetophenone was condensed with chalcone (74) in the presence of or of HC104, jS-phenylpropio-... 

In general, the hydrogenolysis product is also favored by an acidic medium, as illustrated in the hydrogenation over 5° palladium-on-carbon of acetophenone to the hydrogenation product phenylethanol and to the hydrogenolysis product ethylbenzene, with various additives present (S3). 

Platinum, especially as platinum oxide, has been used by many investigators. If this catalyst contains residual alkali, it is apt to be ineffective for aromatic ring reduction unless an acidic solvent is used (1,3,19) or unless the compound also contains a carbonyl group, as in acetophenone, where 1,4-and 1,6-addition are possible (46). Nickel, unless especially active, requires vigorous conditions—conditions that may promote side reactions. 

To a suspension of 500 mg of 160i,17a-dihydroxyprogesterone in 25 ml of freshly redistilled acetophenone isadded 0.125 ml of 72% perchloric acid and the mixture isagitated at room temperature for one hour. The clear solution is washed with dilute sodium bicarbonate to remove excess acid and the acetophenone layer, after addition of chloroform is separated from the aqueous phase. The organic layer is dried over sodium sulfate and after removal of the chloroform and acetophenone in high vacuum the residue is crystallized from 95% alcohol. The pure acetophenone derivative has a melting point of about 142° to 144. ... 

In order to broaden the field of biocatalysis in ionic liquids, other enzyme classes have also been screened. Of special interest are oxidoreductases for the enan-tioselective reduction of prochiral ketones [40]. Formate dehydrogenase from Candida boidinii was found to be stable and active in mixtures of [MMIM][MeS04] with buffer (Entry 12) [41]. So far, however, we have not been able to find an alcohol dehydrogenase that is active in the presence of ionic liquids in order to make use of another advantage of ionic liquids that they increase the solubility of hydrophobic compounds in aqueous systems. On addition of 40 % v/v of [MMIM][MeS04] to water, for example, the solubility of acetophenone is increased from 20 mmol to 200 mmol L ... 

Although enolates, their equivalents, and otherwise stabilized carbanions would be interesting candidates for ARO of weso-epoxides, no efficient catalytic method has been developed to date. Crotti reported that 20 mol% of (salen)Cr-Cl complex 2 promoted the addition of the lithium enolate of acetophenone to cyclohexene oxide with moderate ees (Scheme 7.26) [50], However, the very low yields obtained... 

A report of an unusually high stereoselectivity (93% ee) in the addition of menthyl acetate to acetophenone was later corrected by Solladie et al. The real ee is only 58% see S. Mitsui, K. Konno, 1. Onuma, K. Shimizu, Nippon Kagaku Zasshi 85, 437 (1964) Chem. Ahstr. 61. 13167 f. (1964). 

The complexation of achiral metal enolates by chiral additives, e.g., solvents or complexing agents could, in principle, lead to reagent-induced stereoselectivity. In an early investigation, the Reformatsky reaction of ethyl bromoacetate was performed in the presence of the bidentate ligand (—)-sparteine20. The enantioselectivity of this reaction varies over a wide range and depends on the carbonyl Compound, as shown with bcnzaldehyde and acetophenone. 

Similar stereochemical results were obtained from the addition of the potassium and lithium ions of ethyl acetate, /V,V-dimethylacetamide, acetonitrile, acetophenone and pinacolone to 3-(/erf-butyldimethylsilyloxy)-T-phenylsulfonyl-1-cyclohexene followed by protonation or methylation of the resulting sulfonyl carbanion intermediates7. 

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