Reactions monoacetylation

EtOH). No methoxyl is present. It forms a series of crystalline double chlorides with cadmium, zinc or copper, does not give the thalleioquin reaction, and solutions of its sulphate are not fluorescent. It is diacidie and forms two series of salts of which the nitrate, B. HNOj, crystallises in minute prisms, m.p. 196°, insoluble in water. Cinchonamine hydrochloride, B. HCl, laminae or B. HCl. HjO, cubical crystals, has been suggested for use in the estimation of nitrates. When warmed with strong nitric acid the alkaloid furnishes dinitrocinchonamine. It gives an amorphous, monoacetyl derivative, and forms a methiodide, m.p. 208 , which with silver oxide yields an amorphous methylcinchonamine. Raymond-Hamet found that cinchonamine ves typical indole colour reactions and is probably an indole alkaloid. This seems to have been... 

Tetrahydrostrychnine, CgjHggOgNg. HgO. This substance, also formed by the electrolytic reduction of strychnine, crystallises from alcohol in prisms, m.p. 202°, gives colour reactions of the strychnidine type, and yields both neutral and acid salts the hydrochloride, B. HCl, occurs in small needles readily soluble in water and the dihydriodide, B. 2HI. 2HjO, in pyramidal crystals. The base yields an amorphous nitrosoamine, the hydrochloride of which crystallises from warm water in lustrous, yellowish prisms. It also furnishes a crystalline monoacetyl derivative, and on heating with hydrochloric acid or phosphorus oxychloride is dehydrated to strychnidine. 

Singer and co-workers have investigated the acylation reactions of ferrocene in ionic liquids made from mixtures of [EMIMJI and aluminium(III) chloride (Scheme 6.1-5) [9, 10]. The ionic liquid acts both as solvent and as source of the Friedel-Crafts catalyst. In mildly acidic (X(A1C13) > 0.5 [EMIM]I/A1C13, the monoacetylated ferrocene was obtained as the major product. In strongly acidic [EMIM]I/AlCl3 X(A1C13) = 0.67 the diacylated ferrocene was the major product. Also, when R = alkyl, the diacetylated product was usually the major product, but for R = Ph, the monoacetylated product was favored. 

Phosphoric Acid and its Derivatives.—Triacetyl phosphate18 and diammonium monoacetyl phosphate14 have been obtained by acetylation of phosphoric acid with keten at —10 to —15 °C in diethyl ether and ethyl acetate, respectively the reaction can be controlled to give 90% yields of either product. Long-chain monoalkyl... 

The acetylation over protonic zeolites of aromatic substrates with acetic anhydride was widely investigated. Essentially HFAU, HBEA, and HMFI were used as catalysts, most of the reactions being carried out in batch reactors, often in the presence of solvent. Owing to the deactivation effect of the acetyl group, acetylation is limited to monoacetylated products. As could be expected in electrophilic substitution, the reactivity of the aromatic substrates is strongly influenced by the substituents, for example, anisole > m-xylene > toluene > fluorobenzene. Moreover, with the poorly activated substrates (m-xylene, toluene, and fluoroben-zene) there is a quasi-immediate inhibition of the reaction. It is not the case with activated substrates such as anisole and more generally aromatic ethers. It is why we have chosen the acetylation of anisole and 2-methoxynaphtalene as an example. 

Rhodium acetylacetonate differed considerably from the other metal chelates in the acetylation reaction (26). Under the same conditions that had given extensive acetylation of the cobalt and chromium acetylacetonates, the rhodium chelate reacted very slowly and formed only a small amount of the monoacetylated compound (XX). Fortunately, the hydrolytic stability of rhodium acetylacetonate is such that the Friedel-Crafts reaction can be carried out under vigorous conditions that would rapidly degrade the chromium and cobalt chelates. Thus treatment of rhodium acetylacetonate with acetyl chloride and aluminum chloride in dichloroethane afforded the mono- and diacetylated chelates (XX and XXI). No triacetylated chelate was isolated from this reaction. In a similar manner butyryl-and benzoyl-substituted rhodium chelates (XXIII and XXIV) have been prepared. These and other experiments indicate that the rhodium acetylacetonate ring is less reactive than the cobalt or chromium rings. 

An example of a more structured aryl acetate is offered by the monoacetyl derivative 2 ofp-tert-butylcalix[4]arene-crown-5 (1). The half-life for deacetylation in the presence of 1 mM MeONMe4 in MeOH at 25 °C is 34 weeks, but drops to 8 s upon addition of 1 mM BaBr2 [17]. Also, SrBr2 accelerates the reaction, albeit to a somewhat smaller extent. Kinetic and UV spectroscopic data show that in the absence of metal ions MeO reacts with the unionized form 2, but in the presence of metal ions the reactive species is the metal complex of the ionized form 3, which is present in significant amounts by virtue of the acidity enhancing effect of the metal ion complexed by the polyether chain. 

Acetylation of puupehenone (63) does not afford the expected monoacetyl derivative (64). Instead, the triacetyl derivative (65) was obtained exclusively, indicating the addition of the acetyl group to the conjugated double-bond system of puupehenone. The monoacetyl derivative of puupehenone (64) was obtained as a side product of the addition-elimination reaction sequence of HBr/HCl with puupehenone followed by acetylation which resulted in 66. 

Pyrazino[2,3-d]pyridazine-5,8-dione (104) can be dithiated with phosphorus pentasulfide to give the unisolated intermediate (105), which yields the bis(benzylthio) product (106) on reaction with benzyl chloride. Acetylation and tosylation of this starting dione (104) produce the monoacetyl and the monotosyl products, respectively (66JHC512). 

The former is prepared (Expt 6.15) by the reaction of cyclopentadiene with iron(n) chloride in the presence of diethylamine. Iron(n) chloride is prepared in situ from iron(m) chloride in tetrahydrofuran by reduction with iron metal. This preparation is one of the simplest for ferrocene, although not of general application for substituted ferrocenes. The acetylation of ferrocene in a Friedel-Crafts manner to yield the monoacetyl derivative is described in Expt 6.122. 

In an enzymatic resolution approach, chiral (+)-tra .s-diol (60) was prepared by the stereoselective acetylation of racemic diol with lipases from Candida cylindraceae and P. cepacia. Both enzymes catalyzed the acetylation of the undesired enantiomer of racemic diol to yield monoacetylated product and unreacted desired (+)-trans-diol (60). A reaction yield of 40% and an e.e. of >90% were obtained using each lipase [104],... 

Aminothienopyrimidines 94 were monoacetylated or diacetylated by reaction with acetyl chloride and triethylamine or acetic anhydride, respectively (88LA633). 

During the first 2h of reaction, a decrease in AcOH conversion (from 48 to 43 %) for benzene acetylation at 523 K with an increase in selectivity to the monoacetylated product (from 80 to 90%) can be observed. The only problem involves the low catalyst activity 1.5 mmolh 1g 1 of acetophenone, which corresponds to a TOF value of 2.2 h-1. This means that less than 0.2 g of this acetylated arene can be produced per hour and per gram of catalyst under the operating conditions (i.e. 10 times less than in the liquid phase acetylation of anisole with AA). The kinetic study of the reaction shows an increase in the selectivity with the substrate/acetic acid ratio, but no increase in yield, an increase in acetic acid conversion with the reaction temperature with a significant decrease in selectivity due to a greater formation of diacetylated products.[62,63] HFAU and RE-FAU zeolites do... 

An enzymatic method for resolution of the racemic cis-2,8-diazabicyclo[4.3.0[-nonane has also been described, in which reaction of the S,S-enantiomer with ethyl acetate in the presence of lipase produces the S,S-diacetyl derivative under the reaction conditions and the R, K-eriari liorner is only reacted to form the monoacetyl derivative. The components can be readily separated from the resulting reaction mixture, and then deacetylated [141]. 

Treating 2 with CH3COCI/AICI3 yields the monoacetyl derivative 9 by electrophilic substitution23. The deformed benzene rings, thus, act in a regenerative ( aromatic ) manner with respect to this reaction. The extremely high reaction rate re-... 

Diazepine 243 (R = H) gave a monoacetyl and a nitroso derivative.286 Alkylation of 243 (R = H) with sodamide and dialkylamino-alkyl chlorides in dioxane substitutes only at the 10-position to give 245 289,291 while alkylation of 243 [R= (CH2)2N(C2H6)2] gave 246. This same type reaction has been used to introduce a labeled side chain into 246.292d... 

The reaction enthalpy for monoacetylation of benzidine, ArNH2 = p-IENQJUCfilU NH2-jt> is the likewise exothermic —33.1 kJmol-1. However, per NH2 group, the acetylation of benzidine to diacetyl derivative is —73 kJ mol-1, nearly twice the expected value. In support of this implausible result, the acetylation enthalpy of the monoacetyl to the diacetylbenzidine is — 114 kJ mol 1. The enthalpy of formation of A,A -diacetylbenzidine is likely erroneous. 

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