Acetic anhydride, III

Carry out the following simple experiments with acetic anhydride (compare Section III,89). 

When pyridine is treated with zinc dust and acetic anhydride, a type of reductive coupling occurs and the product is diacetyltetrahydrodipyridyl (I) this undergoes a curious change on heating yielding pyridine and a new diacetyl compound, 1 4 diacetyl 1 4-dihydropyridine (II). The latter is reduced by zinc and acetic acid to 4-ethylpyridine (III). 

Ninhydrin (also named 1 2 3-triketoindane or 1 2 3-triketohydrindene hydrate) is prepared most simply from the inexpensive phthahc anhydride (I). The latter is condensed with acetic anhydride In the presence of potassium acetate to give phthalylacetlc acid (II) reaction of the latter with sodium methoxide in methanol yields 1 3-indanedionecarboxyhc acid, which is decomposed upon warming with dilute hydrochloric or sulphuric acid to indane-1 3-dione (or 1 3-diketohydrindene) (HI). Selenium dioxide oxidation of (III) afibrds indane-1 2 3-trione hydrate (ninhydrin) (IV). 

Fig. 7.1. Nitration of polynuclear hydrocarbons by nitric acid in acetic anhydride, (i) Plot of login (KijK against N. ,g-AnthryI positions A,

The general pattern of alkylation of 2-acylaininothiazoles parallels that of 2-aminothia2ole itself (see Section III.l). In neutral medium attack occurs on the ring nitrogen, and in alkaline medium a mixture of N-ring and N-amino alkylation takes place (40, 43, 161. 163). In acidic medium unusual behavior has been reported (477) 2-acetamido-4-substituted thiazoles react with acetic anhydride in the presence of sulfuric acid to yield 2-acetylimino-3-acetyl-4-phenyl-4-thiazolines (255) when R = Ph. but when R4 = Me or H no acetylation occurs (Scheme 151). The explanation rests perhaps in an acid-catalyzed heterocyclization with an acetylation on the open-chain compound (253), this compound being stabilized... 

Acetates. Anhydrous iron(II) acetate [3094-87-9J, Ee(C2H202)2, can be prepared by dissolving iron scraps or turnings in anhydrous acetic acid ( 2% acetic anhydride) under an inert atmosphere. It is a colorless compound that can be recrystaUized from water to afford hydrated species. Iron(II) acetate is used in the preparation of dark shades of inks (qv) and dyes and is used as a mordant in dyeing (see Dyes and dye intermediates). An iron acetate salt [2140-52-5] that is a mixture of indefinite proportions of iron(II) and iron(III) can be obtained by concentration of the black Hquors obtained by dissolution of scrap iron in acetic acid. It is used as a catalyst of acetylation and carbonylation reactions. 

The brown crystalline manganese(III) acetate dihydrate is of considerable commercial importance because it is often used as the source material for other trivalent manganese compounds. It can be made by oxidation of manganese(II) acetate using chlorine or potassium permanganate, or by reaction of manganese(II) nitrate and acetic anhydride. 

To a solution of 1 g of the mixture of 3-ketal-isomers of compound (II) in 10 cc of acetic anhydride is added a solution of 700 mg of p-toluenesulfonic acid in 7 cc of ecetic anhydride. The reaction mixture is kept at room temperature and under stirring for 5 hours. After some time e crystalline product begins to precipitate and the precipitation is complete by diluting with water. The precipitate is filtered and crystallized from methanol to give 17a-ethynvl-19-nor-testosterone 3,17-diecetate (III), melting point 175°C to 17B°C. 

In an attempt to study the behavior and chemistry of coal in ionic liquids, 1,2-diphenylethane was chosen as a model compound and its reaction in acidic pyri-dinium chloroaluminate(III) melts ([PyHjCl/AlCb was investigated [69]. At 40 °C, 1,2-diphenylethane undergoes a series of alkylation and dealkylation reactions to give a mixture of products. Some of the products are shown in Scheme 5.1-40. Newman also investigated the reactions of 1,2-diphenylethane with acylating agents such as acetyl chloride or acetic anhydride in the pyridinium ionic liquid [70] and with alcohols such as isopropanol [71]. 

Chromium (III) oxide hydrate had been introduced into acetic anhydride causing a very violent hydrolysis of acetic anhydride and the spreading of the products. 

Bismuth(III) triflate is also a powerful acylation catalyst that catalyzes reactions with acetic anhydride and other less reactive anhydrides such as benzoic and pivalic anhydrides.113 Good results are achieved with tertiary and hindered secondary alcohols, as well as with alcohols containing acid- and base-sensitive functional groups. 

Other companies (e.g. Hoechst, now Celanese) have developed a slightly different process in which the water content is low in order to save CO feedstock [1], In the absence of water it turned out that the catalyst precipitates. Also, the regeneration of ihodium(III) is much slower. The formation of the trivalent rhodium species is also slower because the HI content is much lower when the water concentration is low. The water content is kept low by adding part of the methanol in the form of methyl acetate. Indeed, the shift reaction is now suppressed. Stabilisation of the rhodium species and lowering of the HI content can be achieved by the addition of iodide salts (Li, ammonium, phosphonium, etc). Later, we will see that this is also important in the acetic anhydride process. High reaction rates and low catalyst usage can be achieved at low reactor water concentration by the introduction of tertiary phosphine oxide additives [1]. 

In the addition to nonactivated alkenes, where the direct anodic oxidation is less, satisfactorily good yields can be achieved when Mn(OAc)2 is used as mediator (Table 8, entries 6, 7). Sorbic acid precursors have been obtained in larger scale and high current efficiency by a Mn(III)-mediated oxidation of acetic acid/acetic anhydride in the presence of butadiene [112]. 

Solution (1) CgHgNH CrOgCllPCC) (iii) CrOg in the presence of acetic anhydride/... 

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