Diacetyl compound

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). 

The A-monoacetyl derivative is formed from acetic anhydride and pyridine at 100° higher temperatures give the 7V,A-diacetyl compound which does not react with peracid. In either case, there is a complete shift of the double bond from C-20(22) to C-17(20), with no evidence for any C-20(21) olefin. 

By heating the diacetyl compound with sodium hydroxide solution partial saponification of the acetyl groups takes place. 25.6 grams of diacetyl compound are heated to boiling for some hours with 100 cc of 2 N sodium hydroxide solution. The precipitate produced by acidification of the solution with acetic acid is filtered off and treated with dilute sodium carbonate solution. The 4-aminobenzene-sulfonacetylamide passes into solution while the simultaneously formed 4-acetylaminobenzene-sulfonamide remains undissolved. It is filtered with suction and the filtrate again acidified with acetic acid. The 4-aminobenzene-sulfon-acetamide separates out and is recrystallized from water. It forms colorless lustrous rhombic crystals Of MP 1B1°C. 

Raney nickel reduction of 4(5)-nitroimidazole (27 R = H) in a mixture of acetic anhydride and acetic acid gave a diacetylated compound (35%) that was identified as 1- (or 3-) acetyl-4-acetamidoimidazole (57JA2188). 

The diacetyl compound 33 shows MeCO signals corresponding to one Z and one ZZ form with respect to the Ac—C bonds (Scheme 2) at - 122°C, and both H and l3C NMR spectra are in agreement with a system in which 33a and 33b (the EZ forms) are in fast equilibrium by C=C rotation, although all other rotations are slow at this temperature. 

By comparison, a series of mostly monoacylated flavonols is known to date and recent reports increased the number slightly. Four new products came from Pseudognaphalium robustum and Tanacetum microphyllum (both Asteraceae), and from Adina cordifolia (Rubia-ceae). A diacetylated compound (3,5-diacetyltambulin) was recently isolated from the bark of Zanthoxylum integrifoliolum (Rutaceae). Since most of the flavonols are monoacylated, the accumulation of quercetin tetraacetate in Adina cordifolia is a remarkable result. Altogether, the newly reported compounds occur scattered in the plant kingdom their occurrence is so far of little chemosystematic value. Aerial parts of Tanacetum microphyllum (Asteraceae) yielded a derivative, which is structurally not an ester. It is, indeed, a carbo-methoxy derivative of 6-hydroxyluteolin-4 -methyl ether (compound 34 in Table 12.5). No other flavonoid of this type is known so far. 

Poly(chalcones) (183), which themselves are the products of Knoevenagel condensation of aromatic dialdehydes and diacetyl compounds, have been transformed into polylpyrazo-lines) (185) by reaction with phenylhydrazine (184) (72MI11107). The reaction (Scheme 88) was conveniently conducted in excess phenylhydrazine and yielded polymers which were described as being brilliantly fluorescent in solution. The poly(pyrazolines) (185) exhibited glass transition temperatures between 150 and 210 °C and were stable, in some cases, up to 630 °C. 

Acetylation of (114 R = Me, OH) with acetyl chloride in carbon disulfide with aluminum chloride as catalyst gave, in contrast to the above-mentioned reaction, monosubstitution only in the 2-position, but, surprisingly for a Friedel-Crafts acylation, 2,4-disubstitution also occurred. The use of two equivalents of acylating agent gave the diacetyl compound in 84% yield. 

C-Aminoindoles autoxidize extremely rapidly. Consequently, comparatively few chemical reactions have been examined. The 2-amino derivative exists in the 3H-indole tautomeric form (473) and is protonated and alkylated on the annular nitrogen atom (72HC(25-2)179). The 1-methyl derivative (474) exits predominantly as such and not as the alternative 2-imino-3//-indole tautomer and is protonated at the 3-position to give a cation having the same electronic structure as that of the protonated (473). Acylation of (473) yields l-acetyl-2-acetylaminoindole, via the initial acylation of the annular nitrogen atom. Confirmation of this route has been established by the observation that 2-acetylaminoindole, obtained by hydrolysis of the diacetylated compound, is acetylated under identical conditions... 

Substitution at the C-4 position has been described for A-TBDPS /3-sultam (TBDPS = Abutyldiphenylsilyl) by deprotonation followed by reaction with methyl chloroformate or benzophenone yielding only the diacetylated compound 131 and the expected alcohol 132, respectively (Scheme 40) <2004HCA1574>. 

Reaction of an excess of dimethylacetamide and phosphoryl chloride with the 3-phenylindole 20a gave the 7-acetyl compound 35 as the major product in 65% yield, together with 20% of the 2-acetyl compound 36 and 8% of the 2,7-diacetyl compound 3721 (Scheme 11). Vilsmeier aroylation has been applied successfully to the more reactive 3-methylin-dole 7 and leads to a more even distribution of 2- and 7-isomers, but usually with a slight preference for 2-substitution.22,23 Thus, the use of N, V-dimethylbenzamide and 4-chloro-V,V-dimethylbenzamide gave the 2- and 7-acylindoles 38a,b and 39a,b, respectively, in good yields (Scheme 11). 

Pure -nitroabzarin forms orange-yellow needles, which melt at 244°, with partial decomposition [19]. It sublimes in yellow leaflets, undergoing partial decomposition. It dissolves in benzene and glacial acetic acid, and gives a purple-red solution with alkalies. The violet lime-lake is not decomposed by carbonic acid. (Distinction from alizarin.) It forms a diacetyl compound, M.P. 218° [19]. Nitroalizarin dyes orange shades on alumina mordants, and reddish-violet on iron mordants. 

It forms a red diacetyl-compound, -which yields yellow, sparingly soluble salts with acids [49]. 

On heating with acetic anhydride, chrysaniline yields a diacetyl compound [13], CigHjsNj (021130)2, which still possesses basic properties, forming monoacid salts with acids. 

The diacetyl compound, CxgHjg ( 21130)204, is formed by the action of acetic anhydride and sodium acetate [70]. 

In the synthesis of dibenzils ( II,III,VI ), the diacetyl compounds were prepared following a known procedure 13] and were then oxidized by dimethyl sulfoxide. 

From the 3,7-diacetyl compounds 68a and b (with R = CH3) the bispidinine dervatives 70a and b are obtained by heating in mineral acid. The resulting secondary amines open the door to introducing a variety of substituents, which are difficult to obtain with the Mannich approach to bispidine ligands. 

Acetylation of 38 with acetic anhydride afforded only the N,0-diacetyl compound 63 which on hydrolysis gave compound 62, the optical antipode of 54. Although the formation of the two C-7 epimeric alcohols in the reaction of 59 with hydrochloric acid supports an attack on a hydroxyl anion of a C-7 carbonium ion— the formation of a single stereoisomer 63 by the action of acetic anhydride may be more satisfactorily explained if the reaction proceeds by way of cyclic intermediate 64 such as the acetyl cation and an acetoxy anion which are derived from the same molecule of acetic anhydride. 

The acetylation of the Wieland-Gumlich aldehyde (XIV R = OH) and the preparation of diaboline, iVa-aoetyl Wieland-Gumlich aldehyde (XV R = OH) (5), has been studied in some detail by Deyrup et al. (6). Reaction of the aldehyde XIV (R = OH) with acetic anhydride in p3T idine gave two isomeric diacetyl compounds C23H26N2O4. 

Reduction of diaboline and of the epimeric diacetyl compounds (XV and XVI R = OAc) with lithium aluminum hydride gave in all three cases a mixture of the diol XVIII (R = H) and the corresponding Vj-ethyl derivative XVIII (R = Et) the former product was identical with the reduction product of Wieland-Gumlich aldehyde. This confirms that the configuration at C-16 is the same for all four compounds, as here depicted, since inversion of configuration at C-16 is improbable under the reduction conditions. Indeed, it is known (7) that the C-16... 

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