Anhydrides, preparation

Certain features of the addition of acetyl nitrate to olefins in acetic anhydride may be relevant to the mechanism of aromatic nitration by this reagent. The rapid reaction results in predominantly cw-addition to yield a mixture of the y -nitro-acetate and y5-nitro-nitrate. The reaction was facilitated by the addition of sulphuric acid, in which case the 3rield of / -nitro-nitrate was reduced, whereas the addition of sodium nitrate favoured the formation of this compound over that of the acetate. As already mentioned ( 5.3. i), a solution of nitric acid (c. i 6 mol 1 ) in acetic anhydride prepared at — 10 °C would yield 95-97 % of the nitric acid by precipitation with urea, whereas from a similar solution prepared at 20-25 °C and cooled rapidly to —10 °C only 30% of the acid could be recovered. The difference between these values was attributed to the formation of acetyl nitrate. A solution prepared at room... 

In solutions of acetyl nitrate in acetic anhydride, prepared from purified nitric acid, the 0 -ratio increases slightly with increasing concentrations of acetyl nitrate (table 5.7, expts. 11,13,16). The use of fuming nitric acid in the preparation of the acetyl nitrate considerably accelerates the rates of reaction and also increases the proportion of o-substitution (table 5.7, expts. 12, 15, 18). These effects resemble, but are much stronger than the corresponding effects in nitrations with solutions of nitric acid in acetic acid contaimng dinitrogen tetroxide. 

Resin and Resinoid. Natural resins are plant exudates formed by the oxidation of terpenes. Many are acids or acid anhydrides. Prepared resins are made from oleoresins from which the essential oil has been removed. A resinoid is prepared by hydrocarbon extraction of a natural resin. 

In an integrated continuous process, cellulose reacts with acetic anhydride prepared from the carbonylation of methyl acetate with carbon monoxide. The acetic acid Hberated reacts further with methanol to give methyl acetate, which is then carbonylated to give additional acetic anhydride (100,101). 

Boric anhydride. (Prepared by melting boric acid in an air oven at a high temperature, cooling in a desiccator, and powdering.) Mainly used for drying formic acid. 

The benzoic acid moiety common to many of the benzamides is prepared in straightforward manner from the methyl ether of p-aminosalicylic acid 141. Acylation on nitrogen (142) followed by chlorination gives intermediate 143 benzoic acid 144 is then obtained by removal of the acetyl group. Condensation of this acid with an aminopiperidine could be achieved by means of the mixed anhydride (prepared by reaction with ethyl chlonoformate), which affords clebopride (145). Reaction with 3-aminoquinuclidine (146) of the intermediate prepared from acid 144 with carbonyldiimidazole affords zacopride (147) [36]. 

The anhydride prepared above is refluxed in water for 4-5 hours. The solution is cooled and extracted six times with small portions of ether (or better, continuously extracted with ether). Drying (sodium sulfate) of the ethereal solution, followed by evaporation of the solvent gives the desired acid, mp 146-149° (dec). 

On the other hand, 1 g of 7-amino-3-methyl-3-cephem-4-carboxylic acid was suspended in 20 ml of methanol, and 1.4 g of triethylamine was added thereto to be dissolved, and 0,4 ml of acetic acid was further added thereto. This solution was cooled to -20°C and the mixed acid anhydride prepared previously was added thereto. After the mixture was reacted at -20°C for 1 hour, the temperature of the reaction mixture was raised to 0°C over a period of 1 hour, and the mixture was reacted for 3 hours at the same temperature. 

Anhydrides, preparation with phosgene and tnethylamine, 47, 91 Anisole, chlorination with sulfuiyl chloride, 47, 23... 

Solutions required. Acetic anhydride. Prepare 250 mL of a 2.0M solution in ethyl acetate containing 4.0 g of 72 per cent perchloric acid. The solution is made by adding 4.0 g (2.35 mL) of 72 per cent perchloric acid to 150 mL of ethyl acetate in a 250 mL graduated flask. Pipette 8.0 mL of acetic anhydride... 

Bordwell and Garbisch71 contested this conclusion since they found that nitric acid in acetic anhydride prepared at —10 °C contained a much less effective nitrating species (the nitric acid could be recovered quantitatively) than when mixed at 25 °C and cooled to —10 °C (the nitric acid being then mostly unrecoverable). Further, these latter solutions reacted with alkenes to give predominantly cis addition products (nitro-acetates), whi h indicates association of the nitronium ion with some other species. It has been argued72 that this does not necessarily follow, since nitration of aromatics may involve a different... 

Heating pyridine-2,3-dicarboxylic acid anhydride with l-ethyl-2-methylindole has been claimed to yield solely the pyridine-2-carboxylic acid, albeit in low yield. This then clearly reacts with Af,A/-diethyl-3-toluidine in acetic anhydride to give the 7-azaphthalide. This is surprising in view of a later report70 in which a one-pot process has been described. Heating pyridine-2,3-dicarboxylic anhydride, prepared in situ, with the indole and subsequent reaction with 3-/V,/V-diethylamino-phenetol under identical conditions to those used in Scheme 8 (but without intermediate isolations) produced a 20 1 mixture of the 4- and 7-azaisomers 16 and 17. It appears that in the previous report the major intermediate isomer, the pyridine-3-carboxylic acid, has not been isolated. 

Mixed anhydrides prepared according to these methods include ... 

It is to be noticed that although the anhydro ring of levoglucosan is stable to alkali (Tanret s preparative method consisted in the heating of aromatic jS-D-glucosides with aqueous alkali), it readily undergoes scission in the presence of acid. An isomeric glucose anhydride prepared in 1912 by E. Fischer showed, however, very different properties. 

Anhydrides, preparation with phosgene and triethylamine, 47, 91 Aniline, reaction with e-nitrobenzalde-hyde, 48,113... 

Block (cap) residual lysine residues with a carboxylic acid by acylation using succinic anhydride prepared in l-methyl-2-pyrrolidinone,... 

Properties of Chromic Anhydride. Perform the experiment in a jume cupboard 1. Put several crystals of the chromic anhydride prepared in the preceding experiment onto the lid of a crucible and pour two or three drops of ethanol onto them from a pipette. What happens Write the equation of the reaction. 

Scheme 3 Symmetrical Anhydrides Preparation and Peptide Bond Formation 48-511...

Acid Anhydrides Preparation of Acid Anhydrides Ketene Reaction... 

The synthesis of 3 was carried out as described above with the exception that Boc-Lys(Fmoc)-OH was used in the synthesis in place of Boc-Lys(CHO)-OH (Scheme 4). Following completion of the peptide synthesis, the peptide-bound resin 6 (250 mg) was treated with piperidine/DMF (20 80, 20 mL) for 20 min, the solvent removed by filtration, and the resin washed with CH2C12(3 x 20 mL). DMF (5mL) was added to the resin followed by a CH2C12 soln (5 mL) of formic anhydride, prepared as above, and DIPEA (350 xL, 1 mmol). The resin was shaken for 20 min, the solvent removed by filtration, and the formylation repeated by the addition to the resin of DMF (5 mL), a CH2CI2 soln of formic anhydride (5 mL), and DIPEA (350 pL, 1 mmol). The resin was shaken for 15 min, filtered, washed with CH2C12 (3 x 20 mL), and the resin dried under vacuum to yield 3. The peptide-resin was converted into 4 by treatment with HF as described above. 

Attempts to synthesize C-terminal peptide aldehydes using other reductive techniques are less successful. 24"29 The reduction of a-amino acid esters with sodium amalgam and lithium aluminum hydride reduction of tosylated a-aminoacyldimethylpyrazoles resulted in poor yields. 26,29 The Rosemond reduction of TV-phthaloyl amino acid chlorides is inconvenient because the aldehyde is sensitive to hydrazine hydrate that is used to remove the phthaloyl group. 27 28 jV -Z-Protected a-aminoacylimidazoles, which are reduced to the corresponding aldehydes using lithium aluminum hydride, are extremely moisture sensitive and readily decomposed. 25 The catalytic reduction of mixed carbonic/carboxylic acid anhydrides, prepared from acylated a-amino acids, leads to poor reproducibility and low yields. 24 The major problems associated with these techniques are overreduction, racemization, and poor yields. 

Alternative methods for the synthesis of peptide aldehydes include reduction of acid halides, phenyl esters, thioesters, and anhydrides prepared from corresponding acids, isoxazolidides, and the hydrolysis of thiazolidine peptides 17,54-56 Enzymes such as thermolysin, subtilisin, and pronase E have proven valuable as effective semisynthetic alternatives 40,57 5 62 ... 

Pyrolysis of cellobiitol at 350 in vacuo yields — 32% of levoglucosan (1,6-anhydro-/ -D-glucopyranose) and 70% of a mixture of D-glucitol and its anhydrides." Preparation of mono- and di-anhydrohexitols, mixed with linear polyols and polymers, were claimed by application of particular noble metal catalysts, coated with copper, on catalytic hydrogenation of D-glucitol and D-mannitol.9"... 

Thiol esters. These esters can be prepared by reaction of mixed anhydrides prepared from this chloride and a carboxylic acid with thiols in the presence of 4-dimethylaminopyridine (equation I). 

The mercapto group of 9-mercapto-4//-pyrido[ 1,2-a]pyrimidin-4-ones 513 was alkylated with (het)aralkyl bromides and chlorides in the presence of potassium carbonate in dimethylformamide at ambient temperature for several hours. It also was acylated with carboxyl chlorides in the presence of potassium carbonate in acetone at room temperature or with mixed anhydride, prepared from aryl carboxylic acid and ethyl chloroformate,... 

PKR of a Monosubstituted Succinic Anhydride Using (DHQD AQN as Catalyst PKR of (+)-2-Methysuccinic Anhydride (Preparative Scale) [81] (p. 317)... 

Peptide synthesis in methanol or ethanol.1 The dimethylphosphinothioic anhydrides prepared from N-protected amino acids with 1 are stable to water or alcohols in the absence of a base, probably because of the P=S bond. As a consequence these active esters can be used for peptide syntheses in methanol or... 

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