Acid anhydrides preparation

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. 

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. 

Acid Anhydrides Preparation of Acid Anhydrides Ketene Reaction... 

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. 

Phenylhydrazine and pyridine-2,3-dicarboxylic acid anhydride, prepared from the acid in situ, condense in acetic anhydride at 120-130 °C to give 7-phenylpyrido[2,3-[Pg.25]

Precaution Probably combustible incompat. with nitric acid, sulfuric acid, strong oxidizing agents, strong acids, acid chlorides, acid anhydrides preparative hazard sensitive to light... 

Dihydroanthracene-9,10-a,p-succinic Acid Anhydride Preparation Using a Monomode Microwave Apparatus... 

Tab. 4.39, N-Carboxy-a-amino acid anhydrides prepared with triphosgene [894].

Another method to obtain alcohols is to reduce the mixed carbonic acid anhydride prepared with Ethyl Chloroformate with an excess of Sodium Borohydride. This method uses less costly reagents thus it is more useful for synthetic transformations. 

ACID ANHYDRIDES OF ALIPHATIC CARBOXYLIC ACIDS Acid anhydrides of monobasic aliphatic acids may be prepared —... 

Here the phenylacetic anhydride, possessing more reactive a-hydrogen atoms, condenses with benzaldehyde to give a-phenylcinnamic acid. The preparation of the latter is an example of the Oglialoro modiflcation of the Perkin reaction. 

AROMATIC ACID ANHYDRIDES The anhydrides of aromatic acids are prepared —... 

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. 

Another procedure for obtaining a-aminoketones is by reduction of a-nitrosoketones in the presence of the required carboxylic acid. Acylaminoketones are prepared either by reacting acids with the chlorhydrate of a-aminoketones according to the method of Pictet and Gauss (41) or by the action of acid anhydrides upon a-amino acids (550). 

Acyl chlorides react with carboxylic acids to yield acid anhydrides When this reaction is used for preparative purposes a weak organic base such as pyridine is normally added Pyridine is a catalyst for the reaction and also acts as a base to neutralize the hydrogen chloride that is formed... 

Amides are readily prepared by acylation of ammonia and amines with acyl chlorides acid anhydrides or esters... 

These thermal methods for preparing amides are limited m their generality Most often amides are prepared m the laboratory from acyl chlorides acid anhydrides or esters and these are the methods that you should apply to solving synthetic problems... 

This chapter concerns the preparation and reactions of acyl chlorides acid anhydrides thioesters esters amides and nitriles These com pounds are generally classified as carboxylic acid derivatives and their nomenclature is based on that of carboxylic acids... 

Section 20 5 Acid anhydrides may be prepared from acyl chlorides m the laboratory but the most commonly encountered ones (acetic anhydride phthahc anhydride and maleic anhydride) are industrial chemicals prepared by specialized methods... 

Section 20 6 Acid anhydrides are less reactive toward nucleophilic acyl substitution than acyl chlorides but are useful reagents for preparing esters and amides... 

Section 20 7 Esters occur naturally or are prepared from alcohols by Fischer estenfi cation or by acylation with acyl chlorides or acid anhydrides (see Table 20 3)... 

Therapeutics. Compounds containing the furan or tetrahydrofuran ring are biologically active and are present in a number of pharmaceutical products. Eurfurjdamine [617-89-0] is an intermediate in the diuretic, furosemide. Tetrahydrofurfurylamine [4795-29-3] may also have pharmaceutical applications. 5-(E)imethyiaininomethyi)furfuryi alcohol [15433-79-17 is an intermediate in the preparation of ranitidine, which is used for treating ulcers. 2-Acet5dfuran [1192-62-7] prepared from acetic anhydride and furan is an intermediate in the synthesis of cefuroxime, a penicillin derivative. 2-Euroic acid is prepared by the oxidation of furfural. Both furoic acid [88-14-2] and furoyl chloride [527-69-5] are used as pharmaceutical intermediates. 

A series of water-soluble fiber-reactive xanthene dyes has been prepared from the reaction of ben2oxanthenedicatboxylic acid anhydride disulfonic acid with, for example, 3-aminophenyl-P-hydtoxyethyl sulfone to yield dyes, with high brilliance and good fastness properties for dyeing of or printing on leather, wool, sHk, or ceUulosic fibers (53). 

In general, the reactions of the perfluoro acids are similar to those of the hydrocarbon acids. Salts are formed with the ease expected of strong acids. The metal salts are all water soluble and much more soluble in organic solvents than the salts of the corresponding hydrocarbon acids. Esterification takes place readily with primary and secondary alcohols. Acid anhydrides can be prepared by distillation of the acids from phosphoms pentoxide. The amides are readily prepared by the ammonolysis of the acid haUdes, anhydrides, or esters and can be dehydrated to the corresponding nitriles (31). 

Trifluoromethanesulfonic acid anhydride, bp 84°C, is prepared by refluxing the acid over an excess of phosphorous pentoxide (18,26). The anhydride reacts instantaneously with ammonia or amines to form trifluoromethanesulfonamides. The anhydride reacts with most polar organic solvents. 

Inositols, ie, hexaliydrobenzenehexols, are sugars that have received increasing study and are useful in the treatment of a wide variety of human disorders, including vascular disease, cancer, cirrhosis of the Hver, frostbite, and muscular dystrophy (269). Myoinositol esters prepared by reaction with lower fatty acid anhydrides are useful as Hver medicines and nonionic surfactants the aluminum and ammonium salts of inositol hexasulfate are useful anticancer agents (270). Tetraarjloxybenzoquinones are intermediates in the preparation of dioxazine dyes (266,271). The synthesis of hexakis(aryloxy)benzenes has also beenpubUshed (272). 

Sorbic acid anhydride [13390-06-2] can be prepared by heating the polyester of 3-hydroxy-4-hexenoic acid with sorboyl chloride [2614-88-2] or by reaction of sorbic acid with oxalyl chloride (15,16). Preparation of the esters of sorbic acid must be controlled to prevent oxidation and polymerization. The lower sorbic acid esters have a pleasant odor. 

---