Propionic anhydride

Acid Anhydrides. Symmetrical anhydrides of monocarboxylic acids, when unsubstituted, are named by replacing the word acid by anhydride. Anhydrides of substituted monocarboxylic acids, if symmetrically substituted, are named by prefixing bis- to the name of the acid and replacing the word acid by anhydride. Mixed anhydrides are named by giving in alphabetical order the first part of the names of the two acids followed by the word anhydride, e.g., acetic propionic anhydride or acetic propanoic anhydride. Cyclic anhydrides of polycarboxylic acids, although possessing a... 

Yields of the order of 85% were secured in the dry reaction (48). (Propionic anhydride and butyric anhydride can be obtained similarly from their sodium salts.) Inasmuch as dinitrogen tetroxide can be regenerated, the economic prospects of this novel way of making anhydride are feasible. 

Liquid crystal polyesters are made by a different route. Because they are phenoHc esters, they cannot be made by direct ester exchange between a diphenol and a lower dialkyl ester due to unfavorable reactivities. The usual method is the so-called reverse ester exchange or acidolysis reaction (96) where the phenoHc hydroxyl groups are acylated with a lower aHphatic acid anhydride, eg, acetic or propionic anhydride, and the acetate or propionate ester is heated with an aromatic dicarboxyHc acid, sometimes in the presence of a catalyst. The phenoHc polyester forms readily as the volatile lower acid distills from the reaction mixture. Many Hquid crystal polymers are derived formally from hydroxyacids (97,98) and thein acetates readily undergo self-condensation in the melt, stoichiometric balance being automatically obtained. 

Coumarin formation proceeds via an intramolecular attack by enol ester 9 on the ketone to give 10. Dehydration of 10 then affords coumarin 11. It has been observed that coumarins are favored when higher order homologs of acetic anhydride and their corresponding salts such as propionic anhydride/sodium propionate and butyric anhydride/ sodium butyrate are used. 

The ring-contracted analog of alphaprodine is prepared by a variation of the scheme above. Alkylation of 109 with ethyl bromoacetate affords the lower homolog diester (115). Dieckmann cyclization followed by saponification-decarboxylation yields the pyrrolidine (116). Reaction with phenylmagnesium bromide leads to the condensation product (117) acylation with propionic anhydride gives the analgesic agent prolidine (118)... 

Somewhat milder oxidative conditions lead to loss of but one carbon. Periodic acid cleavage of the side chain in 65, leads to the so-called etio acid (66). Reaction with propionic anhydride leads to acylation of the 17-hydroxyl group (67). Possibilities for neighboring group participation severely limit the methods available for activating the acid for esterification. Best results seemed to have been obtained by use of a mixed anhydride from treatment with diphenyl chloro-... 

The excess of N-chlorosuccinimide is destroyed by the addition of about 15 drops of allyl alcohol and 180 ml of water is then added with stirring. This mixture is held at 0°C for about one hour. The precipitated 16/3-methyl-1,4-pregnadiene-9o-chloro-11/3,17o,21-triol-3,20-dione-21-acetate is recovered by filtration. A solution of 250 mg of the chlorohydrin in 5 ml of 0.25N perchloric acid in methanol is stirred for about 18 hours at room temperature to produce 16/3-methyl-9o-chloro-11/3,17o,21-trihydroxy-1,4-pregnadiene-3,20-dione which is recovered by adding water to the reaction mixture and allowing the product to crystallize. Propionic anhydride is then used to convert this material to the dipropionate. 

Betamethasone-21 -methanesu donate Lithium chloride Propionic anhydride... 

Clobetasol is usually converted to the propionate as the useful form by reaction with propionic anhydride. 

A mixture of 1 gram of 2-hydroxymethylene-dihydrotestosterone, 10 cc of pyridine and 2 cc of propionic anhydride was allowed to react at room temperature for 16 hours and then poured into water. The resulting suspension was heated for 1 hour on the steam bath to hydrolyze the excess of propionic anhydride, cooled and extracted with methylene dichloride. The extract was consecutively washed with dilute hydrochloric acid, sodium bicarbonate solution and water, dried over anhydrous sodium sulfate and evaporated to dryness under vacuum. There was thus obtained the dipropionate of 2-hydroxymethylene-dihydrotestosterone which was treated with hydrogen, in methanol solution. 

The starting material is prepared by reacting 1-benzyl-4-piperidone with aniline, reducing the condensation product with lithium aluminum hydride, reacting the product thus obtained with propionic anhydride, than hydrogen. 

Piperidino-isopropyDaminopyridine Propionic anhydride Fumaric acid... 

A mixture of 50 grams of a-dl-1,2-diphenyl-2-hydroxy-3-methyl-4-dimethylaminobutane hydrochloride, 50 grams of propionic anhydride and 50 cc of pyridine was refluxed for about 5 hours. The reaction mixture was cooled to 50°C and ethyl ether was added to the point of incipient precipitation. The hydrochloride salt of 0 -dl-l,2-diphenyl-2-propion-oxy-3-methyl-4-dimethylamlnobutane formed in the reaction precipitated upon cooling and was removed by filtration and washed with anhydrous ether. On recrystallization from a mixture of methanol and ethyl acetate, a-dl-l, 2-diphenyl-2-propionoxy-3-methyl-4-dimethyl amlnobutane hydrochloride melted at 170°-171°C. 

Interestingly, prolonged (60 h) thermolysis of tosyl azide in propionic anhydride in the presence of dimethyl terephthalate produces a moderate yield of dimethyl 1-tosyl-l 7/-azepine-2,5-dicar-boxylate (18) free from the usual accompanying anilide or sulfonamide byproducts.159... 

Propiolic acid, 58,43 Propionaldehyde, 58, 80, 82 Propionic anhydride, 57, 111 Propionyl chloride, 58, 85... 

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