Propionic acid, bromination oxidation

Rosenau, T. Potthast, A. Kosma, R Habicher, W. D. Novel tocopherol compounds XI. Synthesis bromination and oxidation reactions of 3-(5-tocopheryl)propionic acid. Synlett 1999, 3, 291-294. 

The second method of preparation (shown in Scheme 2) depends on treating dehydroepiandrosterone (prepared from cholestrol or sitosterol) with acetylene to form the 17a-ethnyl-17p-hydroxy derivative, which is carbonated to the 17a-propionic acid. Reduction of the unsaturated acid in alkaline solution yields the saturated acid, which cyclizes to the lactone on acidification. Bromination to the 5,6-dibromo-compound, followed by oxidation of the hydroxyl group to the ketone, and then dehydro-bromination to the 7a-hydroxyl derivative, produces spironolactone when esterified with thiolacetic acid. 

From a-a-Di-brom Propionic Acid.—Di-brom propionic acid with both bromine atoms in the alpha position yields pyro-racemic acid by treatment with silver oxide. 

The data of Barger and Ewins did not permit definite allocation of the position of the sulfur atom in ergothioneine, but the stability of the sulfur toward alkali and its ready oxidation by ferric chloride or bromine water suggested the presence of a 2-mercaptoimidazole ( thiolimidazole ) structure. Confirmation of this was provided by Akabori (1933), who reduced the alkali-degradation product (thiolurocanic acid) with sodium amalgam to give 8-2-mercaptoimidazole-4(5)-propionic acid. The structure of this compound was confirmed by synthesis (III) from glutamic acid. 

ETHYL PROPIONATE (105-37-3) Forms explosive mixture with air (flash point 54°F/ 12°C). Violent reaction with strong oxidizers. Incompatible with ammonium persulfate, bromine dioxide, nitrates, permanganates, peroxides, strong acids sulfuric acid, nitric acid. Flow or agitation of substance may generate electrostatic charges due to low conductivity. 

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