Preparation alcohols/permanganate

Alanine, a-amino- -butyric acid, and a-aminoisobutyric acid are prepared by permanganate oxidation of the N-benzoyl derivatives of the corresponding amino alcohols. The free amino acids are obtained from the benzoyl derivatives by hydrolysis with hydrochloric acid followed by treatment with aniline. Over-all yields for the four step process are 45-60%. 

Preparation of the sulphones. Dissolve the 2 4-dinitrophenyl-sulphide in the minimum volume of warm glacial acetic acid and add 3 per cent, potassium permanganate solution with shaking as fast as decolourisation occurs. Use a 50 per cent, excess of potassium permanganate if the sulphide tends to precipitate, add more acetic acid. Just decolourise the solution with sulphur dioxide (or with sodium bisulphite or alcohol) and add 2-3 volumes of crushed ice. Filter off the sulphone, dry, and recrystaUise from alcohol. 

The purification of diethyl ether (see Chapter 4) is typical of liquid ethers. The most common contaminants are the alcohols or hydroxy compounds from which the ethers are prepared, their oxidation products (e.g. aldehydes), peroxides and water. Peroxides, aldehydes and alcohols can be removed by shaking with alkaline potassium permanganate solution for several hours, followed by washing with water, concentrated sulfuric acid [CARE], then water. After drying with calcium chloride, the ether is distilled. It is then dried with sodium or with lithium aluminium hydride, redistilled and given a final fractional distillation. The drying process should be repeated if necessary. 

Codeinone, CjaHijOgN. This ketone (XLVII) corresponds to the secondary alcohol codeine and its stereoisomeride wocodeine. It may be prepared by oxidising codeine with potassium permanganate in acetone or with potassium dichromate in dilute sulphuric acid and in various other ways. Codeinone can be reduced to codeine electrolytically or by chemical methods. It crystallises from alcohol in prisms, m.p. 185-6, [a]J, ° — 205° (EtOH). The hydrochloride, B. HCl. HjO, has m.p. 179-80°, picrate, m.p. 205°, methiodide, B. CHjI. 2H2O, m.p. 180°. 

Pinoglycyl Acetate.—This ester can be prepared by the direct acetylation of pinoglycol, C,gH,.0(0H)g, an alcohol resulting from the oxida-.tion of pinol with permanganate of potassium. It can also be prepared from pinol dibromide and acetate of silver. It is an ester with an excellent fruity odour, of the formula C,gH, 0(CgHg0.2).2, melting at 97° to 98°, and boiling at 155° at 20 mm. pressure, or at 127° at 13 mm. 

Carboxylic acids can be prepared by oxidizing primary alcohols and aldehydes with a strong oxidizing agent, such as acidified aqueous potassium permanganate solution. In some cases, an alkyl group can be oxidized directly to a carboxyl group. This process is very important industrially. 

Further variations on the epoxyketone intermediate theme have been reported. In the first (Scheme 9A) [78], limonene oxide was prepared by Sharpless asymmetric epoxidation of commercial (S)-(-)- perillyl alcohol 65 followed by conversion of the alcohol 66 to the crystalline mesylate, recrystallization to remove stereoisomeric impurities, and reduction with LiAlH4 to give (-)-limonene oxide 59. This was converted to the key epoxyketone 60 by phase transfer catalyzed permanganate oxidation. Control of the trisubstituted alkene stereochemistry was achieved by reaction of the ketone with the anion from (4-methyl-3-pentenyl)diphenylphosphine oxide, yielding the isolable erythro adduct 67, and the trisubstituted E-alkene 52a from spontaneous elimination by the threo adduct. Treatment of the erythro adduct with NaH in DMF resulted... 

The mixed sulfates are prepared by transformation of alcohols obtained from D-( + glucose with chloro methyl sulfite into mixed sulfites which are then oxidized with potassium permanganate under phase transfer catalysis into the corresponding sulfates14. 

The more finely divided the manganese dioxide the more rapid will be the reaction, so that the precipitated reagent is better than finely powdered pyrolusite. It is still better to prepare the precipitated hydroxide Mn(OH)4, by reducing the necessary quantity of potassium permanganate in neutral solution with alcohol and washing the precipitate from soluble potassium salts by decantation. 

---