Trichloroethyl esters, cleavage

Zn, THF-H2O, pH 4.2, 25°, 4 h. The authors suggest that selective cleavage should be possible by this method, since, at pH 4.2, 25°, 2,2,2-trichloroethyl esters are cleaved in 10 min, 2,2,2-trichloroethyl carbamates are cleaved in 30 min, and the 2,2,2-trichloroethyl carbonate of estrone, formed in 87% yield from estrone and the acid chloride, is cleaved in 4 h (97% yield). 

Electrolysis at a Hg cathode, -0.5 to -0.6 V, LiC104, CH3CN, Pyr. The trichloroethyl ester, which requires a greater reduction potential for cleavage, is retained under these conditions." ... 

Cleavage of 2,2,2-trichloroethyl esters. A method for the regeneration of carboxylic... 

If only the O-H, as opposed to the carbonyl, group of a carboxyl function needs to be masked, this can be readily accomplished by the standard esterification techniques. Alkaline hydrolysis is the usual way for regenerating the acid. r-Butyl esters are readily cleaved by mildly acidic conditions because of the facile cleavage of the alkyl oxygen bond. 2,2,2-Trichloroethyl esters find some specialized use. This group can be removed with zinc dust in aqueous acetic acid. 

Demethylation of cocaine was also achieved by 2,2,2-trichloroethyl chloro-formate and reduction, or by using Ollofson s reagent, " vinyl chloro-formate, [via (26)] and subsequent cleavage of the vinyloxycarbonyl group with mild acid. N-Allylnorcocaine [iV-allyl-(22a)] has been synthesized, for biological screening in monkeys. The cycloheptadienone route to tropinones and, in turn, to 3a-tropanols was applied to alanine ester and other derivatives. 

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