Debromination of cholesterol dibromide

Dehalogenation, dehalohydrination. See also yS-Chloroethyl ethyl ether. The debromination of cholesterol dibromide with zinc dust requires only a catalytic amount of acetic acid and once the reaction has started it proceeds with vigor, like... 

Cholestenone has been prepared by oxidation of cholesterol dibromide with chromic acid 1 or potassium permanganate2 and debromination, and by dehydrogenation of cholesterol over copper oxide 3 4 or by the method described above.5... 

An improved route has been described for the degradation of cholesterol to dehydroepiandrosterone,68,69 in which cholesterol is first acetylated and then bromi-nated to give the 5a,6/8-dibromide. This protected cholestane is then isomerized to the 5/3,6a-dibromide prior to chromium trioxide oxidation and zinc debromination. The yield of dehydroepiandrosterone (isolated from the reaction mixture as a 5a,6/3-dibromide) is 20%. 

The cholesterol dibromide that crystallizes from the reaction solution is collected, washed free of the impurities or their dehydrogenation products, and debrominated with zinc dust, with regeneration of cholesterol in pure form. Specific color tests can differentiate between pure cholesterol and tissue cholesterol purified by ordinary methods. 

Mild acid catalyst. A procedure for the preparation of A -cholestene-3-one (5) from cholesterol (1, unpurified) involves oxidation of the dibromide (2), debromination... 

Dehalogenation of vic-dihalides. Schoenheimer used sodium iodide in acetone for recovery of cholesterol from the 5a,6j3-dibromide. Barton and Miller found the isomeric 5/3,6a-dibromide very resistant to debromination and so established that the trans-diaxial configuration is optimal for facile elimination. 

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