Preparation of Lucas reagent of enhanced utility and its use in synthesis of cycloaliphatic chlorides

摘要

Gaseous anhydrous hydrogen chloride is introduced into an aqueous solution of zinc chloride under conditions effective to produce a more efficient Lucas reagent than a Lucas reagent made by mixing solid, anhydrous zinc chloride with 38% hydrochloric acid. For example, the reaction rate of such Lucas reagent with levo-menthol is much faster and requires a much shorter reaction period than Lucas reagent formed in the conventional manner from anhydrous, solid zinc chloride and concentrated (38%) hydrochloric acid. Also, the conversion to levo-menthyl chloride was higher when using Lucas reagent formed using gaseous anhydrous hydrogen chloride and aqueous zinc chloride solution. Also, Lucas reagent made in this manner is highly amenable to recycling, and requires only addition thereto of hydrogen chloride to replenish the catalyst for an ensuing run.