Stability of the dilithium salts formed by the reaction of organolithium derivatives with lithium salts of aromatic carboxylic acids

Abstract

The dilithium salts PhCR(O^–Li⁺)₂, formed by the reaction of organolithium derivatives with lithium carboxylates, are stable in ether heated under reflux for 96 h when R = phenyl, 4-tolyl, or 4- or 2-methoxyphenyl, but decompose to give lithium benzoate and RLi when R = 2,6-dimethoxyphenyl, 2-thienyl, or 2-furyl. The dilithium salts react with water to give ketones; efficient methods for the synthesis of several substituted benzophenones, 2-benzoylthiophen, and 2-benzoylfuran are reported.

Base-induced cleavage of aromatic ketones is formally the reverse of the above reactions. Fluorenone, 2-chlorobenzophenone, 2,6-dimethoxybenzophenone, and 2-benzoylthiophen are cleaved readily when treated with potassium t-butoxide (10 equiv.) and water (3 equiv.) in ether but are unaffected by the analogous reagent prepared with lithium t-butoxide.