Favorskii Rearrangement and Carbon–Carbon Bond-Cleavage of α-Chloro-α-sulfonyl Ketones: A Synthesis of Carboxylic Acids and Their Derivatives from Aldehydes and Ketones

A method for synthesizing carboxylic acids and their derivatives from aldehydes and ketones via α-chloro-α-sulfonyl ketones is described. Acyclic α-chloro-α-sulfonyl ketones were synthesized from aldehydes and 1-chloroalkyl p-tolyl sulfoxides with carbon–carbon coupling in good overall yields. Cyclic α-chloro-α-sulfonyl ketones were synthesized from cyclic ketones in three steps in high overall yields. The Favorskii rearrangement of both acyclic- and cyclic α-chloro-α-sulfonyl ketones with sodium hydride in the presence of amine gave β-sulfonyl amides with skeletal rearrangement in good to excellent yield. Amides and α,β-unsaturated amides were synthesized from the β-sulfonyl amides. Treatment of the cyclic α-chloro-α-sulfonyl ketones with alkoxides and hydroxide gave carboxylic esters and acids with cleavage of the ring in good to excellent yields.