One-carbon Homologation Reaction by Ketene Dithioacetalization

A Horner-Emmons reagent, diethyl (1,3-dithian-2-yl)phosphonate (1), reacts with aldehydes and ketones to afford the ketene dithioacetals. After deprotection, followed by hydrolysis or alkolysis, the intermediate ketenes can be converted to the corresponding homologous carboxylic acids or esters in good yields. The one-carbon homologation reaction is an important transformation in organic synthesis.