Paired electrochemical synthesis of new organosulfone derivatives

Abstract

Electrochemical oxidation of “ cathodically generated 4-aminocatechol ( 2)” has been studied in the presence of 4-toluenesulfinic acid ( 4a) and benzenesulfinic acid ( 4b) as nucleophiles in aqueous solutions, using cyclic voltammetry and controlled-potential coulometry. The results indicate that the o-benzoquinone derived from 4-aminocatechol ( 2) participates in Michael addition reaction with 4a or 4b to form the corresponding new organosulfone derivatives ( 5a and 5b). In this work we have proposed a mechanism for the electrode process. A Fe(CN) 6 3−/Fe(CN) 6 4− redox mediator was used for the anodic oxidation of 4-aminocatechol ( 2) to the corresponding o-quinone 3. The indirect electrochemical process consists of a multi-step such as (a) cathodic reduction of 4-nitrocatechol ( 1) to 4-aminocatechol ( 2), (b) chemical oxidation of 4-aminocatechol ( 2) to 4-aminoquinone ( 3) with the resulting Fe(CN) 6 3−, (c) the chemical reaction of 4-aminoquinone ( 3) with 4-toluenesulfinic acid ( 4a) or benzenesulfinic acid ( 4b), and (d) the anodic regeneration of Fe(CN) 6 3−. The paired electrochemical synthesis of organosulfone derivatives ( 5a and 5b) has been successfully performed in an one-pot process at carbon rod electrode as a working and platinum as a counter electrode in an undivided cell.