Electrochemical oxidation of catechols in the presence of ethyl‐2‐chloroacetoacetate. Synthesis and mechanistic study

Electrochemical oxidation of catechol and some of 3‐substituted catechols ( 1a‐c ) has been studied in the presence of ethyl‐2‐chloroacetoacetate ( 3 ) in water/acetonitrile (90:10) solution using cyclic voltammetry and controlled‐potential coulometry. The results indicate that the quinones derived from catechols ( 1a‐c ) participate in Michael addition reactions with ethyl‐2‐chloroacetoacetate( 3 ), with consumption of only two electrons per molecule of 1 , to form the corresponding benzofurans ( 10a‐c ). The electrochemical synthesis of benzofurans ( 10a‐c ) has been successfully performed at a carbon rod electrode and in an undivided cell with good yields and purity. A new two‐electron mechanism for the electrode process is proposed.