Cyclocondensation of o ‐Phenylenediamines with 2‐Oxo‐ethanimidothioates: A Novel Synthesis of 2‐Amino‐3‐(het)aryl‐quinoxalines

Abstract 2‐Amino‐3‐(het)aryl‐quinoxalines were synthesized by the cyclization reaction between 2‐oxo‐ethanimidothioates and o ‐phenylenediamine in the presence of acid catalyst p ‐TSA in toluene at 80 °C. The products were obtained in 58–84 % yields. The required substrates 2‐oxo‐ethanimidothioates were synthesized by the condensation reaction between α ‐oxodithioester and amine in the presence of sodium hydride in DMF followed treatment with methyl iodide.