Abstract Dichlorocatechols (DCC) are common metabolites in the aerobic degradation of dichlorobenzenes. Their synthesis is therefore possible either enzymatically, or chemically by several two-step-syntheses starting from cycloalkanones or suitable dichlorophenols. A modified ultrasonic Reimer/Tiemann reaction and subsequent Dakin oxidation was used to prepare 3, 5-DCC and 4, 5-DCC. A new UV-photoradical single step synthesis of 3, 4- ...