Synthesis of 13C- and 14C-labelled catechol

13C- and 14C-uniformly labelled catechol was synthesized from phenol in three steps. Phenol was derivatized with 2-chloro-5-nitrobenzophenone in THF containing NaH, followed by ortho-hydroxylation with 35 per cent aqueous H2O2 in sulphuric acid/glacial acetic acid solution, and by cleavage with piperidine, giving an overall 80 per cent yield with respect to phenol.