1,3-dihydroxybenzene-2-13C: Its preparation and reaction with chlorine and bromine in aqueous solution

1,3‐cyclohexanedione‐2‐13C was prepared by intramolecular Claisen condensation of methyl 5‐oxohexanote‐6‐13C with sodium methoxide. Formation of the ketoester starting material involved treatment of a mixed dicarboxylic anhydride with an isotopicallylabelled Grignard reagent, methyl‐13C magnesium iodide. Dehydrogenation of carbon‐13 labelled cyclohexanedione over a palladium/carbon catalyst produced 1,3‐dihydroxybenzene‐2‐13C. Chlorination and bromination of dihydroxybenzene in aqueous solution yielded isotopically‐labelled chloroform and bromoform, each having enriched carbon‐13 contents equivalent to that of the organic substrate.