Multiple tritium labelling of (+)‐7‐chloro‐8‐hydroxy‐1‐phenyl‐3‐methyl‐2,3,4,5‐tetrahydro‐1hZ‐3‐benzazepine (sch23390)

We previously reported the synthesis of the antidopaminergic‐antipsychotic agent SCH23390 labelled with tritium In the 9 position of the benzazepine ring system at a specific activity of 5.6 Ci/mmole as the racemic mixture. Here, we report the preparation of the higher specific activity (+)‐Isomer of SCH23390 labelled with tritium In both aromatic rings as well as the N‐methyl group. Multiple labelling was achieved by reductive debromination with carrier‐free tritium gas of a dibrominated N‐normethyl derivative over 5% Pd/C and subsequent N‐methylatlon with high specific activity methyl Iodide. The specific activity obtained for the Nor‐SCH23390 was 8.8 Ci/mmole and 93.8 Ci/mmole for the SCH23390.