Preparation of tritium‐labeled PF‐622, a novel fatty acid amide hydrolase inhibitor

To make a detailed characterization of the mechanism of inhibition and selectivity of a novel fatty acid amide hydrolase inhibitor PF‐622 , 3 tritium isotopomers were prepared. [ 3 H] PF‐622a labeled at the piperazine ring B and [ 3 H] PF‐622b labeled at both the ring B and phenyl ring A were synthesized via catalytic H(hydrogen)‐T(tritium) exchange, utilizing 1 equiv and excess of Crabtree's catalyst, respectively. The preparation of [ 3 H] PF‐622c labeled only at the phenyl ring A was achieved via tritiodebromination of the bromide precursor, using Pd(PPh 3 ) 4 as a catalyst. The observations from these tritiation reactions might open a new perspective in the labeling for the targets having a similar moiety.