1-(2,6-Dichlorophenyl)piperazine-d8 Hydrochloride is the isotope analog of 1-(2,6-Dichlorophenyl)piperazine Hydrochloride. 1-(2,6-Dichlorophenyl)piperazine Hydrochloride is used in the preparation of pyrazolopyrimidones and pyrazolopyridones as tankyrase inhibitors which are useful in the treatment of cancer.