Cyclotrimerization of p-chloro-ethynylbenzene is carried out to regioselectively afford 1,3, 5-Tri (p- chlorophenyl) benzene in poly(ethylene glycol)-400 (PEG-400). The method is of high yield. It is worthy that the reaction is conducted under environmentally benign conditions and the catalyst could be properly recycled. The structure is cha...