Milled and efficient synthesis and structural study of 4-phenylsulfonyl-2,3,5,6-tetrachloropyridine

4-phenylsulfonyl-2,3,5,6-tetrachloropyridine was synthesized by the reaction of pentafluoropyridine with sodium benzenesulfonate under ultrasonic irradiation. This new methodology provides the excellent yield in a very short reaction time at 0 oC. In the presence of ultrasound irradiation, the yield was 90% after 8 min, by using our previously established method the yield was 85% after 10 h. Also, in this research, the substituent effect in meta and para position of phenyl ring on intramolecular halogen bond strength has been investigated by theoretical studies. The calculations were performed with Gaussian09 software in M05-2X/6-311++G(d,p) level. The results show that one of the oxygen atoms of the SO2 group is co-planer with the pyridine ring and the other oxygen atom is out of this plane. Also, it is observed that the electron-withdrawing groups in meta and para positions reinforced the halogen bond that the oxygen atom of the SO2 group is co-planer with pyridine ring. An opposite behavior is observed for electron-donating groups.