Synthesis of o-Halothiobenzamide Derivatives from the Selective Thiolysis Reaction of o-Halobenzonitrile Mediated by CO2

Abstract

A method for the selective synthesis of o-halothiobenzamide by thiolysis reaction of o-halobenzonitrile with NaHS under the action of CO2 was explored. CO2/H2O/NaHS was used as a buffer system to provide a suitable pH environment, which would make HS- attack the nitrile-based carbon selectively to produce the corresponding o-halothiobenzamide. Moreover, the buffer system also provided the additionally required hydrogen atom for the thiolysis reaction of o-haloben-zonitrile with NaHS. Further studies have found that the CO2/Na2S•9H2O buffer system could also efficiently promote the thiolysis reaction of o-halobenzonitrile to form the corresponding o-halothiobenzamide. This synthetic method could be used to prepare different substituted o-halobenzonitriles, which is a simple, efficient and high atom-economic reaction.