Improved procedure to aryl thiocyanates: a new synthetic application of dry arenediazonium o-benzenedisulfonimides

Aryl thiocyanates (22 examples) were easily prepared by reaction of dry arenediazonium o-benzenedisulfonimides and sodium thiocyanate in anhydrous acetonitrile at room temperature (20-25 °C) in the presence of copper powder (Procedure A) and at 50 °C or room temperature without the metal catalyst (Procedure B). The yields were from very good to excellent in Procedure A (average yield = 83%), and from modest to excellent in Procedure B (average yield = 63%). In comparison with the thiocyanodediazoniation carried out under traditional Sandmeyer-type conditions, the yields of products were higher and the isothiocyanate isomers were formed only in traces. Moreover, the results obtained in the absence of copper confirm the role of the anion of arenediazonioum salts as an electron transfer agent