Palladium-catalyzed direct cyanation of indole derivatives using potassium cyanate and nitromethane as the cyanation system

Aryl nitriles are one of the most important organic compounds found in biological, agrochemical, pharmaceutical and natural products. On the other hand, nitrile group can be served as an intermadiate for synthesis of aldehydes, ketones, amids, amines, terazoles and carboxylic acids.[1]For more than a centuary, Rosenmund-von Braund and sandmeyer reactions have been used as the traditional methods for the synthesis of aryl nitriles. Aryl halides and aryl diazonium salts are used as the starting materials in the above mentioned reactions and equimolar amounts of heavy metal waste, arising from the use of stoichiometric amounts of CuCN as a cyanid source, is produced. Therefore, development of new methods using alternant cyanation agents is of considerable importance.[2]Recently, much attention has been paid to direct C–H functionalization reactions as the more efficient and greener methods. In this work, a new method for direct cyanation of indoles using Pd salts as the catalyst in the present of potassium cyanate and nitromethane as the cyanation reagent system is developed.