An efficient palladium catalytic system for microwave assisted cyanation of aryl halides

Application of a new catalytic system for cyanation reaction of various aryl halides using K4[Fe(CN)6] as cyanating source was examined. The reactions were performed under microwave irradiation and results showed that application of this catalytic system and DMF at 130 °C minimized the reaction times from hours to minutes in good to excellent yields.

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► Benzonitriles were synthesized by addition of stoichiometric amount of CuCN as cyanating agent to aryl halides (Sandmeyer reaction and Rosenmund-von Braun reaction) [7], 7a, 7b, 7c, 7d, 7e, 7f and 7g, however this copper mediated reaction has required harsh conditions such as elevated temperature, sometimes more than 150 °C [8].
► Moreover, workup of the reaction mixture for removing of Cu salts from reaction mixture is also harsh [9].
► Other toxic cyanating sources also were used [10], [11], [12], [13], [14] and [15]. Therefore, researches for finding the new and more safe reagents were performed recently, and K4[Fe(CN)6] was chosen as a secure source for cynation [16], [17], [18], [19], [20] and [21].
► Since presence of free cyanide ion in the solution causes deactivation of the catalyst [22]; Therefore, employing this weakly ionizable source [23] has more advantages over the other cynation reagents [22], 24a, 24b and [24].