Nitriles (Cyanides)

Direct Oxidative Conversion of Methylarenes into Aromatic Nitriles

“…Study of the practical transition-metal free methods for the preparation of aromatic nitriles is very important since they are precursors for the preparation of amides, esters, primary amines, carboxylic acids, aldehydes, ketones, and nitrogen-containing heterocycles, such as tetrazoles and oxazoles . They have also great importance in the synthesis of agrochemicals, therapeutic drugs, functional materials, natural products, dyes, and pigments. , Today, the most conventional methods for the preparation of aromatic nitriles are the dehydration of primary aromatic amides , with SOCl 2 , TsCl/Py, P 2 O 5 , POCl 3 , COCl 2 , (EtO) 3 P/I 2 , Ph 3 P/CCl 4 , or (COCl) 2 /DMSO and the Sandmeyer reaction of aromatic diazonium ion with toxic CuCN. , Recently, the direct transformation of aromatic bromides into the corresponding aromatic nitriles was actively studied with CuCN in N,N -dimethylformamide (DMF) at 153 °C (the Rosenmund–von Braun reaction), and related reactions with palladium and metal cyanide were reported. − However, all of these reactions require toxic metal cyanides. Typical examples of cyanide-free and transition-metal-free methods for the preparation of aromatic nitriles are the reaction of electron-rich aromatics with chlorosulfonylisocyanate to form N -chlorosulfonyl amides and the subsequent treatment with DMF to give aromatic nitriles, together with generation of SO 3 and HCl, , and the reaction of indoles or pyrroles with triphenylphosphine–thiocyanogen (TPPT) .…”