Anodic cyanation of 1‐arylpyrroles

Abstract

The electrooxidation of several 1‐arylpyrroles has been carried out in methanol containing sodium cyanide at a platinum anode in a divided cell. In all instances, replacement of a heteroaromatic hydrogen by a cyano group occurred. On the basis of electroanalytical results, the anodic cyanation of the title compounds could be designed an EC process. As a result of two‐electron oxidation, the corresponding pyrrole cyanides were obtained in yields ranging from 76‐85%. The advantages of electrochemistry synthesis of pyrrole cyanides are simple reaction condition, low cost and high purity products.

Expedient Access to Cyanated N‐Heterocycles by Direct Flow‐Electrochemical C(sp2)−H Activation

“…Yoshida and Yin, for example, demonstrated the dual function of sodium cyanide as electrolyte and reagent in the electrochemical cyanation of N-substituted pyrroles and indoles. [37,48] After an extensive screening of the reaction conditions, nBu 4 NCN in a 5 : 2 : 0.1 mixture of 2-methyltetrahydrofuran, methanol and water with Pt electrodes in an undivided cell were found to be optimal [49] (see the Supporting Information for the full optimization table). As shown in Scheme 1, these electrolysis conditions led to the successful electrochemical cyanation of 1-phenyl-1H-pyrrole 1 (73 %) as well as 1cyclohexane-1H-pyrrole 2 (82 %), 1-(4-methoxyphenyl)-1Hpyrrole 3 (71 %), 1-(2,4-methoxyphenyl)-1H-pyrrole 4 (67 %) and 2-(1H-pyrrol-1-yl)pyridine 5 (69 %).…”