Herein, we report a straightforward methodology for direct deaminative cyanation of anilines via aryl diazonium salts as fleeting intermediates. The approach leverages the kinetic stability of nitrate and copper cyanide, iron's ability to facilitate nitrate reduction, and appropriate relative rates to ensure the product-forming kinetic reaction pathway despite several thermodynamically favored, undesired reactions. We present insight into the previously unappreciated nitrate reduction mechanism by simple sulfur-based reductants, such as SO2. The oxylanion radical transfer mechanism is rarely encountered in synthetic chemistry but has ample precedent in biology and could provide a general, useful strategy for chemical nitrate reduction.
Behera et al. (Mon,) studied this question.