A mechanistic study of photocyanation of pyrene in oil-in-water emulsion systems

A highly efficient one-step photocyanation reaction of pyrene was shown to proceed in oil-in-water emulsion systems. As a typical example, photoirradiation of pyrene in the presence of 1,4-dicyanobenzene and NaCN in a benzonitrile/water mixture (1/100, vol %) under vigorous stirring gave 1-cyanopyrene in a conversion yield of 83%, while an analogous reaction in an acetonitrile/water mixture (9/1, vol %) yielded this product in 61% yield. We evaluated the quantum yield of photocyanation in the oil-in-water emulsion system to be 0.17. Under optimum conditions, the quantum yield was improved to 0.68. Characteristics and possible mechanisms of the photocyanation reaction are discussed in detail.