Radical-nucleophilic aromatic substitution experiments

The photocyanation of pyrene in a microchaimel through an oil-water interface was investigated by Ueno et al. [13]. The microchips employed are made of polystyrene by embossing with a silicone template. The phase transfer reaction proceeds in four steps as depicted in Figure 16.2. In the first step, a photoinduced electron transfer in the oil phase (polycarbonate) occurs from the aromatic hydrocarbon pyrene (DH) to the electron acceptor 1,4-dicyanobenzene (A). The cationic DH " radical is subsequently the target of the nucleophilic attack of the cyanide anion at the oil-water interface. The cyanated product DCN is insoluble in water and goes back into the oil phase. Experiments without a cyanide source (NaCN) in the aqueous phase show no reaction. Hence it can be excluded that the nudeophilic-substituted cyanide originates from the electron acceptor 1,4-dicyanobenzene. 

---