Redox-Neutral α-Arylation of Alkyl Nitriles with Aryl Sulfoxides: A Rapid Electrophilic Rearrangement

A facile alpha-arylation of nitriles has been developed by simply introducing Tf2O and DABCO to the mixture of nitriles and aryl sulfoxides. The transformation consists of two sequential steps: (i) Tf2O-initiated electrophilic assembly and and (ii) DABCO-triggered rearrangement. Each step can be tuned independently by changing the temperature and/or base. This adjustability allows the method to accommodate a wide range of substrates. Notable features of this new protocol include remarkable efficiency (20 min, 30 C), exclusive regioselectivity, and high functional group compatibility, which can be challenging issues in traditional approaches. NMR studies not only identified a unique, highly unstable sulfonium imine complex but also demonstrated the importance of temperature in the formation and manipulation of this key intermediate. Further DFT calculations suggested that an electrophilic assembly, followed by removal of HQTf (by base), and finally [3,3]-sigmatropic rearrangement are three key stages in the reaction. The versatile transformability of the products and easy scalability of this reaction are also exhibited here.