Radical cyclisation onto nitriles

Iminyl radicals, generated by 5-exo cyclisation of alkyl, vinyl and aryl C-centred radicals onto nitriles, undergo β-scission (nitrile translocation), reduction or tandem cyclisation onto alkenes depending on the nature of the α-substituent. 5-exo Cyclisations of aryl radicals onto nitriles undergo nitrile translocation when the α-substituent is CN, CO2R, SO2Ph or CONMe2. The rate of translocation is faster than 5- or 6-exo cyclisation onto alkenes or 1,5-hydrogen abstraction of allylic hydrogens. When the α-substituents are alkyl, the intermediate iminyl radicals do not undergo nitrile translocation.