Radical cyclisation onto nitriles

Iminyl radicals, generated by 5-exo cyclisation of alkyl, vinyl and aryl C- centred radicals onto nitriles, undergo beta -scission (nitrile translocati on), reduction or tandem cyclisation onto alkenes depending on the nature o f the alpha -substituent. 5-exo Cyclisations of aryl radicals onto nitriles undergo nitrile translocation when the alpha -substituent is CN, CO2R, SO2 Ph or CONMe2. The rate of translocation is faster than 5- or 6-exo cyclisat ion onto alkenes or 1,5-hydrogen abstraction of allylic hydrogens. When the alpha -substituents are alkyl, the intermediate iminyl radicals do not und ergo nitrile translocation. (C) 2000 Elsevier Science Ltd. All rights reser ved.