β-Scission of thioimidoyl radicals (R1–N–CS–R2): A theoretical scale of radical leaving group ability

A theoretical study of the β-scission reactions for some thioimidoyl radicals (R1–NC–S–R2) using a recently introduced homofugality index, ν is presented. This index, that was defined as a descriptor of the leaving group ability in homolytic substitution reactions, predicts that S–R2 fragmentation is always favoured compared to the N–R1 scission, in agreement with the experimental data. This result can be explained on the basis of the regional spin softness of the leaving radical group at the transition state during the homolytic fragmentation.