Simple methods for the preparation of N-triflyl guanidines and the structure of compounds with the CF3SO2NCN fragment

Two novel and simple approaches to N-triflyl guanidines are elaborated. Owing to very strong conjugation the formally double CN bond of TfNC(NHR)2 is longer than the formally single NC bonds. Energetic effect of the triflyl group on the conjugation in the NCN moiety is estimated to be ≥150 kcal/mol.