Brønsted acid-promoted aziridination of electron-deficient olefins

A combined theoretical and experimental approach was used to systematically study the Brønsted acid-promoted aziridination of electron-deficient olefins. It was found that Brønsted acid-promoted aziridination of electron-deficient olefins proceeded through the attack of the internal nitrogen of the azide to the terminal carbon of protonated olefin, which afforded an acyclic adduct that subsequently discharged N2 to produce the aziridine ring. The basicity of the electron-deficient olefins is an important parameter to determine the efficiency of Brønsted acid-promoted aziridination. More basic carbonyl compounds including vinyl ketones and acrylamides were predicted to be readily activated by Brønsted acid such as TfOH, whereas less basic carbonyl compounds were predicted to be poor substrates. Significantly, all these theoretical predictions were demonstrated to be consistent with the experimental data. Furthermore, a systematic evaluation of TfOH-promoted aziridination of acrylamides was performed, which established a new, single-step method for the preparation of a number of aziridine-2-carboxamides.