Cyclization Cascade of Allenyl Azides: Synergy Between Theory and Experiment.

Collaborative work between experimentalists and computational chemists have demonstrated a stong synergy which allowed the rationalization of allenyl azide chemistry and permited the development of an efficient synthetic tool aimed at the preparation of several alkaloids. Saturated allenyl azides undergo a reaction cascade involving key diradical intermediates that follow the Curtin-Hammett model whereas unsaturated allenyl azides form indolidene intermediates that furnish the final indole products via electrocyclic ring closure events taking place out of the Curtin-Hammett regime. The regiochemistry of the reaction cascade with the latter substrates can be manipulated by Cu(I) addition to the reaction mixture.