Computational insights into the mechanisms and origins of switchable selectivity in gold(i)-catalyzed annulation of ynamides with isoxazoles 6π-electrocyclizations of azaheptatrienyl cations.

Electrocyclizations of acyclic conjugated π-motifs have emerged as a versatile and effective strategy for accessing various ring systems with excellent functional group tolerability and controllable selectivity. Typically, the realization of 6π-electrocyclization of heptatrienyl cations to afford seven-membered motif has proven difficult due to the high-energy state of the cyclizing seven-membered intermediate. Instead, it undergoes the Nazarov cyclization, affording a five-membered pyrrole product.