Anionic aza 8π-electrocyclization as an unprecedented pathway versus 7-endo-dig: DFT study on the mechanism of base-catalyzed benzofuroazepine synthesis via cyclization of (2-alkynylbenzyl)oxy nitriles.

Abstract

DFT calculations are used to disclose the mechanism of Brønsted base-mediated cyclization of (2-alkynylbenzyl)oxy nitriles for the synthesis of benzofuroazepines. In 2015, the synthesis of substituted benzofuroazepines was reported by Zeni et al. via a stepwise mechanism known as 7-endo-dig. However, DFT calculations revealed that the anionic aza 8π-electrocyclization is more favorable than the proposed 7-endo-dig mechanism.