A facile synthesis of [1,2,3]triazolo[1,5-a]quinazolines via a copper-catalyzed tandem reaction and their denitrogenative transformation into 2-acyl-quinazolines

Abstract

A one-pot reaction protocol of 2-bromobenzyl azides with substituted acetonitriles for highly effective synthesis of [1,2,3]triazolo[1,5-a]quinazolines was developed. The reaction process involved base-promoted [3 + 2] cyclization, Cu-catalyzed Ullmann coupling, oxidative aromatization, and Dimroth rearrangement sequences. Furthermore, the obtained [1,2,3]triazolo[1,5-a]quinazolines could transform into 2-acyl-quinazolines via a Cu-catalyzed denitrogenative ring-opening reaction under acidic conditions. The mechanism was investigated using additional DFT calculations, and the ring-opening and ring-closing (RORC) process of Dimroth rearrangement probably was driven by thermodynamic stability.