Cycloaddition of Phenyltriazolinedione with Carbazole-Alkynes and Yne-Carbamates to Access Diazacyclobutenes

J Org Chem. 2024 Apr 5;89(7):4990-4999. doi: 10.1021/acs.joc.4c00213. Epub 2024 Mar 17.

Abstract

Previously, we described the synthesis of stable, bicyclic examples of the rather rare diazacyclobutene (DCB) motif by means of a cycloaddition between triazolinediones and electron-rich thiolated alkynes. Here, we report the investigation of the cycloaddition of triazolinediones with related electron-rich yne-carbamates and carbazole-alkynes. Bicyclic DCBs arising from yne-carbamates were isolated in 8-65% yield, while those arising from carbazole-alkynes were isolated in 28-59% yield. Mechanistic studies and characterization of isolable byproducts shed light on the underlying issues leading to poor to moderate yields.