Well-Defined Cesium Benzotriazolide as an Active Catalyst for Generating Disubstituted Ureas from Carbon Dioxide and Amines

The reaction of alkali metal carbonates with various azole compounds produced a new series of alkali metal azolides, and they were applied as active catalysts for the production of disubstituted ureas from the carboxylation of various amines with CO₂. Among them, cesium benzotriazolide (Cs[BTd]) was found to be the most active for the carboxylation reaction and was structurally characterized by single-crystal X-ray diffraction. The crystal structure of highly hygroscopic Cs[BTd] was found to be [BTA]⋅⋅⋅Cs[BTd], which explains why it is a water-tolerant active species for this carboxylation reaction, leading to a maximum turnover frequency of 344 h⁻¹ as well as high recyclability even after five successive runs.