Black TiO2 nanoparticles with efficient photocatalytic activity under visible light at low temperature: regioselective C–N bond cleavage toward the synthesis of thioureas, sulfonamides, and propargylamines

Abstract

Several different colored forms of TiO₂ were prepared through the easy treatment of white TiO₂ and NaBH₄ as a safe hydrogen source. These types of modified TiO₂ showed a quite acceptable visible light response. Then, tertiary amines were harnessed toward the regioselective synthesis of three prominent scaffolds, namely sulfonamides, thioureas, and propargylamines, using black TiO₂ under visible light. For the first time, this type of modified TiO₂ was easily prepared and exploited to handle organic transformations under visible light. Black TiO₂-catalyzed oxidative C–N cleavage of tertiary amines was the key point of these transformations. Herein, the first report of the visible-light-driven synthesis of unsymmetrical thioureas and propargylamines from tertiary amines has been presented.