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†
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.