Rh/TiO2‑Photocatalyzed Acceptorless Dehydrogenation of N‑Heterocycles upon Visible-Light Illumination.pdf
Creators: name: Mamiyev, Zamin
Publisher: name: figshare
Year: 2020
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description: TiO2 is an effective and extensively employed photocatalyst,but its practical use in visible-light-mediated organic synthesis is mainlyhindered by its wide band gap energy. Herein, we have discovered that RhphotodepositedTiO2 nanoparticles selectively dehydrogenate N-heterocyclicamines with the concomitant generation of molecular hydrogen gasin an inert atmosphere under visible light (λmax = 453 nm) illumination atroom temperature. Initially, a visible-light-sensitive surface complex isformed between the N-heterocycle and TiO2. The acceptorlessdehydrogenation of N-heterocycles is initiated by direct electron transferfrom the HOMO energy level of the amine via the conduction band ofTiO2 to the Rh nanoparticle. The reaction condition was optimized byexamining different photodeposited noble metals on the surface of TiO2and solvents, finding that Rh0 is the most efficient cocatalyst, and 2-propanol is the optimal solvent. Structurally diverse N-heterocycles such as tetrahydroquinolines, tetrahydroisoquinolines, indolines,and others bearing electron-deficient as well as electron-rich substituents underwent the dehydrogenation in good to excellent yields.The amount of released hydrogen gas evinces that only the N-heterocyclic amines are oxidized rather than the dispersant. Thisdeveloped method demonstrates how UV-active TiO2 can be employed in visible-light-induced synthetic dehydrogenation of aminesand simultaneous hydrogen storage applications.