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Noble-Metal-Free Deoxygenation of Epoxides: Titanium Dioxide as a Photocatalytically Regenerable Electron-Transfer Catalyst

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journal contribution
posted on 06.06.2014, 00:00 by Yasuhiro Shiraishi, Hiroaki Hirakawa, Yoshiki Togawa, Takayuki Hirai
Catalytic deoxygenation of epoxides into the corresponding alkenes is a very important reaction in organic synthesis. Early reported systems, however, require noble metals, high reaction temperatures (>373 K), or toxic reducing agents. Here, we report a noble-metal-free heterogeneous catalytic system driven with alcohol as a reducing agent at room temperature. Photoirradiation (λ <420 nm) of semiconductor titanium dioxide (TiO2) with alcohol promotes efficient and selective deoxygenation of epoxides into alkenes. This noble-metal-free catalytic deoxygenation is facilitated by the combination of electron transfer from surface Ti3+ atoms on TiO2 to epoxides, which promotes deoxygenation of epoxides, and photocatalytic action of TiO2, which regenerates oxidized surface Ti atoms with alcohol as a reducing agent.