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Visible Light-Gated Organocatalysis Using a RuII-Photocage |
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| Authors: | Dr José A González-Delgado Dr Miguel A Romero Dr Francisco Boscá Dr Jesús F Arteaga Prof Dr Uwe Pischel |
| Institution: | 1. CIQSO—Center for Research in Sustainable Chemistry and, Department of Chemistry, University of Huelva, Campus de El Carmen s/n, 21071 Huelva, Spain;2. Instituto Universitario Mixto de Tecnología Química (ITQ-UPV), Universitat Politècnica de València, Av. de los Naranjos s/n, 46022 Valencia, Spain |
| Abstract: | The light-gated organocatalysis via the release of 4-N,N-dimethylaminopyridine (DMAP) by irradiation of the Ru(bpy)2(DMAP)2]2+ complex with visible light was investigated. As model reaction the acetylation of benzyl alcohols with acetic anhydride was chosen. The pre-catalyst releases one DMAP molecule on irradiation at wavelengths longer than 455 nm. The photochemical process was characterized by steady-state irradiation and ultrafast transient absorption spectroscopy. The latter enabled the observation of the 3MLCT state and the spectral features of the penta-coordinated intermediate Ru(bpy)2(DMAP)]2+. The released DMAP catalyzes the acetylation of a wide range of benzyl alcohols with chemical yields of up to 99 %. Control experiments revealed unequivocally that it is the released DMAP which takes the role of the catalyst. |
| Keywords: | organocatalysis photochemistry photorelease ruthenium complexes time-resolved spectroscopy |