TEMPO‐Mediated Oxidation of Primary Alcohols to Aldehydes under Visible Light and Air

Abstract

A homogeneous visible light photoredox TEMPO-mediated selective oxidation of primary alcohols to the corresponding carbonyl compounds was developed using molecular oxygen from air as the terminal oxidant. Ru(bpy) 3 (PF 6 ) 2 (bpy: bipyridyl) and Ir(dtb-bpy)(ppy) 2 (PF 6 ) (dtb-bpy: 4,4'-di-tert-butyl-2,2'-bipyridyl; ppy: 2-phenylpyridine) were used as the sensitizers.

Dye-Sensitized Photoelectrosynthesis Cells for Benzyl Alcohol Oxidation Using a Zinc Porphyrin Sensitizer and TEMPO Catalyst

“…37,38 Light driven alcohol oxidation catalyzed by a TEMPO derivative has been demonstrated in homogeneous systems with a dye in presence of a sacrificial electron acceptor (typically Co(NH 3 ) 5 Cl 3 ). [39][40][41][42][43] TEMPO mediated alcohol oxidation was also described with a visible light absorbing n-type semiconductor such as BiVO 4 or WO 3 as photoanode. 14,[44][45][46] Interestingly, TEMPO derivatives were successfully implemented as redox mediators in dye sensitized solar cells proving that hole transfer could be efficiently realized from an oxidized sensitizer to the nitroxide radical even with a weak driving force.…”

“…[47][48][49][50] Moreover, visible light photocatalytic TEMPO-mediated oxidation of alcohols to aldehydes has been reported with dyes upon oxidative quenching by a sacrificial electron acceptor in solution or with a hybrid system consisting of TiO 2 or ZnO dye-sensitized nanoparticles. 39,40,42,43 In this study, we investigate the fabrication of a TiO 2 based DSPEC for alcohol oxidation using for the first time a TEMPO catalyst covalently appended to an organic sensitizer (Figure 1). The purposes of this study are two folds.…”

“…A catalytic photocurrent density of about 130 μA/cm 2 was measured upon light irradiation (200 mW/cm 2 ) with an applied potential of 0.75 V versus a saturated calomel electrode (SCE). Nitroxides in general and 2,2,6,6-tetramethyl-1-piperidine N -oxyl (TEMPO) in particular are very active, cheap, and green catalysts for alcohol oxidation, that is even applied to chemical industry. , Light-driven alcohol oxidation catalyzed by a TEMPO derivative has been demonstrated in homogeneous systems with a dye in the presence of a sacrificial electron acceptor (typically Co­(NH 3 ) 5 Cl 3 ). − TEMPO-mediated alcohol oxidation was also described with a visible light-absorbing n-type semiconductor such as BiVO 4 or WO 3 as the photoanode. ,− Interestingly, TEMPO derivatives were successfully implemented as redox mediators in dye-sensitized solar cells (DSSCs), proving that hole transfer could be efficiently realized from an oxidized sensitizer to the nitroxide radical even with a weak driving force. − Moreover, visible light photocatalytic TEMPO-mediated oxidation of alcohols to aldehydes has been reported with dyes upon oxidative quenching by a sacrificial electron acceptor in solution or with a hybrid system consisting of TiO 2 or ZnO dye-sensitized nanoparticles. ,,, …”

Direct Synthesis of Enones by Visible-Light-Promoted Oxygenation of Trisubstituted Olefins Using Molecular Oxygen

“…•-] 15 (Figure 1). Singlet oxygen can be generated by energy transfer from an activated ruthenium complex (*Ru II ) through path a. Alternatively, the activated ruthenium complex might react with an electron donor to…”

Integrating TEMPO and Its Analogues with Visible‐Light Photocatalysis

“…[24] Coupling TEMPO with a[ Ru(bpy) 3 ](PF 6 ) 2 or [Ir(ppy) 2 (dtbbpy)]PF 6 PC enables the oxidation of alcohols in air under 14 Wc ompact fluorescent light (CFL) irradiation (Scheme 6). [25] For the protocol with CH 3 CN as as olventa nd [Ru(bpy) 3 ](PF 6 ) 2 as aP C, only benzyl alcohols with electron-donating groups can be transformed into the corresponding aldehydes in the presence of an organic base, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).…”