C–H Alkylation of Heteroarenes with Alkyl Oxalates by Molecular Photoelectrocatalysis

Synlett ◽  
2020 ◽  
Author(s):  
Hai-Chao Xu ◽  
Fan Xu ◽  
Xiao-Li Lai
Keyword(s):  
Alkylation Reaction ◽  
Metal Free ◽  
Molecular Catalyst ◽  
Oxidative Transformations

AbstractAn oxidant- and metal-free photoelectrocatalytic C–H alkylation reaction of heteroarenes with alkyl oxalates has been developed. Several classes of heteroaromatics, such as quinolines, isoquinolines, pyridines, and phenanthridines, can be alkylated with tertiary or secondary alkyl oxalates. The photoelectrochemical synthesis employs 2,4,5,6-tetra-9H-carbazol-9-ylisophthalonitrile as a molecular catalyst and allows the oxidative transformations to proceed through evolution of hydrogen without a sacrificial chemical oxidant.

Synthesis of Bis(indolyl)methanes through an Alkylation Reaction of Indoles with Sodium Alkoxides

Synthesis ◽  
2021 ◽  
Author(s):  
Xue Chen ◽  
Yunkui Liu ◽  
Hong-Wei Jin ◽  
Bingwei Zhou
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Alkylation Reaction ◽  
Hydrogen Acceptor ◽  
Metal Free

Herein we wish to describe an alkylation reaction of indoles with sodium alkoxides for the synthesis of bis(indolyl)methanes. 1-Tetralone was proved to be an efficient hydrogen acceptor thus avoiding the use of precious transition metals such as Ru and Ir. This reaction features transition metal-free conditions, readily available starting materials, and gram-scale synthesis.

Uses of K2S2O8 in Metal-Catalyzed and Metal-Free Oxidative Transformations

ACS Catalysis ◽  
2018 ◽  
Vol 8 (6) ◽  
pp. 5085-5144 ◽  
Author(s):  
Sudip Mandal ◽  
Tishyasoumya Bera ◽  
Gurudutt Dubey ◽  
Jaideep Saha ◽  
Joydev K. Laha
Keyword(s):  
Metal Free ◽  
Oxidative Transformations ◽  
Metal Catalyzed

Photocatalytic transition-metal-free direct 3-alkylation of 2-aryl-2H-indazoles in dimethyl carbonate

2021 ◽  
Author(s):  
Chunhua Ma ◽  
Zhiwen Feng ◽  
Jing Li ◽  
Dandan Zhang ◽  
Wei Li ◽  
...  
Keyword(s):  
Transition Metal ◽  
Visible Light ◽  
Visible Light Irradiation ◽  
Dimethyl Carbonate ◽  
Light Irradiation ◽  
Alkylation Reaction ◽  
Metal Free ◽  
Mild Conditions

A general transition-metal-free photocatalytic decarboxylative 3-alkylation reaction of 2-aryl-2H-indazoles was developed under visible-light irradiation under mild conditions.

scholarly journals A heavy metal-free CuInS2 quantum dot sensitized NiO photocathode with a Re molecular catalyst for photoelectrochemical CO2 reduction

2019 ◽  
Vol 55 (55) ◽  
pp. 7918-7921 ◽  
Author(s):  
Jing Huang ◽  
Bo Xu ◽  
Lei Tian ◽  
Palas Baran Pati ◽  
Ahmed S. Etman ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Quantum Dot ◽  
Co2 Reduction ◽  
Metal Free ◽  
Molecular Catalyst

Heavy metal-free CuInS2 QDs as a photosensitizer and a Re molecular catalyst have been successfully employed to co-sensitize a NiO photocathode for CO2 reduction into CO.

Transition-metal-free Decarbonylative Alkylation of N-Aryl a-Hydroxy Amides via Triple C–C Bond Cleavages and Their Selective Deuteration

2021 ◽  
Author(s):  
Chengyu Sun ◽  
Yang Yu ◽  
Xiao Zhang ◽  
Yonghai Liu ◽  
Chengtao Sun ◽  
...  
Keyword(s):  
Transition Metal ◽  
Alkylation Reaction ◽  
Metal Free ◽  
Selective Deuteration ◽  
First Time

We disclose a transition-metal-free decarbonylative alkylation reaction for the synthesis of N-aryl a-hydroxy amides via precise cleavages and reorganizations of three C–C s bonds. For the first time, the medium-sized...

Electrocatalytic O2 Reduction by an Organometallic Pd(III) Complex via a Binuclear Pd(III) Intermediate

2021 ◽  
Author(s):  
Soumalya Sinha ◽  
Liviu M. Mirica
Keyword(s):  
Reduction Reaction ◽  
Electrocatalytic Reduction ◽  
Organometallic Complex ◽  
Molecular Catalyst ◽  
O2 Reduction ◽  
Oxidative Transformations ◽  
Pd Complexes ◽  
Reactivity Study ◽  
Molecular Catalysts

<p>The development of electrocatalysts for the selective O<sub>2</sub>-to-H<sub>2</sub>O conversion, the O<sub>2</sub> reduction reaction (ORR), is of great interest for improving the performance of fuel cells. In this context, molecular catalysts that are known to mediate the 4H<sup>+</sup>/4e<sup>–</sup> reduction of O<sub>2</sub> to H<sub>2</sub>O tend to be marred by limited stability and selectivity in controlling the multi-proton and multi-electron transfer steps. Thus, evaluation of new transition metal complexes, including organometallic species, for ORR reactivity could uncover new molecular catalysts with improved properties. We have previously reported the synthesis and characterization of various organometallic Pd<sup>III</sup> complexes stabilized by the tetradentate ligand N,N′-di-<i>tert</i>-butyl-2,11-diaza[3.3](2,6)pyridinophane (<sup>t</sup>BuN4). These complexes were shown to react with O<sub>2</sub> and undergo oxidatively-induced C–C and C–heteroatom bond formation reactions in the presence of O<sub>2</sub>. These O<sub>2</sub>-induced oxidative transformations prompted us to evaluate the ORR reactivity of such organometallic Pd complexes, which to the best of our knowledge has never been studied before for any molecular Pd catalyst. Herein, we report the ORR reactivity of the [(<sup>t</sup>BuN4)Pd<sup>III</sup>MeCl]<sup>+</sup> complex, under both homogeneous and heterogeneous conditions in a non-aqueous and acidic aqueous electrolyte, respectively. Cyclic voltammetry and hydrodynamic electrochemical studies for [(<sup>t</sup>BuN4)Pd<sup>III</sup>MeCl]<sup>+</sup> revealed the electrocatalytic reduction of O<sub>2</sub> to H<sub>2</sub>O proceeds with Faradaic efficiencies (FE) of 50-70% in the presence of acetic acid (AcOH) in MeCN. The selectivity toward H<sub>2</sub>O production further improved to a FE of 80-90% in an acidic aqueous medium (pH 0), upon immobilization of the molecular catalyst onto edge plane graphite (EPG) electrodes. Analysis of electrochemical data suggests the formation of a binuclear Pd<sup>III</sup> intermediate in solution, likely a Pd<sup>III</sup>-peroxo-Pd<sup>III</sup> species, which dictates the thermochemistry of the ORR process for [(<sup>t</sup>BuN4)Pd<sup>III</sup>MeCl]<sup>+</sup> in MeCN, and thus being a rare example of a bimolecular ORR process. The maximum second-order turnover frequency TOF<sub>max</sub><sup>(2)</sup> = 2.76 x 10<sup>8</sup> M<sup>–1</sup> sec<sup>–1</sup> was determined for 0.32 mM of [(<sup>t</sup>BuN4)Pd<sup>III</sup>MeCl]<sup>+</sup> in the presence of 1 M AcOH in O<sub>2</sub>-saturated MeCN with an overpotential of 0.32 V. By comparison, a comparatively lower TOF<sub>max</sub><sup>(2)</sup> = 1.25 x 10<sup>5</sup> M<sup>–1</sup> sec<sup>–1</sup> at a higher overpotential of 0.8 V was observed for [(<sup>t</sup>BuN4)Pd<sup>III</sup>MeCl]PF<sub>6</sub> adsorbed onto EPG electrodes in O<sub>2</sub>-saturated 1 M H<sub>2</sub>SO<sub>4</sub> aqueous solution. Overall, reported herein is a detailed ORR reactivity study using a novel Pd<sup>III</sup> organometallic complex and benchmark its selectivity and energetics toward O<sub>2</sub> reduction in MeCN and acidic aqueous solutions. </p>

scholarly journals Electrocatalytic O2 Reduction by an Organometallic Pd(III) Complex via a Binuclear Pd(III) Intermediate

2021 ◽  
Author(s):  
Soumalya Sinha ◽  
Liviu M. Mirica
Keyword(s):  
Reduction Reaction ◽  
Electrocatalytic Reduction ◽  
Organometallic Complex ◽  
Molecular Catalyst ◽  
O2 Reduction ◽  
Oxidative Transformations ◽  
Pd Complexes ◽  
Reactivity Study ◽  
Molecular Catalysts

<p>The development of electrocatalysts for the selective O<sub>2</sub>-to-H<sub>2</sub>O conversion, the O<sub>2</sub> reduction reaction (ORR), is of great interest for improving the performance of fuel cells. In this context, molecular catalysts that are known to mediate the 4H<sup>+</sup>/4e<sup>–</sup> reduction of O<sub>2</sub> to H<sub>2</sub>O tend to be marred by limited stability and selectivity in controlling the multi-proton and multi-electron transfer steps. Thus, evaluation of new transition metal complexes, including organometallic species, for ORR reactivity could uncover new molecular catalysts with improved properties. We have previously reported the synthesis and characterization of various organometallic Pd<sup>III</sup> complexes stabilized by the tetradentate ligand N,N′-di-<i>tert</i>-butyl-2,11-diaza[3.3](2,6)pyridinophane (<sup>t</sup>BuN4). These complexes were shown to react with O<sub>2</sub> and undergo oxidatively-induced C–C and C–heteroatom bond formation reactions in the presence of O<sub>2</sub>. These O<sub>2</sub>-induced oxidative transformations prompted us to evaluate the ORR reactivity of such organometallic Pd complexes, which to the best of our knowledge has never been studied before for any molecular Pd catalyst. Herein, we report the ORR reactivity of the [(<sup>t</sup>BuN4)Pd<sup>III</sup>MeCl]<sup>+</sup> complex, under both homogeneous and heterogeneous conditions in a non-aqueous and acidic aqueous electrolyte, respectively. Cyclic voltammetry and hydrodynamic electrochemical studies for [(<sup>t</sup>BuN4)Pd<sup>III</sup>MeCl]<sup>+</sup> revealed the electrocatalytic reduction of O<sub>2</sub> to H<sub>2</sub>O proceeds with Faradaic efficiencies (FE) of 50-70% in the presence of acetic acid (AcOH) in MeCN. The selectivity toward H<sub>2</sub>O production further improved to a FE of 80-90% in an acidic aqueous medium (pH 0), upon immobilization of the molecular catalyst onto edge plane graphite (EPG) electrodes. Analysis of electrochemical data suggests the formation of a binuclear Pd<sup>III</sup> intermediate in solution, likely a Pd<sup>III</sup>-peroxo-Pd<sup>III</sup> species, which dictates the thermochemistry of the ORR process for [(<sup>t</sup>BuN4)Pd<sup>III</sup>MeCl]<sup>+</sup> in MeCN, and thus being a rare example of a bimolecular ORR process. The maximum second-order turnover frequency TOF<sub>max</sub><sup>(2)</sup> = 2.76 x 10<sup>8</sup> M<sup>–1</sup> sec<sup>–1</sup> was determined for 0.32 mM of [(<sup>t</sup>BuN4)Pd<sup>III</sup>MeCl]<sup>+</sup> in the presence of 1 M AcOH in O<sub>2</sub>-saturated MeCN with an overpotential of 0.32 V. By comparison, a comparatively lower TOF<sub>max</sub><sup>(2)</sup> = 1.25 x 10<sup>5</sup> M<sup>–1</sup> sec<sup>–1</sup> at a higher overpotential of 0.8 V was observed for [(<sup>t</sup>BuN4)Pd<sup>III</sup>MeCl]PF<sub>6</sub> adsorbed onto EPG electrodes in O<sub>2</sub>-saturated 1 M H<sub>2</sub>SO<sub>4</sub> aqueous solution. Overall, reported herein is a detailed ORR reactivity study using a novel Pd<sup>III</sup> organometallic complex and benchmark its selectivity and energetics toward O<sub>2</sub> reduction in MeCN and acidic aqueous solutions. </p>

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