scholarly journals A Bio-Inspired Lanthanum-Ortho Quinone Catalyst for Aerobic Oxidation of Alcohol

2020 ◽  
Author(s):  
Ruipu Zhang ◽  
Long Zhang ◽  
Ming-Tian Zhang ◽  
Sanzhong Luo
Keyword(s):  
Aerobic Oxidation ◽  
Earth Metal ◽  
Open Shell ◽  
Oxidation Catalysis ◽  
Oxidation Catalyst ◽  
Oxidation Reactions ◽  
Reductive Activation ◽  
Ambient Conditions ◽  
Semiquinone Radicals ◽  
Oxidation Of Alcohols

<p>Oxidation reactions are fundamental transformations in organic synthesis and chemical industry. With oxygen or air as terminal oxidant, aerobic oxidation catalysis provides the most sustainable and economic oxidation processes. Most aerobic oxidation catalysis employs redox metal as its active center. While nature provides non-redox metal strategy as in pyrroloquinoline quinone (PQQ)-dependent methanol dehydrogenases (MDH), such an effective chemical version is unknown. Inspired by the recently discovered rare earth metal-dependent enzyme Ln-MDH, here we show that an open-shell semi-quinone anionic radical species in complexing with lanthanum could serve as a very efficient aerobic oxidation catalyst under ambient conditions. In this catalyst, the lanthanum metal serves only as a Lewis acid promoter and the redox process occurs exclusively on the semiquinone ligand. The catalysis is initiated by 1e<sup>-</sup>-reduction of lanthanum-activated <i>ortho</i>-quinone to a semiquinone-lanthanum complex La(<b>SQ<sup>-.</sup></b>)<sub>2</sub>, which undergoes a coupled O-H/C-H dehydrogenation for aerobic oxidation of alcohols with up to 330 h<sup>-1</sup> TOF. This study suggests a possible functional mode of semiquinone radicals, widely observed with quinoproteins in Nature. Moreover, this unique reductive activation strategy as well as the resulted radical anion as redox ligand creates a new turning point in the development of efficient aerobic oxidation catalysis.</p>

scholarly journals A Bio-Inspired Lanthanum-Ortho Quinone Catalyst for Aerobic Oxidation of Alcohol

2020 ◽  
Author(s):  
Ruipu Zhang ◽  
Long Zhang ◽  
Ming-Tian Zhang ◽  
Sanzhong Luo
Keyword(s):  
Aerobic Oxidation ◽  
Earth Metal ◽  
Open Shell ◽  
Oxidation Catalysis ◽  
Oxidation Catalyst ◽  
Oxidation Reactions ◽  
Reductive Activation ◽  
Ambient Conditions ◽  
Semiquinone Radicals ◽  
Oxidation Of Alcohols

<p>Oxidation reactions are fundamental transformations in organic synthesis and chemical industry. With oxygen or air as terminal oxidant, aerobic oxidation catalysis provides the most sustainable and economic oxidation processes. Most aerobic oxidation catalysis employs redox metal as its active center. While nature provides non-redox metal strategy as in pyrroloquinoline quinone (PQQ)-dependent methanol dehydrogenases (MDH), such an effective chemical version is unknown. Inspired by the recently discovered rare earth metal-dependent enzyme Ln-MDH, here we show that an open-shell semi-quinone anionic radical species in complexing with lanthanum could serve as a very efficient aerobic oxidation catalyst under ambient conditions. In this catalyst, the lanthanum metal serves only as a Lewis acid promoter and the redox process occurs exclusively on the semiquinone ligand. The catalysis is initiated by 1e<sup>-</sup>-reduction of lanthanum-activated <i>ortho</i>-quinone to a semiquinone-lanthanum complex La(<b>SQ<sup>-.</sup></b>)<sub>2</sub>, which undergoes a coupled O-H/C-H dehydrogenation for aerobic oxidation of alcohols with up to 330 h<sup>-1</sup> TOF. This study suggests a possible functional mode of semiquinone radicals, widely observed with quinoproteins in Nature. Moreover, this unique reductive activation strategy as well as the resulted radical anion as redox ligand creates a new turning point in the development of efficient aerobic oxidation catalysis.</p>

Oxidase Catalysis via an Aerobically Generated Dess-Martin Periodinane Analogue

2018 ◽  
Author(s):  
Asim Maity ◽  
Sung-Min Hyun ◽  
Alan Wortman ◽  
David Powers
Keyword(s):  
Chemical Synthesis ◽  
Aerobic Oxidation ◽  
Substrate Oxidation ◽  
Oxidation Catalysis ◽  
Hypervalent Iodine ◽  
Oxidation Reactions ◽  
Broad Array ◽  
Oxidation Chemistry ◽  
Reactive Oxidants

<p>Hypervalent iodine(V) reagents, such as Dess-Martin periodinane (DMP) and 2-iodoxybenzoic acid (IBX), are broadly useful oxidants in chemical synthesis. Development of strategies to access these reagents from O2 would immediately enable use of O2 as a terminal oxidant in a broad array of substrate oxidation reactions. Recently we disclosed the aerobic synthesis of I(III) reagents by intercepting reactive oxidants generated during aldehyde autoxidation. Here, we couple aerobic oxidation of iodobenzenes with disproportionation of the initially generated I(III) compounds to generate I(V) reagents. The aerobically generated I(V) reagents exhibit substrate oxidation chemistry analogous to that of DMP. Further, the developed aerobic generation of I(V) has enabled the first application of I(V) intermediates in aerobic oxidation catalysis.</p>

scholarly journals Aerobic oxidation catalysis with stable radicals

2014 ◽  
Vol 50 (35) ◽  
pp. 4524-4543 ◽  
Author(s):  
Qun Cao ◽  
Laura M. Dornan ◽  
Luke Rogan ◽  
N. Louise Hughes ◽  
Mark J. Muldoon
Keyword(s):  
Molecular Oxygen ◽  
Selective Oxidation ◽  
Aerobic Oxidation ◽  
Point Of View ◽  
Oxidation Catalysis ◽  
Industrial Scale ◽  
Oxidation Reactions ◽  
Traditional Methods ◽  
Stable Radicals ◽  
Selective Oxidation Reactions

Selective oxidation reactions are challenging when carried out on an industrial scale. Many traditional methods are undesirable from an environmental or safety point of view. There is a need to develop sustainable catalytic approaches that use molecular oxygen as the terminal oxidant. This review will discuss recent advances in the use of stable radicals in aerobic oxidation catalysis.

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