Oxidative 1,2-Difunctionalization of Ethylene via Gold-Catalyzed Oxyarylation

Oxidative 1,2-Difunctionalization of Ethylene via Gold-Catalyzed Oxyarylation
Matthew J. Harper†, Edward J. Emmett, John F. Bower , and Christopher A. Russell

School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
Syngenta, Jealott’s Hill International Research Centre, Bracknell, Berkshire RG42 6EY, United Kingdom

Link:J. Am. Chem. Soc., 2017, 139 (36), pp 12386–12389

DOI: 10.1021/jacs.7b06668
Publication Date (Web): August 22, 2017



Abstract



Under the conditions of oxidative gold catalysis, exposure of ethylene to aryl silanes and alcohols generates products of 1,2-oxyarylation. This provides a rare example of a process that allows catalytic differential 1,2-difunctionalization of this feedstock chemical.

Merging Visible Light Photoredox Catalysis with Metal Catalyzed C–H Activations: On the Role of Oxygen and Superoxide Ions as Oxidants

http://pubs.acs.org/doi/abs/10.1021/acs.accounts.6b00275
David C. Fabry† and Magnus Rueping*‡
† Institute of Organic Chemistry, RWTH-Aachen University, Landoltweg 1, 52072 Aachen, Germany
‡ King Abdullah University of Science and Technology (KAUST), KAUST Catalysis Center (KCC), Thuwal, 23955-6900Saudi Arabia
Acc. Chem. Res., 2016, 49 (9), pp 1969–1979
DOI: 10.1021/acs.accounts.6b00275
Publication Date (Web): August 24, 2016


Abstract 

The development of efficient catalytic systems for direct aromatic C–H bond functionalization is a long-desired goal of chemists, because these protocols provide environmental friendly and waste-reducing alternatives to classical methodologies for C–C and C–heteroatom bond formation. A key challenge for these transformations is the reoxidation of the in situ generated metal hydride or low-valent metal complexes of the primary catalytic bond forming cycle. To complete the catalytic cycle and to regenerate the C–H activation catalyst, (super)stoichiometric amounts of Cu(II) or Ag(I) salts have often been applied. Recently, “greener” approaches have been developed by applying molecular oxygen in combination with Cu(II) salts, internal oxidants that are cleaved during the reaction, or solvents or additives enabling the metal hydride reoxidation. All these approaches improved the environmental friendliness but have not overcome the obstacles associated with the overall limited functional group and substrate tolerance. Hence, catalytic processes that do not feature the unfavorable aspects described above and provide products in a streamlined as well as economically and ecologically advantageous manner would be desirable.


In this context, we decided to examine visible light photoredox catalysis as a new alternative to conventionally applied regeneration/oxidation procedures. This Account summarizes our recent advances in this expanding area and will highlight the new concept of merging distinct redox catalytic processes for C–H functionalizations through the application of visible light photoredox catalysis. Photoredox catalysis can be considered as catalytic electron-donating or -accepting processes, making use of visible-light absorbing homogeneous and heterogeneous metal-based catalysts, as well as organic dye sensitizers or polymers. As a consequence, photoredox catalysis is, in principle, an ideal tool for the recycling of any given metal catalyst via a coupled electron transfer (ET) process.


Here we describe our first successful endeavors to address the above challenges by combining visible light photoredox catalysis with different ruthenium, rhodium, or palladium catalyzed C–H activations. Since only small amounts of the oxidant are generated and are immediately consumed in these transformations, side reactions of substrates or products can be avoided. Thus, usually oxidant-sensible substrates can be used, which makes these methods highly suitable for complex molecular structure syntheses. Moreover, mechanistic studies shed light on new reaction pathways, intermediates, and in situ generated species. The successful development of our dual catalysis concept, consisting of combined visible light photoredox catalysis and metal catalyzed C–H functionalization, provides many new opportunities for further explorations in the field of C–H functionalization.

Conversion of CO2 from Air into Methanol Using a Polyamine and a Homogeneous Ruthenium Catalyst

http://pubs.acs.org/doi/abs/10.1021/jacs.5b12354
 
Conversion of CO2 from Air into Methanol Using a Polyamine and a Homogeneous Ruthenium Catalyst
Jotheeswari Kothandaraman, Alain Goeppert, Miklos Czaun, G. K. Surya Prakash, and George A Olah
J. Am. Chem. Soc., Just Accepted Manuscript
DOI: 10.1021/jacs.5b12354
Publication Date (Web): December 29, 2015
Copyright © 2015 American Chemical Society

Abstract: A highly efficient homogeneous catalyst system for the continuous production of CH3OH from CO2 using PEHA and Ru-Macho-BH (1) at 125-165 °C in an ethereal solvent has been developed (initial TOF = 70 h-1 at 145 °C). Ease of separation of CH3OH is demonstrated by simple distillation from the reaction mixture. The robustness of the catalytic system was shown by recycling the catalyst over 5 runs without significant loss of activity (TON>2000 h-1). Various sources of CO2 can be used for this reaction including the air, despite its low CO2 concentration (400 ppm). For the first time, we have demonstrated that CO2 captured from air can be directly converted to CH3OH in 79% yield using the homogeneous catalytic system.

Closing the loop: captured CO2 as a feedstock in the chemical industry

http://pubs.rsc.org/en/content/articlelanding/2015/ee/c5ee02591e#!divAbstract

Alexander Otto, Thomas Grube, Sebastian Schieben, and Detlef Stolten

Energy Environ. Sci. 2015, 8, 3283-3297

Abstract: The utilization of ‘captured’ CO₂ as a feedstock in the chemical industry for the synthesis of certain chemical products offers an option for preventing several million tons of CO₂ emissions each year while increasing independence from fossil fuels. For this reason, interest is increasing in the feasibility of deploying captured CO₂ in this manner. Numerous scientific publications describe laboratory experiments in which CO₂ has been successfully used as a feedstock for the synthesis of various chemical products. However, many of these publications have focused on the feasibility of syntheses without considering the ancillary benefits of CO₂ emissions reduction if the CO₂ is sourced from effluent or the potential profitability of this process. Evaluating these environmental and economic benefits is important for promoting the further development of benign CO₂ applications. Given the multitude of CO₂ utilization reactions in the laboratory context, an initial assessment must be undertaken to identify those which have the most potential for future technical exploration and development. To achieve this, 123 reactions from the literature were identified and evaluated with the help of selection criteria specifically developed for this project. These criteria incorporate both the quantitative potential of reducing CO₂ and possible economic benefits of these syntheses. The selected reactions are divided into bulk and fine chemicals. Of the bulk chemicals, formic acid, oxalic acid, formaldehyde, methanol, urea and dimethyl ether, and of the fine chemicals, methylurethane, 3-oxo-pentanedioic acid, 2-imidazolidinone, ethylurethane, 2-oxazolidone and isopropyl isocyanate, mostly fulfil the selection criteria in each category.