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Role of Metal-heterogeneous Catalysts in Organic Synthesis
Published in Varun Rawat, Anirban Das, Chandra Mohan Srivastava, Heterogeneous Catalysis in Organic Transformations, 2022
Oxidation reaction is considered an important reaction in chemical industries that produce a wide range of applications. For example, oxidation of ethylbenzene produces key products such as acetophenone and 1-phenylethanol that are used as precursors for the synthesis of a variety of drugs, chiral alcohols, hydrazones and chalcones [16]. For oxidation reactions, homogeneous catalysts have been extensively used for the synthesis of bulk as well as fine chemicals. However, homogeneous catalysts are non-recyclable, environmentally hazardous and also, they corrode the industrial materials raising the maintenance costs. To sort out these problems, the homogeneous catalysts could be prepared by the dispersion of a metal on an insoluble solid support to keep the metal on the surface where the catalysis reaction takes place [17]. Therefore, heterogeneous catalysts are considered to be a better choice for organic synthesis because they are easy to separate at the end of the reaction and also, they are easy to handle.
Quantitative PCR Approaches for Predicting Anaerobic Hydrocarbon Biodegradation
Published in Kenneth Wunch, Marko Stipaničev, Max Frenzel, Microbial Bioinformatics in the Oil and Gas Industry, 2021
Courtney R. A. Toth, Gurpreet Kharey, Lisa M. Gieg
Oxygen-independent hydroxylation involves the addition of H2O to the alkyl group of some substituted aromatic hydrocarbons and n-alkanes (Figure 11.1b, Ball et al. 1996, Heider et al. 2016b). The best characterized enzyme facilitating this reaction is ethylbenzene dehydrogenase (EBDH), which was initially discovered and characterized within a few closely related denitrifying strains within the betaproteobacterial family Rhodocyclaceae, with Aromatoleum aromaticum strain EbN1 serving as the paradigm for this mechanism (Kniemeyer and Heider 2001). Ethylbenzene dehydrogenase adds water to the methylene group on ethylbenzene forming (S)- 1-phenylethanol, which is then converted to acetophenone and ultimately to benzoyl-CoA. Genetic, genomic, proteomic, and enzymatic analyses of strain EbN1 have also helped to design a handful of qPCR assays for the catalytic subunit (ebhA) of EBDH, as seen in Table 11.1 (Heider et al. 2016b). In addition, paralogous enzymes to EBDH have been proposed to catalyze the hydroxylation of propylbenzene, p-cymene, and p-ethylphenol (Rabus and Widdel 1995, Strijkstra et al. 2014). An analogous hydroxylation mechanism has also been proposed for alkane-degrading Desulfococcus oleovorans strain Hxd3 that does not utilize fumarate addition, as genes encoding an enzyme closely related to EBDH have been identified in this organism (Callaghan et al. 2009, So et al. 2003).
Catalytic Enantioselective Hydrogenation of Ketones and Imines Using Platinum Metal Complexes
Published in Dale W. Blackburn, Catalysis of Organic Reactions, 2020
Brian R. James, Ajey M. Joshi, Pál Kvintovics, Robert M. Morris, Ian S. Thorburn
The procedure of Reaction 5 was used to synthesize or form in situ the required species. For example, use of benzoic acid and triphenylphosphite with the iridium(I) cyclooctene precursor yields the complex IrHCl(O2CPh){P(OPh)3}3, 3, although its geometry (cf. 1 and 2) is uncertain.43 This particular isolated complex is completely inactive as a catalyst for hydrogen transfer from 2-propanol to ketones. However, closely related in situ species with a range of carboxylate ligands do effect enantioselective hydrogenation of acetophenone to 1-phenylethanol, but a maximum optical yield of only 12% has been realized so far (Table 2); the catalyst is formed using Ir/P(OMe)3/R-acetylmandelic acid at a ratio of 1:4:1 with some added base. Use of R-mandelic acid itself has given a maximum 8% ee of the S-l-phenylethanol, and choice of S-mandelic acid does lead to the other enantiomer of 1-phenylethanol. Mandelic acid was chosen initially because it was thought that the hydroxy substituent might hydrogen-bond with the substrate carbonyl, a factor that was invoked within a more effective chiral rhodium-hydroxyalkyl(ferrocenyl)phosphine system45; however, the replacement of -OH by -OCCH3 in our system improves the ee, and such H bonding is clearly not essential.
Synthesis and characterization of new ruthenium(III) complexes derived from fluoreneamine-based Schiff base ligands and their catalytic activity in transfer hydrogenation of ketones
Published in Journal of Coordination Chemistry, 2020
Veerasamy Nagalakshmi, Raja Nandhini, Galmari Venkatachalam, Kasturi Balasubramani
We started our study by examining the transfer hydrogenation of acetophenone to 1-phenylethanol using synthesized ruthenium Schiff base complexes. All complexes efficiently catalyze the transfer hydrogenation of acetophenone with maximum conversion within 5 h. Among the tested complexes, 1 is highly efficient in the transfer hydrogenation of ketones to alcohol with high conversion of 99%. The result of transformations is given in Table 1. The lowest conversion observed is 72% for 6. The catalytic process is more efficient with 1 followed by 2, 3, 4, 5 and 6 showing the least activity among all six complexes. It was observed that the efficiency of catalysts was simply dependent on the structure of Schiff base ligands. The electron donating substituent (-OCH3) group present in the Schiff base ligand in 2 and bulky naphthyl group in 3 shows less activity than the catalyst 1. Further, it is observed that the complex catalyst containing PPh3 group shows higher activity than the complexes possessing AsPh3.