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The Use of Small Particle Catalysts in Pursuit of Green and Sustainable Chemistry
Published in Ahindra Nag, Greener Synthesis of Organic Compounds, Drugs and Natural Products, 2022
The accessibility of the nanocatalyst atoms enhances the kinetics of more efficient chemical conversion of the reactants to products via the catalytic cycle when compared with conventional catalysts.14,15 The understanding of catalytic structure and performance at the molecular level is required to transform novel nanomaterials into effective catalysts.16 The features of high activity, safer reagents, waste minimization, energy efficiency, improved economy, and reduced global warming enhance the attractiveness of nanocatalysts.17 The broad spectrum of nanocatalyst applications can be found as developing examples of new technology (Figure 9.3).
Bimodal Reaction Sequences as Nonequilibrium Processes
Published in Robert Bakhtchadjian, Bimodal Oxidation: Coupling of Heterogeneous and Homogeneous Reactions, 2019
The existence of reaction cycles in the complex chemical transformation is evidence of self-organization in the chemical system. The chemical system, completing one catalytic cycle, itself creates the conditions necessary for a new catalytic cycle. This is a natural peculiarity of both the chain-radical and catalytic reaction systems. However, this is considered a low-level emergence of this phenomenon.
Understanding oxidative addition in organometallics: a closer look
Published in Journal of Coordination Chemistry, 2022
Nabakrushna Behera, Sipun Sethi
Different catalysts that are capable of producing aldehydes from this reaction include Co2(CO)8, Co2(CO)8/PR3 (R = n-Bu or similar groups), HRh(CO)(PPh3)3, etc. [5]. Oxidative addition is one of the major steps in its catalytic cycle which basically facilitates the product formation. Different catalysts operate at different reaction parameters to provide linear (46) as well as branched chain isomers (47) (Scheme 20), but the linear isomer is predominant. However, enantioselective hydroformylation which utilizes HRh(CO)2(R,S)-BINAPHOS as catalyst results in relatively more branched isomer than the linear ones, and with good enantiomeric excess. Huge amount (> 7 × 106 tons/year) of aldehydes are produced worldwide in order to meet the requirements at various levels [5]. These aldehydes serve as the source for alcohol preparation; specifically short chain alcohols find extensive use as solvents in the lacquer industry for making plasticizers that has wide applications, and long chain alcohols for making synthetic detergents.
Copper-assisted synthesis of five-membered O-heterocycles
Published in Inorganic and Nano-Metal Chemistry, 2020
Navjeet Kaur, Yamini Verma, Neha Ahlawat, Pooja Grewal, Pranshu Bhardwaj, Nirmala Kumari Jangid
Jiang et al.[67] described that alkenes underwent oxidative [3 + 2] cycloaddition with anhydrides and Cu catalyst. The carboesterification of alkenes with anhydrides delivered γ-lactones under reaction conditions though the formation of carbon–oxygen and Csp3–Csp3 bonds. Excellent yields were obtained from all substrates containing weakly or strongly electron-withdrawing or electron-donating groups. The conjugated dienes have exclusive selectivity for terminal olefin under optimized conditions. But the desired product was not obtained from internal olefins (Scheme 18). Initially, the Cu(OTf)2 coordinated with the enol and alkene of anhydride. Then, intermediate I was produced by a cis oxycupration. Subsequently, intermediate II was generated by an intramolecular insertion into enol. Finally, intermediate II furnished product with the assistance of molecular O2 and the catalytic cycle was completed with the regeneration of copper(II).[68]
γ-aminobutyric acid and collagen peptides as recyclable bifunctional biocatalysts for the solvent-free one-pot synthesis of 2-aminobenzothiazolomethyl-2-naphthols
Published in Green Chemistry Letters and Reviews, 2018
Maryam Fardpour, Ali Safari, Shahrzad Javanshir
Based on the above results and the previous reports, plausible mechanisms for these two methods are given in Schemes 2 and 3. The reaction mechanism for method A starts with the nucleophilic addition of the amine group of amino acid to the carbonyl group of aldehyde followed by dehydration which leads to the formation of iminium ion A that undergoes reaction with 2-naphtol to give the Mannich base B. Intermediate B is in equilibrium with its zwitterion form C that undergoes amino acid elimination to form the ortho-quinone methide D. Finally, o-QM D readily reacts with 2-aminobenzothiazole to produce the desired product 5 and GABA goes back to the catalytic cycle as an active catalyst (Scheme 2). The proposed mechanism for method B is depicted in Scheme 3.