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Substituent

About: Substituent is a research topic. Over the lifetime, 42877 publications have been published within this topic receiving 516716 citations. The topic is also known as: side chain & side group.


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Journal ArticleDOI
TL;DR: Introduction of a chelate-assisting substituent such as [PPh2] is effective in altering the kinetic selectivity and lowering the activation barrier for the catalytic processes.
Abstract: The selective catalytic activation and functionalization of carbon−carbon bonds in a series of substituted cyclopropane substrates has been developed using commercially available transition metal catalysts. Catalytic hydrogenation and olefination procedures, tolerant of a range of functional groups, have been discovered. Introduction of a chelate-assisting substituent such as [PPh2] is effective in altering the kinetic selectivity and lowering the activation barrier for the catalytic processes.

122 citations

Journal ArticleDOI
TL;DR: In this paper, a non-linear relationship between reaction temperature and enantioselectivity was observed in the Mn-salen catalyzed asymmetric epoxidation of some olefins.

122 citations

Journal ArticleDOI
TL;DR: All of the 18 new complexes described here are catalysts for the dismutation of superoxide, and substantial substituent effects are observed with kcat...
Abstract: Superoxide radical anion has been demonstrated to be a mediator of many disease states, including inflammatory, autoimmune, and cancerous diseases. As a consequence, we have developed a program to design, synthesize, and test synthetic low-molecular weight superoxide dismutase (SOD) mimics as potential pharmaceutical agents. A critical feature of the design of metal-based drugs is not only high activity as an enzyme mimic but also chemical stability. In this report we describe the synthesis and characterization of a series of C-substituted 1,4,7,10,13-pentaazacyclopentadecane, [15]aneN5, ligands, 1, and their corresponding Mn(II) complexes, 2 and 3, as their dichloro complexes, [Mn([15]aneN5)Cl2]. The purpose of the work is to probe the role that substituent (methyl and fused cycloalkyl) groups exert on the catalytic activity and stability of the complexes. All of the 18 new complexes described here are catalysts for the dismutation of superoxide, and substantial substituent effects are observed with kcat...

122 citations

Journal ArticleDOI
TL;DR: Electrochemical analyses of the methylthio substituent in the copper complex shows electronic effects similar to those of the free ligand stabilizing the phenoxyl radical state of the cofactor moiety in the Cu(II) complex.
Abstract: The electronic effect of the thioether linkage between Tyr 272 and Cys 228 (the novel organic cofactor) of galactose oxidase has been examined by using model compounds, 2-(methylthio)-p-cresol (1H), 2-(methylthio)-4,6-dimethylphenol (2H), and 2-(methylthio)-4-methyl-6-[[bis[2-(2-pyridyl)ethyl]amino]methyl]phenol (3H), the physicochemical properties of which are compared to those of 2-[[bis[2-(2-pyridyl)ethyl]amino]methyl]-4-methylphenol (4H) and p-cresol (5H). 1H NMR and electrochemical studies indicate that the methylthio group has essentially an electron-donating nature. On the other hand, the lower pKa values of 1H and 2H as compared to that of 5H suggest that the methylthio group also has a 2pπ−3dπ electron conjugative effect, stabilizing the negative charge on the phenolate oxygen. Furthermore, the electron-sharing conjugative effect of the substituent in the radical state has been clearly demonstrated by ESR studies and semiempirical molecular orbital calculations. Dimer copper(II) complexes [CuII2(...

122 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023660
20221,273
2021568
2020787
2019753
2018858