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Shweta Bhagat Minhajul Arfeen Gourav Das Neha Patel Prasad V. Bharatam 《Journal of computational chemistry》2019,40(5):726-733
Carbocyclic carbenes (CCCs) are a class of nucleophilic carbenes which are very similar to N-heterocyclic carbenes (NHCs) in terms of their reactivity, but they do not contain a stabilizing heteroatom in their cyclic ring system. In this study, 17 representative known CCCs and 34 newly designed CCCs are evaluated using quantum chemical methods, and the results are compared in terms of their stability, nucleophilicity, and proton affinity (PA) parameters. The results are divided on the basis of ring size of the known and reported CCCs. The stability, nucleophilicity, PA, complexation energy, and bond strength–related parameters were estimated using M06/6-311++G(d,p) method. The results indicated that the CCCs known in the literature are strong σ-electron donating species and have considerable π-accepting properties. This study led to the design and identification of a few new CCCs with dimethylamine and diaminomethynyl substituents which can be singlet stable and are substantially nucleophilic. © 2018 Wiley Periodicals, Inc. 相似文献
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Importance of cytochromes in cyclization reactions: Quantum chemical study on a model reaction of proguanil to cycloguanil 下载免费PDF全文
Minhajul Arfeen Dhilon S. Patel Sheenu Abbat Nikhil Taxak Prasad V. Bharatam 《Journal of computational chemistry》2014,35(28):2047-2055
Proguanil, an anti‐malarial prodrug, undergoes cytochrome P450 catalyzed biotransformation to the pharmacologically active triazine metabolite (cycloguanil), which inhibits plasmodial dihydrofolate reductase. This cyclization is catalyzed by CYP2C19 and many anti‐malarial lead compounds are being designed and synthesized to exploit this pathway. Quantum chemical calculations were performed using the model species (Cpd I for active species of cytochrome and N4‐isopropyl‐N6‐methylbiguanide for proguanil) to elucidate the mechanism of the cyclization pathway. The overall reaction involves the loss of a water molecule, and is exothermic by approximately 55 kcal/mol, and involves a barrier of approximately 17 kcal/mol. The plausible reaction pathway involves the initial H‐radical abstraction from the isopropyl group by Cpd I, followed by two alternative paths‐ (i) oxygen rebound to provide hydroxyl derivative and (ii) loss of additional H‐radical to yield 1,3,5‐triazatriene, which undergoes cyclization. This study helped in understanding the role of the active species of cytochromes in this important cyclization reaction. © 2014 Wiley Periodicals, Inc. 相似文献
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The methanolic extract of the aerial parts of Datura innoxia afforded a new withanolide, daturacin, the structure of which was elucidated as (20R, 22S)-21,24-epoxy-1,6-dioxo-14alpha-methoxy-5beta-witha-2,25(27)-dienolide (1) by an analysis of the spectroscopic data, including extensive NMR experiments. 相似文献
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JPC – Journal of Planar Chromatography – Modern TLC - A reliable and sensitive thin-layer chromatographic (TLC)-densitometric method is developed for the analysis of danazol in its... 相似文献
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Neha Patel Minhajul Arfeen Tejender Singh Shweta Bhagat Ajay Sakhare Prasad V. Bharatam 《Journal of computational chemistry》2020,41(31):2624-2633
Nitreones are compounds with oxidation state 1 at the nitrogen, these compounds carry formal positive charge as well as two lone pairs of electrons at nitrogen center. These compounds are also known as divalent NI compounds and can be represented with the general formula L → N+ ← L, where L is an electron donating ligand. In the recent past, several divalent NI compounds have been reported with L = N-heterocyclic carbene (NHC), remote N-heterocyclic carbene (rNHC), carbocyclic carbene (CCC) and diaminocarbene. Recently, our group reported that a novel six-membered CCC (cyclohexa-2,5-diene-4-[diaminomethynyl]-1-ylidene) can stabilize N+ center in nitreones. As an independent carbene, this species is very unstable. In this work, modulation of this CCC using (a) annulation, (b) heterocyclic ring modification, (c) substitutions adjacent to the carbenic carbon, (d) exocyclic double bond insertion and (e) ring contraction, has been reported. These modulations and quantum chemical analyses helped in the identification of five new six-membered CCCs which carry improved donation and stability properties. Further, these CCCs were employed in the design of new divalent NI compounds (nitreones) which carry coordination bonds between ligands and N+ center. The molecular and electronic structure properties, and the donor→acceptor coordination interactions present in the resultant low oxidation state divalent NI compounds have been explored. 相似文献
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Design,Synthesis, and Structural Analysis of Divalent NI Compounds and Identification of a New Electron‐Donating Ligand 下载免费PDF全文
Prof. Dr. Prasad V. Bharatam Minhajul Arfeen Neha Patel Priyanka Jain Sonam Bhatia Prof. Dr. Asit K. Chakraborti Dr. Sadhika Khullar Vijay Gupta Prof. Dr. Sanjay K. Mandal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):1088-1096
The dative‐bond representation (L→E) in compounds with main group elements (E) has triggered extensive debate in the recent past. The scope and limits of this nonclassical coordination bond warrant comprehensive exploration. Particularly compounds with (L→N←L′)+ arrangement are of special interest because of their therapeutic importance. This work reports the design and synthesis of novel chemical species with the general structural formula (L→N←L′)+ carrying the unusual ligand cyclohexa‐2,5‐diene‐4‐(diaminomethynyl)‐1‐ylidene. Four species belonging to the (L→N←L′)+ class carrying this unconventional ligand were synthesized. Quantum chemical and X‐ray diffraction analyses showed that the electronic and geometric parameters are consistent with those of already reported divalent NI compounds. The molecular orbital analysis, geometric parameters, and spectral data clearly support the L→N and N←L′ interactions in these species. The newly identified ligand has the properties of a reactive carbene and high nucleophilicity. 相似文献
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