- Novel Carbocyclic Dianions: NMR Study of Charge Delocalization, Paratropicity, and Structure in the Dianions of Acephenanthrylene and Aceanthrylene
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The mode of electron delocalization of novel polycyclic dianions, viz. acephenanthrylene dianion (22-) and aceanthrylene dianion (32-), is deduced from their 1H and 13C NMR parameters (1D and 2D NMR).While the reduction of acephenanthrylene (2) afforded only the respective dianion (22-), the reduction of aceanthrylene (3) afforded dianion (32-) followed by monoanion (4).The electron delocalization of the neutral systems (2, 3) as well as the respective dianions (22-, 32-) is discussed.It is concluded that there exists a preferred path of electron delocalization which dominates.Interestingly, the paths of electron delocalization of the charged systems differ from those of the neutral systems.In the neutral systems 1, 2, and 3 the "aromatic" structures that dominate are 1b, 2b, and 3b, respectively, whereas the bridge double bond represents only a small perturbation.On the other hand in the dianions 12-, 22-, and 32- the bridges are part of the path of the electron delocalization.These differences of the paths of electron delocalization are accompanied by structural changes as manifested by the X-ray structures and by the coupling constants of the bridge protons and corroborated by calculations.It is demonstrated that in each case the path of electron delocalization that dominates is the one which has the minimum paratropic contribution.
- Cohen, Yoram,Roelofs, Nicolas H.,Reinhardt, Gerd,Scott, Lawrence T.,Rabinovitz, Mordecai
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- Usnic Acid Enaminone-Coupled 1,2,3-Triazoles as Antibacterial and Antitubercular Agents
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(+)-Usnic acid, a product of secondary metabolism in lichens, has displayed a broad range of biological properties such as antitumor, antimicrobial, antiviral, anti-inflammatory, and insecticidal activities. Interested by these pharmacological activities and to tap into its potential, we herein present the synthesis and biological evaluation of new usnic acid enaminone-conjugated 1,2,3-triazoles 10-44 as antimycobacterial agents. (+)-Usnic acid was condensed with propargyl amine to give usnic acid enaminone 8 with a terminal ethynyl moiety. It was further reacted with various azides A1-A35 under copper catalysis to give triazoles 10-44 in good yields. Among the synthesized compounds, saccharin derivative 36 proved to be the most active analogue, inhibiting Mycobacterium tuberculosis (Mtb) at an MIC value of 2.5 μM. Analogues 16 and 27, with 3,4-difluorophenacyl and 2-acylnaphthalene units, respectively, inhibited Mtb at MIC values of 5.4 and 5.3 μM, respectively. Among the tested Gram-positive and Gram-negative bacteria, the new derivatives were active on Bacillus subtilis, with compounds 18 [3-(trifluoromethyl)phenacyl] and 29 (N-acylmorpholinyl) showing inhibitory concentrations of 41 and 90.7 μM, respectively, while they were inactive on the other tested bacterial strains. Overall, the study presented here is useful for converting natural (+)-usnic acid into antitubercular and antibacterial agents via incorporation of enaminone and 1,2,3-triazole functionalities.
- Bangalore, Pavan K.,Vagolu, Siva K.,Bollikanda, Rakesh K.,Veeragoni, Dileep K.,Choudante, Pallavi C.,Misra, Sunil,Sriram, Dharmarajan,Sridhar, Balasubramanian,Kantevari, Srinivas
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supporting information
p. 26 - 35
(2020/01/03)
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- Catalyst-Free Photodriven Reduction of α-Haloketones with Hantzsch Ester
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Catalyst-free dehalogenation of α-haloketones under visible light irradiation is studied. The reactions were carried out in common organic solvent. The outcomes of dechlorination are excellent in yields up to 92%, and it is also applicable to bromides, which give even higher yields. The reaction is tolerable to a broad spectrum of substrates, especially to aromatic ketones, including various aryl and hetaryl groups. There are two examples of aliphatic ketones presented in the paper, although their reactivities are not as high as that of the aromatic ketones.
- Lu, Zheng,Yang, Yong-Qing
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p. 508 - 515
(2019/01/10)
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- Alkenyl bromides by brominative deoxygenation of ketones in one or two steps
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The conversion of ketones into alkenyl bromides is accomplished in one or two steps by 2,2,2-tribromo-2,2-dihydro-1,3,2-benzodioxaphosphole or by the dibromomethyl methyl ether prepared therefrom. Investigations of the scope and limitations provide some hints for the preparative planning and improvement.
- Von Roman,Ruhdorfer,Knorr
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p. 985 - 992
(2007/10/02)
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