- Microwave-assisted α-halogenation of 2-methylquinolines with tetrabutylammonium iodide and 1,2-dichloroethane (1,2-dibromoethane)
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A simple and efficient methodology permitting the halogenation of 2-methylquinolines into 2-(chloromethyl)quinolines or 2-(bromomethyl)quinolines in the tetrabutylammonium iodide and 1,2-dichloroethane (1,2-dibromoethane) system has been developed for the first time. The halogenation can be rapidly completed with good to excellent yields and high selectivity under microwave irradiation.
- Xie, Yuanyuan,Li, Lehuan
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supporting information
p. 3892 - 3895
(2014/07/08)
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- Time-resolved long-lived luminescence imaging method employing luminescent lanthanide probes with a new microscopy system
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Superior fluorescence imaging methods are needed for detailed studies on biological phenomena, and one approach that permits precise analyses is time-resolved fluorescence measurement, which offers a high signal-to-noise ratio. Herein, we describe a new fluorescence imaging system to visualize biomolecules within living biological samples by means of time-resolved, long-lived luminescence microscopy (TRLLM). In TRLLM, short-lived background fluorescence and scattered light are gated out, allowing the long-lived luminescence to be selectively imaged. Usual time-resolved fluorescence microscopy provides fluorescence images with nanosecond resolution and has been used to image interactions between proteins, protein phosphorylation, the local pH, the refractive index, ion or oxygen concentrations, etc. Luminescent lanthanide complexes (especially europium and terbium trivalent ions (Eu 3+ and Tb3+)), in contrast, have long luminescence lifetimes on the order of milliseconds. We have designed and synthesized new luminescent Eu3+ complexes for TRLLM and also developed a new TRLLM system using a conventional fluorescence microscope with an image intensifier unit for gated signal acquisition and a xenon flash lamp as the excitation source. When the newly developed luminescent Eu3+ complexes were applied to living cells, clear fluorescence images were acquired with the TRLLM system, and short-lived fluorescence was completely excluded. By using Eu 3+ and Tb3+ luminescent complexes in combination, time-resolved dual-color imaging was also possible. Furthermore, we monitored changes of intracellular ionic zinc (Zn2+) concentration by using a Zn2+-selective luminescent Eu3+ chemosensor, [Eu-7]. This new imaging technique should facilitate investigations of biological functions with fluorescence microscopy, complementing other fluorescence imaging methodologies.
- Hanaoka, Kenjiro,Kikuchi, Kazuya,Kobayashi, Shigeru,Nagano, Tetsuo
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p. 13502 - 13509
(2008/09/17)
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- Tissue specific fluorescent chelates possessing long wavelength UV excitation
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Fluorescent chelates of lanthanide, terbium, europium and dysprosium with tetraazamacrocyclic compounds are discussed which can be used as fluorescent in vitro or in vivo diagnostic agents. These chelates are tissue specific imaging agents for soft tissue cancers.
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- Inverted regioselectivities in the reactions of chlorine atoms with heteroarylmethanes
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The relative reactivities of the two methyl groups of 2,6-dimethylquinoline (2,6-DMQ) and 2,7-dimethylquinoline (2,7-DMQ) toward several radicals were assessed by intramolecular competitions. The regioselectivities observed for t-BuO* and Br* (k6/k2, k7/k2 > 1) are consistent with electrophilic characteristics of these radicals and estimates of relative stability of the resulting radicals. In contrast, Cl* displays inverted selectivities (k6/k2, k7/k2 1 suggesting a directive effect of the DMQ nitrogen. Complexation of Cl* by the N lone pair of dimethylquinolines, followed by a novel intramolecular hydrogen abstraction through a 5-center cyclic transition state, explains the regioselectivities observed in these reactions. Although bromine atoms also complex with heteroaromatics, these Br* complexes have a low reactivity toward benzylic hydrogens. Evidence from intermolecular competition experiments, laser flash photolysis studies, semiempirical MO calculations, and dimethylbutane quenching experiments is presented in support of the proposed intramolecular hydrogen abstraction process.
- Khanna, Rajive K.,Armstrong, Becky,Cui, Hong,Tanko, James M.
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p. 6003 - 6006
(2007/10/02)
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