- 2,4 and 2,5-bis(benzooxazol-2′-yl)hydroquinone (DHBO) and their borate complexes: Synthesis and optical properties
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This article describes the multistep synthesis and the solution/solid-state optical properties of a series of highly fluorescent dyes based on either a 2,4 or a 2,5-bis(benzooxazol-2′-yl)hydroquinone (DHBO) scaffold. Their fluorescence emission stems from
- Benelhadj, Karima,Massue, Julien,Ulrich, Gilles
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p. 5877 - 5884
(2016/07/19)
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- Liquid crystalline bis(N-salicylideneaniline)s: Synthesis and thermal behavior of constitutional isomers
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The first examples of mesogenic bis(N-salicylideneaniline)s (BSANs), wherein two lipophilic (half-disk shaped) entities are interlinked through the dihydroxydiformylbenzene core, were synthesized and characterized. In particular, three constitutional (positional) isomeric BSANs were prepared by the facile twofold condensation of 3,4,5-tris(alkoxy)anilines with 2,3-dihydroxyterephthalaldehyde, 4,6-dihydroxyisophthalaldehyde, and 2,5-dihydroxyterephthalaldehyde and their structures were established by elemental analyses, FT-IR, 1H NMR, and 13C NMR. Proton NMR experiments demonstrated their existence in enol-imine (OH) form solely. Polarizing optical microscopic, differential scanning calorimetric, and powder X-ray diffraction studies evidenced the occurrence of columnar mesomorphism in two sets of isomers.
- Hiremath, Uma S.
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p. 3419 - 3423
(2013/07/04)
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- Synthesis and properties of bimetallic Hoveyda-Grubbs metathesis catalysts
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The catalytic activity of ruthenium Hoveyda-Grubbs complexes in olefin metathesis is a function of complex steric and electronic effects acting on initiation and propagation steps. In order to study the π-electron factors influencing the initiation process, we attempted syntheses of bimetallic complexes with common organic ligands bearing two chelate rings. While most of the studied ligand exchange reactions of the isomeric bis-chelating benzene derivatives gave mixtures of unstable complexes, a homodinuclear derivative of 1,4-dimethoxy-2,5-divinylbenzene was sparingly soluble and precipitated from the reaction mixture in a pure form. The complex was studied with spectroscopic and X-ray methods, which confirmed the symmetrical bimetallic structure. However, in model metathesis reactions the catalyst displayed activity very comparable to the related monometallic complexes. This suggests that in the bimetallic system two consecutive initiation processes of the metathesis catalyst (first, bimetallic complex + olefin → monometallic complex + propagating species; second, monometallic complex + olefin → styrene + propagating species) proceed at similar rates and, thus, no cooperativity between the two steps is displayed. Properties of the family of bimetallic complexes were probed with NMR studies, and π-electronic effects operating in the systems were discussed.
- Grudzien, Krzysztof,Malinska, Maura,Barbasiewicz, Michal
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p. 3636 - 3646
(2012/07/13)
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- Conjugated macrocycles related to the porphyrins. Part 18: Synthesis and spectroscopic characterization of electron-rich benzi- and oxybenziporphyrins: Influence of steric and electronic factors on porphyrinoid aromaticity
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Although 4,6-dihydroxyisophthalaldehydes failed to condense with tripyrranes to produce porphyrinoid products, the related dimethoxydialdehydes reacted with tripyrrane 9 to give, following oxidation with aqueous ferric chloride solution, nonaromatic dimet
- Richter, Daniel T,Lash, Timothy D
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p. 3657 - 3671
(2007/10/03)
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- Synthesis of monosulphur and monoselenium analogues of psoralen
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The synthesis of new, highly efficient DNA photoinactivating agents comprising an atom of sulfur or selenium in place of oxygen in the psoralen system is described.
- Jakobs, Andreas E.,Christiaens, Leon E.,Renson, Marcel J.
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p. 9315 - 9324
(2007/10/02)
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- SYNTHESIS OF AROMATIC ALDEHYDES VIA 2-ARYL-N,N'-DIACYL-4-IMIDAZOLINES
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Diacylimidazolium ions yield adducts with aromatic compounds.Thus the N,N'-diacetylimidazolium ion and indole gives 1,3-diacetyl-2-(3-indolyl)-4-imidazoline.Less reactive substrates such as thiophene, anisole and 1,3-dimethylbenzene fail to react with this reagent but do form adducts (e.g. 1,3-bis-(trifluoroacetyl)-2-(2-thienyl)-4-imidazoline) with an imidazole/trifluoroacetic anhydride reagent.All of the adducts could be converted to the corresponding aldehyde under mild conditions.The synthetic scope of the new synthesis is similar to that of the Vilsmeier-Haack reaction.
- Bergman, Jan,Renstroem, Lars,Sjoeberg, Birger
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p. 2505 - 2512
(2007/10/02)
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