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Ephrath Solel Doron Pappo Ofer Reany Tom Mejuch Renana Gershoni-Poranne Mark Botoshansky Amnon Stanger Ehud Keinan 《Chemical science》2020,11(48):13015
Flat corannulene has been considered so far only as a transition state of the bowl-to-bowl inversion process. This study was driven by the prediction that substituents with strong steric repulsion could destabilize the bowl-shaped conformation of this molecule to such an extent that the highly unstable planar geometry would become an isolable molecule. To examine the substituents'' effect on the corannulene bowl depth, optimized structures for the highly-congested decakis(t-butylsulfido)corannulene were calculated. The computations, performed with both the M06-2X/def2-TZVP and the B3LYP/def2-TZVP methods (the latter with and without Grimme''s D3 dispersion correction), predict that this molecule can achieve two minimum structures: a flat carbon framework and a bowl-shaped structure, which are very close in energy. This rather unusual compound was easily synthesized from decachlorocorannulene under mild reaction conditions, and X-ray crystallographic studies gave similar results to the theoretical predictions. This compound crystallized in two different polymorphs, one exhibiting a completely flat corannulene core and the other having a bowl-shaped conformation.The first flat metal-free corannulene derivative was predicted by computations and achieved by synthesis. 相似文献
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Summary A method has been developed for the fluorimetric determination of boric acid, which gives a blue fluorescence with resacetophenone in sulphuric acid or phosphoric acid medium. The method has the advantage that the reaction does not require much time, because the fluorescence intensity reaches its maximum immediately after mixing the reagents and does not also decrease with time. The intensity of fluorescence can be measured with a fluorimeter and the amount of boric acid determined from a calibration curve. 相似文献
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Products of reactions of hydroxyanthraquinones with boric acid exist as equilibrium mixtures of tautomeric boron complexes and boric acid esters in which one or two boron atoms are not coordinated to carbonyl groups. Tautomerism is responsible for the appearance of several πl,π bands in the electronic absorption spectra and considerable differences in the data obtained by different authors. Boron-containing quinizarin derivatives have mostly 1,10-quinoid structures. The use of quinizarin as an analytical reagent for the determination of boron is based on replacement of tautomeric equilibria due to complex formation rather than on coordination-induced red shift of the absorption maximum. 相似文献
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Alexander J. Bridges 《Tetrahedron letters》1980,21(46):4401-4404
The title complex reacts with propargyl halides and, in situ generated, propargyl mesylates to produce thioallenes in good yields, via an allylic inversion. 相似文献
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Cyclopropanation of active methylene compounds has been achieved in good yields with ethylene carbonate as the cyclopropanating agent in the presence of a simple base. 相似文献
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A facile synthesis of 2,4,6-trichloroborazine from boron trichloride-dimethylsulfide complex and ammonium chloride 总被引:1,自引:0,他引:1
<正>2,4,6-Trichloroborazine has been recognized as a desirable monomer for the preparation of high-performance boron nitride fibers through polymer derived ceramics route.So a high yield and facile synthesis of 2,4,6-trichloroborazine is essential in practice. Using boron trichloride-dimethylsulfide complex((CH_3)_2S·BCl_3) and ammonium chloride(NH_4Cl) as starting materials and toluene(C_6H_5CH_3) as solvent,the synthesis of 2,4,6-trichloroborazine to give high yield is reported. 相似文献
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Samarium(III)-(R)- or (S)-propylenediaminetetraacetate complex resolved the enantiomer signals of alpha-amino acids on high-field (1)H and (13)C NMR with remarkably less line broadening than was previously reported for the Eu(III) complex of the same ligand. A widely observed regularity between the absolute configuration of enantiomers and the relative shift of their NMR signals is useful for the assignment of absolute configuration. 相似文献
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Hiroyoshi Kamogawa Toshiyuki Sueki 《Journal of polymer science. Part A, Polymer chemistry》1985,23(7):1963-1972
p-Vinylphenylsulfonylnitromethane ( 3 ) was synthesized by the reaction of sodium p-styrenesulfinate with nitromethane. Free radical copolymerizations of 3 with styrene and N-vinyl-2-pyrrolidone provided soluble copolymers. Conversions of RCH2X (X = Br, OAc) with the copolymers as reagents proceeded in a different manner from the corresponding lowmolecular-weight compound, phenylsulfonylnitromethane, to afford RCOOH in addition to the expected RCH2CH2NO2 and RCH2COOH; no nitriles were formed. 相似文献
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The compound 2,2'-dimercaptodiethylsulphide has been investigated with regard to the stability of its solutions to air oxidation, its acid strength, its reactivity towards metal ions, the nature of its Ni(II) and Pd(II) complexes in solution, and its applicability to the determination of small amounts of Ni(II) and Pd(II). Studies on the Ni(II) complex extend the work reported previously by others and are not in complete accord with it. The results presented show that 2,2'-dimercaptodiethylsulphide is a promising analytical reagent. 相似文献
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Yasutomo Yamamoto 《Tetrahedron letters》2008,49(31):4582-4584
A lithium ester enolate was activated by both a chiral etheral ligand and a lithium amide to form a ternary complex reagent that reacted with enoates giving the corresponding Michael addition products in reasonably high enantioselectivity of up to 97% ee. 相似文献