Heteroatom Chemistry最新文献

1-Aminopyrimidine-2-one derivatives (1a-c) were prepared in two steps from furan-2,3-diones and semicarbazones in toluene/benzene. Pyrimidin-[1(2H)-yl] acetamide derivatives and isophthalimide derivatives were synthesized from the nucleophilic acyl substitution reactions of compounds 1a-c with chloroacetyl chloride. The structures of compounds 2a-f were verified by IR, ¹H NMR, ¹³C NMR and elemental analyses. The obtained final organic compounds were tested as catalysts in the Mizoroki-Heck coupling reaction. They mostly exhibited very high catalytic activity results for the coupling reaction of styrene with different aryl bromide derivatives.

A series of tris[2-(4′-substituted butoxyphenyl)]phosphine oxides [2-X(CH₂)₄OC₆H₄]₃PO (X = OAc (2), OH (3), OSO₂Me (4), Br (5), and N₃ (6)) useful as precursors of new tripodal ligands have been prepared. Alkylation of initial tris(2-hydroxyphenyl)phosphine oxide (1) resulted in triacetate 2, which was deprotected to triol 3. The latter has been converted into trimesylate 4, which has been treated with LiBr or NaN₃ to give the corresponding tribromo or triazido derivatives 5 and 6, respectively. According to X-ray diffraction, the molecules of compounds 2, 5, and 6 in crystal adopt conformation where two side arms are oriented to the same direction as the P=O group, while the third side arm is oriented in the opposite manner.

The synthesis, aromaticity, and optical and electrochemical properties of zinc(II) complexes of 10,15,20-triaryl-15-aza-5-oxaporphyrin (TriAAOP) were investigated. Metal-templated cyclization of a zinc(II) 1,19-dichloro-5,10,15-triaryl-10-azatetrapyrrin complex with an oxygen source afforded 20π TriAAOP in the neutral form. Oxidation of 20π TriAAOP with silver (I) hexafluorophosphate generated the 19π radical cation or 18π dication depending on the content of oxidant used. The interconversion between the three oxidation states (18π, 19π, and 20π) resulted in distinct changes in the aromaticity and optical properties of the 15-aza-5-oxaporphyrin π-system. Nuclear magnetic resonance spectroscopy of 20π TriAAOP revealed its antiaromatic character, whereas that of the 18π TriAAOP dication showed its aromatic character. The combined effect of the two meso-heteroatoms was directly reflected in the redox properties of the porphyrin ring; TriAAOP was reduced more easily and more difficult to oxidize than the zinc(II) complex of 5,10,15,20-tetraaryl-5,15-diaz-aporphyrin (TADAP). In the ultraviolet-visible-near–infrared spectra of the materials, the lowest-energy electronic excitations of the 19π and 18π TriAAOP derivatives were considerably red-shifted compared with those of the isoelectronic TADAP derivatives. Based on the results of density functional theory calculations, it was concluded that the observed differences between TriAAOP and TADAP would arise from the high electronegativity of oxygen; specific frontier orbitals of the TriAAOP π-systems were energetically stabilized relative to those of the TADAP π-system. The present findings corroborate that the meso-modification of a porphyrin rings with different kinds of heteroatoms is a promising strategy to fine tune their light-response properties that are switchable by reversible single electron transfer processes.

We have designed and synthesized tetraferrocenyloligothiophenes, namely, 4,4′5,5′-tetraferrocenyl-2,2′-bithiophene (TFBT) and 4,4″,5,5″-tetraferrocenyl-2,2′:5′,2″-terthiophene (TFTT). By using an electrochemical technique, we revealed that tetraferrocenyloligothiophenes show multi-redox reactions derived from four ferrocene fragments and one α-oligothiophene spacer, and a number of the thiophene rings in the α-oligothiophene spacer can be attuned to the redox potentials and the multiple electron transfer process. Consequently, we have succeeded in the construction of different types of multi-step multi-electron redox systems by constructing four organometallic redox-active ferrocenes and one organic redox-active α-oligothiophene differing in the number of thiophene rings.

Stable conjugated oligomer dications 1²⁺ and 2²⁺ composed of 2,5-di(2-thienyl)-N-methylpyrrole (DTP) units at the both ends of the π-systems with methoxy substituents at the 3-position of thienyl units and methylthio end-capping group and benzo[2,1-b:3,4-b′]dithiophene (BDT) unit(s) at the central part with sterically demanding phenyl substituents were synthesized. From DFT calculations and ESR experiments, it was concluded that the diradical character in 1²⁺ and 2²⁺ was reduced in comparison with the radical character of their reference compound 3^·+ composed of one DTP and one BDT units. In addition, the shorter 1²⁺ was considered to have a further lower diradical character than that of 2²⁺. Nevertheless, judging from the results of VT-UV-vis-NIR measurements, both 1²⁺ and 2²⁺ showed a comparable π-dimerization ability at the DTP moiety in dichloromethane solution with 3^·+.

New activated indolylpyrrolidones—their methylthiopyrrolinium salts—in the reactions with several CH-acids were studied. 2-Nitromethylene- and 2-dicyanomethyleneindolylpyrrolidines were obtained from 5-indolyl-2-methylthiopyrrolinium salts with good yields. The reduction in these nitro compounds yields the respective aminomethylpyrolidines. The rigid structure of the starting compounds has significant stereoelectronic requirements of nucleophilic agents.

The reaction of phosphonothioates having a binaphthyl group with alkoxides proceeded via transfer of the axial chirality of the binaphthyl group to the central chirality of the phosphorus atom to give P-stereogenic phosphonothioates with moderate-to-excellent diastereoselectivities. The reaction of phosphonoselenoates also proceeded in a similar fashion. The selenium atom of the obtained product could be excluded with tributylphosphine to give a trivalent phosphonite, which was isolated as a boron complex.

A series of alkali metal tetrakis(carbochalcogenoato)-gallates and -indates M[M′(EOCR)₄](solv.) (M = alkali metal; M′ = Ga, In; E = S, Se) and tris(carbodithioato)aluminum, -gallates and -indates M′ (SSCR)₃ (M′ = Al, Ga, In) were prepared by the reactions of alkali metal carbochalcogenate with metal trihalogenides (M′X₃; M′ = Al, Ga, In; X = Cl, Br) and by those of piperidinium carbodithioates or carbodithioic and carboselenoic acids with M′X₃, respectively. An X-ray molecular structure analysis revealed that they have an acetone molecule as a crystal solvent. The reactions of the potassium complexes K[M′ (EOCR)₄](H₂O) (E = S, Se) with methanol and primary and secondary amines gave the corresponding methyl ester and amides in good yields, while the reactions with iodomethane and iodine gave S- and Se-methyl chalcogenoesters RCOEMe (E = S, Se) in good yields. Similar reactions of the tris(carbodithioato)gallates and -indates led to the corresponding O-methyl thioesters, thioamides, and S-methyl dithioesters in moderate to good yields. Oxidation of the tetrakis- and tris-derivatives with iodine afforded the corresponding diacyl dichalcogenides (RCOE)₂ (E = S, Se) and di(carbothioyl) disulfides in quantitative yields. These reactions appeared to occur on the carbonyl or selenium atom of the tetrakis compounds and on the sulfide sulfur or thiocarbonyl carbon atom of the tris-compounds, respectively. A possible mechanism for these I₂-oxidation reactions is discussed.

From a biological point of view, Schiff base probes containing fluorescent groups are chemically modified to provide an effective method for the detection of amino acids. According to this method, three molecular probes containing Schiff base and hydroxyl group have been designed and synthesized. UV-Vis and fluorescent data indicated that compound 2 showed strong sensitivity and high selectivity for arginine (Arg) among normal twenty kinds of amino acids. In addition, compound 2 displayed high combining ability with Arg and low cytotoxicity in MCF-7 cell from 0 to 150 μg/mL. The above results showed the synthesized probes also can be used a biosensor for the Arg detection in vivo.

Polysubstituted isocoumarins were synthesized by the reaction of substituted 2-(trimethylsilyl)aryl triflates with trifluoromethylated β-diketones in the presence of CsF. The reaction proceeded through carbon-carbon bond insertion of aryne and intramolecular cyclization to form intermediates of alcohol anions, which extruded trifluoromethyl anion to afford isocoumarins. By using CuBr as a catalyst, 2 eq. of aryne reacted with β-diketones to afford phenanthrenes and 1,2-diarylethanones. Although reaction of 2-(trimethylsilyl)phenyl triflate with 1,1,1-trifluoro-4′-methylbenzoylacetone in the presence of CsF gave 3-(4′-methylphenyl)isocoumarin in 67% yield, addition of 0.2 eq. of CuCN resulted in the formation of 9-(4-methylbenzoyl)-10-trifluoromethylphenanthrene in 35% yield.