A new facile synthesis of shikalkin

A short and convergent approach for the synthesis of shikalkin （dl-shikonin） is presented. Stobbe reaction was employed to construct the aromatic skeleton 6. This is followed by a practical method to prepare the key epoxides 9 from aldehydes 8 in high yield. Finally, shikalkin is achieved by Grignard reaction and oxidation.     

Novel triazene dyes from N-heterocyclic carbenes and azides: syntheses,stability, and spectroscopic properties

A series of substituted triazene dyes were synthesized by coupling functionalized imidazol-2-ylidenes with various azides (alkyl, vinyl, aryl, and heteroaryl), in moderate to excellent yields. Their structures were confirmed by spectroscopic studies (IR, NMR, UV–vis, and HRMS). Additionally, the solid-state structure of triazene dye 7 was secured by single crystal X-ray diffraction. Electron delocalization between the two coupled components was studied using UV–vis spectroscopy. The respective triazenes were found to exhibit λ_max values ranging between 294 and 450 nm.     

A facile synthesis of the oxazolidinone antibacterial agent linezolid

A facile synthetic route of linezolid 1 has been developed.Using commercially available(R)epichlorohydrin as the starting material,1 was obtained through a sequence of cyclization,substitution, a Goldberg coupling,aminolysis and acetylation reactions.The synthetic route is easy to perform and can be scaled up.     

A facile synthesis of cajaninstilbene acid and its derivatives

A facile synthesis of cajaninstilbene and its derivatives by using a building block has been developed.     

Solvent polarity indicators: Extraction of some coumarin indicator dyes

Study of the extraction of ten different coumarins (unsubstituted, 6-methyl-, 7-methyl-, 4-hydroxy-, 7-hydroxy-, 7-hydroxy-4-methyl-, 7-methoxy-, 7-amino-4-methyl-, 7-diethyl-amino-4-methyl-, and 3-carboxy-) with nine organic solvents shows that the percentage extraction is generally high. Cyclohexanone and heptane were found to be, respectively, the most and least effective extracting solvents for the compounds under study. The results are discussed in terms of the effect of different solvent polarity parameters on the extraction process.     

A facile synthesis of solid-emissive fluorescent dyes: dialkylbenzo[b]naphtho[2,1-d]furan-6-one-type fluorophores with strong blue and green fluorescence emission properties

A new type of organic fluorophores, dialkylbenzo[b]naphtho[2,1-d]furan-6-one-type fluorophores, exhibiting strong blue and green emission in the solid state has been easily synthesized by an one-step reaction. The X-ray crystal structure demonstrated that the structural form with a chair-shape with the sterical hindered dialkyl substituents and the 9-dibutylamino group prevents the fluorophores from forming short intermolecular contacts and produces intense solid-state fluorescence emission.     

A facile synthesis of the spiroindoline-based growth hormone secretagogue,MK-677

A facile and improved route for the synthesis of the orally active spiroindoline-based growth hormone secretagogue,MK-677 was described.The key step adopted the Fischer indole/reduction strategy.The preparation of the key intermediates N-protected piperidine carboxaldehyde 5 and the N-Boc-O-benzyl-D-serine(2) are also optimized.     

苯并咪唑-噻碳菁染料的合成及性质

2-(β-苯胺基乙烯基)-5-R-3-(γ-磺酸丙基)苯并噻唑内铵盐同5,6-二氯-1-乙基-2-甲基-3-(γ-磺酸丙基)苯并咪唑内铵盐在乙酸酐-三乙胺存在下缩合生成苯并咪唑-噻碳菁染料, 合成并表征了七个不对称苯并咪唑-噻碳菁, 其中六个为新化合物. 测试了它们的紫外可见吸收光谱和荧光发射光谱, 结果表明 不对称染料的Brooker偏离值与取代基R的Hammettσ~m常数呈线性关系. 取代的苯并噻唑杂环碱性顺序: 4,5-苯并＞5-CH~3＞5-H＞5-OCH~3＞5-F＞5-Cl＞5-CF~3 .     

Rational design, synthesis, and spectroscopic and photophysical properties of a visible-light-excitable, ratiometric, fluorescent near-neutral pH indicator based on BODIPY

A visible-light-excitable, ratiometric, brightly fluorescent pH indicator for measurements in the pH range 5-7 has been designed and synthesized by conjugatively linking the BODIPY fluorophore at the 3-position to the pH-sensitive ligand imidazole through an ethenyl bridge. The probe is available as cell membrane permeable methyl ester 8-(4-carbomethoxyphenyl)-4,4-difluoro-3-[2-(1H-imidazol-4-yl)ethenyl]-1,5,7-trimethyl-3a,4a-diaza-4-bora-s-indacene (I) and corresponding water-soluble sodium carboxylate, sodium 8-(4-carboxylatophenyl)-4,4-difluoro-3-[2-(1H-imidazol-4-yl)ethenyl]-1,5,7-trimethyl-3a,4a-diaza-4-bora-s-indacene (II). The fluorescence quantum yield Φ(f) of ester I is very high (0.8-1.0) in the organic solvents tested. The fluorescence lifetime (ca. 4 ns) of I in organic solvents with varying polarity/polarizability (from cyclohexane to acetonitrile) is independent of the solvent with a fluorescence rate constant k(f) of 2.4×10(8) s(-1). Probe I is readily loaded in the cytosol of live cells, where its high fluorescence intensity remains nearly constant over an extended time period. Water-soluble indicator II exhibits two acid-base equilibria in aqueous solution, characterized by pK(a) values of 6.0 and 12.6. The Φ(f) value of II in aqueous solution is high: 0.6 for the cationic and anionic forms of the imidazole ligand, and 0.8 for neutral imidazole. On protonation-deprotonation in the near-neutral pH range, UV/Vis absorption and fluorescence spectral shifts along with isosbestic and pseudo-isoemissive points are observed. This dual-excitation and dual-emission pH indicator emits intense green-yellow fluorescence at lower pH and intense orange fluorescence at higher pH. The influence of ionic strength and buffer concentration on the absorbance and steady-state fluorescence of II has also been investigated. The apparent pK(a) of the near-neutral acid-base equilibrium determined by spectrophotometric and fluorometric titration is nearly independent of the added buffer and salt concentration. In aqueous solution in the absence of buffer and in the pH range 5.20-7.45, dual exponential fluorescence decays are obtained with decay time τ(1)=4.3 ns for the cationic and τ(2)=3.3 ns for the neutral form of II. The excited-state proton exchange of II at near-neutral pH becomes reversible on addition of phosphate (H(2)PO(4)(-)/HPO(4)(2-)) buffer, and a pH-dependent change of the fluorescence decay times is induced. Global compartmental analysis of fluorescence decay traces collected as a function of pH and phosphate buffer concentration was used to recover values of the deactivation rate constants of the excited cationic (k(01)=2.4×10(8) s(-1)) and neutral (k(02)=3.0×10(8) s(-1)) forms of II.     

Converting a solvatochromic fluorophore into a protein-based pH indicator for extreme acidity

Live-cell pH measurements: An environment-sensitive fluorophore (green) was site-specifically introduced on HdeA, an acid-resistant chaperone showing pH-mediated conformational changes under low pH conditions. A survey of the attachment sites led to the discovery of one position on HdeA at which the attached fluorophore showed a strong fluorescence increase upon acidification.     

A facile synthesis of 2,4,6-trichloroborazine from boron trichloride-dimethylsulfide complex and ammonium chloride

<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.     

A facile synthesis of 2-oxazolines using a PPh3–DDQ system

A facile and efficient synthesis of 2-oxazolines from N-(2-hydroxyethyl)amides using a triphenylphosphine–2,3-dichloro-5,6-dicyanobenzoquinone (PPh₃–DQQ) system is described. The reaction proceeds under neutral and mild conditions, and excellent yields are obtained.     

A facile synthesis of chiral polyazamacrocycles and the UV spectroscopic and CD spectra studies on metal complexes

A series of chiral polyazamacrocycles with 12, 18, 24, 27, 36-membered rings were designed and synthesized using (S)-α-phenylethylamine as initial chiral source. Herein 11 new chiral polyazamacrocycles were successfully prepared. The UV spectroscopic titration experiments of polyazamacrocycle 3b with metal ions were carried out and the binding constants and free energy changes were calculated according to the modified Benesi-Hildebrand equation. Circular dichroism spectra were recorded for 3b with metal ions.     

A facile and efficient Bi(III) catalyzed synthesis of 1,1-dihydroperoxides and 1,2,4,5-tetraoxanes

Bismuth triflate is a remarkably efficient and mild catalyst for the synthesis of both 1,1-dihydroperoxides and 1,2,4,5-tetraoxanes. The successful application of this methodology for the synthesis of both symmetrical and unsymmetrical tetraoxanes is demonstrated.     

Methylenepyran based dipolar and quadrupolar dyes: synthesis,electrochemical and photochemical properties

This paper presents the synthesis of a series of push–pull and quadrupolar π-conjugated structures incorporating pro-aromatic methylenepyran electron-donor groups and various electron-attracting groups. Some of the methylenepyran derivatives were oxidized by I₂ to give, after reduction by Na₂S₂O₃, bismethylenepyran compounds via successive steps.     

Analysis of sulphonated phthalocyanine dyes by capillary electrophoresis

Sulphonated phthalocyanine dyes may be prepared either by direct sulphonation or by mixed condensation methods. Both syntheses will produce mixtures of products. Such mixtures may be analysed by capillary electrophoresis to identify the various degrees of substitution and to indicate the approximate composition of the mixtures.     

A facile synthesis of cyclotriveratrylene

Cyclotriveratrylene (CTV) can be readily synthesized by chloromethylation or bromomethylation of dimethoxybenzene with halomethyloctyl ether in the presence of SnCl₄. The reaction provides the trimer exclusively and in high yield. Recrystallizations from benzene or CHCl₃ yielded the solvent inclusion complexes and did not remove other inclusion impurities. Flash chromatography on silica yielded the pure CTV.¹³C NMR shows only five signals and no impurities.     

A facile synthesis of polyfoluoroalkyl-lactonization

2(-Benzoxazolyl substituted cyclopropane derivatives were synthesized in the yield of 73-89% from the reaction of telluronium ylides with chalcones.     

A facile synthesis of N-sulfinylaldimines

A simple and efficient procedure for the synthesis of N-sulfinylaldimines (sulfinimines) from sulfinamides and aldehydes is described. The reaction was carried out in the presence of t-BuOK or NaOH. The method is applicable for the synthesis of optically active sulfinimines.     

A facile synthesis of muscimol

The psychoactive isoxazole muscimol $\text{10}$ has been synthesized in three steps from propargyl chloride.