The regiochemistry and stereochemistry of 1,3-dipolar cycloadditions of 1-fluoro- and 1,1-difluoroallene

1,3-Dipolar cycloadditions of diazoalkanes, nitrones and nitrileoxides occur with high regioselectivity to 1,1-difluoroallene and fluoroallene, and with variable syn or anti π-facial diastereoselectivity with regard to additions to the latter. The roles of steric effects, frontier molecular orbital effects, electrostatic interactions and other factors which may be involved in determining the observed regioselectivity and π-facial diastereoselectivity are discussed.     

Cycloadditions of aromatic azomethine imines with 1,1-cyclopropane diesters

The cycloaddition of aromatic azomethine imines to 1,1-cyclopropane diesters was achieved using Ni(ClO4)2 as catalyst. The methodology gives access to unique tricyclic dihydroquinoline derivatives with dr up to 6.6:1. A nonconcerted mechanism is proposed on the basis of stereochemical analysis of the reaction.     

Reactions of electron-withdrawing thiophene 1,1-dioxides with furans. A novel reaction pathway

Reactions of thiophene dioxides containing electron-withdrawing substituents with furans were studied. The reactions with unsubstituted furan followed the inverse-electron-demand Diels-Alder mechanism. Subsequent elimination of sulfur dioxide from the adduct afforded products of the tetrahydrobenzofuran series. The reactions with substituted furans gave benzylcarbonyl compounds in high yields. The observed regiochemistry of the reaction was explained in terms of the frontier orbital theory using the calculated orbital coefficients. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 687–692, April, 2006.     

A novel fluorescence probe for cilnidipine assay

A general route for preparation of dye-encapsulated polymer particles via an emulsion polymerization process has been described. 1-Naphthaleneboronic acid (NBA) was encapsulated, the resultant particles were used as a fluorescence probe for cilnidipine assay based on fluorescence quenching. The sensitivity of NBA-encapsulated probe to cilnidipine was largely improved in comparison with that of free NBA. The probe showed a linear response toward cilnidipine over the concentration range of 2.0 × 10⁻⁷ to 1.1 × 10⁻⁵ mol l⁻¹, with high sensitivity, fast response time, and good selectivity.     

A novel fluorescent probe for NAD-consuming enzymes

A novel, fluorescent NAD derivative is processed as substrate by three different NAD-consuming enzymes. The new probe has been used to monitor enzymatic activity in a continuous format by changes in fluorescence and, in one case, to directly visualize alternative reaction pathways.     

A novel fluorogenic probe for monoamine oxidase assays

Monoamine oxidase is flavoenzymes, widely distributed in mammals. It is well recognized that MAOs serve an important role in metabolism that they have close relationship with health .Along with the discoveries between MAOs and neurotic disease, more and more studies have been jumped in .In this paper, we design a new probe for assaying the activities of MAOs. The results showed that the probe [7-（3-aminopropoxy）coumarin] is simple, effective and sensitive for MAOB.     

一种新型快速检测半胱氨酸的荧光探针EI北大核心CSCD

基于三苯胺母体的强供电子能力,设计合成了一种共轭性良好的新型半胱氨酸(Cys)荧光探针。采用荧光光谱法和紫外-可见光谱法研究了目标探针T-Probe对半胱氨酸(Cys)的光谱响应。结果表明:目标探针分子与Cys作用后,荧光发射波长有约20 nm红移,荧光强度发生明显的增强,在365 nm紫外灯下,溶液由青色变为蓝色;探针分子选择性识别Cys的检测限为98.4 nmol/L,且灵敏度较高。     

A novel synthesis of 1,5-disubstituted fluorinated tetrazoles from 1,1-difluoroazides

A new one-step reaction between 1,1-difluoroazides and primary amines is reported as an efficient synthetic approach for tetrazole formation. Examples include the syntheses of fluorine-containing 1,5-substituted tetrazoles from three fluorinated azide precursors and various amines. Greater substituent diversity in comparison with conventional methods is achieved.     

A novel method for the synthesis of 2,2-diaryl-1,1-difluoroethenes

β,β-Difluoro-α-phenylvinylstannane 3 was prepared in 60% yield from the reaction of β,β-difluoro-α-phenylvinylsulfone 2 with tributyltin hydride in refluxing benzene for 5 h. The cross-coupling reaction of 3 with aryl iodides bearing substituents such as proton, fluoro, chloro, bromo, methoxy, methyl, trifluoromethyl, and nitro on ortho, meta, para positions of the benzene ring in the presence of 10 mol % Pd(PPh₃)₄/10 mol % CuI afforded the corresponding 2,2-diaryl-1,1-difluoroethenes 4 in 22-82% yields.     

A novel dansyl-based fluorescent probe for Fe3+

Research on Chemical Intermediates - A novel structurally simple dansyl-based fluorescent probe, 5-(dimethylamino)-N,N-bis(2-hydroxyethyl)naphthalene-1-sulfonamide, was synthesized from dansyl...     

A novel water-soluble fluorescent probe for the determination of methylamine

A novel water-soluble fluorescent probe, monosodium 7-(4,6-dichloro-1,3,5-triazinylamino)-1,3-naphthalenedisulfonic acid (DTND), was synthesized by reacting cyanuric chloride with 7-amino-1,3-naphthalenedisulfonic acid monopotassium salt at 0-5 degrees C. This new reagent was used for the determination of methylamine. The linear range is 3x10(-6)-2x10(-4) mol L(-1) with a detection limit (S/N=3) of 7.2x10(-8) mol L(-1), and the relative S.D. is 1.3% for ten replicate determinations of 1x10(-5) mol L(-1) CH3NH2. Common species in the aqueous environment have no or only slight influence on the determination. The method can be used to determine methylamine in real water samples.     

Some novel oxime ethers. The synthesis of 1,1-difluoro-2-alkoxymethanimines

The syntheses of four novel 1,1-difluoro-2-alkoxymethanimines, RONCF₂, are reported. The oxime ethers are prepared in excellent yield by dehydrofluorination of the amines, RON(H)CF₃ (RCF₃, (CF₃)₂CF, CH₃, (CH₃)₃C) with KF. These oxime ethers are thermally stable at 24°C and are characterized by IR, NMR, and physical properties. The two perfluoro compounds undergo dimerization to give CF₃N(OR)CFNOR in the presence of CsF at room temperature.     

A novel method for the oxidation of thiophenes. Synthesis of thiophene 1,1-dioxides containing electron-withdrawing substituents

A novel method for the synthesis of thiophene 1,1-dioxides by oxidation of substituted thiophenes with trifluoroperoxyacetic acid was developed. The effect of the solvent nature on the course of the reaction was studied and optimum conditions for the oxidation of thiophenes containing various functional groups were found. Previously unknown thiophene dioxides were obtained.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2144–2150, October, 2004.     

A novel dual channel responsive zinc(II) probe

A novel compound, 1, which is based on a 1,10-phenanthroline scaffold with cofacial BODIPY units, is synthesized via a three-step reaction sequence. It is noteworthy that 1 can be utilized for both visual and turn-off fluorometric detection of Zn²⁺ ions in aqueous acetonitrile solution. The fluorescence response is based on cation-mediated oxidative photoinduced electron transfer (PET). The digital action of a two-input NOR logic gate is also demonstrated.     

Oxalate/hydrogen peroxide chemiluminescence reaction. A 19F NMR probe of the reaction mechanism

The mechanism of the oxalate/hydrogen peroxide chemiluminescence reaction has been examined by magnetic resonance techniques. Investigation of the reactive intermediates involved in chemiluminescence was carried out with bis(2,6-difluorophenyl)oxalate (DFPO) using 19F NMR to probe its reactions with aqueous hydrogen peroxide. Formation and reactions of the intermediate hydroperoxy oxalate ester B along with the formation of the half ester product C and difluorophenol D were monitored by 19F NMR. When the reaction of DFPO and aqueous hydrogen peroxide was carried out in the presence of dansylphenylalanine, a typical fluorescent analyte, the intensity of the resonance due to the intermediate B was diminished in direct proportion to the concentration of the analyte. Comparison of the time/intensity profile of the chemiluminescence emission with that of the 19F NMR transient suggests that the hydroperoxy oxalate ester B is the likely 'reactive' intermediate, capable of participating in a chemically initiated electron exchange luminescence mechanism.