氯铬酸甲铵/硅胶载体氧化剂的制备及其对醇的氧化研究

利用硅胶作载体，负载氯铬酸甲铵盐制备了一种新的载体铬(Ⅵ)氧化剂。该试剂制备方法简单、性质稳定。可在多种反应介质中对伯醇和仲醇氧化，高收率得到相应的醛和酮，反应操作简单，提纯方便。     

Isoquinolinium bromochromate： An efficient and stable reagent for bromination of hydroxylated aromatic compounds and oxidation of alcohols

The new chromium(Ⅵ) oxidizing reagent isoquinolinium bromochromate(IQBC) was prepared and characterized.The IQBC has been found to be stable and an efficient solid reagent which can be easily prepared in good yield.It act as an efficient brominating reagent for hydroxylated aromatic compounds as well as good oxidizing reagent for the conversion of alcohols to carbonyl compounds in good to excellent yield.The synthesized isoquinolinium bromochromate is more ideal reagent,with number of specification inclu...     

Pulsed reagent introduction through a membrane reactor for flow-injection systems

A method of intermittent reagent introduction, functionally equivalent to stop-go pumping, is described. A pneumatically pressurized reagent reservoir is used to deliver liquid through a high-speed on/off valve to the outer channel of an annular tube assembly. Except for this single entry point, the outer channel is otherwise sealed. The inner flow channel bearing the principal flow stream contains a short microporous membrane tube. When the reagent delivery valve is activated, reagent flows radially inward through the membrane into the principal flow stream.     

A flow injection analysis technique for the determination of chloride using reflectance detection

A flow injection (FI) determination for chloride has been developed using the light reflectance of the precipitate formed by the reaction of chloride with silver(I) as the method of detection rather than turbidimetry, as in the previous FI method using this reaction. The dynamic range of the analysis is increased to 0-10 mM chloride with a 10 mM silver(I) reagent and to 0-50 mM chloride with a 50 mM silver(I) reagent by using this mode of detection. The ability to select the injected reagent from an option of two concentrations via the control program is incorporated into the FI system, enhancing the versatility of the analysis. The dynamic range is further extended to 100 mM chloride by measuring the signal levels at the trailing portion of the response curve. The consumption of reagent is kept to a minimum by merging injected zones of sample and reagent instead of using a constant reagent stream.     

Study of the behaviour of the absorbent blanks in analytical procedures by using the H-Point standard additions method (HPSAM)

This paper studies the behaviour of reagent blank in different extractive-colorimetric procedures (determination of sympathomimetic amines with NQS reagent) by using the H-Point Standard Additions Method (HPSAM) in order to study and characterize the different possibilities that the blank can introduce in an analytical procedure. We define two kinds of blanks: the external blank (from reagent alone solutions data) and the internal blank (from extrapolation of reagent plus analyte solutions data). Comparison between both gives the information about the reproducibility of the behaviour of the reagent blank. A procedure to evaluate, and characterize, errors (if they exist) is described, and a guide for optimizing the measuring procedure is presented.     

o-Diamines as reagents for selenium : Part I. 4-dimethylamino-1,2-phenylenediamine

4-Dimethylamino-1,2-phenylenediamine is investigated as a photometric and qualitative reagent for selenium. With this reagent selenium (IV) forms 5-dimethylamino-2,1,3-benzoselenadiazole, a red colored compound, with an absorption maximum in the visible region at 500 mμ. Variables such as reagent stability, extinction stability, reaction rate, influence of acidity, foreign ions, validity of Beer's law are discussed. The reagent is highly selective for selenium, has good sensitivity and recproducibility, and is also useful for qualitative purposes.     

Strained silacycles in organic synthesis: a new reagent for the enantioselective allylation of aldehydes

A new reagent for the enantioselective allylation of aliphatic aldehydes has been developed. The reagent is easily prepared in a single step from commercially available materials and may be stored without significant decomposition. The reactivity of the reagent is attributed to strain-release Lewis acidity.     

Synthesis of a new N-acetyl thiazolidinethione reagent and its application to a highly selective asymmetric acetate aldol reaction

[reaction: see text] A new N-acetyl thiazolidinethione reagent, which undergoes highly diastereoselective aldol reactions upon enolization with dichlorophenylborane and (-)-sparteine and subsequent treatment with a variety of aldehydes, is described. This reagent is pseudoenantiomeric to an L-tert-leucine-derived reagent recently described by us and is useful because it avoids the prohibitively costly D-tert-leucine.     

Studies in the analytical chemistry of sodium : 6:8-Dichlorobenzoylene urea as a reagent for sodium

6:8-Dichlorobcnzoylene urea has been. examined as a reagent for sodium. The reagent cannot be recommended for this purpose. Precipitation is incomplete and the reagent tends to hydrolyse so that it is impossible to differentiate sodium in the presence of potassium.     

REALISIS: a medicinal chemistry-oriented reagent selection, library design, and profiling platform

REALISIS is a software system for reagent selection, library design, and profiling, developed to fit the workflow of bench chemists and medicinal chemists. Designed to be portable, the software offers a comprehensive graphical user interface and rapid, integrated functionalities required for reagent retrieval and filtering, product enumeration, and library profiling. REALISIS is component-based, consisting of four main modules: reagent searching; reagent filtering; library enumeration; and library profiling. Each module allows the chemist to access specific functionalities and diverse filtering and profiling mechanisms. By implementing the entire process of reagent selection, library design, and profiling and by integrating all the necessary functionalities for this process, REALISIS cuts the time required to design combinatorial and noncombinatorial libraries from several days to a few hours.     

Metal-assisted reactions—Part 11: Rapid reduction of N-nitrosoamines to N,N-disubstituted hydrazines; the utility of some low-valent titanium reagents

The rapid reduction of N-nitrosoamines to N,N-disbustituted hydrazines by a low-vanet titanium reagent is described. The reagent is selective in that many other functional groups are unaffected by it. The nature of the low-valent titanium reagent is discussed in terms of experimental results of comparisons of its reactivity and that of other low-valent titanium reducing agents.     

氯铬酸三甲铵/氧化铝的制备及其对醇和苯偶姻类化合物的氧化

本文报道了氯铬酸三甲铵/氧化铝的制备方法及其对醇和苯偶姻类化合物的氧化反应。 该试剂制备简单、性质稳定。氧化反应条件温和、操作简单、提纯方便、收率良好。     

Pyridine assisted oxidations of alcohols to carbonyl compounds by means of 3-car☐ypyridinium dichromate (ndc) reagent

3-Car☐ypyridinium dichromate (NDC),readly prepared from nicotinic acid and chromium trioxide, is an efficient reagent for the oxidation of alcohols into carbonyl compounds in the presence of pyridine. The optimum molar ratio substrate:reagent:pyridine to ensure complete oxidation of starting material in a short reaction time was found 1:2.5:20 respectively. A brief comparison between this reagent and pyridinium dichromate (PDC) is made. In contrast to the PDC reagent, NDC allows selective oxidation between benzylic alcohols and aliphatic alcohols. The NDC-pyridine system has been successfully extended to the oxidation of N-(2-hidroxy-2-phenyl or 2-methylethyl)-β-lactams into their corresponding carbonyl compounds as N-H azetidin-2-one precursors. In contrast, primary N-(2-hydroxyethyl)-β-lactams upon treatment with this reagent system afforded N-formylazetidin-2-ones.The influence of pyridine in oxidations by means of NDC is further shown in the conversion of hydroquinones into quinones. Another interesting feature associated with the use of this reagent is the ease of purification of the final products.     

A soluble polymer-supported triflating reagent: a high-throughput synthetic approach to aryl and enol triflates

[reaction: see text] The high-yielding synthesis and application of the first example of a polymer-supported reagent for the preparation of trifluoromethanesulfonates (triflates) is described. This new reagent efficiently triflates aryl alcohols and lithium enolates in high yield (>90%). A simple precipitation and filtration to remove the excess reagent and byproduct facilitate purification of the triflate products. The PEG-supported approach is highly efficient, as the PEG-supported byproduct can be quantitatively recovered and recycled into reagent 1.     

原位生成的高价碘试剂在有机合成中的应用进展

原位生成的高价碘试剂具有原子经济性、性能温和和绿色环保等优点,在诸多合成和不对称催化等反应中表现活跃.详细介绍了原位生成高价碘的概念以及反应机理,根据不同的反应类型分别对原位生成的三价碘、五价碘以及手性高价碘试剂在有机合成反应中的应用进行了归纳总结,分析了原位生成的高价碘试剂目前面临的问题,并对今后的发展趋势作了展望.     

Chemically removable derivatization reagent for liquid chromatography I. 2-(N-Phthalimido)ethyl 2-(dimethylamino)ethanesulfonate

A sulfonate derivatization reagent, 2-(N-phthalimido)ethyl 2-(dimethylamino)ethanesulfonate, was synthesized and examined for use in liquid chromatography. The reagent contains two key moieties, a chromophore (phthalimido) necessary for detection and a dimethylamino function that is chemically removable after derivatization. The reagent was applied to the derivatization of 2,4,6-trichlorophenol as a model analyte. The results indicated that the reagent can be readily removed after derivatization by simple acid treatment.     

Spectrophotometry Determination of Molybdenum with N-Cyanoacylacetaldehyde Hydrazone

N-cyanoacylacetaldehyde hydrazone (CAAH), which is a laboratory synthetic reagent, is proposed as a new reagent for spectrophotometry determination of microamounts of molybdenum at λ_max 790 nm. The reagent forms 1:1 blue coloured complex with molybdenum (VI) in phosphoric acid solution. The stable blue colour is obtained finally after changing from yellow to green. The colour development depends on temperature, time and concentration of phosphoric acid. This reagent is applied for the determination of molybdenum in steel alloys and the results are satisfactory.     

Synthesis of l-(5-Nitro-2-Pyridylazo)-2.7-Dihydroxy-naphthalene and its Color Reaction with Cobalt (Ⅱ)

Pytrdylazo reagent is an important chromogenic reagent. PAN is typical one. The new reagent, l-(5-nitro-2-Pyridylazo)-2.7-dihydroxy-naphthalene (5-NO₂-PADN) has been synthesized by to take up -OH and -NO₂ groups at the PAN, and it was confirmed with IR and elements analysis.     

Polymer-supported thioanisole: a versatile platform for organic synthesis reagents

A new cross-linked polystyrene-supported thioanisole reagent is reported. This reagent incorporates the flexible JandaJel™ cross-linker and can be treated with methyl trifluoromethanesulfonate to form the corresponding sulfonium salt. This salt can in turn be deprotonated to form a polymer-supported sulfur ylide that is able to react with aldehydes and ketones to form epoxides. The thioanisole reagent can also be oxidized to form an insoluble sulfoxide reagent that is useful in Swern oxidation reactions. In these reactions, the polymer-supported thioanisole-based reagents can be recovered, regenerated and reused.     

Potentiometric Titration of Some Sulphide Forming Ions by Dithiopyrilmethane

Dithiopyrilmethane (DTPM) is the sulphur containing derivative of pyrazolone. This reagent forms active mono- or biprotonated form giving stable, often colored complexes with sulphide forming metal ions. It is the most common that the reagent as a bidentate neutral ligand exists in these complexes giving cation or neutral complexes. This reagent is used in spectrophotometric and extractive spectrophotometric methods of analysis of sulphide forming metal ions.