新型高选择性芳环溴化剂

苄基三甲基三溴化铵是新型高选择性的芳环溴化剂。在ＣＨ２Ｃｌ２－ＣＨ３ＯＨ或ＣＨ３ＣＯＯＯＨ－ＺｎＣｌ２中，它与酚，芳胺，酰胺，芳醚，芳烃及芳杂环化合物等反应，选择性得到对应的单，双或三溴化产物。     

COMMUNICATION. B-THIOACYLTHIO-9-BBN AS A THIOACYLATING REAGENT

Abstract

Convenient syntheses of S-aryldithioesters and thioamides are described: thus, thiols and amines are readily thioacylated with the S-borondithioester formed in situ, by the mild reaction of a dithioacid with 9-BBN.     

SULFURATED BOROHYDRIDE EXCHANGE RESIN: A NOVEL REAGENT FOR SELECTIVE REDUCTION OF ALDEHYDES

Selective reduction of aldehydes is carried out by using sulfurated borohydride exchange resin as a novel reducing reagent. Other sensitive groups like F, Cl, Br, NO₂, CN, OMe, ester and methylenedioxy remain intact under these reaction conditions. The isolation of pure products by simple filtration and evaporation is an important feature of this method.     

TETRACHLOROPYRIDINE: A NEW REAGENT FOR THE DEHYDRATION OF ALDOXIMES UNDER MICROWAVE*

ABSTRACT

Dehydration of aldoximes to nitriles using tetrachloropyridine under microwave in dry media is described. The procedure is applicable to a variety of aldoximes and the reagent can be recycled and reused.

     

断裂醚键的一种新试剂系统

Kollonitsch^[1]曾报道乙硼氢与四氢呋喃在Carius管中60℃加热64小时,生成硼酸丁酯,产率61%;若反应在室温下进行,需16周才能完成。继后,Past^[2]将φSBH₂与醚R'OR"反应,获得φSR'和H₂BOR"。Freeguard等^[3,4]将乙硼氢,戊硼氢-9或钠硼氢和卤素(Cl₂、Br₂、I₂、ICl)与醚类或醇类在常温下反应,醚键很快发生断裂,生成相应的卤化物和硼酸酯,产率达80%以上;二苯醚与具有β-卤素取代基的醇则不能顺利反应。     

N,N-DIBROMOBENZENESULFONAMIDE: A USEFUL REGENRABLE REAGENT FOR BROMINATION OF VARIOUS CARBANIONIC SUBSTRATES

N,N-Dibromobenzenesulfonamide(dibromoamine-B), which is prepared easily in high yield, has been employed as effective brominating agent for carbanionic substrates under mild conditions. β-Diketones and β-ketoesters were brominated by this reagent without using any bases. The reagent can be recovered, rebrominated, and reused several times.     

CHLOROMETHYL-DICHLOROPHOSPHANE: A USEFUL REAGENT FOR THE SYNTHESIS OF NEW HETEROCYCLES WITH DICOORDINATE PHOSPHORUS

Abstract

Only a limited number of heterophospholes are known. A general synthesis¹ involves the [4 + 1]-cyclocondensation of a reactive phosphorus(III) compound with an appropriate four-membered chain, as in the synthesis of the 2H-1,2,3-diazaphospholes.² The limiting factor in this case is the poor availability of four-membered chains with the necessary functionality at the ends.     

FERRIC CHLORIDE HEXAHYDRATE: A CONVENIENT REAGENT FOR THE OXIDATION OF HANTZSCH 1,4-DIHYDROPYRIDINES

A general and practical route for the moderate yield oxidative conversion of readily accessible 1,4-dihydropyridines (1,4-DHPs) to the corresponding pyridines was described using a relatively benign oxidant, i.e. ferric chloride hexahydrate (FeCl₃·6H₂O). The reaction was carried out under mild and convenient condition. However, oxidation of 4-isopropyl-1,4-DHP 1b with FeCl₃·6H₂O afforded the dealkylated pyridine 2a.     

SILICA GEL SUPPORTED JONES REAGENT (SJR): A SIMPLE,VERSATILE, AND EFFICIENT REAGENT FOR OXIDATION OF ALCOHOLS IN NON-AQUEOUS MEDIA

Oxidation of alcohols to carbonyl compounds has been carried out by utilization of Jones reagent supported on silica gel (SJR). The SJR procedure has advantages over traditional Jones oxidation procedure. This procedure is safer to carry out and simplified workup by allowing organic media.     

THE PHOTOCHEMISTRY OF ACETYL-SUBSTITUTED AROYL AZIDES: THE DESIGN OF PHOTOLABELING AGENTS FOR INERT SITES IN HYDROPHOBIC REGIONS

The photochemistry, photophysics and hydrolytic stability of three substituted aroyl azides were investigated. The azides were selected as model compounds for potential photolabeling agents based on the extreme electrophilic reactivity of aroylnitrenes. Each of the azides studied is a derivative of benzoyl azide containing an acyl group to act as an internal triplet sensitizer and an additional functional group useful for linking the azide to a site-selecting probe molecule. The findings show that benzoyl azides containing the three substituents in a 1,3,5-pattern might be useful for labeling of lipophilic molecules.     

A NEW SULFINATODEHALOGENATION REAGENT:THIOUREA DIOXIDE

The reaction of perfluoroalkyliodides,perfluoroalkylbromide,1,1,1-trifluoro-2,2,2-trichloro-ethane,and carbon tetrachloride with thioureadioxide in aqueous acetonitrile solution gave the corresponding sulfinate ingood yield.     

A general strategy for the facile synthesis of 2,7-dibromo-9-heterofluorenes

[reaction: see text] A facile, highly efficient, and economical procedure for the preparation of 6,6'-diiodo-4,4'-dibromo-3,3'-dimethoxylbiphenyl has been found. From this compound, a general synthetic strategy for the preparation of 2,7-dibromo-9-heterofluorenes has been developed. Five 2,7-dibromo-9-heterofluorenes have been easily synthesized for the first time according to the procedure presented, opening the door to new classes of inorganic and organometallic conjugated polymeric materials of polyheterofluorenes.     

光学活性的醛酮鉴定试剂

醛酮鉴定试剂很多,利用肼基与羰基缩合的尤其常用,如苯肼、氨基脲等等。     

New ferrocenyl heterometallic complexes of 2,7-diethynylfluoren-9-one

A new series of rigid-rod alkynylferrocenyl precursors with central fluoren-9-one bridge, 2-bromo-7-(2-ferrocenylethynyl)fluoren-9-one (1b), 2-trimethylsilylethynyl-7-(2-ferrocenylethynyl)fluoren-9-one (2) and 2-ethynyl-7-(2-ferrocenylethynyl)fluoren-9-one (3), have been prepared in moderate to good yields. The ferrocenylacetylene complex 3 can provide a direct access to novel heterometallic complexes, trans-[(η⁵-C₅H₅)Fe(η⁵-C₅H₄)CCRCCPt(PEt₃)₂Ph] (4), trans-[(η⁵-C₅H₅)Fe(η⁵-C₅H₄)CCRCCPt(PBu₃)₂CCRCC(η⁵-C₅H₄)Fe(η⁵-C₅H₅)] (5), [(η⁵-C₅H₅)Fe(η⁵-C₅H₄)CCRCCAu(PPh₃)] (6) and [(η⁵-C₅H₅)Fe(η⁵-C₅H₄)CCRCCHgMe] (7) (R=fluoren-9-one-2,7-diyl), following the CuI-catalyzed dehydrohalogenation reactions with the appropriate metal chloride compounds. All the new complexes have been characterized by FTIR, ¹H-NMR and UV–vis spectroscopies and fast atom bombardment mass spectrometry. The solid state molecular structures of 3, 5, 6 and 7 have been established by X-ray crystallography. The redox chemistry of these mixed-metal species has been investigated by cyclic voltammetry and oxidation of the ferrocenyl moiety is facilitated by the presence of the heavy metal centre and increased conjugation in the chain through the ethynyl and fluorenone linkage units.     

A new mesogenic fluorene derivative: 2,7-bis(4-pentylphenyl)-9,9-diethyl-9H-fluorene

The title compound, 2,7-bis(4-pentylphenyl)-9,9-diethyl-9H-fluorene, is a new mesogenic compound containing the fluorene moiety. It exhibits a monotropic nematic liquid crystalline behaviour, with isotropisation temperature of 53°C. The compound is also polymorphic in the solid state, with one crystal phase melting at 103°C and another one melting at 71°C. The crystal and molecular structure of the high melting solid phase have been determined from single crystal X-ray diffraction analysis. Crystals are monoclinic, with cell dimensions a = 16.649(6) Å, b = 8.305(3) Å, c = 24.598(7) Å, β = 111.60(2)?, space group P2₁/c and four molecules in the unit cell. Refinement leads to R = 0.0558. The two terminal alkyl chains and one phenyl ring are disordered over two split positions. The imbricated molecular packing observed in the solid state seems to resemble that of the nematic phase that is formed upon cooling the melt.     

2,4-DINITROPHENYLHYDROXYLAMINE: AN EFFICIENT AND MORE GENERAL REAGENT FOR IRON-CATALYZED ALLYLIC AMINATION

2,4-Dinitrophenylhydroxylamine (1) is an efficient reagent for the iron-catalyzed regioselective allylic amination of olefins. Moderate to excellent yields of N-DNP-N-allyl amines (2) are obtained resulting from introduction of the N-DNP group at the less substituted vinylic carbon with accompanying double bond transposition. N-alkylation of 2 and subsequent treatment with MeNH₂ affords secondary N-alkyl-N-allyl amines (5) in good overall yield.     

基准试剂纯度定值研究

本文介绍了基准试剂纯度定值装置的工作原理,研究制作了用于反映库仑滴定终点的终点指示器,并对基准试剂的纯度分析方法进行了研究,使定值精度达到了国内外先进水平。