Uncatalysed coupling of an activated aryl chloride with aryllithium and aryl Grignard reagents

Substitution of the chloro group in 2-(2-chlorophenyl)-4,4-dimethyl-2-oxazoline to afford biaryls occurs upon reaction with either aryllithium reagents or aryl Grignard reagents. The reactions with Grignard reagents occur under similar conditions to a previously reported manganese-catalysed procedure. The reactions with lithium reagents, whilst not always affording greater yields of product than the Grignard reagents, involve much shorter reaction times and afford yields, which are comparable with those obtained from the corresponding fluoro derivative.     

Stereoselective Synthesis of (Z)- and (E)-Allylic Silanes by Copper-Mediated Substitution Reactions of Allylic Carbamates with Grignard Reagents

Both (Z)- and (E)-allylic silanes were prepared with high stereoselectivity by the copper-mediated substitution of allylic carbamates by organometallic reagents. The reaction of alkylmagnesium reagents with (E)-allylic carbamates provides (Z)-allylic silanes, whereas both alkylmagnesium and alkyllithium reagents react with (Z)-allylic carbamates to afford (E)-allylic silanes. Because Grignard reagents are often more facile to prepare than alkyllithium species, these reagents are the optimal nucleophiles for the synthesis of both (Z)- and (E)-allylic silanes. This method also allows readily available nonracemic allylic carbamates to be converted to chiral, nonracemic (Z)- and (E)-allylic silanes with high stereoselectivity.     

Investigation of Chemiluminescence with Electrogenerated Reagents and Its Analytical Application

In this paper, studies on chemiluminescence (CL) systems with electrogenerated reagents, including BrO^-, ClO^-, Br2, [Cu-(HIO6)2]^5-, H2O2, Mn^3 , Co^3 and Ag^2 , are described.The analytical applications of the CL system with electrogenerated reagents are reviewed.     

多卤代变色酸双偶氮类稀土显色剂的合成及分子结构与吸光性能的关系

本文设计、合成了一类新型稀土显色剂--多卤代变色酸双偶氮衍生物,它们易溶于水、乙醇和丙酮,不溶于苯、己醚和氯仿,是具有高灵敏度、高选择性、显色酸度高、空白值低的优良稀土显色剂,本文还研究了试剂的分子结构和吸光性能的关系,当助色基及其取代位置一定时,具有-AsO₃H₂、-COOH、-PO_3H、-Cl络合功能基的性质,其灵敏度较高。     

Lithiation of 3-(Acylamino)-2-unsubstituted-, 3-(Acylamino)-2-ethyl-, and 3-(Acylamino)-2-propyl-4(3H)-quinazolinones: Convenient Syntheses of More Complex Quinazolinones(1)

3-(Pivaloylamino)- and 3-(acetylamino)-4(3H)-quinazolinones react with alkyllithium reagents to give 1,2-addition products in very good yields. Lithiation takes place with LDA and is regioselective at position 2. The lithium reagents thus obtained react with a variety of electrophiles to give the corresponding substituted derivatives in very good yields. Reactions of the lithium reagents with iodine give oxidatively dimerized cyclic structures. 3-(Pivaloylamino)- and 3-(acetylamino)-2-ethyl-4(3H)-quinazolinones and 3-(pivaloylamino)- and 3-(acetylamino)-2-propyl-4(3H)-quinazolinones are lithiated at the benzylic position with LDA. The lithium reagents so produced also react with a variety of electrophiles to give the corresponding 2-substituted-4(3H)-quinazolinone derivatives in very good yields. However, lithiation of 3-(acylamino)-2-(1-methylethyl)-4(3H)-quinazolinones was unsuccessful, as were lithiations of compounds having a diacetylamino group at position 3. The amide groups have been cleaved in good yield under basic or acidic conditions from some of the products to provide access to the free amino compounds.     

Two new spectrophotometric reagents for copper

Two ferroin-type compounds are proposed as spectrophotometric reagents for copper(I): 6-methyl-2-pyridylhydrazidine, which forms a yellow complex with lambda(max) 426 nm and molar absorptivity 700 l.mole(-1).mm(-1), and 3-(6-methyl-2-pyridyl)-5,6-diphenyl-1,2,4-triazine, which forms a red-orange complex with (lambda)max 492 nm and molar absorptivity of 955 l.mole(-1).mm(-1). These reagents are specific for copper and the complexes can be extracted into isopentanol for increased sensitivity.     

Air monitoring of aldehydes by use of hydrazine reagents with a triazine backbone

Two hydrazine reagents, 4- N, N-dimethylamino-6-(4'-methoxy-1'-naphthyl)-1,3,5-triazine-2-hydrazine (DMNTH) and N-methyl-4- N', N'-dimethylamino-6-(4'-methoxy-1'-naphthyl)-1,3,5-triazine-2-hydrazine (MDMNTH) have been synthesized and used for the determination of aldehydes in air samples. Test tubes with the reagents coated on silica gel were prepared and used for monitoring of carbonyls in air. After elution with acetonitrile the hydrazones formed were separated by reversed-phase liquid chromatography. Detection was performed by UV-visible and fluorescence spectroscopy. The results were validated by use of standard atmospheres of the carbonyls and of nitrogen dioxide and ozone, as potential interferents. In comparison with established hydrazine reagents, e.g. 2,4-dinitrophenylhydrazine (DNPH), the results from use of MDMNTH correlate well; lower recoveries were obtained by use of DMNTH. The limits of detection for the new reagents are superior to those for DNPH, because of the possibility of fluorescence detection.     

偶氮胂酸型荧光试剂测定铝的研究

比较了５种新试剂及偶氮胂－Ｉ的铝铬合物的荧光性能，讨论了试剂结构与性能之间的关系。试验出７－〔（４－甲基－２－胂酸基苯）偶氮〕－８－羟基喹啉－５－磺酸为铝的优良荧光试剂，并用其测定茶叶、含茶叶饲料，以及大白鼠排泄物中的铝和水样中的铝，结果满意。     

Preparation of ω-tetrahydropyran-2-ylsulfanylalkylmagnesium chlorides: Useful reagents for the synthesis of 1-(ω-mercaptoalkyl)-1,2-dihydrobuckminsterfullerenes (C60)

ω-Tetrahydropyran-2-ylsulfanylalkylmagnesium chlorides are prepared as Grignard reagents containing protected mercaptoalkyl chains, which are useful for the direct introduction of ω-mercaptoalkyl chains to electrophiles. In order to prove the usefulness of these reagents, they were reacted with buckminsterfullerene (C₆₀) to give 1-(ω-mercaptoalkyl)-1,2-dihydrobuck minsterfullerenes after the deprotection of THP group with TFA.     

聚苯乙烯负载的β-溴乙烯基硒化合物的合成及其在固相合成多取代烯烃中的应用

多取代烯烃的合成一直是有机合成的重要内容之一,在维生素、前列腺素和昆虫信息素等天然产物中都含有（Z）-或（E）-构型的多取代烯基结构单元,元素及金属有机化合物组成的1,2-双官能团化合物在立体选择性地合成多取代烯烃方面的应用研究一直是有机合成的热点。     

Efficient synthesis of sterically crowded biaryls by palladium-phosphinous acid-catalyzed cross-coupling of aryl halides and aryl grignards

A series of sterically hindered biaryls have been obtained by palladium- and nickel-phosphinous acid-catalyzed Kumada-Corriu cross-coupling of ortho-substituted aryl halides and Grignard reagents. This method allows formation of di- and tri-ortho-substituted biaryls in 87-98% yield under mild reaction conditions even when electron-rich aryl chlorides are used. The reaction also proceeds with aryl iodides at -20 degrees C, and under these conditions, functional groups that are generally not compatible with Grignard reagents are tolerated.     

Novel Substitution Reactions of 5-(4-Nitrophenyl)-10,15,20-triphenyl porphyrin with Nucleophilic Reagents

Substitution reactions of 5-(4-nitrophenyl)-10,15,20-triphenylporphyrin (1)and its Ni(Ⅱ) complexe 2 with different nucleophilic reagents were studied for preparing asymmetric porphyrin. The reaction products are different with the nucleophilic reagents changing. Diporphyrin (3) was obtained when compound 1 reacted with sodium phenoxide or diphenoxide ion in DMF solution. Whereas the nitro group was reduced and 5-(4-amino-phenyl)-10,15,20-triphenylporphyrinato Nickel(Ⅱ) (4) was achieved when compound 2 reacted with above nuleophilic reagents in the same condition. The reductive product 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (5) was also achieved when 1 reacted with mercaptoethanol or thiophene and lithium hydroxide. While the nitro group was substituted by cyanide anion and 5-(4-nitrilephenyl)-10,15,20-triphenylporphyrin (6) was achieved when 1 reacted with sodium cyanide.     

LiCl-mediated preparation of highly functionalized benzylic zinc chlorides

In the presence of zinc dust (1.5-2.0 equiv) and LiCl (1.5-2.0 equiv), various benzylic chlorides bearing functional groups (iodide, cyanide, ester, ketone) are smoothly converted at 25 degrees C to the corresponding zinc reagents without homo-coupling (<5%). The utility of these benzylic zinc reagents is demonstrated by a short synthesis of papaverine.     

Spectrophotometric determination of flucloxacillin and dicloxacillin in pure and dosage forms

A simple, rapid and accurate spectrophotometric method for the determination of antibiotic drugs, flucloxacillin (Fluclox) and dicloxacillin (Diclox), in pure form and different pharmaceutical preparations has been developed. The charge transfer (CT) reactions between Fluclox and Diclox as electron donors and 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE) as pi-acceptors to give highly coloured complex species have been spectrophotometrically studied. The optimum experimental conditions for these CT reactions have been studied carefully. Beer's law is obeyed over the concentration ranges of 4-180 microg mL(-1) and 4-70 microg mL(-1) for Fluclox and Diclox drugs using TCNQ and TCNE reagents, respectively. The Sandell sensitivities (S) are found to be 0.016-0.035 microg cm(-2) and 0.011-0.016 microg cm(-2) for Fluclox and Diclox, respectively, which indicate the high sensitivity of the proposed method. The relative standard deviations (R.S.D.: 0.08-0.49 and 0.15-0.80) for the determination of Fluclox and (R.S.D.: 0.05-0.75 and 0.13-0.75) for Diclox were obtained for four to six replicates using TCNQ and TCNE reagents, respectively, refer to the high accuracy and precision of the proposed method. These results are also confirmed by the between-day precision and the percent recovery of 99.90-100.1 and 99.60-100.4 for Fluclox and 99.90-100.5 and 99.40-100.1 for Diclox using TNCQ and TCNE reagents, respectively. The results obtained for the two reagents are comparable with those obtained by the official method.     

Addition of Organolithium and Grignard Reagents to Pyrimidine-2(1H)-thione: Easy Access to 4-Substituted 3,4-Dihydropyrimidine-2(1H)-thiones

Organolithium and Grignard reagents are added to pyrimidine-2(1H)-thione, yielding 4-substituted 3,4-dihydropyrimidine-2-(1H)-thiones. Since the synthetic procedure can be performed on a multigram scale, and since pyrimidine-2(1H)-thione as well as the majority of organometallic reagents are readily available, the process described provides an easy access and complementary to other methods to 4-substituted 3,4-dihydropyrimidine-2-(1H)-thiones.     

Addition of grignard reagents to aryl acid chlorides: an efficient synthesis of aryl ketones

[chemical reaction: see text]. Direct addition of Grignard reagents to acid chlorides in the presence of bis[2-(N,N-dimethylamino)ethyl] ether proceeds selectively to provide aryl ketones in high yields. A possible tridentate interaction between Grignard reagents and bis[2-(N,N-dimethylamino)ethyl] ether moderates the reactivity of Grignard reagents, preventing the newly formed ketones from nucleophilic addition by Grignard reagents.     

Preparation of ω-tetrahydropyran-2-ylsulfanylalkylmagnesium chlorides: Useful reagents for the synthesis of 1-(ω-mercaptoalkyl)-1,2-dihydrobuckminsterfullerenes (C60)

ω-Tetrahydropyran-2-ylsulfanylalkylmagnesium chlorides are prepared as Grignard reagents containing protected mercaptoalkyl chains, which are useful for the direct introduction of ω-mercaptoalkyl chains to electrophiles. In order to prove the usefulness of these reagents, they were reacted with buckminsterfullerene (C₆₀) to give 1-(ω-mercaptoalkyl)-1,2-dihydrobuck minsterfullerenes after the deprotection of THP group with TFA.     

Synthesis of 5S-(1-Oxoalkyl and Aryl)-2-pyrrolidinone Derivatives1

N-Benzyl pyroglutamate esters react with aryllithium reagents and methyllithium to give moderate to good yields of 5-(1-oxoaryl) or 5-(1-oxoalkyl)-2-pyrrolidinone derivatives. The reaction proceeds without racemization, but is accompanied by formation of 5-(1-hydroxy-1-alkyl)-2-pyrrolidinone derivatives. This reaction gives very poor yields of ketone products with most other alkyl organolithium reagents such as n-butyllithium. Grignard reagents react to give primarily the alcohol.     

Highly enantiomerically enriched alpha-haloalkyl Grignard reagents

alpha-Chloro- and alpha-bromoalkyl Grignard reagents 11 and 30 with > 97% ee (enantiomeric excess) were generated by a sulfoxide/magnesium exchange reaction from the enantiomerically and diastereomerically pure sulfoxides 25 and 27. The resulting alpha-haloalkyl Grignard reagents are configurationally stable at -78 degrees C. Racemization sets in at or above -60 degrees C, especially when the solution contains bromide ions. In the absence of halide ions, the configurational stability extends up to -20 degrees C, when chemical decomposition commences.     

Diastereoselective addition of arylzinc reagents to sugar aldehydes

The diastereoselective arylation of sugar-derived aldehydes is described. The arylating reagents are generated in situ by a boron-to-zinc exchange reaction of arylboronic acids with Et(2)Zn to generate arylethylzinc reagents. The exquisite reactivity of the arylzinc reagents allowed for an efficient and mild arylation, delivering the corresponding products in diastereoisomeric ratios of up to >20:1. The utility of the methodology is highlighted with an efficient formal synthesis of (+)-7-epi-goniofufurone, a member of the styryllactone family of natural products.