State of Polymethine (Styryl and Carbocyanine) Indolium Derivatives in Aqueous Solution and Their Analytical Properties

The state of new polymethine (styryl and carbocyanine) 1,3,3-trimethyl-3H-indolium derivatives in aqueous solutions have been studied by spectrophotometry. Depending on the acidity, the reagents can occur in the ionic (singly (R⁺) or doubly (HR²⁺) charged) or the hydrolyzed (ROH) state. The main spectrophotometric characteristics and protolysis constants of the reagents have been calculated. A possible mechanism of protolytic transformations in solutions of polymethine reagents is proposed based on quantum-chemical calculations of charge distributions in their molecules and on electron and ¹H NMR spectroscopy data. The results demonstrate the advisability of using polymethine compounds as efficient analytical reagents.     

Stereoselective C(sp3)-C(sp2) Negishi coupling of (2-amido-1-phenylpropyl)zinc compounds through the steric control of β-amido group

A controllable diastereoselective C(sp2)-C(sp3) Negishi coupling reaction of secondary benzylic zinc reagents with aryl bromides has been demonstrated for the first time, forming medicinally important 1-arylphenylethylamines. In the presence of Pd(OAc) 2 and S-phos, open-chain (2-amido-1-phenylethyl)zinc reagents bearing a -NHAc or NHCHO group underwent cross-coupling reaction to give syn 1-arylphenylethylamine as the major products, whereas the zinc reagents bearing a sterically hindered-NHCOC(CH3)2 OTBS group specifically yielded anti 1-arylphenylethylamines.     

Facile Oxidation of Aldehydes to Carboxylic Acids with Chromium(V) Reagents

Recently we reported a convenient method of oxidation of alcohols to carbonyl compounds using chromium(V) reagents.¹ Although a variety of reagents are available for effecting this transformation, there are only a few reagents which have been successfully used for the oxidation of aldehydes to carboxyllc adds. Chromic acid, silver oxide and potassium permanganate are commonly employed for this purpose and reactions are performed in protic media under conditions which are not that mild.² The “non-aqueous” chromium(VI) reagent, pyridinium dichromate, recently reported by Corey³ oxidises alcohols and aldehydes to carboxylic acids in DMF at room temperature. Although Cr(V) species is postulated as an intermediate in all oxidations with Cr(VI), no systematic oxidation studies have been reported with these reagents. This note reports the results of some fruitful investigations on aldehyde → carboxylic acid conversion involving some “non-aqueous” chromium (V) complexes 1, 2, 3 and 5 under anhydrous conditions.     

Highly stereoselective synthesis of 6-perfluoroalkyl-6-fluoroalka-2,3,5-(Z)-trienols through carbometallation-elimination of 5-perfluoroalkyl-substituted 4(E)-alken-2-ynols with Grignard reagents

A highly regio- and stereoselective sequential carbometallation and Z-selective β-elimination reaction of 5-perfluoroalkyl-4(E)-en-2-ynols with Grignard reagents in Et₂O has been developed to afford various 6-perfluoroalkyl-6-fluoroalka-2,3,5(Z)-trienols in good to excellent yields. Primary or secondary alkyl or aryl Grignard reagents may be used to introduce the R² group to the 2-position of the starting materials referring to the hydroxyl group. A mechanism for this transformation has been proposed.     

Selective reagents for solvent extraction of metals—II. Bis-quinaldic acids

Bis-quinoline-2-carboxylic acids in which the quinoline rings were joined via ether linkages to the 8-position have been synthesized and tested for metal extraction. The reagents extracted Cu²⁺ and Zn²⁺ selectively in the presence of Fe²⁺ and Fe³⁺ from aqueous sulphate solution.     

The effect of ethylenediaminetetraacetic acid on the ferrous/ferric and cuprous/cupric redox systems

The effect of ethylenediaminetetraacetic acid on the redox systems Fe⁺²/Fe⁺³ and Cu⁺/Cu⁺² has been examined. In each case the oxidation potential of the system was markedly reduced, thus making the lower valency state a more powerful reductant. It has been established that the oxidation potentials of the two systems, in the presence of EDTA, at PH 4–5, are 0.12 and 0.13 v respectively.Because of these enhanced reducing powers, attempts were made to use ferrous-EDTA and cuprous-EDTA as reductimetric reagents. A variety of oxidants was in fact successfully titrated, but neither titrant possessed any advantage over existing reagents.The reducing properties of both systems lie intermediate between those of stannous and titanous chlorides.Theoretical considerations suggest the existence of a cuprous-EDTA complex with a formation constant of ca. 10¹⁸.     

Methylation of Arenols through Ni‐catalyzed C—O Activation with Methyl Magnesium Bromide

Direct alkylation of arenols with alkyl organometallic reagents has never been approached. Herein we reported the first successful example of nickel‐catalyzed methylation of arenols with methyl Grignard reagents to construct C(sp²)‐C(sp³) bond under mild conditions. The transformation was compatible with broad substrate scope of 2‐naphthol derivatives. Benzyl alcohol and biphenols were also suitable substrates for this methylation.     

Loss of trace impurities during NAA of liquid reagents

The loss of trace elements during NAA of five liquid reagents, hydrofluoric acid, hydrochloric acid, nitric acid, hydrogen peroxide and deioniyed water, has been investigated using 17 radioactive tracers of⁴⁶Sc,⁵¹Cr,⁵⁴Mn,⁵⁹Fe,⁶⁰Co,⁶⁴⁵Zn,⁷⁵Se,⁸⁵Sr,⁹⁵Zr,¹¹³Sn,¹²⁴Sb,¹⁵¹Eu,¹⁶⁰Yb,¹⁷⁷Lu,¹⁸²Ta,²³³Pa. Two kinds of container quartz and polyethylene have been used for irradiation and also for preconcentration of the reagents. The containers were cleaned before use by washing-leaching-rinsing procedure. The reagents were preconcentrated by subboiling evaporation under the infrared lamp in clean bench. The loss of trace elements has been revealed to be severer for the reagents of hydrochloric acid and nitric acid in the container of quartz than for the other cases, while that is lowest for hydrogen peroxide.     

Dissolution of cellulose in ionic liquids as a way to obtain test materials for metal-ion detection

Cellulose films containing entrapped analytical reagents suitable for metal-ion detection are produced by joint dissolution of cellulose and the reagents in ionic liquids then precipitation with water. The conditions of preparation of these test materials have been optimized and their properties have been studied. The film obtained by use of the ionic liquid 1-butyl-3-methylimidazolium chloride and 1-(2-pyridylazo)-2-naphthol has been used for colorimetric determination of divalent zinc, manganese, and nickel with detection limits at the 10⁻⁶ mol L⁻¹ level.     

Effect of Light on the Formation of Grignard Reagents

The effect of reflected sunlight on the formation of Grignard reagents has been reported¹. In the present work irradiation of mixtures of magnesium turnings and organic halides in dry diethyl ether by the method of Evans et al.² gave elevated yields of Grignard reagents as compared to those achieved in control experiments carried out in the absence of light. Four organic halides: 2-bromofluorene, 2-bromothiophene, chlorobenzene and chlorodiphenylmethane were selected for study in the light of their reputed poor performance in the Grignard reaction³. A quantitative estimate of the amount of Grignard reagent formed in each reaction was carried out by the method of Gorog and Szepesi⁴. The experimental results are shown in the table.     

Cu2+/BH−4 reduction system: Synthetic utility and mode of action

Cu²⁺/BH⁻₄ offers a mild, method of reduction for aromatic and aliphatic tertiary nitro groups. Its mode of action has been studied, in comparison with related reagents, by deuterium isotope experiments.     

CIS- and Trans-Opening of Oxirane by Vinyl Grignard Reagents

The copper catalysed opening of oxiranes by Grignard reagents is a frequently used method for the generation of carbon-carbon bonds.^2–6 As only trans-opening has been reported,^3,4,6 we selected this method to prepare trans-2-vinyl-cyclohexanol 1 needed, as starting material, in our recent synthesis of a-methylene-butyrolactones.⁷     

Addition of Organocuprates to Cyclobutenyl Esters. Synthesis of (±)-Grandisol

The conjugate addition of organocuprates to certain esters², methylene lactones³, and enol lactones⁴ has been demonstrated. We report herein that cyclobutenyl esters readily undergo conjugate addition with these reagents, and that this reaction has been used to synthesize the boll weevil pheromone (±)-grandisol (18).⁵     

Selection of shift reagents for 17O NMR. Application to line assignments

Chemical shifts and line broadenings induced by a series of lanthanide dipivaloylmethanates Ln(dmp)₃ on the ¹⁷O NMR signal of methanol have been measured. The best high-field shift reagents are those containing the cations Tb⁺³ and Dy⁺³; very large shifts have been observed for even quite low concentrations of reagent. The shift reagents are able to discriminate between different oxygen functions and can, in principle, be used for line assignments.     

Facile synthesis of two oxocan derivatives using some chemical strategies

There are several studies for the synthesis of oxacycle derivatives using some reagents which require special conditions have been reported. The aim of this study was to synthesize two oxocan derivatives from either imidazole or 2-methylimidazole. The chemical structure was evaluated through both ¹H NMR and ¹³C NMR spectroscopic analysis. The results showed a moderate yielding from oxocan derivatives. It should be mentioned that reagents used in this investigation are not expensive and do not require special conditions for handling.     

An insight into copper catalyzed allylation of alkyl zinc halides. Comparison of reactivity profiles for catalytic and stoichiometric alkylzinc-copper reagents

The γ-selective allylation of catalytic and stoichiometric alkylzinc-cuprates have been kinetically studied. The reactivity profiles generated by allylation reactions of n-butylzinc chloride catalyzed by CuX compounds (X = I, Br, Cl, CN, SCN) and also catalyzed by n-butylzinc-copper reagents and di n-butylzinc-copper reagents were evaluated. Reactivity profiles for allylation of stoichiometric n-butylzinc-copper reagents and di n-butylzinc-copper reagents were also prepared. All CuX compounds have been screened for the preparation of Grignard reagent derived n-butylzinc-copper reagents and di n-butylzinc-copper reagents.The evaluation of the profiles indicates that the active catalyst might be RCu(X)ZnCl and also to some degree, R₂CuZnCl · ZnClX, which both could favor formation of γ-product. All data supports the reductive elimination of σ-allyl Cu (III) complex formed at vinylic terminal to give γ-allylated product with a quite slow isomerization to σ-allyl Cu (III) complex formed at allylic terminal to give α-allylated product. In the allylation mechanism of zinc cuprates, the role of counter ion, ZnCl⁺ has been discussed.     

Synthesis of Various Fused Heterocyclic Rings from Oxoindenyl Esters and their Pharmacological and Antimicrobial Evaluations

Methyl (Z)‐2‐O‐carboxyphenyl‐3‐(3,4,5‐trimethoxyphenyl)acrylate 1 was prepared and cyclized in different conditions to give the indenone 2 . Also, 1 was utilized to synthesize the isochroman dione derivatives 8 , 10 , 12 , and 13 and isoquinoline derivatives 16 and 18 . On the other hand, the reactions of 2 with some nucleophilic reagents such as Grignard reagents and hydrazine derivatives afforded the novel heterocyclic systems 3 , 4a , b , 5 , 6 , and 7 . Isochroman dione 12 was allowed to react with primary amines to give 14 , 15 , 17 , and 19 . The structures of the synthesized new compounds have been elucidated by spectroscopic data: IR, ¹H‐NMR, ¹³C‐NMR, mass spectra, and elemental analyses. The antimicrobial and anticancer activities have been evaluated.     

Paradigm Shift from Alkaline (Earth) Metals to Early Transition Metals in Fluoroorganometal Chemistry: Perfluoroalkyl Titanocene(III) Reagents Prepared via Not Titanocene(II) but Titanocene(III) Species

Perfluoroalkyl (R_F) titanocene reagents [Cp₂Ti^IIIR_F] synthesized via [Cp₂Ti^IIICl] rather than [Cp₂Ti^II] show new types of perfluoroalkylation reactions. The [Cp₂Ti^IIIR_F] reagents exhibit a wide variety of reactivity with carbonyl compounds including esters and nitriles, and selectivities far higher than those reported for conventional R_FLi and R_FMgX reagents.     

Syntheses of azo dyes containing 4,5-diphenylimidazole and their evaluation as analytical reagents

Eight azo dyes containing the 4,5-diphenylimidazole group have been synthesized, and their potential for determinations of metals has been studied spectrophotometrically. Of these reagents, the pyridylazo and quinolylazo derivatives are suitable as chromogenic reagents, the best being 2-(quinolylazo)-4,5-diphenylimidazole (QAI), which reacts with several metal ions. The copper and mercury complexes of QAI show molar absorptivities of the order of 80 000 l mol^?1 cm^?1.     

Ein zweikerniger tetraphenylcyclobutadien-nickel(0)-komplex mit cyclooctatetraen als brückenligand

Tetraphenylcyclobutadiene(η⁴-cyclooctatetraene)nickel(0) reacts with a variety of reagents, e.g. lithium, CpCo(C₂H₄)₂ or benzonitrile, to give the binuclear complex bis(tetraphenylcyclobutadiene-nickel(0))-μ₂-η⁴-cyclooctatetraene, which structure has been assigned using IR, UV, ¹H NMR and mass spectral methods, also the properties and reactions have been investigated.