A New Colorimetric Reagent for Carbon Monoxide

Abstract

A new colorimetric reagent for carbon monoxide is described. The reaction sequence apparently involves reduction by carbon monoxide of [PdCl₄]^2-, which then reduces [Fe^III EDTA]^? to [Fe^IIEDTA]^2-. The latter undergoes ligand exchange with 2,2′-dipyridyl or 1,10-phenanthroline to form the more stable colored [FeL₃]²⁺, which is measured spectrophotometrically. Sodium molybdate enhances the overall reaction. The color intensity produced is non-linear but reproducible. The method is unique in that a soluble colored compound is produced rather than a metal sol.     

Rhodium-catalyzed convenient synthesis of functionalized tetrahydronaphthalenes

Convenient as well as convergent synthesis of functionalized tetrahydronaphthalenes has been accomplished under mild reaction conditions by the cationic rhodium(I)/H₈-BINAP complex-catalyzed [2+2+2] cycloaddition of 1,7-octadiyne derivatives with functionalized monoynes. The effect of the diyne tether lengths was investigated, which revealed that 1,6-heptadiyne and 1,7-octadiyne exhibit higher reactivity than 1,8-nonadiyne. Mechanistic studies indicated that the present rhodium-catalyzed [2+2+2] cycloaddition proceeds through the rhodacyclopentadiene intermediate generated by oxidative coupling of a diyne with rhodium. On the other hand, in the reactions of diynes and dimethyl acetylenedicarboxylate, the rhodacyclopentadiene intermediate generated by oxidative coupling of a diyne and a monoyne with rhodium would also be involved.     

Chemical Oxidative Degradation of Acridine Orange Dye in Aqueous Solution by Fenton's Reagent

Degradation of acridine orange (AO) in aqueous solution by Fenton's reagent (Fe²⁺ and H₂O₂) was investigated. The effects of different reaction parameters such as initial AO concentration, pH value of solution, ferrous concentration, hydrogen peroxide concentration, and the presence of chloride ion on the oxidative degradation of AO were investigated. Under optimum conditions, 2 mM H₂O₂, 0.4 mM Fe²⁺ and pH 3.0, the initial 0.2 mM AO solution was reduced by 95.8% within 10 min. The primary intermediates of the degradation reaction of AO were identified. The analytical results indicated that the N‐de‐methylation degradation of AO dye took place in a stepwise manner to yield mono‐, di‐, tri‐, and tetra‐N‐de‐methylated AO species generated during the Fenton process. The probable degradation pathways were proposed and discussed.     

Fenton’s reagent for kinetic determinations

The use of the Fenton’s reagent (FR) (a mixture of H₂O₂ and Fe²⁺) for the kinetic determination of individual chemical species is proposed. The possibilities of the reagent arise from the oxidant power of intermediate species generated during the slow oxidation of Fe²⁺ by H₂O₂, but very few analytical applications of the reagent can be found. The oxidation of organic compounds (known as the Fenton reaction) is in fact an induced chain reaction that proceeds to an extension which is influenced by the reaction conditions. Experimental design has been used for optimization thinking of the analytical application. The pesticide atrazine has been used as analyte to test the analytical possibilities of the FR. Partial least squares regression (PLS), applied to reaction profiles between 206 and 270 nm, was used as algorithm to make the calibration model. Atrazine concentrations ranging from 0.46 to 13.4×10⁻⁵ M have been used for calibration, and mean errors under 2.5% both for calibration and validation have been found. Other classical methods of calibration such as those using absolute values of absorbance, initial rates, etc. gave poor results in the cases considered. According to the study of interferences, the main drawback of the reagent is the lack of selectivity, but some possible ways of improving it are discussed. The method was applied for the determination of atrazine in several commercial atrazine-based pesticide preparations. In general, good results were obtained when compared with those found by gas-liquid chromatography as a reference. Recovery studies also gave satisfactory results.     

A Convenient Preparation of Fluorinating Reagent F‐TEDA Bearing Bisphenylsulfonylimide Counterion and Its Fluorination to Oxindoles

The direct preparation of a kind of fluorinating reagent 1 [F‐TEDA‐N(SO₂Ph)₂] was realized in high yield via the complexation of N‐fluorobenzenesulfonimide (NFSI) with 1‐(chloromethyl)‐1,4‐diazabicyclo[2.2.2]octan‐1‐ium N′,N′‐bis‐(benzenesulfonylimide) salt. In its fluorination to oxindoles, the fluorinating products 6 were afforded in moderate to high yields.     

[(SIPr)Ag(CF2H)]: A Shelf-Stable,Versatile Difluoromethylation Reagent

Due to its unique physical and electrophilic properties, the difluoromethyl group (−CF₂H) has been playing an irreplaceable role in the field of pharmaceutical and agrochemical industry. Methods that could efficiently incorporate the difluoromethyl group into the target molecules are increasing in the recent years. Developing a stable and efficient difluoromethylating reagent is thus highly attractive. In this review, we describe the development of a nucleophilic difluoromethylation reagent [(SIPr)Ag(CF₂H)], including its elemental reaction, difluoromethylation reaction with different types of electrophiles, and its application in the synthesis of a nucleophilic and an electrophilic difluoromethylthiolating reagent.     

Ionic Liquid in Synthesis: A Phase Transfer Reagent and a Redox Mediating Medium

Ionic liquids (ILs) with chloride anion or bromide anion were attempted as a phase transfer reagent to depolymerize MX₂ (M = Pt, Pd; X = Br, Cl) in chloroform for reaction with 2,2′‐bipyridine (= bpy) to give the (bpy)MX₂ product. Supersonic irradiation of equiv‐molar bpy, PdX₂, and IL in CHCl₃ produced almost quantitative precipitate of (bpy)PdX₂ in a short time at ambient temperature, where IL is either [BEIm]Br or [BMIm]Br. That is, ILs and sono‐techniques assisted greatly on the synthesis of (bpy)PdX₂. For preparation of (bpy)PtX₂, nonetheless, free bpy always remained in mixture even after a long time of supersonic treatment. The system of equiv‐molar bpy, PtBr₂, and IL in CHCl₃, produced yellow (bpy)PtBr₂ and orange (bpy)PtBr₄, both being characterized with ¹H NMR and ¹⁹⁵Pt NMR in d₆‐Me₂SO as well as with single crystal X‐ray diffraction. Overall for PtX₂ reactions with halide anions in highly polar environments attributable to ILs, the redox pathway becomes important in that Pt(II) transforms to Pt(IV) to yield (bpy)PtBr₂ and (bpy)PtBr₄.     

Homoleptic Zincate‐Promoted Room‐Temperature Halogen–Metal Exchange of Bromopyridines

Homoleptic lithium tri‐ and tetraalkyl zincates were reacted with a set of bromopyridines. Efficient and chemoselective bromine–metal exchanges were realized at room temperature with a substoichiometric amount of nBu₄ZnLi₂?TMEDA reagent (1/3 equiv; TMEDA=N,N,N′,N′‐tetramethylethylenediamine). This reactivity contrasted with that of tBu₄ZnLi₂?TMEDA, which was inefficient below one equivalent. DFT calculations allowed us to rationalize the formation of N???Li stabilized polypyridyl zincates in the reaction. The one‐pot difunctionalization of dibromopyridines was also realized using the reagent stoichiometrically. The direct creation of C? Zn bonds in bromopyridines enabled us to perform efficient Negishi‐type cross‐couplings.     

A Facile Preparation of Tebbe Reagent and its Subsequent Reactions

A facile preparation of Tebbe reagent (1) by reacting AlMe₃ solution with Cp₁TiCl₂ is reported. After complete removal of solvent and excess of AlMe₃, the crude Tebbe reagent could be used without purification to react with ketones in a Wittig-type manner.     

Improved Negishi Cross‐Coupling Reactions of an Organozinc Reagent Derived from l‐Aspartic Acid with Monohalopyridines

The Negishi cross‐coupling reaction of an organozinc derivative prepared from protected l ‐aspartic acid with monohalopyridines was improved by employing a combination catalyst of Pd₂(dba)₃ and P(2‐furyl)₃ and removing an extra Zn from the organozinc reagent via centrifugation. The reactivity of halogenated pyridines (Cl, Br, I) with substituents at the C2, C3, and C4 positions of the pyridine ring was investigated, and it was found that the use of 4‐iodopyridine as a substrate gave the best yield (90%) for the cross‐coupling reaction.     

Synthesis of phospholipids containing perfluorooctyl group and their interfacial properties

Highly fluorinated single-chained and/or double-chained phospholipids containing the perfluorooctyl group as the terminal segment of hydrophobic chains and a phosphocholine moiety as the hydrophilic headgroup were synthesized in order to investigate the effect of fluorinated segments on the stability of phospholipid monolayers formed at the air-water interface. Judging from the equilibrium spreading pressures (π_es) of their monolayers at the air-water interface, all of the fluorinated phospholipids formed more stable monolayers than the corresponding non-fluorinated counterparts. In addition, the fluorinated double-chained phosphatidylcholine containing C-C triple bond (monoyne group) formed stable and fluid vesicle membranes in water, although the single-chained phospholipids did not form vesicle membranes but micellar solutions under the present conditions.     

Oxidative addition of heteroaromatic halides to Negishi reagent and subsequent cross-coupling reactions

Heteroarylzirconocene halides were prepared via the oxidative addition of heteroaryl halides to the Negishi reagent ‘Cp₂ZrBu₂’. The palladium-catalyzed cross-coupling of the in situ generated organozirconium reagents with functionalized aryl and heteroaryl halides proceeded smoothly in the presence of CuCl to produce the cross-coupling products in high yields.     

NEW PRODUCTS OF REACTION OF LAWESSON'S REAGENT WITH DIOLS

Reaction of the Lawesson's reagent (LR) with aliphatic 1,2- and 1,3-diols as well as with aromatic 2,2′-dihydroxybiphenyl led to new products. Stable di-tert-butylammonium salts of bis-anisyldithiophosphonic acids 6 were isolated and were then converted into unique 9-, 9-, and 10-membered cyclic disulfides 7 and into S,S-dimethyl esters 8. The salts of bis-anisyldithiophosphonic acids 6 were shown to be capable of splitting the disulfide bond of Ellman's reagent.     

Advantages of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes as Metallocene Sources Towards Other Synthetically used Systems

Active species for synthetic and catalytic applications are formed from well defined complexes or mixtures of compounds. For group 4 metallocenes, three pathways for the formation of the reactive complex fragment [Cp′₂M] are known: (i) reductive mixtures and well defined complexes which are able to form the metallocene fragments either by (ii) addition or (iii) substitution reactions. In this account for each of theses systems (i)–(iii) a prominent example will be discussed in detail, (i) the Negishi reagent Cp₂ZrCl₂/n-BuLi, (ii) bis(η⁵ : η¹-pentafulvene) complexes and (iii) metallocene bis(trimethylsilyl)acetylene complexes, to show the advantages and the disadvantages for each of these methods for synthetic applications. This account summarizes some main advantages of group 4 metallocene bis(trimethylsilyl)acetylene complexes as metallocene generating agents over other synthetically used systems. For each of the special purposes, all described systems have advantages as well as disadvantages. The aim of this overview is to help synthetic chemists in selecting the most effective system on the basis of [Cp′₂M] (M=Ti, Zr) for synthetic or catalytic puposes.     

Powerful Fluoroalkoxy Molybdenum(V) Reagent for Selective Oxidative Arene Coupling Reaction

We introduce the novel fluoroalkoxy molybdenum(V) reagent 1 which has superior reactivity and selectivity in comparison to MoCl₅ or the MoCl₅/TiCl₄ reagent mixture in the oxidative coupling reactions of aryls. Common side reactions, such as chlorination and/or oligomer formation, are drastically diminished creating a powerful and useful reagent for oxidative coupling. Theoretical treatment of the reagent interaction with 1,2‐dimethoxybenzene‐type substrates indicates an inner‐sphere electron transfer followed by a radical cationic reaction pathway for the oxidative‐coupling process. EPR spectroscopic and electrochemical studies, X‐ray analyses, computational investigations, and the experimental scope provide a highly consistent picture. The substitution of chlorido ligands by hexafluoroisopropoxido moieties seems to boost both the reactivity and selectivity of the metal center which might be applied to other reagents as well.     

Thermal analysis of 1,4‐di[n′‐(quinolyl)]buta‐1,3‐diynes,structure, and topo‐oligomerization: Polymerization of 3‐ethynylquinoline with the triethyl aluminum/vanadium 2,4‐pentanedionate catalyst system

Conjugated 1,4‐bis(n′‐quinolyl)‐1,3‐butadiynes were obtained through the oxidative dimerization of the corresponding n′‐ethynylquinolines catalyzed by cuprous chloride. Differential scanning calorimetry analysis of the 1,4‐bis[n′‐(quinolyl)]buta‐1,3‐diyne molecules produced evidence of a syn–anti rotational equilibrium around the 1,3‐diyne axis and an irreversible transformation into a thermopolymer. The topo‐oligomerization of 1,4‐bis[3′‐(quinolyl)]buta‐1,3‐diyne, which took place by irradiation with sunlight, was investigated with matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. Accurate X‐ray molecular structure and refinement analysis of 1,4‐bis[3′‐(quinolyl)]buta‐1,3‐diyne was conducted. The molecular crystalline packing consisted of parallel arrays of two groups of centrosymmetric molecules (antirotamer) in a herringbone assemblage in the solid state. The polymerization of 3‐ethynylquinoline was carried out with the AlEt₃/V(acac)₃ system to produce a mixture of 1,2,4‐ and 1,3,5‐tris(3′‐quinolyl)benzene cyclotrimers and a trans–cisoid polyene structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6031–6040, 2004     

Reversed-phase high performance liquid chromatographic separation of diastereomers of β-amino alcohols and microwave assisted synthesis of Marfey's reagent,its chiral variants and diastereomers

Ten chiral derivatizing reagents (CDRs) were synthesized by replacing the l-Ala–NH₂ moiety in Marfey's reagent (MR) by seven l-amino acid amides and three l-amino acids employing microwave irradiation (MW) and were characterized. Ten racemic amino alcohols were derivatized with these CDRs under MW. The diastereomers were separated on a reversed-phase C₁₈ column using binary mixtures of acetonitrile with aqueous trifluoroacetic acid (TFA) and triethylammonium phosphate buffer (TEAP). In general, amino acid variants of MR provided better separation of diastereomers in comparison to amino acid amide variants. The method was also found successful for the separation of 20 diastereomers from a mixture.     

Kinetic Study of the Thermal Polymerization Reactions between Diazide and Internal Diyne

The reaction kinetics between diazide(4,4′‐biphenyl dibenzyl azide) and internal diyne(bis[2‐(phenyl)ethynyl]dimethylsilane) was studied in this study by means of differential scanning calorimetry (DSC) and nuclear magnetic resonance spectra (¹H NMR). DSC was carried out to analyze the reaction in bulk polymerization condition, whereas ¹H NMR for solution reaction polymerization. The apparent activation energy (e_α) calculated by Kissinger's method was 90.83 kJ/mol, which was confirmed by Friedman's method, and 87.67 kJ/mol by ¹H NMR, respectively. The polymerization between the diazide and internal diyne was the second‐order reaction based on calculation from both of DSC and ¹H NMR.     

Kinetic studies of CuBr-PMDETA catalyzed 1,3-dipolar cycloaddition polymerization

The kinetics for the reaction of diazide (4,4′-biphenyl dibenzyl azide) and diyne (dipropargyl bisphenol A) catalyzed by CuBr-PMDETA (N, N, N′, N″, N″-pentamethyldiethylenetriamine) was studied in this paper by means of nuclear magnetic resonance spectra (¹H-NMR) and differential scanning calorimetry (DSC). ¹H-NMR was carried out to analyze solution polymerizations under different CuBr-PMDETA ratios in DMSO-d₆. The results showed that CuBr-PMDETA catalytic system was easy to be oxidation under ambient condition. However, different CuBr-PMDETA ratios influenced the catalytic efficiency and the optimal ratios were found in nitrogen gas. DSC was carried out to analyze bulk polymerizations. The results showed that the apparent activation energy (E_α) calculated by Kissinger's method was 69.2 kJ/mol, which was confirmed by Friedman's method. The two tests indicated that the catalyzed polymerization of diazide and diyne was a second order reaction.     

One‐Pot Approach to Organo‐Phosphorus–Chalcogen Macrocycles Incorporating Double OP(S)SCn or OP(Se)SeCn Scaffolds: A Synthetic and Structural Study

The development of new methodology for the preparation of functional macrocycles with practical applications is an important research area in macromolecular science. In this study, we report a new one‐pot route for the synthesis of a series of macro‐heterocycles by incorporating two phosphorus atoms and two chalcogen atoms and two oxygen atoms (double OP(S)SC_n or OP(Se)SeC_n scaffolds). The three‐component condensation reactions of 2,4‐diferrocenyl‐1,3,2,4‐diathiadiphosphetane 2,4‐disulfide ( FcLR , a ferrocene analogue of Lawesson's reagent) or 2,4‐bis(4‐methoxyphenyl)‐1,3,2,4‐dithiadiphosphetane 2,4‐disulfide ( LR , Lawesson's reagent), or 2,4‐diphenyl‐1,3,2,4‐diselenadiphosphetane 2,4‐diselenide ( WR , Woollins’ reagent), disodium alkenyl‐diols, and dihalogenated alkanes are performed, giving rise to soluble and air or moisture‐stable macrocycles in good‐to‐excellent yields (up to 92 %). This is the first systemically preparative and readily scalable example of one‐pot ring opening/ring extending reaction of three‐components to prepare phosphorus–chalcogen containing macrocycles. We also provide a systematic crystallographic study.