Direct oxidative conversion of alkyl halides into nitriles with molecular iodine and 1,3-diiodo-5,5-dimethylhydantoin in aq ammonia

Various benzylic halides were smoothly and directly converted into the corresponding aromatic nitriles in high yields using molecular iodine and 1,3-diiodo-5,5-dimethylhydantoin, respectively, in aq ammonia. Similarly, primary alkyl halides were also converted into corresponding nitriles in moderate to good yields using molecular iodine and 1,3-diiodo-5,5-dimethylhydantoin in aq ammonia, although a long reaction time was required. The present reaction is a new method for the preparation of aromatic nitriles from benzylic halides and a new method for the conversion of alkyl halides into corresponding nitriles with retention of the number of carbon atoms.     

The determination of iodine in biological and environmental standard reference materials

Iodine is an element with excellent intrinsic sensitivity when determined by thermal neutron activation. However, in most real samples, the preponderance of chlorine and bromine, relative to iodine, makes the direct determination of iodine virtually impossible. Over the past 20 years, there probably have been as many publications on the separation of iodine as there have been for any other radionuclide. Upon review, however, the methods are essentially the same. After irradiation, the samples are subjected to a rapid destructive process to free the iodine from the matrix and then the iodine is separated from the other halides either by liquid-liquid extraction or by liquid ion exchange. Both of these procedures are, however, rather complex and do not effect a complete separation of the halides in one pass. In the work presented here, a simple procedure is described for the quantitative separation of iodine from chlorine. The procedure utilizes a gas phase separation on hydrated manganese dioxide with iodine collected on silvered quartz wool. The described procedure has been used for the determination of iodine in numerous new and old SRM's at the NBS.     

Indium-mediated cleavage of diphenyl diselenide and diphenyl disulfide: efficient one-pot synthesis of unsymmetrical diorganyl selenides, sulfides, and selenoesters

A convenient and efficient method was developed for the synthesis of alkyl phenyl selenides, sulfides, and selenoesters in one-pot reaction by using indium metal. The reaction showed the selectivity for tert-alkyl, benzylic, and allylic halides over primary and secondary alkyl halides. For the reaction of primary and secondary alkyl iodides and bromides, the yields of selenides were improved by the addition of a catalytic amount of iodine.     

On the Radical Nature of Iron‐Catalyzed Cross‐Coupling Reactions

The radical nature of iron‐catalyzed cross‐coupling between Grignard reagents and alkyl halides has been studied by using a combination of competitive kinetic experiments and DFT calculations. In contrast to the corresponding coupling with aryl halides, which commences through a classical two‐electron oxidative addition/reductive elimination sequence, the presented data suggest that alkyl halides react through an atom‐transfer‐initiated radical pathway. Furthermore, a general iodine‐based quenching methodology was developed to enable the determination of highly accurate concentrations of Grignard reagents, a capability that facilitates and increases the information output of kinetic investigations based on these substrates.     

Polymer-supported organotin reagents for regioselective halogenation of aromatic amines

[reaction: see text] Polymer-supported triorganotin halides were used in the halogenation reaction of aromatic amines. Treatment of aromatic amines with n-butyllithium and polymer-supported organotin halides gave the corresponding polymer-bound N-triorganostannylamines, which by treatment with bromine or iodine monochloride gave the para-halogenated aromatic amines with high yields and high selectivities. The polymer-supported organotin halides reagents regenerated during the course of the halogenation reaction can be reused without loss of efficiency. The presence of tin residues in halogenated aromatic amines was also investigated and evaluated at under 20 ppm after three runs.     

Metal-free one-pot oxidative conversion of benzylic alcohols and benzylic halides into aromatic amides with molecular iodine in aq ammonia, and hydrogen peroxide

Various primary alcohols, particularly benzylic alcohols, could be converted into the corresponding aromatic amides in good yields in a one-pot manner by treatment with molecular iodine in aq. NH₃, followed by reaction with ∼30% aq H₂O₂. Similarly, various benzylic halides could be also converted into the corresponding aromatic amides in good yields in a one-pot manner by treatment with molecular iodine in aq NH₃, followed by reaction with ∼30% aq H₂O₂. The present reactions involve the metal-free one-pot oxidative conversion of benzylic alcohols and benzylic halides into the corresponding aromatic amides, respectively.     

Determination of organotrithiocarbonates with iodine and iodine halides in non-aqueous media

The determination of organotrithiocarbonates with iodine and iodine halides in acetonitrile medium by visual and potentiometric method is described. The visual end-point is indicated by a sharp colour change from straw yellow to deep yellow caused by the first drop of oxidant solution in excess. Potentiometric titrations are performed with antimony or modified calomel reference electrodes and a bright platinum wire as an indicator electrode. The proposed method is simple, requires very little time because of the rapidity of the reaction, and the minimum of apparatus.     

Sequential copper-catalyzed vinylation/cyclization: an efficient synthesis of functionalized oxazoles

A modular and practical synthesis of highly substituted oxazoles has been developed. The transformation consists of a sequential copper-catalyzed amidation of vinyl halides followed by cyclization promoted by iodine. A wide variety of functionalized oxazoles and polyazoles can be obtained in a selective manner from simple and easily accessible precursors.     

Halodephosphorylation of α,β-unsaturated phosphonic acid monoesters

Reaction of α,β-ethylenic and acetylenic phosphonic acid monoesters with (biscollidine)iodine(I) or (biscollidine)bromine(I) hexafluorophosphate led to α,β-unsaturated halides by, without precedent, dephosphorylation reactions.     

Iodine as an efficient and available activator of sodium and potassium halides in carbon dioxide addition to epoxides

Sodium and potassium halides in combination with molecular iodine are efficient catalysts for the solvent-free addition of CO₂ (10–56 atm) to epoxides giving organic carbonates.

     

Charge-transfer-to-solvent-driven dissolution dynamics of I- (H2O)2-5 upon excitation: excited-state ab initio molecular dynamics simulations

In contrast to the extensive theoretical investigation of the solvation phenomena, the dissolution phenomena have hardly been investigated theoretically. Upon the excitation of hydrated halides, which are important substances in atmospheric chemistry, an excess electron transfers from the anionic precursor (halide anion) to the solvent and is stabilized by the water cluster. This results in the dissociation of hydrated halides into halide radicals and electron-water clusters. Here we demonstrate the charge-transfer-to-solvent (CTTS)-driven femtosecond-scale dissolution dynamics for I-(H2O)n=2-5 clusters using excited state (ES) ab initio molecular dynamics (AIMD) simulations employing the complete-active-space self-consistent-field (CASSCF) method. This study shows that after the iodine radical is released from I-(H2O)n=2-5, a simple population decay is observed for small clusters (2 相似文献   

Determination of the total amount of organically bound chlorine,bromine and iodine in environmental samples by instrumental neutron activation analysis

The determination of chlorine, bromine and iodine present as non-polar, hydrophobic hydrocarbons in environmental samples is reported. The organohalogen compounds are separated from water into an organic phase by on-site liquid—liquid extraction, and from biological material by procedures based on lipid phase extraction and codistillation. After removal of inorganic halides by washing with water and concentration of the sample by evaporation of the solvent, the resulting extracts are analyzed for their chlorine, bromine and iodine contents by instrumental neutron activation analysis. Strict attention is paid to the possibility of contamination in every step of the procedure. Background values in routine analysis are approximately 100–200 ng of chlorine, <5 ng of bromine and <3 ng of iodine.     

Uranyl Schiff base complexes as new heterogeneous catalysts for halogen exchange reactions between alkyl halides and elemental halogens

Mild and effective procedure for the halogen exchange reaction of alkyl halides with elemental iodine and bromine catalyzed with uranyl Schiff base complexes in various aprotic solvents was developed. Corresponding alkyl bromides and iodides were obtained with high yields within 20—70 min. The structures of the target products were confirmed by physical and spectroscopic data.     

Darstellung neuer Halogeno-kohlenoxid-Komplexe des Eisens

The dicarbonyl complex Fe(CO)₂(TP)I₂ is obtained by CO-substitution of Fe(CO)₄I₂ with 1,1.1-tris(diphenylphosphinomethylene)ethane (TP), in which the tridentate phosphorus ligand functions only bidentate. By a further reaction with iodine the tetraiodo complex Fe(CO)₂(TP)I₄ is formed, in which ever two iodine atoms are bonded to the metal and to the phosphorus. The same compound type is also formed by the oxydation of the trigonal-bipyramidally configurated Fe(CO₂)TP with the halides chlorine, bromine and iodine in a molar ratio 1:2.     

Secondary processes in mass spectrometry of alkylmercury halides

The sensitivity of the mass spectrometer towards RHgX alkylmercury halides in the electron impact technique was found to decrease in the order X = Cl > Br > I. The intense peaks corresponding to the more heavy halides registered in the mass spectra of RHgX were shown to arise owing to the secondary processes of halogen exchange occurring in the mass spectrometer. The non-volatile bromine and iodine compounds adsorbed in some form on metallic surfaces of the ionization chamber (so-called ‘memory effect’) could be the source of heavy halogens. These reactions are hampered in chemical ionization mass spectrometry under the sufficiently high pressure of the reagent gas (NH₃).     

Research on a number of substituted arylamides of dithiocarboxylic acids

Dithiomalonic acid diarylamldes are cyclized to 3,5-diarylamino-1,2-dithiolium halides by oxidation with an equivalent amount of bromine (iodine) in chloroform solution; the same amides are cyclized to 4-bromo-3,5-diarylamino-1,2-dithiolium bromides with excess bromine and to 3-arylamino-5-arylimino-1,2-dithiols in alkaline media with potassium ferricyanide. The behavior of the synthesized substituted 1,2-dithiols with respect to various reagents was studied.     

Reactions of hypervalent iodine reagents with palladium: mechanisms and applications in organic synthesis

The unique reactivity of hypervalent iodine reagents with Pd0 and PdII complexes has been exploited for a variety of synthetically useful organic transformations. For example, IIII reagents have been used in place of aryl halides for diverse Pd-catalyzed C-C and C-heteroatom bond-forming cross-coupling reactions. In addition, these reagents have found application in Pd-catalyzed oxidation reactions, including the oxidative functionalization of C-H bonds and the 1,2-aminooxygenation of olefinic substrates. This review discusses both the synthetic utility and the interesting mechanistic features of these transformations.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. XLI. Darstellung und Thermolyseprodukte von Methyltitanhalogeniden

Contributions to the Chemistry of Transition Metal Alkyl Compounds. XLI. Preparation and Thermolysis Products of Methyl Titanium Halides (CH₃)_nTiX_{4 ? n} derivatives (X = Cl, Br, I) can be prepared by comproportionation reactions of tetramethyl titanium with titanium tetrahalides at deep temperature. Furthermore, the methyl titanium iodides are formed from tetramethyl titanium and iodine. Thermolysis of CH₃TiX₃ derivatives yields titanium(III) halides. At decomposition of the (CH₃)₂TiX₂ compounds in ether solution titanium(II) halides are obtained in a fine-distributed, very reactive form.     

Preparation of 2-Picolylarsonic Acid and its Reductive Cleavage by Ascorbic Acid/Iodine and by Thiophenol

Contrary to dialkylaminoethyl halides, 2-picolyl chloride reacts with alkaline arsenite to give nearly quantitative yields 2-picolylarsonic acid. This acid is decomposed by ascorbic acid in the presence of catalytic amounts of iodine to 2-picoline and arsenious acid, most likely by hydride transfer from the ascorbic acid. Thiophenol decomposes this arsonic acid very quickly to 2-picoline, diphenyl disulfide and triphenyl trithioarsenite. In this case a proton from the thiophenol is transferred to the incipient 2-picolyl carbanion.     

From metal‐catalyzed radical telomerization to metal‐catalyzed radical polymerization of vinyl chloride: Toward living radical polymerization of vinyl chloride

The metal‐catalyzed radical polymerization of vinyl chloride (VC) in ortho‐dichlorobenzene initiated with various activated halides, such as α,α‐dihaloalkanes, α,α,α‐trihaloalkanes, perfloroalkyl halides, benzyl halides, pseudohalides, allyl halides, sulfonyl halides, α‐haloesters, α‐halonitriles, and imidyl halides, in the presence of Cu(0)/2,2′‐bipyridine, Fe(0)/o‐phenantroline, TiCp₂Cl₂, and other metal catalysts is reported. The formation of the monoadduct between the initiator and VC was achieved with all catalysts. However, propagation was observed only for metals in their zero oxidation state because they were able to reinitiate from geminal dihalo or allylic chloride structures. Poly(vinyl chloride) with molecular weights larger then the theoretical limit allowed by chain transfer to VC were obtained even at 130 °C. In addition, the most elemental features of a living radical polymerization, such as a linear dependence of the molecular weight and a decrease of polydispersity with conversion, were observed for the most promising systems based on iodine‐containing initiators and Cu(0), that is, I? CH₂? Ph? CH₂? I/Cu(0)/bpy (where bpy = 2,2′‐bipyridyl), at 130 °C. However, because of the formation of inactive species via chain transfer to VC and other side reactions, the observed conversions were in most cases lower than 40%. A mechanistic interpretation of the chain transfer to monomer in the presence of Cu species is proposed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3392–3418, 2001