Vinylation of Alkyl Halides Catalyzed by Palladium Catalyst

The palladium catalyzed vinylation of alkyl halides, especially benzyl chlorides, with a variety of olefins has been studied. A possible free radical mechanism was proposed.     

Carbonylation of Tertiary Alkyl Halides Synthesis of Pivaloyl Halides

The carbonylation of tert-butyl halides in a two-phase system, RSO₃H/CCl₄, under carbon monoxide pressure affords the corresponding pivaloyl halides in good yields and selectivities.     

Nickel-Catalyzed Direct Electrochemical Cross-Coupling between Aryl Halides and Activated Alkyl Halides

The electrochemical reduction of a mixture of aryl halides and activated alkyl halides in DMF in the presence of catalytic amount of NiBr(2)bipy leads to cross-coupling products in good to high yields. The method applies to the synthesis of alpha-aryl ketones, alpha-aryl esters, and allylated compounds from readily available organic halides. Optimization of the process has been obtained by slowly adding the most reactive organic halide (usually the activated alkyl halide) during the electrolysis which is best conducted at 70 degrees C when aryl bromides are involved.     

Symmetrical and Unsymmetrical Coupling of Alkyl Halides Mediated by Grignard Reaction

A simple method for extending the carbon chain via the coupling of alkyl or aryl halides has been developed. The versatility of this reaction has been demonstrated by symmetrical and unsymmetrical coupling of alkyl, alkenyl or alkynyl halides.     

Nickel-Catalyzed Electrochemical Reductive Relay Cross-Coupling of Alkyl Halides to Aryl Halides

A highly regioselective Ni-catalyzed electrochemical reductive relay cross-coupling between an aryl halide and an alkyl halide has been developed in an undivided cell. Various functional groups are tolerated under these mild reaction conditions, which provides an alternative approach for the synthesis of 1,1-diarylalkanes.     

Cross‐Electrophile Coupling of Vinyl Halides with Alkyl Halides

An improved method for the reductive coupling of aryl and vinyl bromides with alkyl halides that gave high yields for a variety of substrates at room temperature with a low (2.5 to 0.5 mol %) catalyst loading is presented. Under the optimized conditions, difficult substrates, such as unhindered alkenyl bromides, can be coupled to give the desired olefins with minimal diene formation and good stereoretention. These improved conditions also worked well for aryl bromides. For example, a gram‐scale reaction was demonstrated with 0.5 mol % catalyst loading, whereas reactions at 10 mol % catalyst loading completed in as little as 20 minutes. Finally, a low‐cost single‐component pre‐catalyst, (bpy)NiI₂ (bpy=2,2′‐bipyridine) that is both air‐ and moisture‐stable over a period of months was introduced.     

Electrophoretic Separation and Quantitative Determination of Halides and Iodohalides of the Choline Series

Iodohalides and halides of the choline series were separated by capillary electrophoresis using an unmodified fused-silica capillary. The developed procedures ensure the determination of iodohalides in the presence of ammonium ions. They were tested in the analysis of model pharmaceuticals of the composition organic iodohalide : polyvinyl pyrrolidone (PVP) (1 : 4). The proposed procedure ensures the estimation of the concentration of choline-mimetic substances in the range from 1 × 10^–5 to 5 × 10^–3 M.     

Photocatalyzed Aminomethylation of Alkyl Halides Enabled by Sterically Hindered N-Substituents

The catalytic C(sp³)−C(sp³) coupling of alkyl halides and tertiary amines offers a promising tool for the rapid decoration of amine skeletons. However, this approach has not been well established, partially due to the challenges in precisely distinguishing and controlling the reactivity of amine-coupling partners and their product homologues. Herein, we developed a metal-free photocatalytic system for the aminomethylation of alkyl halides through radical-involved C(sp³)−C(sp³) bond formation, allowing for the synthesis of sterically congested tertiary amines that are of interest in organic synthesis but not easily prepared by other methods. Mechanistic studies disclosed that sterically hindered N-substituents are key to activate the amine coupling partners by tuning their redox potentials to drive the reaction forward.     

Barbier-Type Addition of Alkyl Halides to Aldehydes Promoted by Pentacarbonyliron

The yield and structure of products of the Barbier-type addition of alkyl halides (perfluorobutyl iodide, allyl bromide, allyl iodide, and hexyl iodide) to para-substituted benzaldehydes in the presence of pentacarbonyliron are essentially determined, on the one hand, by the ability of alkyl halide to be reduced to carbanion and, on the other, by the electrophilicity of the aldehyde reaction center which in turn depends on the nature of para-substituent in the aromatic ring.     

Cobalt-Catalyzed Asymmetric Remote Borylation of Alkyl Halides

Enantioselective functionalization of racemic alkyl halides is an efficient strategy to assemble complex chiral molecules, but remains one of the biggest challenges in organic chemistry. The distant and selective activation of unreactive C−H bonds in alkyl halides has received growing interest as it enables rapid generation of molecular complexity from simple building blocks. Here, we reported a cobalt-catalyzed remote borylation of alkyl (pseudo)halides (alkyl−X, X=I, Br, Cl, OTs) with pinacolborane (HBpin) and presented a robust approach for the generation of valuable chiral secondary organoboronates from racemic alkyl halides. This migration borylation reaction is compatible with primary, secondary, and tertiary bromides, offering direct access to a broad range of alkylboronates. The extension of this catalytic system to the borylation of aryl halides was also demonstrated. Preliminary mechanistic studies revealed that this remote borylation involved a radical reaction pathway.     

Direct vs Indirect Grafting of Alkyl and Aryl Halides

The direct and indirect electrochemical grafting of alkyl and aryl halides (RX, ArX) on carbon, metal and polymer surfaces is examined. Their electrochemical reduction occurs at highly negative potential in organic solvents and very often produces carbanions because the reduction potentials of RX and ArX are more negative than those of their corresponding radicals. Therefore, direct electrografting of alkyl and aryl radicals generated from RX and ArX is not easy to perform. This obstacle is overcome using aryl radicals derived from the 2,6-dimethylbenzenediazonium salt (2,6-DMBD), which do not react on the electrode surface due to their steric hindrance but react in solution by abstracting an iodine or bromine atom from RX (X=I, Br) or ArI to give alkyl or aryl radicals. As a consequence, alkyl and aryl radicals are generated at very low driving force by diverting the reactivity of aryl radicals derived from an aryl diazonium salt; they attack the electrode surface and form strongly attached organic layers. This strategy applies to the chemical modification of polymers (polyethylene, polymethylmethacrylate) by alkyl halides under heating.     

Photoinduced Nal-Promoted Radical Borylation of Alkyl Halides and Pseudohalides

Main observation and conclusion A method for photoinduced Nal-promoted radical borylation of aliphatic halides and pseudohalides with bis(catecholato)diboron(B2...     

Mechanically Initiated Reaction of Aluminum with Alkyl Halides

Mechanochemical reactions of aluminum with alkyl halides were examined at room temperature. The reaction was initiated by mechanical activation of vibromilling without any activator. It was found that the initiation was not due to the temperature rise at mechanical contact but the active sources formed on aluminum surface by vibromilling. The reactivity of milled aluminum was well correlated with the intensity of exoelectron emission. Both the reactivity and the emission intensity increased sharply after 60 min of milling. The decaying characteristics by exposure of preactivated aluminum were observed for both the reactivity and the emission intensity. The role of exoelectron on the reaction was discussed.     

Photopromoted Carbonylation of Alkyl Halides Under Ambient Conditions

Photopromoted carbonylation of alkyl halides with carbon monoxide can be carried out under ambient conditions with non-precious transition metal complexes(such as cobalt complexes) catalysts.Our preliminary work sowed that alkyl halides can be transformed into alkene and alkane directly under irradiation,but the esters can not be transformed.It is assumed that the carbonylation of alkyl halides may be proceeded in two ways.     

Manganese-Catalyzed Redox-Neutral Thiolation of Alkyl Halides with Thioformates

Transition metal-catalyzed C−S cross-coupling has emerged as an important strategy to furnish thioethers; however, the dominant utilization of noble metal catalysts as well as the construction of challenging C(sp³)−S bonds by transition metal-catalysis remain highly problematic. Earth-abundant manganese has gathered increasing interest as an attractive catalyst for new reaction development; nevertheless, C(sp³)−S cross-coupling reaction by manganese catalysis has not been reported. Herein, we disclose a highly efficient manganese-catalyzed redox-neutral thiolation of a broad range of alkyl halides with thioformates as practical sulfuration agents. Strategically, employing easily synthesized thioformates as thiyl radical precursors allows access to various aryl and alkyl thioethers in good to excellent yields. Notably, this redox-neutral method avoids the utilization of strong bases, external ligands, forcing reaction conditions, and stoichiometric manganese, thus presenting apparent advantages, such as broad substrate scope, excellent functional group compatibility, and mild reaction conditions. Finally, the utilities of this method are also illustrated by downstream transformations and late-stage thiolation of structurally complex natural products and pharmaceuticals.     

Reductions of Alkyl and Aryl Halides with Magnesium and Methanol

The combination of magnesium in methanol provides a convenient, efficient system for the selective hydrogenolysis of alkyl and aryl iodides and bromides. Vinyl bromides are also reduced if conjugated to an aromatic ring while only benzylic, allylic and naphthalenic chlorides are affected. Deuterium may be selectively introduced via utilization of methanol-d as solvent.     

Chromatographic Separation of the Halides

Abstract

Column chromatography with the liquid ion exchanger Aliquat 336 was evaluated for the separation of the halides in aqueous solution. The separation was successfully accomplished by a gradient elution technique using 0.1 M sodium acetate and various concentrations of sodium nitrate as eluants. A comparison of two methods of column loading was made.     

The Separation of 24 OPA-AA Of Natural Origin and Quantitative Analysis of Tyrosine by Means of HPLC

Abstract

The separation of a mixture of 24 amino-acids (AA) of natural origin is carried out by column HPLC μ. Bondapak C18 10 μm, following pre-column derivatization using orthophthalaldehyde (OPA). Because of the large numbers of AA to separate, the use of a linear gradient making use of the diversity of the AA polarities ensures the resolution of the mixture in less than 45 min.

The gradient is established through the progressive addition of acetonitrile to monopotassic phosphate solution (pH 6.80). The thioisoindol derivatives, which are thus formed and wich absorb greatly at 340 nm, are detected with a spectrophotometer. Quantitative analysis of tyrosine is carried out by means of the internal calibration method with two calibration substances: glutathion and 6amino caproic acid.

This analysis, which is directly applicable in industrial surroundings to the separation of primary AA, is both reproducible and sensitive.