Promoting nontransition metal alkylation with organic halides in the presence of binary systems based on an organometallic compound and a transition metal compound: V. Effect of the nature of the transition metal compound in the binary system on the rate of a steady-state process

The example of alkylation of commercial zinc and cadmium powders with organic halides in the presence of binary systems comprising an organometallic and a transition metal compounds was used to show that the nature of the transition metal compound in the binary system strongly affects the rate of a steady-state process. Therewith, the significant factors are both the nature of the transition metal and the ligand composition. It was found that the activity of the binary systems correlates with the activity of the transition metal compound in the transmetalation reaction with the organometallic component of the binary system (reduction of the transition metal compound).     

Promoting non-transition metal alkylation with organic halides in the presence of binary systems based on an organometallic compound and a transition metal compound: VIII. Selectivity of the binary systems action

Selectivity of action of binary systems based on an organometallic compound and a transition metal compound in a direct synthesis of organometallic compounds via alkylation of metals with organic halides has been considered. Study of the side reactions in the course of zinc and cadmium powders alkylation (gaseous hydrocarbons evolution) taken as an example has demonstrated that the increase in activity of the binary system components is accompanied by decrease in its selectivity. The intensity of the side reactions is steeply increased above certain temperature determined by the nature of the reactants and components of the binary system. The surface of the alkylated metal containing adatoms and small clusters of the transition metal promotes the side processes.     

Synthesis of Zinc Dialkyls from Zinc and Alkyl Bromides

Zinc dialkyls with linear radicals were prepared from zinc and alkyl bromides in the presence of stimulating systems based on a transition metal derivative and an organometallic compound capable of reducing the transition metal derivative under the reaction conditions.     

A Solution-Solid Phase Equilibrium in Ternary Systems Containing d-Elements Salts and Mixed Oxygen-Donor Solvent

Russian Journal of General Chemistry - The results of the study of ternary systems containing copper, cobalt, nickel, and cadmium halides and sulfates in binary water-organic and mixed organic...     

Promoting of non-transition metal alkylation with organyl halides in the presence of binary systems based on an organometallic compound and a transition metal compound: I. Hypothetical stepwise scheme and verification of the system efficiency

A hypothetical scheme has been proposed for the alkylation of non-transition metals with organyl halides in the presence of binary systems consisting of an organometallic compound and a transition metal compound. The scheme implies catalysis by transition metal atoms, small clusters, and subhalides adsorbed on the surface of metal to be alkylated. These particles are formed during the process as a result of interaction between the binary system components. The alkylation of commercial zinc powder with ethyl bromide has been used as a model reaction to demonstrate that the binary system ethylzinc bromide-copper(I) iodide is superior in its efficiency and experimental simplicity to all other examined methods for stimulation of the alkylation of elements with organyl halides yielding organometallic compounds.     

Solvent Role in the Synthesis of Organometallic and Metal-Containing Compounds by Direct Oxidation of a Metal

Solubility of certain magnesium, zinc, and cadmium halides in a number of organic substances was determined. A maximum in the dependence of the rate of metal oxidation with halogen-containing compounds on the donor number of the solvent does not correlate with the solubility of the corresponding salts in these solvents.     

Radical-polar crossover domino reactions involving organozinc and mixed organocopper/organozinc reagents

A domino process involving Michael addition and carbocyclization has been developed starting from beta-N-allylamino enoates and various organometallic reagents (organozinc halides, diorganozinc reagents, and copper/zinc mixed species). In all cases the mechanism of this domino reaction has been evidenced to involve a radical-polar crossover mechanism.     

Promoting non-transition metal alkylation with organic halides in the presence of binary systems based on an organometallic compound and a transition metal compound: IX. Alkylation of aluminum and concluding remarks

Study of aluminum powder alkylation with ethyl bromide in the presence of ethylaluminum sesquibromide and copper(I) iodide has revealed that binary systems based on an organometallic compound and a transition metal compound are efficient promotors of direct synthesis of organoaluminum compounds as well. Major conclusions drawn in a series of studies on non-transition metals (Zn, Cd, and Al) alkylation with organic halides in the presence of the binary systems are summarized.     

Solid-liquid extraction as a preconcentration technique in trace element analysis Extraction of trace impurities from metal chlorides

Microgram quantities of iron, cobalt, copper, zinc and cadmium are extracted with various aqueous, organic and mixed solvents from chlorides of sodium, potassium, nickel, cadmium, barium and lead prepared by evaporation of aqueous sample solutions. An ultrasonic field accelerates the extraction, and satisfactory trace recoveries and separation factors are achieved in several systems within a reasonable time. The application to a polarographic determination and a two-stage separation technique are also described.     

Fluorinated stannanes : Part 1. The stereospecific synthesis of fluorinated stannanes via a novel transmetalation of fluorinated zinc and cadmium reagents

Fluorinated stannanes are versatile synthetic intermediates. Reaction of fluorinated vinyl, alkyl and aryl zinc or cadmium reagents with tri-n-butyltin chloride at room temperature yielded the corresponding tri-n-butyl stannanes in moderate to excellent yields. The zinc or cadmium reagents also reacted efficiently with other trialkyl and triaryl chlorostannanes. These zinc and cadmium reagents were prepared in excellent yields by stirring the fluorinated halides with activated zinc or cadmium metal.     

Tuning of regioselectivity in the coupling reaction involving allenic/propargylic palladium species

Two different types of coupling patterns for the Pd(0)-catalyzed coupling reaction of allenic/propargylic zinc reagents with organic halides or propargylic carbonates (acetate) with the corresponding organometallic reagents were observed. After studying the controlling factors on the regioselectivity of this reaction, we demonstrated that the steric hindrance of both reactants and the types of organic halides determine the regioselectivity of this coupling reaction. By subtle choosing of the substrates, the regioselectivity can be tuned. On the basis of these results, new methodologies for the highly regio- and stereoselective synthesis of 6-substituted hex-5-yn-2-enoates and 4,6-dialkylhexa-2,4,5-trienoates have been developed. Some of the products synthesized by the carbonate protocol cannot be prepared by the lithiation protocol because the regioselectivity of lithiation of dialkyl-substituted internal alkynes is an intrinsic problem.     

Ultrasonics in organoborane chemistry,rapid synthesis of triorganylboranes via a modified organometallic route

A variety of triorganylboranes were prepared in a rapid and highly efficient manner, directly from organic halides, by a modified organometallic route employing ultrasound.     

Molecular emission cavity analysis: stimulation of metal halide emissions

Some metal halides (Mn, Co, Ni, Pb and possibly Fe) emit metal(I) halide spectra from the MECA cavity in hydrogen-nitrogen-air flames, in contrast to their behaviour in conventional aspiration flame systems. However, the emission intensity is too weak to provide sensitive analytical applications. Indium halides give intense emissions by either the MECA or aspiration method. Halogenated organic compounds give intense CH and C₂ emissions. Cadmium halides give only an intense atomic emission. Sensitive methods for halides, indium, cadmium and organic compounds are thus possible. Mercury (II) halides and metal fluorides give no measurable emission in the cavity method.     

Promoting alkylation of non-transition metals with organic halides in the presence of binary systems based on organometallic compound and transition metal compound: II. Comparative study of efficiency of various agents in the course of destruction of passivating film on the surface of alkylated metal

It has been demonstrated that alkylzinc halides efficiently destroy the passivating film on the zinc-copper pair in the course of its alkylation with ethyl bromide to give ethylzinc bromide. The alkylzinc halides efficiency is comparable to that of ethyl iodide and exceeds that of salts of transition or non-transition metals as well as of ultraviolet irradiation. Addition of alkylzinc halides or metal salts as well as ultraviolet irradiation have practically no effect on the developed reaction. The results have demonstrated that the organometallic component of the binary systems is polyfunctional; this permits a generalization of known features of a number of known methods promoting direct synthesis of organometallic compounds.     

Electrochemical reduction of ZnBr<Subscript>2</Subscript> in the presence of organic halides

Electrochemical reduction of zinc bromide in dimethylformamide, acetonitrile, and tetrahydrofuran in the presence of organic halides (RX) results in the formation of organozinc compounds by oxidative addition of RX to electrochemically generated Zn(0). Effects of the solvent and the nature of organic halides on the electrochemical reduction of zinc (II) ions are analyzed.     

Metal-mediated entry to functionalized 3-substituted 3-hydroxyindolin-2-ones via regiocontrolled carbonylallylation, bromoallylation, 1,3-butadien-2-ylation, propargylation, or allenylation reactions of isatins in aqueous media

Reactions of 2,3-indolinediones (isatins) with stabilized organometallic reagents were investigated in aqueous media. Isatins and a variety of stabilized organic halides undergo coupling under Barbier-type conditions in the presence of different metals (indium, tin, zinc) and additives (ammonium chloride, hydrobromic acid, bismuth(III) chloride, hafnium(IV) chloride). The regiochemistry of the processes (carbonylallylation, bromoallylation, 1,3-butadien-2-ylation, propargylation, or allenylation reactions) were generally excellent. On this basis, simple and fast protocols for the synthesis of the potentially bioactive 3-substituted 3-hydroxyoxindole moiety were developed.     

Reactions of organic halides with organometallic compounds and terminal acetylenes catalyzed by palladium complexes

The results of the investigation of the cross-coupling of organometallic compounds and terminal acetylenes with organic halides catalyzed by transition metal complexes are generalized and analyzed. The influence of different factors on the rate and selectivity of catalytic cross-coupling is discussed. A detailed mechanism of the cross-coupling of Grignard reagents with organic halides is suggested. The cross-coupling reaction involving organotin compounds proceeds under very mild conditions in the presence of a ligand-free Pd catalyst. Examples of using catalytic cross-coupling of organic halides with organomagnesium, organozinc, and organotin compounds are presented.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2148–2167, September, 1996.     

Synthesis of functionalized 2-arylpyridines from 2-halopyridines and various aryl halides via a nickel catalysis

An efficient nickel-catalyzed method devoted to the direct formation of functionalized 2-arylpyridines is described avoiding the prior preparation of organometallic species. Various functionalized 2-arylpyridines are obtained in moderate to excellent yields by a one-step chemical procedure from corresponding halides. The NiBr₂(2,2′-bipyridine) complex appears to be an extremely suitable catalyst for the activation in the presence of manganese dust of aromatic halides and pyridyl halides functionalized by reactive groups. The versatility of this original process represents a simple alternative to most known methods using organometallic reagents.     

Catalysts for cross-coupling reactions with non-activated alkyl halides

Despite the problems inherent to metal-catalyzed cross-coupling reactions with alkyl halides, these reactions have become increasingly important during the last few years. Detailed mechanistic investigations have led to a variety of novel procedures for the selective cross-coupling of non-activated alkyl halides bearing beta hydrogen atoms with a variety of organometallic nucleophiles under mild reaction conditions. This Minireview highlights selected examples of metal-catalyzed coupling methods and is intended to encourage chemists to exploit the potential of these approaches in organic synthesis.     

Fluorinated stannanes : Part 2. The stereospecific synthesis of fluorinated stannanes via a Barbier-type reaction between fluorinated halides and tributyltin chloride mediated by zinc or cadmium

Fluorinated stannanes are valuable synthons in synthetic organofluorine chemistry. Fluorinated vinyl, alkyl and aryl halides reacted efficiently with tri-n-butyltin chloride in the presence of zinc or cadmium to yield the corresponding stannanes in good yields. In some cases, yield of the stannanes showed a dramatic improvement over the transmetalation method. In all other cases, comparable yields were obtained.