Reaction Of Alkyl Halides Research Articles

Cobalt-catalyzed coupling reaction of alkyl halides with allylic grignard reagents.

Facile construction of quaternary carbon centers: The cobalt-catalyzed coupling reaction of not only primary and secondary but also tertiary alkyl halides with allylic Grignard reagents proceeds smoothly (see scheme; dppp=1,3-bis(diphenylphosphanyl)propane; R=primary, secondary, or tertiary alkyl group). A radical mechanism is proposed for the oxidative addition of alkyl halides to cobalt. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2002/z19929_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Cobalt‐Catalyzed Heck‐Type Reaction of Alkyl Halides with Styrenes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Cobalt-catalyzed Heck-type reaction of alkyl halides with styrenes.

A cobalt complex, CoCl2[1,6-bis(diphenylphosphino)hexane], catalyzes an alkylation reaction of styrenes in the presence of Me3SiCH2MgCl in ether to yield beta-alkylstyrenes. A variety of alkyl halides including alkyl chlorides can be employed as an alkyl source. A radical mechanism is strongly suggested for this alkylation reaction.

Solution-phase combinatorial synthesis using multicomponent Grignard reagents

Mixtures of up to 8 different alkyl Grignard reagents were prepared from the reaction of alkyl halides with magnesium. These multicomponent Grignard reagents were reacted with aldehydes, ketones or esters to produce mixtures of alcohols. Analysis of the product mixtures showed that from the reactions of aldehydes and ketones uniform mixtures of products were formed, while from the reaction with esters uniform libraries were only obtained after slow addition of the Grignard reagent.

Reduction of organic halides with lanthanum metal: a novel generation method of alkyl radicals.

Results of the reaction of alkyl halides with lanthanum metal have been shown. The reduction of alkyl iodide with 1/3 equiv of lanthanum metal efficiently proceeded to give the corresponding reductive dimerized products along with the formation of reduction and dehydroiodination products. In the case of alkyl bromides and chlorides, the reaction did not proceed under the same reaction conditions as that of alkyl iodides; however, the reaction was dramatically promoted by the addition of a catalytic amount of iodine. A reaction pathway including alkyl radicals was suggested.

Synthesis of alpha-amino acid derivatives and amines via activation of simple alkyl halides by zinc in water.

A method for the synthesis of alpha-amino acid derivatives and amines is developed via a zinc-mediated conjugate addition reaction of alkyl halides to alpha-phthalimidoacrylate derivatives and nucleophilic addition to imines in the presence of NH4Cl in water. No reaction was observed in the absence of water.

ChemInform Abstract: Novel Phosphonium Chloride Catalyzed Dehydrohalogenative Si—C Coupling Reaction of Alkyl Halides with Trichlorosilane.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Rate Enhancement with High Ratio of the Monoalkylated Product to the Dialkylated Product in the Alkylation of the Lithium Enolate of 1‐Tetralone with Reactive Alkyl Halides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Heterocyclization of 1-aryl/alkyl-2-thiobiureas to 4-aryl/alkyl-3-substituted-Δ2-1,2,4-triazolin-5-ones

Synthesis of a range of 1,2,4-triazolin-5-ones has been carried out by thermally induced cyclization of 1-aryl/alkyl-2-alkyl isothiobiureas 4. The required isothiobiureas were generated in situ by the reaction of alkyl halides with 1-aryl/alkyl-2-thiobiureas 3 in acidic medium at reflux. The reaction proceeds after S-alkylation of the thiobiureas and is demonstrated by the isolation of the alkyl isothiobiurea intermediates and their subsequent acid catalyzed thermal cyclization.

Rate enhancement with high ratio of the monoalkylated product to the dialkylated product in the alkylation of the lithium enolate of 1-tetralone with reactive alkyl halides.

The reactions of the lithium enolate of 1-tetralone with reactive alkyl halides were examined in the absence and in the presence of 3 eq of various ligands for the lithium. It is shown that the rates of the reactions are enhanced greatly in the presence a tetradentate amine (1,1,4,7,10,10-hexamethyltriethylenetetramine), and the ratio of the monoalkylated product to the dialkylated product is increased under shorter reaction times.

Stereoselective Reactions. Part 31: Catalytic Asymmetric Alkylation of Achiral Lithium Enolates Using a Chiral Tetradentate Amine in the Presence of an Achiral Bidentate Amine

Catalytic asymmetric alkylation of achiral lithium enolates of 1-tetralone and cyclohexanone with reactive alkyl halides was realized by using a combination of a chiral tetradentate amine (∼0.05 equiv.) and an achiral bidentate amine (2 equiv.).

Asymmetric alkylation catalyzed by chiral alkali metal alkoxides of TADDOL. Synthesis of α-methyl amino acids

It is shown that sodium alkoxides formed from (4R,5R)-2,2-dimethyl-1,3-dioxolane-4,5-bis(diphenylmethanol) ((R,R)-TADDOL) and some of its derivatives can be used as chiral catalysts for enantioselective alkylation of Schiff's bases derived from alanine with reactive alkyl halides. Acid hydrolysis of the reaction products affords (R)-α-methylphenyl-alanine, (R)-α-allylalanine, and (R)-α-methylnaphthylalanine in 61–93% yields and withee 69–94%. When (S,S)-TADDOL is used, the (S)-amino acid is formed. A mechanism explaning the observed features of the reaction is proposed.

Synthesis of 3-alkylated triacetonamine derivatives

Reaction of a lithiated imine derivative of 2,2,6,6-tetramethyl-4-piperidone (triacetonamine, 1) with activated or less reactive alkyl halides or styrene oxide and subsequent hydrolysis afforded 3-alkylated triacetonamine derivatives. Thus, 3-benzyl-2,2,6,6-tetramethyl-4-piperidone (3), 3-(n-butyl)-2,2,6,6-tetramethyl-4-piperidone (4), 3-(3-chloropropyl)-2,2,6,6-tetramethyl-4-piperidone (5), 2,2,3,6,6-pentamethyl-4-piperidone (6) and two diastereomers of 3-(2-hydroxy-2-phenylethyl)-2,2,6,6-tetramethyl-4-piperidone (7) were prepared in 26–53% yield. Reaction of the imine anion derived from 1 with benzyl bromide to give 3 has to be performed at low temperatures in order to avoid a competing proton transfer. No reaction at the unprotected piperidine nitrogen was observed.

Kinetic evidence for a novel, Grob-like substitution/fragmentation mechanism for the reaction of nucleophiles with trialkylammoniomethyl halides

Kinetic evidence is presented in favor of a concerted, bimolecular mechanism for the unusual nucleophilic substitution/fragmentation reactions of iodide ion with (halomethyl)trimethylammonium salts. The relative reactivities of allyl, ethyl and methyl groups for this Grob-like reaction are also determined. Activation parameters are presented for the thermal reactions of 1-iodo-N,N,N-trimethylmethaniminium iodide (log A = 8.7, Ea = 19.0 kcal mol–1) and 1-iodo-N-allyl-N,N-dimethylmethaniminium iodide (log A = 14.6, Ea = 25.7 kcal mol–1) in acetonitrile, the latter reaction having an observed second order rate constant 39 times larger than the former at 70 °C. The results are compared with the classic data of Hughes, Ingold and Conant for SN2 reactions of alkyl halides.

Stereoselective reactions. 30. Enantioselective alkylation of the lithium enolates of six-membered cyclic ketones using tetradentate chiral amines in the presence of lithium bromide

An efficient enantioselective alkylation of the lithium enolates of cyclohexanone and I-tetralone with reactive alkyl halides was realized using a stoichiometric amount of a tetradentate chiral amine as a ligand for the lithium in the presence of lithium bromide in toluene.

Practical methodology for the asymmetric synthesis of organofluorine compounds

Pseudoephedrine α-fluoroacetamide ( 1), a nonvolatile, crystalline solid, is alkylated efficiently and with high diastereoselectivity with reactive alkyl halides. The alkylation products can be hydrolyzed under mild basic conditions to form α-fluoro carboxylates with high enantiomeric enrichment.

Carbon-Carbon Bond Cleavage of .ALPHA.-Substituted Benzoins by Retro-Benzoin Condensation; A New Method of Synthesizing Ketones.

When α-benzylbenzoin (3a, α-benzyl-α-hydroxybenzyl phenyl ketone) was treated with potassium cyanide (1) in N, N-dimethylformamide at 80°C for 1 h, the carbon-carbon bond was cleaved, resulting in the formation of deoxybenzoin (4a, benzyl phenyl ketone) and benzaldehyde (2a). This carbon-carbon bond cleavage proceeds through a retro-benzoin condensation mechanism. This mothod of synthesizing ketones was applied to several α-substituted benzoins (3), and the corresponding ketones (4) were formed in good yields. Further, we found that the cyanide ion-donating ability of tetrabutylammonium cyanide (6, Bu4NCN) is more effective than that of potassium cyanide (1, KCN). As expected from the chemical analogy between cyanide ion and azolium ylide, serveral azolium salts (7) can also be employed in the retro-benzoin condensation as catalysts.The benzoin derivatives 3 were synthesized in the following three ways; reaction of alkyl halide (9) with benzoin (5), Michael addition of benzoin (5) with acceptors (10), and Grignard reaction of benzils (8). Alkylation of the benzoins without isolation, followed by carbon-carbon bond cleavage, readily afforded the corresponding ketones (4).

Reactions of alkyl halides with distonic acylium radical cations

Molecular orbital calculations (Becke3LYP/3-21G(d)) indicate that the distonic acylium ions •CH 2CH 2CH 2CO + and •CH 2CH 2CO + are localized σ-radicals with a spin density of 0.95 e and 0.92 e at the terminal methylene carbon, respectively. Most of the positive charge (+0.88) is localized on the carbonyl carbon. The radical site carries a charge that is only slightly more positive than that in the neutral ethyl radical. Based on these values, the distonic acylium ions may be expected to behave like neutral alkyl radicals. However, an examination of the reactivity of gaseous •CH 2CH 2CO + and •CH 2CH 2CH 2CO + toward a series of alkyl halides in a dual-cell Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR) revealed that their reactivity is greatly influenced by the charged group. The ions •CH 2CH 2CO + and •CH 2CH 2CH 2CO + are unreactive toward alkyl chlorides but react with alkyl bromides and iodides by electron, halogen atom, alkyl radical and/or hydrogen atom abstraction. While hydrogen and halogen atom abstraction reactions are common for neutral alkyl radicals, electron and alkyl abstractions are not. A mechanism that involves catalysis by the charge site is proposed for the alkyl abstraction reactions.

ChemInform Abstract: Bimolecular Reactions of Alkyl Halides and Acylgermanes: Formation of Ketones, Diketones, and Other Products by Radical‐Radical Reaction.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Conjugate Addition Reactions Mediated by Samarium(II) Iodide.

Samarium(II) iodide in conjunction with a catalytic low-valent transition metal species has been employed to promote the conjugate addition reaction of primary and secondary alkyl halides onto alpha,beta-unsaturated esters and amides. The method has been determined to be quite general and hence has been extended to the cyclization reactions of alkyl halides onto alpha,beta-unsaturated lactones, lactams, and nitriles. The cyclization reactions described herein provide a very general approach to the synthesis of functionalized carbocycles from simple acyclic precursors with excellent diastereoselectivity and under very mild reaction conditions.