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PubMed Journals Articles About "Iron Hydride Radical Reductive Alkylation Unactivated Alkenes" RSS

13:18 EDT 5th April 2020 | BioPortfolio

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Showing "Iron Hydride Radical Reductive Alkylation Unactivated Alkenes" PubMed Articles 1–25 of 3,500+

Iron Hydride Radical Reductive Alkylation of Unactivated Alkenes.

Iron-catalyzed hydrogen atom transfer-mediated intermolecular C-C coupling reactions between alkenes and tosylhydrazones, followed by in situ cleavage of the tosylhydrazine intermediates using EtN, are described. The process involves a new strategic bond disconnection resulting in the reductive alkylation of nonactivated alkenes. The reaction is operationally simple, proceeds under mild conditions, and has a wide substrate scope.


Intermolecular Reductive Heck Reaction of Unactivated Aliphatic Alkenes with Organohalides.

A general intermolecular reductive Heck reaction of organohalides with both terminal and internal unactivated aliphatic alkenes has been first realized in high yield with complete anti-Markovnikov selectivity. The challenging vinyl bromides, aryl chlorides, and polysubstituted internal alkenes were first applied. More than 100 remote carbofunctionalized alkyl carboxylic acid derivatives were rapidly synthesized from easily accessible starting materials. The synthesis of drug molecules has further demonstrat...

Directed Copper-Catalyzed Intermolecular Aminative Difunctionalization of Unactivated Alkenes.

A diverse collection of copper-catalyzed intermolecular aminative difunctionalizations of unactivated alkenes with N-halodialkylamines as the terminal dialkylamino source is reported. A bidentate auxiliary tethered on the alkene substrates is crucial, which can promote the migratory insertion of nonactivated alkenes into the aminyl radical-metal complex and stabilize the resultant high-valent copper intermediate to allow for further transformations. By employing this strategy, the intermolecular aminohaloge...


Catalyzing the Hydrodefluorination of CF3-substituted Alkenes by PhSiH3. H• Transfer from a Nickel Hydride.

The hydrodefluorination of CF3-substituted alkenes can be catalyzed by a nickel(II) hydride bearing a pincer ligand. The cata-lyst loading can be as low as 1 mol%. gem-Difluoroalkenes containing a number of functional groups can be formed in good to excellent yields, by a radical mechanism initiated by H• transfer from the nickel hydride. The relative reactivity of various substrates supports the proposed mechanism, as does a TEMPO trapping experiment.

Reductive Allylic Defluorinative Cross-Coupling Enabled by Ni/Ti Cooperative Catalysis.

Unactivated alkyl chlorides are abundant building blocks in organic synthesis, but they have been rarely engaged in cross-electrophile coupling. Herein, we report a Ni/Ti-cocatalyzed reductive allylic defluorinative cross-coupling between trifluoromethyl alkenes and unactivated alkyl chlorides and bromides, enabling the efficient preparation of diverse functional-group-rich -difluoroalkenes. Notably, synthesis of the -difluoroalkene analogues of azaperone, haloperidol, and benperidol was also accomplished u...

Copper-Catalyzed Regioselective Borocarbonylative Coupling of Unactivated Alkenes with Alkyl Halides: Synthesis of ß-Boryl Ketones.

The borocarbonylative coupling of unactivated alkenes with alkyl halides remains a challenge. In this communication, a Cu-catalyzed borocarbonylative coupling of unactivated alkenes with alkyl halides for the synthesis of ß-boryl ketones has been developed. A broad range of β-boryl ketone derivatives was prepared in moderate to excellent yields with complete regioselectivity.

Photosensitized intermolecular carboimination of alkenes through persistent radical effect.

An intermolecular, two-component vicinal carboimination of alkenes has been accomplished via energy transfer catalysis. Oxime esters of alkyl carboxylic acids are used as bifunctional reagents to generate both alkyl and iminyl radicals. Subsequently, the addition of alkyl radical to alkenes generates a transient radical for selective radical-radical cross coupling with persistent iminyl radical. Furthermore, this protocol readily allows for direct access to aliphatic primary amines and α -amino acids throu...

Visible-Light-Driven Nitrogen Radical-Catalyzed 3 + 2 Cyclization of Vinylcyclopropanes and -Tosyl Vinylaziridines with Alkenes.

A visible light photoredox-promoted and nitrogen radical catalyzed [3 + 2] cyclization of vinylcyclopropanes and -tosyl vinylaziridines with alkenes is developed. Key to the success of this process is the use of the readily tunable hydrazone as a nitrogen radical catalyst. Preliminary mechanism studies suggest that the photogenerated nitrogen radical undergoes reversible radical addition to the vinylcyclopropanes and -tosyl vinylaziridines to enable their ring-opening C-C and C-N bond cleavage and ensuing c...

Three-component difluoroalkylamination of alkenes mediated by photoredox and iron cooperative catalysis.

A three-component difluoroalkylamination of alkenes with BrCF2CO2Et and amines mediated by visible-light photoredox and iron cooperative catalysis is described. Electron rich, electron poor, and internal styrenes are all tolerated giving the desired products in good yields. The Csp3-Csp3 and Csp3-N bonds are simultaneously formed under mild conditions. A radical pathway is proposed by experimental studies.

Nickel-Catalyzed Reductive Arylalkylation via a Migratory Insertion/Decarboxylative Cross-Coupling Cascade.

Reported is a nickel-catalyzed reductive arylalkylation of unactivated alkenes tethered to aryl iodides with redox active -hydroxyphthalimide esters as the alkyl source through successful merging of migratory insertion and decarboxylative cross-coupling in a cascade. This new method avoids the use of pregenerated organometallic reagents and thus enables the synthesis of diverse benzene-fused carbo- and heterocyclic compounds with high tolerance of a wide range of functional groups.

Enantioselective Pd(II)-Catalyzed Oxidative Aminofluorination of Unactivated Alkenes Using Et4NF·3HF as a Fluoride Source.

The first asymmetric Pd(II)-catalyzed aminofluorination of unactivated alkenes using chiral quinoline-oxazolines (Quox) as ligand has been developed, which provides an easy access to a wide array of enantiomerically enriched β-fluoropiperidines in good yields with excellent enantioselectivities. Notably, Et4NF·3HF as a readily accessible nucleophilic fluoride source was found to play an essential role in the enantioselective control, and CsOCF3 also acts an key additive to improve the excellent ee value o...

Direct Regio- and Diastereoselective Synthesis of δ-Lactams from Acrylamides and Unactivated Alkenes Initiated by Rh -Catalyzed C-H Activation.

We report a Rh -catalyzed regio- and diastereoselective synthesis of δ-lactams from readily available acrylamide derivatives and unactivated alkenes. The reaction provides a rapid route to a diverse set of δ-lactams in good yield and stereoselectivity, which serve as useful building blocks for substituted piperidines. The regioselectivity of the reaction with unactivated terminal alkene is significantly improved by using Cp ligand on the Rh catalyst. The synthetic utility of the reaction is demonstrated b...

Nickel-catalyzed C-H alkylation of indoles with unactivated alkyl chlorides: evidence of a Ni(i)/Ni(iii) pathway.

A mild and efficient nickel-catalyzed method for the coupling of unactivated primary and secondary alkyl chlorides with the C-H bond of indoles and pyrroles is described which demonstrates a high level of chemo and regioselectivity. The reaction tolerates numerous functionalities, such as halide, alkenyl, alkynyl, ether, thioether, furanyl, pyrrolyl, indolyl and carbazolyl groups including acyclic and cyclic alkyls under the reaction conditions. Mechanistic investigation highlights that the alkylation proce...

Controlling the selectivity of an intramolecular Friedel-Crafts alkylation with alkenes using selenium under mild conditions.

An efficiently divergent intramolecular Friedel-Crafts alkylation by unactivated alkenes with seleniranium ion-controlled Markovnikov/anti-Markovnikov specificities under mild conditions has been investigated. 2-Benzoxepin, isochroman, and isochromene can be produced in one-pot procedures from the same substrate in high yields and with high regio- and stereospecificity. The products are challenging to access via 7-endo-trig carbocyclizations and by 7-endo-trig carbocyclization/rearrangement/6-exo-trig oxycy...

Ni-Catalyzed Reductive Arylacylation of Alkenes toward Carbonyl-Containing Oxindoles.

An easy-to-handle Ni-catalyzed three-component reductive arylacylation of alkenes using isobutyl chloroformate as a CO source was described. This reaction operates under mild reaction conditions without the need to use toxic CO gas or metal carbonyl reagents. In addition, this method allows for rapid synthesis of 3,3-disubstituted oxindoles with an all-carbon quaternary stereocenter containing a ketone group in good yields with broad substrate scope.

Copper(I)-Catalyzed Asymmetric Reactions Involving Radicals.

Asymmetric functionalization of alkyl radicals represents a robust yet underdeveloped method for efficient construction and decoration of carbon skeletons in chiral organic molecules. In this field, we have been inspired by the excellent redox, alkyl radical trapping, and Lewis acidic properties of copper to develop several catalytic modes for asymmetric reactions involving alkyl radicals. At the beginning, we discovered tandem radical hydrotrifluoromethylation of unactivated alkenes and enantioselective al...

Radical Acylfluoroalkylation of Olefins through N-Heterocyclic Carbene Organocatalysis.

Fluorinated ketones are widely prevalent in numerous biologically interesting molecules, and the development of novel transformations to access these structures is an important task in organic synthesis. As an emerging powerful strategy, the concurrent installation of fluorine and ketone moieties into target molecules from simple, variable, and abundant feedstocks remains synthetically challenging and underdeveloped. Here, we report a multicomponent radical acylfluoroalkylation of olefins in the presence of...

Fe-catalyzed reductive couplings of terminal (hetero)aryl alkenes and alkyl halides under aqueous micellar conditions.

The combination of a vinyl-substituted aromatic or heteroaromatic and an alkyl bromide or iodide leads, in the presence of Zn and a catalytic amount of an Fe(II) salt, to a net reductive coupling. The new C-C bond is regiospecifically formed at rt at the -site of the al-kene. The coupling only occurs in an aqueous micellar medium, where an atypical carbanionic, as opposed to radical, process is likely, supported by several control experiments. A mechanism based on these data is proposed.

Generation of Halomethyl Radicals by Halogen Atom Abstraction and Their Addition Reactions with Alkenes.

α-Aminoradicals undergo halogen atom abstraction to form halomethyl radicals in reactions initiated by the combination of -butyl hydroperoxide, aliphatic trialkylamine, halocarbon, and copper(I) iodide. The formation of the α-aminoradical circumvents preferential hydrogen atom transfer in favor of halogen atom transfer, thereby releasing the halomethyl radical for addition to alkenes. The resulting radical addition products add the tert-butylperoxy group to form α-peroxy-β,β-dichloropropylbenzene produ...

A Reversible Electron Relay to Exclude Sacrificial Electron Donors in the Photocatalytic Oxygen Atom Transfer Reaction with O in Water.

Using light energy and O for the direct chemical oxidation of organic substrates is a major challenge. A limitation is the use of sacrificial electron donors to activate O by reductive quenching of the photosensitizer, generating undesirable side products. A reversible electron acceptor, methyl viologen, can act as electron shuttle to oxidatively quench the photosensitizer, [Ru(bpy) ] , generating the highly oxidized chromophore and the powerful reductant methyl-viologen radical MV . MV can then reduce an i...

Enantioselective Radical-Polar Crossover Reactions of Indanonecarboxamides with Alkenes.

Highly efficient asymmetric intermolecular radical-polar crossover reactions were realized by combining a chiral N,N'-dioxide-NiII complex catalyst with Ag2O under mild reaction condition. Various terminal alkenes and indanonecarboxamides/ester underwent radical addition/cyclization reactions to afford spiroiminolactones and spirolactone with good to excellent yields (up to 99%) and enantioselectivities (up to 96% ee). Furthermore, a range of different radical-mediated oxidation/elimination or epoxide ring-...

NHC-Stabilized Silyl-Substituted Chlorosilylene.

The first N-heterocyclic carbene (NHC) stabilized silyl-substituted chlorosilylene () was isolated via selective dehydrochlorination by NHC from silyl-based Si(IV) precursor BuSiSiHCl. Compound can form an iron chlorosilylene complex () with an iron carbonyl dimer and undergoes chloride/hydride metathesis to yield a stable NHC-silylene hydride borane adduct (). Upon treatment with additional NHC, chlorosilylene was converted into silyl-substituted silyliumylidene ions ().

Iron-Catalyzed β-Alkylation of Alcohols.

β-Branched alkylated alcohols have been prepared in good yields using a double-hydrogen autotransfer strategy in the presence of our diaminocyclopentadienone iron tricarbonyl complex . The alkylation of some 2-arylethanol derivatives was successfully addressed with benzylic alcohols and methanol as alkylating reagents under mild conditions. Deuterium labeling experiments suggested that both alcohols (2-arylethanol and either methanol or benzyl alcohol) served as hydrogen donors in this cascade process.

Diastereoselective Intramolecular Hydride Transfer Triggered by Electrophilic Halogenation of Aryl Alkenes.

Diastereoselective hydride transfer could be triggered by electrophilic halogenation (bromination or fluorination) of homoallylic alcohol O-Bn ethers. The resulting diastereomerically enriched haloalkyl alcohols underwent subsequent intramolecular nucleophilic substitution to afford the corresponding tetrahydrofurans.

Mechanism of Ni-Catalyzed Reductive 1,2-Dicarbofunctionalization of Alkenes.

Ni-catalyzed cross-electrophile coupling reactions have emerged as an appealing method to construct organic molecules without the use of stoichiometric organometallic reagents. The mechanisms are complex: plausible pathways, dubbed "radical chain" and "sequential reduction", are dependent on the sequence of the activation of electrophiles. A combination of kinetic, spectroscopic, and organometallic studies reveals that a Ni-catalyzed, reductive 1,2-dicarbofunctionalization of alkenes proceeds via a "sequent...


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