- Preparation of alkylzinc bromides using a new Mn/Cu catalyzed bromine-zinc exchange reaction
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The reaction of functionalized primary alkyl bromides with Et2Zn in DMPU in the presence of a catalytic mixed metal system constituted of MnBr2 (or FeCl3) and CuCl provides functionalyzed alkylzinc bromides (>80% yield). In the presence of PdCl2(dppf) or CuCN-2LiCl, these organozinc species react with a range of electrophiles providing various polyfunctional molecules in good yields.
- Klement,Klement, Ingo,Knochel,Knochel, Paul,Chau,Chau, Khi,Cahiez,Cahiez, Gerard
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- A Ball-Milling-Enabled Cross-Electrophile Coupling
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The nickel-catalyzed cross-electrophile coupling of aryl halides and alkyl halides enabled by ball-milling is herein described. Under a mechanochemical manifold, the reductive C-C bond formation was achieved in the absence of bulk solvent and air/moisture sensitive setups, in reaction times of 2 h. The mechanical action provided by ball milling permits the use of a range of zinc sources to turnover the nickel catalytic cycle, enabling the synthesis of 28 cross-electrophile coupled products.
- Jones, Andrew C.,Nicholson, William I.,Leitch, Jamie A.,Browne, Duncan L.
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supporting information
p. 6337 - 6341
(2021/08/23)
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- Dumbbell-Shaped 2,2’-Bipyridines: Controlled Metal Monochelation and Application to Ni-Catalyzed Cross-Couplings
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2,2’-Bipyridine ligands (dsbpys) with dumbbell-like shapes and differently substituted triarylmethyl groups at the C5 and C5’ positions showed high ligand performance in the Ni-catalyzed cross-electrophile coupling and the Ni/photoredox-synergistically catalyzed decarboxylative coupling reactions. The superior ligand effects of dsbpys compared to the conventional bpy ligands were attributed to the monochelating nature of dsbpys.
- Kim, Yongjoon,Iwai, Tomohiro,Fujii, Sho,Ueno, Kosei,Sawamura, Masaya
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supporting information
p. 2289 - 2293
(2020/12/07)
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- Mechanical metal activation for Ni-catalyzed, Mn-mediated cross-electrophile coupling between aryl and alkyl bromides
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Liquid-assisted grinding has been successfully applied to eliminate the requirements of chemical activators and anhydrous solvents in nickel-catalyzed, manganese-mediated cross-electrophile coupling between aryl and alkyl bromides. In addition to the traditional reaction parameters, mechanical ones,e.g.the rotational speed of mill, the filling degree of jar and ball size, have been found to affect the catalytic efficiency remarkably, implying the involvement of the regeneration of nickel(0) species in the rate-determining steps. A combined evaluation of the reaction and mechanical parameters led to an optimal condition under which a variety ofn-alky aromatics with various functional groups could be readily obtained in good yields with a 1 mol% catalyst loading. The practical application of liquid-assisted grinding-enabled aryl/alkyl cross-electrophile coupling has been demonstrated in the gram-scale synthesis of 6-methoxytetralone.
- Wu, Sisi,Shi, Weijia,Zou, Gang
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supporting information
p. 11269 - 11274
(2021/07/02)
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- Preparation method of substituted butyrate derivatives
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The invention discloses a preparation method of substituted butyrate derivatives. The method specifically comprises the following steps: by taking compounds shown in a formula 1, a formula 2 and a formula 3 as raw materials, carrying out an illumination reaction process in the presence of a photocatalyst and a hydrogen transfer catalyst to obtain a target compound shown in a formula I through one-step reaction. The invention discloses a free radical-mediated olefin bifunctional reaction without a cyclopropanation intermediate. The reaction can realize a product which can be obtained through cyclopropanation and cyclopropane ring opening processes traditionally in one step. Meanwhile, the preparation method of the compound is simple, uses cheap and easily available compounds as raw materials, and has the beneficial effects of one-step synthesis, mild reaction conditions, fast reaction, low cost, less generated waste, simple and safe operation, high atom economy, high selectivity, extremely wide substrate applicability, high yield and the like.
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Paragraph 0085-0088
(2020/07/15)
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- Radical-Mediated Strategies for the Functionalization of Alkenes with Diazo Compounds
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One of the most common reactions of diazo compounds with alkenes is cyclopropanation, which occurs through metal carbene or free carbene intermediates. Alternative functionalization of alkenes with diazo compounds is limited, and a methodology for the addition of the elements of Z-CHR2 (with Z = H or heteroatom, and CHR2 originates from N2 CR2) across a carbon-carbon double bond has not been reported. Here we report a novel reaction of diazo compounds utilizing a radical-mediated addition strategy to achieve difunctionalization of diverse alkenes. Diazo compounds are transformed to carbon radicals with a photocatalyst or an iron catalyst through PCET processes. The carbon radical selectively adds to diverse alkenes, delivering new carbon radical species, and then forms products through hydroalkylation by thiol-assisted hydrogen atom transfer (HAT), or forms azidoalkylation products through an iron catalytic cycle. These two processes are highly complementary, proceed under mild reaction conditions, and show high functional group tolerance. Furthermore, both transformations are successfully performed on a gram-scale, and diverse γ-amino esters, γ-amino alcohols, and complex spirolactams are easily prepared with commercially available reagents. Mechanistic studies reveal the plausible pathways that link the two processes and explain the unique advantages of each.
- Su, Yong-Liang,Liu, Geng-Xin,Liu, Jun-Wen,Tram, Linh,Qiu, Huang,Doyle, Michael P.
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supporting information
p. 13846 - 13855
(2020/09/21)
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- Replacing conventional carbon nucleophiles with electrophiles: Nickel-catalyzed reductive alkylation of aryl bromides and chlorides
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A general method is presented for the synthesis of alkylated arenes by the chemoselective combination of two electrophilic carbons. Under the optimized conditions, a variety of aryl and vinyl bromides are reductively coupled with alkyl bromides in high yields. Under similar conditions, activated aryl chlorides can also be coupled with bromoalkanes. The protocols are highly functional-group tolerant (-OH, -NHTs, -OAc, -OTs, -OTf, -COMe, -NHBoc, -NHCbz, -CN, -SO2Me), and the reactions are assembled on the benchtop with no special precautions to exclude air or moisture. The reaction displays different chemoselectivity than conventional cross-coupling reactions, such as the Suzuki-Miyaura, Stille, and Hiyama-Denmark reactions. Substrates bearing both an electrophilic and nucleophilic carbon result in selective coupling at the electrophilic carbon (R-X) and no reaction at the nucleophilic carbon (R-[M]) for organoboron (-Bpin), organotin (-SnMe3), and organosilicon (-SiMe2OH) containing organic halides (X-R-[M]). A Hammett study showed a linear correlation of σ and σ(-) parameters with the relative rate of reaction of substituted aryl bromides with bromoalkanes. The small ρ values for these correlations (1.2-1.7) indicate that oxidative addition of the bromoarene is not the turnover-frequency determining step. The rate of reaction has a positive dependence on the concentration of alkyl bromide and catalyst, no dependence upon the amount of zinc (reducing agent), and an inverse dependence upon aryl halide concentration. These results and studies with an organic reductant (TDAE) argue against the intermediacy of organozinc reagents.
- Everson, Daniel A.,Jones, Brittany A.,Weix, Daniel J.
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supporting information; experimental part
p. 6146 - 6159
(2012/05/07)
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- Direct method for carbon-carbon bond formation: The functional group tolerant cobalt-catalyzed alkylation of aryl halides
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(Figure Presented). A new protocol for the direct cobaltcatalyzed alkylation of aryl halides has been developed that proceeds smoothly in the presence of phosphanes or bipyridines as ligands with a variety of alkyl halides, including challenging alkyl electrophiles bearing β hydrogen atoms (see scheme). Sensitive functional groups are tolerated on both coupling partners, thus, significantly extending the general scope of transition-metal-catalyzed alkylation of aryl halides.
- Amatore, Muriel,Gosmini, Corinne
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supporting information; experimental part
p. 5848 - 5852
(2010/09/03)
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- Highly efficient, general procedure for the preparation of alkylzinc reagents from unactivated alkyl bromides and chlorides
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(Matrix presented) Alkylzinc bromides have been efficiently prepared by the direct insertion of zinc metal (dust, powder, granule, shot), activated with 1-5 mol % I2, into alkyl bromides in a polar aprotic solvent. The zinc reagents thus formed undergo Ni- and Pd-catalyzed cross-coupling with aryl halides to produce functionalized alkylarenes in excellent yields.
- Huo, Shouquan
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p. 423 - 425
(2007/10/03)
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- Highly reactive forms of zinc and reagents thereof
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A novel zerovalent zinc species and an organozinc reagent are disclosed. The zerovalent zinc species is directly produced by reaction of a reducing agent on a zinc salt, preferably Zn(CN)2. The organozinc reagent results from the reaction of the zerovalent zinc species and an organic compound having one or more stable anionic leaving groups. These organozinc reagents include a wide spectrum of functional groups in the organic radical, and are useful in a variety of reactions schemes.
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- The Direct Formation of Functionalized Alkyl(aryl)zinc Halides by Oxidative Addition of Highly Reactive Zinc with Organic Halides and Their Reactions with Acid Chlorides, α,β-Unsaturated Ketones, and Allylic, Aryl, and Vinyl Halides
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Highly reactive zinc, prepared by the lithium naphthalenide reduction of ZnCl2, readily undergoes oxidative addition to alkyl, aryl, and vinyl halides under mild conditions to generate the corresponding organozinc compounds in excellent yields.Significantly, the reaction will tolerate a spectrum of functional groups on the organic halides.Accordingly, this approach can now be used to prepare a wide variety of highly functionalized organozinc compounds.In the presence of Cu(I) salts, the organozinc compounds cross-couple with acid chlorides, conjugatively add to α,β-unsaturated ketones, and regioselectively undergo SN2' substitution reactions with allylic halides.They also cross-couple with aryl or vinyl halides with Pd(0) catalysts.
- Zhu, Lishan,Wehmeyer, Richard M.,Rieke, Reuben D.
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p. 1445 - 1453
(2007/10/02)
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