- Hydrocobaltation-Dehydrocobaltation Reactions in Synthesis: A New Approach to the Controlled Cross-Coupling between sp2 Carbon Centres leading to Functionalised Alkenes
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Cross-coupling reactions between two alkenes, leading to new functionalised alkenes, can be brought about via 'hydrocobaltation' of one of the alkenes followed by irradiation of the resulting organocobalt reagent in the presence of the second alkene subst
- Bhandal, Harcharan,Pattenden, Gerald
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- Nickel-Catalyzed Isomerization/Allylic Cyanation of Alkenyl Alcohols
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Herein reported is a nickel-catalyzed isomerization/allylic cyanation of alkenyl alcohols, which complements current methods for the allylic substitution reactions. The specific diphosphite ligand and methanol as the solvent are crucial for the success for this transformation. A gram-scale regioconvergent experiment and formal synthesis of quebrachamine demonstrate the high potential of this methodology.
- Ding, Ying,Long, Jinguo,Sun, Feilong,Fang, Xianjie
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supporting information
p. 6073 - 6078
(2021/08/16)
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- Nickel-Catalyzed Markovnikov Transfer Hydrocyanation in the Absence of Lewis Acid
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Hydrocyanation in the absence of toxic HCN gas is highly desirable. Addressing that challenge, transition-metal-catalyzed transfer hydrocyanation using safe HCN precursors has been developed, but these reagents generally require a Lewis acid for activation, and the control of regioselectivity often remains problematic. In this Letter, a Ni-catalyzed highly Markovnikov-selective transfer hydrocyanation that operates in the absence of any Lewis acid is reported. The readily prepared pro-aromatic 1-isopropylcyclohexa-2,5-diene-1-carbonitrile is used as the HCN source, and the reaction shows a broad substrate scope and high functional group tolerance. Terminal styrene derivatives, dienes, and internal alkynes are converted with good to excellent selectivities. Mechanistic studies provide insights into the origin of the regioselectivity.
- Frye, Nils L.,Bhunia, Anup,Studer, Armido
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supporting information
p. 4456 - 4460
(2020/06/03)
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- I2/Li2CO3-promoted cyanation of diarylalcohols through a dual activation process
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One-step base promoted strategy for cyanation of α,α-diaryl alcohols has been developed under mild and transition metal-free conditions. This method provides a straightforward and facile way towards the synthesis of β,γ-unsaturated nitriles and α-phenylnitiriles from α-vinyl carbinols and α,α-diaryl methanols, respectively, up to 99% yield. Moreover, various azides and ethers could also be accessed from their respective nucleophiles under standard reaction conditions.
- Hu, Liangzhen,Hussain, Muhammad Ijaz,Deng, Qingfu,Liu, Qing,Feng, Yangyang,Zhang, Xiaohui,Xiong, Yan
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p. 308 - 314
(2018/12/11)
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- Nickel-Catalyzed Cyanation of Benzylic and Allylic Pivalate Esters
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A nickel-catalyzed cyanation reaction of benzylic and allylic pivalate esters is reported using an air-stable Ni(II) precatalyst and substoichiometric quantities of Zn(CN)2. Alkene additives were found to inhibit catalysis, suggesting that avoiding β-hydride elimination side reactions is essential for productive catalysis. An enantioenriched allylic ester undergoes enantiospecific cross-coupling to produce an enantioenriched allylic nitrile. This method was applied to an efficient synthesis of (±)-naproxen from commercially available starting materials.
- Michel, Nicholas W. M.,Jeanneret, Alexandria D. M.,Kim, Hyehwang,Rousseaux, Sophie A. L.
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p. 11860 - 11872
(2018/10/02)
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- Olefin-Migrative Cleavage of Cyclopropane Rings through the Nickel-Catalyzed Hydrocyanation of Allenes and Alkenes
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A nickel-catalyzed hydrocyanation triggered by hydronickelation of the carbon-carbon double bonds of allenes followed by cyclopropane cleavage is described. The observed regio- and stereochemistries in the products are strongly influenced by the initial hydronickelation step, and allenyl- and methylenecyclopropanes reacted smoothly to promote the cleavage of cyclopropane. In contrast, this cleavage was not observed with vinylidenecyclopropanes, because the initial hydronickelation does not give a suitable intermediate for cleavage of the cyclopropanes. (Figure presented.).
- Hori, Hiroto,Arai, Shigeru,Nishida, Atsushi
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p. 1170 - 1176
(2017/04/13)
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- A new protocol for nickel-catalysed regio- and stereoselective hydrocyanation of allenes
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Regio- and stereoselective hydrocyanation under nickel catalysis is described. This report shows that allenyl C-C double bonds are discriminated and converted to the corresponding carbonitriles as a single product. The key functionalities for achieving high regio- and stereocontrol are aryl and cyclopropyl groups in the substrates. This journal is
- Arai, Shigeru,Hori, Hiroto,Amako, Yuka,Nishida, Atsushi
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p. 7493 - 7496
(2015/05/04)
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- Efficient assembly of α-aryl and α-vinyl nitriles via iron-catalyzed ether bond activation
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A novel and practical method for the synthesis of diverse α-aryl and α-vinyl nitriles was developed via an iron-catalyzed sp3 C-O ether bond cleavage with C-C bond formation in the reaction of π-activated ethers with TMSCN.
- Fan, Xiaohui,Guo, Kun,Guan, Yong-Hong,Fu, Lin-An,Cui, Xiao-Meng,Lv, Hao,Zhu, Hong-Bo
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supporting information
p. 1068 - 1071
(2014/02/14)
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- Efficient assembly of α-aryl and α-vinyl nitriles via iron-catalyzed ether bond activation
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A novel and practical method for the synthesis of diverse α-aryl and α-vinyl nitriles was developed via an iron-catalyzed sp3 C-O ether bond cleavage with C-C bond formation in the reaction of π-activated ethers with TMSCN.
- Fan, Xiaohui,Guo, Kun,Guan, Yong-Hong,Fu, Lin-An,Cui, Xiao-Meng,Lv, Hao,Zhu, Hong-Bo
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supporting information
p. 1068 - 1071
(2015/02/18)
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- Copper-Catalyzed Regioselective Allylic Cyanation of Allylic Compounds with Trimethylsilyl Cyanide
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The copper-catalyzed regioselective allylic cyanation of allylic compounds with trimethylsilyl cyanide (TMSCN) is described. Copper(I) iodide (CuI), copper(I) cyanide (CuCN) and copper(II) chloride (CuCl2) are shown to effectively catalyze the cyanation of various allylic substrates to afford the corresponding allylic cyanides in good yields and high regioselectivities. The reaction in the presence of 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO) reveals that the cyanation proceeds via a radical pathway.
- Munemori, Daisuke,Tsuji, Hiroaki,Uchida, Kenta,Suzuki, Tomoaki,Isa, Kazuki,Minakawa, Maki,Kawatsura, Motoi
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p. 2747 - 2750
(2015/10/28)
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- The synthesis of an aziridinyl analogue of unit A of cryptophycin-1
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A novel analogue of unit A of cryptophycin-1 was prepared starting from commercial trans-cinnamaldehyde. The modifications introduced into the new structure related to the replacement of the epoxide with an aziridine moiety, and the inclusion of the 1,3-enone moiety into an aromatic ester frame through the synthesis of a key aromatic ketone. Asymmetry was induced during the later steps of the synthetic pathway. The optical purity of compounds was monitored by chiral HPLC and polarimetric measurements.
- Mezrai,Drici,Lesur,Kajima Mulengi,Wadouachi,Pilard
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p. 259 - 267
(2014/05/20)
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- Chemoselective and direct functionalization of methyl benzyl ethers and unsymmetrical dibenzyl ethers by using iron trichloride
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Methyl and benzyl ethers are widely utilized as protected alcohols due to their chemical stability, such as the low reactivity of the methoxy and benzyloxy groups as leaving groups under nucleophilic conditions. We have established the direct azidation of chemically stable methyl and benzyl ethers derived from secondary and tertiary benzyl alcohols. The present azidation chemoselectively proceeds at the secondary or tertiary benzylic positions of methyl benzyl ethers or unsymmetrical dibenzyl ethers and is also applicable to direct allylation, alkynylation, and cyanation reactions, as well as the azidation. The present methodologies provide not only a novel chemoselectivity but also the advantage of shortened synthetic steps, due to the direct process without the deprotection of the methyl and benzyl ethers. Ethers exchanged: Methyl and benzyl ethers are chemically stable and generally tolerant under nucleophilic substitution conditions. Iron-catalyzed direct functionalizations (e.g., azidation, allylation, alkynylation, and cyanation) of methyl and benzyl ethers derived from secondary and tertiary benzyl alcohols were established with excellent regioselectivities (see scheme; PG: protecting group; Bn: benzyl; Nu: nucleophile; TMS: trimethylsilyl). Copyright
- Sawama, Yoshinari,Goto, Ryota,Nagata, Saori,Shishido, Yuko,Monguchi, Yasunari,Sajiki, Hironao
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supporting information
p. 2631 - 2636
(2014/03/21)
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- Self-assembled bidentate ligands for the nickel-catalyzed hydrocyanation of alkenes
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(Chemical Equation Presented) Well-stocked library: A catalyst with interesting activity, regioselectivity (rs), and functional-group tolerance could be identified from a 5x4 library of isoquinolone-or aminopyridine-derived self-assembled bidentate ligand
- De Greef, Michiel,Breit, Bernhard
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supporting information; experimental part
p. 551 - 554
(2009/04/14)
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- Facile preparation of α-aryl nitriles by direct cyanation of alcohols with TMSCN under the catalysis of InX3
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(Chemical Equation Presented) A convenient and efficient synthesis of α-aryl nitrites was developed by direct cyanation of alcohols with TMSCN under the catalysis of Lewis acid. Using 5-10 mol % of InBr3 as the catalyst, a variety of benzylic alcohols can be converted to the corresponding nitriles in 5-30 min with yields of 46-99%.
- Chen, Gang,Wang, Zheng,Wu, Jiang,Ding, Kuiling
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supporting information; experimental part
p. 4573 - 4576
(2009/05/07)
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- Nickel(0)-catalyzed asymmetric hydrocyanation of 1,3-dienes
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1,2-Bis-diarylphosphinites are excellent ligands for the Ni(0)-catalyzed hydrocyanation of certain types of 1,3-dienes. 1-Phenyl-1,3-butadiene, 1-vinyl-3,4-dihydronaphthalene, and 1-vinylindene undergo highly regioselective hydrocyanation under ambient co
- Saha, Biswajit,RajanBabu
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p. 4657 - 4659
(2007/10/03)
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- Nickel-catalyzed electrochemical couplings of vinyl halides: Synthetic and stereochemical aspects
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Homo- and cross-coupling involving alkenyl halides have been performed efficiently using an electroassisted nickel-complex catalysis. Valuable product such as conjugated dienes, β,γ- or γ,δunsaturated esters, ketones, or nitriles, as well as alkenylated aryl compounds are thus prepared with high yields and high stereoselectivity. Partial isomerization is only observed in a few cases, when the alkenyl halide is involved in a late step of the catalytic cycle. This is the case in the preparation of (Z,Z)-1,3-diene.
- Cannes,Condon,Durandetti,Perichon,Nedelec
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p. 4575 - 4583
(2007/10/03)
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- Cobalt-Mediated Intermolecular Radical Additions to Carbon-to-Carbon Double Bonds leading to New Functionalised Alkenes
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Alkyl radicals generated by photolytic homolysis of cobalt salophen reagents, e.g. (6) and (15), are shown to add to activated carbon-to-carbon double bonds, i.e. ethyl acrylate, methyl vinyl ketone, acrylonitrile, and styrene, producing preparatively useful yields of new alkene products, viz. (9), (10), (12) and (14) , and (16) .The reactions proceed via radical (Michael) additions, followed by 'dehydrocobaltation' from the presumed organocobalt intermediates (2) (Scheme 4).By use of this chemistry, in combination with the Schrauzer 'hydrocobaltation' reaction of alkenes, a new method for the cross-coupling reactions between two alkenes, leading to new functionalised alkenes, e.g. (24), (25), (26), (27), (28), and (29), is developed .
- Bhandal, Harcharan,Howell, Amy R.,Patel, Vinod F.,Pattenden, Gerald
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p. 2709 - 2714
(2007/10/02)
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- A Facile Synthesis of 1,5-Dienes and β,γ-Unsaturated Nitriles via Trityl Perchlorate-Catalyzed Allylation
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In the presence of a catalytic amount of trityl perchlorate, secondary and tertiary allyl ethers smoothly react with allylsilanes and silyl cyanide to give the corresponding 1,5-dienes and β,γ-unsaturated nitriles, respectively, in good yields.
- Murakami, Masahiro,Kato, Takashi,Mukaiyama, Teruaki
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p. 1167 - 1170
(2007/10/02)
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