- Zirconium-Catalyzed Synthesis of Alkenylaminoboranes: From a Reliable Preparation of Alkenylboronates to a Direct Stereodivergent Access to Alkenyl Bromides
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A simple procedure has been optimized for the preparation of alkenylaminoborane from alkynes using diisopropylaminoborane and HZrCp2Cl. Coupled with a magnesium-catalyzed dehydrogenation, it allowed for the use of air- and moisture-stable diisopropylamine. This synthesis has been extended to a one-pot sequence leading directly to bromoalkenes with controlled stereochemistry. As such, it provides an easy, scalable, cheap process to access alkenylboronates and both (E)- and (Z)-bromoalkenes from commercially available alkynes.
- Birepinte, Mélodie,Chabaud, Laurent,Liautard, Virginie,Pucheault, Mathieu
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supporting information
p. 2838 - 2843
(2020/04/16)
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- Remote Nucleophilic Allylation by Allylrhodium Chain Walking
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Metal migration through a carbon chain is a versatile method for achieving remote functionalization. However, almost all known examples involve the overall net migration of alkylmetal species. Here, we report that allylrhodium species obtained from hydrorhodation of 1,3-dienes undergo chain walking toward esters, amides, or (hetero)arenes over distances of up to eight methylene units. The final, more highly conjugated allylrhodium species undergo nucleophilic allylation with aldehydes and with an imine to give Z-homoallylic alcohols and amines, respectively.
- Groves, Alistair,Martínez, Jose I.,Smith, Joshua J.,Lam, Hon Wai
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supporting information
p. 13432 - 13436
(2018/09/21)
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- Stereodivergent Olefination of Enantioenriched Boronic Esters
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A stereodivergent coupling reaction between vinyl halides and boronic esters is described. This coupling process proceeds without a transition-metal catalyst, instead proceeding by electrophilic selenation or iodination of a vinyl boronate complex followed by stereospecific syn or anti elimination. Chiral, nonracemic boronic esters could be coupled with complete enantiospecificity. The process enables the highly stereoselective synthesis of either the E or Z alkene from a single isomer of a vinyl coupling partner.
- Armstrong, Roly J.,García-Ruiz, Cristina,Myers, Eddie L.,Aggarwal, Varinder K.
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supporting information
p. 786 - 790
(2017/01/14)
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- Nickel-Catalyzed Reductive Cross-Coupling of Vinyl Bromides with Unactivated Alkyl Halides
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The use of pyridine as the sole ligand for the reductive vinylation of unactivated secondary alkyl halides under Ni-catalyzed conditions has been developed. Both alkyl- and aryl-substituted vinyl bromides are suitable, in which alkyl-decorated α-alkenyl bromides resulted in the α-products in good results.
- Gu, Jun,Qiu, Canbin,Lu, Wenbin,Qian, Qun,Lin, Kunhua,Gong, Hegui
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supporting information
p. 1867 - 1873
(2017/04/06)
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- Ni-catalyzed reductive coupling of α-halocarbonyl derivatives with vinyl bromides
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This work describes the vinylation of α-halo carbonyl compounds with vinyl bromides under Ni-catalyzed reductive coupling conditions. While aryl-conjugated vinyl bromides entail pyridine as the sole labile ligand, the alkyl-substituted vinyl bromides require both bipyridine and pyridine as the co-ligands.
- Qiu, Canbin,Yao, Ken,Zhang, Xinghua,Gong, Hegui
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supporting information
p. 11332 - 11335
(2016/12/18)
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- Preparation of Vinyl Arenes by Nickel-Catalyzed Reductive Coupling of Aryl Halides with Vinyl Bromides
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This work emphasizes the synthesis of substituted vinyl arenes by reductive coupling of aryl halides with vinyl bromides under mild and easy-to-operate nickel-catalyzed reaction conditions. A broad range of aryl halides, including heteroaromatics, and vinyl bromides were employed to yielding products in moderate to excellent yields with high functional-group tolerance. The nickel-catalytic system displays good chemoselectivity between the two C(sp2)-halide coupling partners, thus demonstrating a mechanistic pathway distinct from other stepwise protocols.
- Liu, Jiandong,Ren, Qinghua,Zhang, Xinghua,Gong, Hegui
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supporting information
p. 15544 - 15548
(2016/12/09)
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- A new entry of highly nucleophilic CHBr3-TiCl4-Mg system for the stereoselective synthesis of 1-alkenyl bromides
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This TiCl4-Mg promoted coupling of CHBr3 with various aldehydes and ketones, especially in sterically hindered or enolizable ketones, provides a simple, practical, and stereoselective carbonyl-bromomethylenation leading primarily to (E)-vinyl bromides.
- Bhorge, Yeshwant Ramchandra,Chang, Su-Haur,Chang, Cheng-Ta,Yan, Tu-Hsin
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experimental part
p. 4846 - 4851
(2012/08/07)
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- TBAF-promoted dehydrobrominations of vicinal dibromides having an adjacent O-functional group
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Regioselective HBr elimination of vicinal dibromides having an adjacent oxygen functional group to give the corresponding 2-bromoalk-1-enes was controlled using 1.1 equivalents of TBAF. Two-step elimination to give the corresponding alkynes was controlled using 5.0 equivalents of TBAF. High yield and high selectivity require the presence of an oxygen functional group at the neighboring position of the elimination site.
- Kutsumura, Noriki,Kubokawa, Keisuke,Saito, Takao
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experimental part
p. 2717 - 2720
(2010/12/25)
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- Palladium-catalyzed carbene insertion into vinyl halides and trapping with amines
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Palladium is shown to catalyze the three-component coupling of vinyl halides, trimethytsilyldiazomethane, and amines to generate allylamines. The mechanism is believed to Involve formation of an R-Pd=CHSiMe3 intermediate that undergoes migratio
- Devine, Sean K. J.,Van Vranken, David L.
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p. 2047 - 2049
(2008/02/02)
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- A new and facile method for stereoselective synthesis of (E)-styryl bromides by the reduction of 1,1-dibromoalkenes using LiAlH4-EtOAc (1:1)
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A facile method for stereoselective synthesis of (E)-styryl bromides by the reduction of 1,1-dibromoalkenes using LiAlH4-EtOAc (1:1) is described. We believe that the present procedure is a good alternative to the Tokuda's microwave method with good stereoselectivity.
- Horibe, Hideo,Kondo, Kazuhiro,Okuno, Hiroaki,Aoyama, Toyohiko
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p. 986 - 988
(2007/10/03)
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- Stereoselective hydrogenolysis of 1,1-dibromo-1-alkenes and stereospecific synthesis of conjugated (Z)-alkenyl compounds
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The Pd-catalyzed hydrogenolysis of 1,1-dibromoalkenes with Bu3SnH occurs at room temperature stereoselectively to give (Z)-1-bromo-1-alkenes. We sought to determine the optimal reaction conditions and illustrate the scope of this method with 32 dibromoalkenes including alkenyl- and alkynyl- conjugated 1,1-dibromo-1-alkenes 7a-h and 2,2-disubstituted 1,1-dibromo-1- alkenes 9af. Triphenylphosphine was the best ligand for the Pd-catalyzed hydrogenolysis. A wide range of solvents can be used for this reaction excluding EtOH, AcOH, and CHCl3. However, the reaction proceeds even in these solvents with the addition of a cosolvent or radical scavenger. The reaction of 1,1-diiodo-1-alkene (3) gave a mixture of (Z)-1-iodo-1-alkene (4), (Z)-1-tributylstannyl-1-alkene (5), and a terminal alkene 6, while that of 1,1-dichloroalkene did not occur. This selectivity can be explained by the stereoselective insertion of Pd(0) to a trans bromine-alkenyl carbon bond, successive transmetalation with Bu3SnH, and reductive elimination. The Suzuki and Sonogashira couplings of the resulting (Z)-1-bromo-1-alkenes with alkenyl(dialkoxy)borane and terminal alkyne occurred to give conjugated polyenes and enynes stereospecifically. The Pd-catalyzed hydrogenolysis of 1,1-dibromo-1-alkene and successive cross-coupling can be carried out either in a stepwise manner or in one-pot under the same Pd catalysis. These two processes should be useful for the synthesis of geometrically pure polyene and enyne with a Z-alkenyl unit.
- Uenishi, Jun'ichi,Kawahama, Reiko,Yonemitsu, Osamu,Tsuji, Jiro
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p. 8965 - 8975
(2007/10/03)
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- A general and convenient synthetic method of geometrically pure (Z)-1-bromo-1-alkenes
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Palladium catalyzed hydrogenolysis of 1,1-dibromo-1-alkenes by tributyltin hydride proceeds smoothly to give (Z)-1-bromo-1-alkenes with excellent stereoselectivity in good yields. Dibromomethylenation of aldehydes by a combination of CBr4 and P
- Uenishi, Jun'ichi,Kawahama, Reiko,Shiga, Yasuhiko,Yonemitsu, Osamu,Tsuji, Jiro
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p. 6759 - 6762
(2007/10/03)
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- Stereochemistry in carbenoid formation by bromine/lithium and bromine/zinc exchange reactions of gem-dibromo compounds
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Stereochemistry in generation of lithium and zincate carbenoids by bromine/metal exchange reactions of gem-dibromo compounds with BuLi and lithium triorganozincates, respectively, has been investigated. Both lithium and zincate carbenoids derived from 1,1
- Harada, Toshiro,Katsuhira, Takeshi,Hattori, Kazuhiro,Oku, Akira
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p. 7987 - 8002
(2007/10/02)
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- Vinyl Cation Formation by Decomposition of Vinyllead(IV) Triacetates. Part 2.
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The products resulting from the reductive elimination of lead(II) acetate from four E- and Z-pairs of vinyllead triacetates have been examined for evidence that these highly unstable lead compounds are a potential source of vinyl cations, including the le
- Pinhey, John T.,Stoermer, Martin J.
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p. 2455 - 2460
(2007/10/02)
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- A convenient synthesis of 1-bromoolefins and acetylenes by a chain extension of aldehydes
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Aldehydes are easily converted to 1-bromoolefins or terminal acetylenes by the use of Wittig reaction of bromomethylenetriphenylphosphorane which is prepared from bromomethyltriphenylphosphonium bromide with potassium tert-butoxide.
- Matsumoto, Masakatsu,Kuroda, Keiko
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p. 4021 - 4024
(2007/10/02)
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