- Preparation and properties of high birefringence phenylacetylene isothiocyanato-based blend liquid crystals
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A series of compounds of with high birefringence containing alkoxy–phenylacetylene–isothiocyanato structure were synthesized and characterized. The chemical structures of these compounds were confirmed by FT-IR and 1H-NMR, and transition temperatures and birefringence were measured. One of these compounds with good liquid crystal property and high birefringence was mixed with host liquid crystal to form blend liquid crystal. The effects of the concentration of the compound on phase temperature range, birefringence, resistivity, dielectric anisotropy and photoelectric properties were discussed. The results showed that blend liquid crystal (with 7 wt% compound) exhibited excellent comprehensive performance.
- He, Zemin,Wang, Haiyang,Zhang, Huimin,Zhang, Yongming,Zhao, Yang,Zhao, Yuzhen
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- Selective Rhodium-Catalyzed Hydroformylation of Terminal Arylalkynes and Conjugated Enynes to (Poly)enals Enabled by a π-Acceptor Biphosphoramidite Ligand
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The hydroformylation of terminal arylalkynes and enynes offers a straightforward synthetic route to the valuable (poly)enals. However, the hydroformylation of terminal alkynes has remained a long-standing challenge. Herein, an efficient and selective Rh-catalyzed hydroformylation of terminal arylalkynes and conjugated enynes has been achieved by using a new stable biphosphoramidite ligand with strong π-acceptor capacity, which affords various important E-(poly)enals in good yields with excellent chemo- and regioselectivity at low temperatures and low syngas pressures.
- Zhao, Jiangui,Zheng, Xueli,Tao, Shaokun,Zhu, Yuxin,Yi, Jiwei,Tang, Songbai,Li, Ruixiang,Chen, Hua,Fu, Haiyan,Yuan, Maolin
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supporting information
p. 6067 - 6072
(2021/08/16)
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- Illuminatinganti-hydrozirconation: controlled geometric isomerization of an organometallic species
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A general strategy to enable the formalanti-hydrozirconation of arylacetylenes is reported that mergescis-hydrometallation using the Schwartz Reagent (Cp2ZrHCl) with a subsequent light-mediated geometric isomerization atλ= 400 nm. Mechanistic delineation of thecontra-thermodynamic isomerization step indicates that a minor reaction product functions as an efficientin situgenerated photocatalyst. Coupling of theE-vinyl zirconium species with an alkyne unit generates a conjugated diene: this has been leveraged as a selective energy transfer catalyst to enableE→Zisomerization of an organometallic species. Through anUmpolungmetal-halogen exchange process (Cl, Br, I), synthetically useful vinyl halides can be generated (up toZ?:?E= 90?:?10). This enabling platform provides a strategy to access nucleophilic and electrophilic alkene fragments in both geometric forms from simple arylacetylenes.
- Gilmour, Ryan,Hostmann, Theresa,Nevesely, Tomá?
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p. 10643 - 10648
(2021/08/20)
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- Cyclic Diaryl λ3-Bromanes: A Rapid Access to Molecular Complexity via Cycloaddition Reactions
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Biaryls have widespread applications in organic synthesis. However, sequentially polysubstituted biaryls are underdeveloped due to their challenging preparation. Herein, we report the synthesis of dissymetric 2,3,2′,3′,4-substituted biaryls via pericyclic reactions of cyclic diaryl λ3-bromanes. The functional groups tolerance and atom economy allow access to molecular complexity in a single reaction step. Continuous flow protocol has been designed for the scale-up of the reaction, while postfunctionalizations have been developed taking advantage of the residual Br-atom.
- Lanzi, Matteo,Ali Abdine, Racha Abed,De Abreu, Maxime,Wencel-Delord, Joanna
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supporting information
p. 9047 - 9052
(2021/12/06)
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- Alkenylation and Arylation of Peptides via Ni-Catalyzed Reductive Coupling of α- C-Tosyl Peptides with Csp2Triflates/Halides
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A Ni-catalyzed reductive cross-coupling between α-C-tosyl peptides and Csp2 triflates/halides has been developed. This protocol enables the formation of various unnatural di- and tripeptides containing vinyl and aryl side chains, and it expands the applications of Ni-catalyzed reductive cross-coupling in late-stage diversification of peptides.
- Chen, Yunrong,Gong, Hegui,Ma, Guobin,Qian, Qun,Song, Yanhong,Sun, Deli,Tao, Xianghua
-
supporting information
p. 7418 - 7422
(2021/10/12)
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- Iron-Catalyzed Regioselective Alkenylboration of Olefins
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The first examples of an iron-catalyzed three-component synthesis of homoallylic boronates from regioselective union of bis(pinacolato)diboron, an alkenyl halide (bromide, chloride or fluoride), and an olefin are disclosed. Products that bear tertiary or quaternary carbon centers could be generated in up to 87 % yield as single regioisomers with complete retention of the olefin stereochemistry. With cyclopropylidene-containing substrates, ring cleavage leading to trisubstituted E-alkenylboronates were selectively obtained. Mechanistic studies revealed reaction attributes that are distinct from previously reported alkene carboboration pathways.
- Yu, Xiaolong,Zheng, Hongling,Zhao, Haonan,Lee, Boon Chong,Koh, Ming Joo
-
supporting information
p. 2104 - 2109
(2020/11/30)
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- The hydrodebromination of 1,1-dibromoalkenes via visible light catalysis
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Vinyl bromides are versatile synthetic intermediates and widely applied in organic synthesis and pharmaceuticals. Herein, a hydrodebromination reaction of 1,1-dibromoalkenes was established via visible light catalysis. A variety of structurally different vinyl bromides were obtained in moderate to excellent yields.
- Sun, Wencheng,Teng, Qiaoling,Cheng, Dongping,Li, Xiaonian,Xu, Xiaoliang
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supporting information
(2019/12/05)
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- Iron-Catalyzed Reductive Vinylation of Tertiary Alkyl Oxalates with Activated Vinyl Halides
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We present herein a rare and efficient method for the creation of vinylated all carbon quaternary centers via Fe-catalyzed cross-electrophile coupling of vinyl halides with tertiary alkyl methyl oxalates. The reaction displays excellent functional group tolerance and broad substrate scope, which allows cascade radical cyclization and vinylation to afford complex bicyclic and spiral structural motifs. The reaction proceeds via tertiary alkyl radicals, and the putative vinyl-Br/Fe complexation appears to be crucial for activating the alkene and enabling a possibly concerted radical addition/C-Fe forming process.
- Chen, Haifeng,Gong, Hegui,Yao, Ken,Ye, Yang
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supporting information
(2020/03/13)
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- Photocatalytic Isomerization of Styrenyl Halides: Stereodivergent Synthesis of Functionalized Alkenes
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An efficient and general method for the isomerization of styrenyl halides under different photocatalytic conditions (fac-Ir(ppy)3 in methanol for E to Z isomerization and fluorescein in 1,4-dioxane for Z to E isomerization, respectively) is disclosed. A series of stereospecific transformations constitute preliminary validation of this strategy in the synthesis of functionalized alkenes, including two diaryl alkenes, a styrenyl boronic ester and an enyne. The photocatalytic isomerization and subsequent cross coupling reaction can be run in a one-pot manner. The stereodivergent synthesis of all four isomers of a conjugated diene, as well as the antitumor agent DMU-212 and its (Z)-isomer highlights the synthetic applicability of this method.
- Zhang, Hao,Xu, Qing,Yu, Lei,Yu, Shouyun
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supporting information
p. 1472 - 1477
(2019/11/03)
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- A Simplified Protocol for the Stereospecific Nickel-Catalyzed C-S Vinylation Using NiX 2 Salts and Alkyl Phosphites
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A Ni-catalyzed C-S cross-coupling using only NiI 2 (0.5-2.5 molpercent) and P(O i Pr) 3 (2.0-10.0 molpercent) is reported. Using an air-stable Ni(II) precatalyst, and a cheap and commercially available ligand, a scalable and robust method was developed to cross-couple various thiophenols and styryl bromides, including some sterically encumbered thiols, an α-bromocinnamaldehyde as well as a thiolation-cyclization.
- Larin, Egor M.,Lautens, Mark,Marchese, Austin D.,Mirabi, Bijan
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p. 311 - 319
(2019/12/28)
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- Construction of Phenanthrenes and Chrysenes from β-Bromovinylarenes via Aryne Diels-Alder Reaction/Aromatization
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A highly efficient transition-metal-free general method for the synthesis of polycyclic aromatic hydrocarbons like phenanthrenes and chrysenes (and tetraphene) from β-bromovinylarenes and arynes has been developed. The reactions proceed via an aryne Diels-Alder (ADA) reaction, followed by a facile aromatization. This is the first report on direct construction of chrysenes (and tetraphene) using the ADA approach. Unlike the literature method which is limited to only 9/10-substituted derivatives, this method gives access to a wide variety of functionalized phenanthrenes.
- Singh, Vikram,Verma, Ram Subhawan,Khatana, Anil K.,Tiwari, Bhoopendra
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supporting information
p. 14161 - 14167
(2019/10/28)
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- Dual nickel- and photoredox-catalyzed reductive cross-coupling of aryl vinyl halides and unactivated tertiary alkyl bromides
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A novel reductive cross-coupling of aryl vinyl halides and unactivated tertiary alkyl bromides has been realized via photoredox/nickel dual catalysis to produce vinyl arene derivatives bearing all-carbon quaternary centers with excellent E-selectivity. A stoichiometric metal reductant could be avoided by employing commercially available N,N,N′,N′-tetramethylethylenediamine (TMEDA) as the terminal reductant.
- Yu, Weijie,Chen, Long,Tao, Jiasi,Wang, Tao,Fu, Junkai
-
supporting information
p. 5918 - 5921
(2019/05/27)
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- Direct Cross-Coupling of Allylic C(sp3)?H Bonds with Aryl- and Vinylbromides by Combined Nickel and Visible-Light Catalysis
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An efficient protocol for the direct allylic C(sp3)?H bond activation of unactivated tri- and tetrasubstituted alkenes and their functionalization with aryl- and vinylbromides by nickel and visible-light photocatalysis has been developed. The method allows C(sp2)?C(sp3) formation under mild reaction conditions with good functional-group tolerance and excellent regioselectivity.
- Huang, Long,Rueping, Magnus
-
supporting information
p. 10333 - 10337
(2018/07/31)
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- Palladium-Catalyzed Decarboxylative γ-Olefination of 2,5-Cyclohexadiene-1-carboxylic Acid Derivatives with Vinyl Halides
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This study explores a Pd-catalyzed decarboxylative Heck-type Csp3-Csp2 coupling reaction of 2,5-cyclohexadiene-1-carboxylic acid derivatives with vinyl halides to provide γ-olefination products. The olefinated 1,3-cyclohexadienes can be further oxidized to produce meta-alkylated stilbene derivatives. Additionally, the conjugated diene products can also undergo a Diels-Alder reaction to produce a bicyclo[2.2.2]octadiene framework.
- Chang, Chi-Hao,Chou, Chih-Ming
-
supporting information
p. 1949 - 1952
(2018/04/16)
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- A Facile Access to trans -3-Styryl-4-hydrazinocyclopentenes via Palladium-Catalyzed Ring Opening of Diazanorbornenes with (Z)-β-Bromostyrenes/2,3-Dibromohydrocinnamic Acids
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trans -3-Styryl-4-hydrazinocyclopentenes have been synthesized via palladium-catalyzed desymmetrization of diazanorbornenes with (Z)-β-bromostyrenes. The reaction also works well with (Z)-β-bromostyrenes generated in situ from 2,3-dibromohydrocinnamic acids. The synthesized hydrazinocyclopentenes provide an easy route towards synthetic intermediates of many scaffolds of biological potential.
- Saranya,Chand, S. Sarath,Gopalan, Greeshma,Jijitha,Radhakrishnan
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p. 184 - 192
(2017/10/13)
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- cis-β-Bromostyrene derivatives from cinnamic acids via a tandem substitutive bromination-decarboxylation sequence
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cis-β-Bromostyrene derivatives were synthesized stereospecifically from cinnamic acids through β-lactone intermediates. The synthetic sequence did not require the purification of the β-lactone intermediates although they were found to be stable and readily purified in most cases.
- Tang, Khanh G.,Kent, Greggory T.,Erden, Ihsan,Wu, Weiming
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p. 3894 - 3896
(2017/09/15)
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- A stereoselective synthesis of (E)- or (Z)-β-arylvinyl halides via a borylative coupling/halodeborylation protocol
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A new stereoselective method for the synthesis of (E)-β-arylvinyl iodides and (E)- or (Z)-β-arylvinyl bromides from styrenes and vinyl boronates on the basis of a one-pot procedure via borylative coupling/halodeborylation is reported. Depending on the halogenating agent as well as the mode of the halodeborylation reaction, (E) or (Z) isomers are selectively formed.
- Szyling, Jakub,Franczyk, Adrian,Pawlu?, Piotr,Marciniec, Bogdan,Walkowiak, J?drzej
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p. 3207 - 3215
(2017/04/21)
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- Stereoselective Synthesis of Vinyl Iodides through Copper(I)-Catalyzed Finkelstein-Type Halide-Exchange Reaction
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An efficient method for the stereoselective synthesis of vinyl iodides is described. The reactions of vinyl bromides with potassium iodide proceed smoothly in the presence of a copper catalyst under mild reaction conditions to produce the corresponding vinyl iodides stereospecifically and in satisfactory to excellent yields.
- Feng, Xiujuan,Zhang, Haixia,Lu, Wenbo,Yamamoto, Yoshinori,Almansour, Abdulrahman I.,Arumugam, Natarajan,Kumar, Raju Suresh,Bao, Ming
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supporting information
p. 2727 - 2732
(2017/06/13)
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- Decarboxylative bromination of α,β-unsaturated carboxylic acids via an anodic oxidation
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A novel bromination of α,β-unsaturated carboxylic acids was developed via a decarboxylation by virtue of a direct anodic electro-oxidation. In this method, ammonium bromide was employed as a bromine source and the reaction features transition-metal-free, short time, and no additional supporting electrolyte.
- Bi, Mei-Xiang,Qian, Peng,Wang, Yu-Kang,Zha, Zheng-Gen,Wang, Zhi-Yong
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p. 1159 - 1162
(2017/06/19)
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- Ohmic Heating and Ionic Liquids in Combination for the Indium-Promoted Synthesis of 1-Halo Alkenyl Compounds: Applications to Pd-Catalysed Cross-Coupling Reactions
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We have explored the combination of ohmic heating (ΩH) with ionic liquids for indium-promoted reactions and report herein the indium-promoted dehalogenation of gem-dibromo alkenes and the indium-mediated reductive elimination of chlorohydrins for the synthesis of 1-halo alkenyl derivatives. Heck, Stille, Suzuki, Kumada and Sonogashira couplings of the resulting 1-halo-1-alkenes with appropriate reagents were carried out to give alkenes, dienes and enynes. We report herein the combination of ohmic heating (ΩH) with ionic liquids for the indium-promoted dehalogenation of gem-dibromo alkenes and the indium-mediated reductive elimination of chlorohydrins. The 1-halo alkenyl derivatives synthesized were then submitted to a series of cross-coupling reactions to give conjugated alkenes, dienes and enynes.
- Soengas, Raquel G.,Silva, Vera L. M.,Pinto, Joana,Rodríguez-Solla, Humberto,Silva, Artur M. S.
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- Metal-Mediated Debromination of gem-Dibromoalkenes under Mild Conditions
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We describe the facile and efficient metal-promoted reduction of C-Br bonds of gem-dibromides. When the reaction is mediated by indium, the corresponding vinyl bromides are obtained in good yields and high E-stereoselectivities. Alternatively, when the reduction is mediated by samarium diiodide, vinyl bromides are obtained in moderate yields and good Z-selectivities.
- Soengas, Raquel G.,Rodríguez-Solla, Humberto,Silva, Artur M.S.
-
supporting information
p. 1096 - 1099
(2016/05/19)
-
- ANTI-HIV COMPOUNDS
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This invention provides, among other things, tetrahydroisoquinolines useful for treating viral infections, pharmaceutical formulations containing such compounds, as well as methods of inhibiting the replication of a virus, such as HIV, or treating a disease, such as AIDS.
- -
-
Paragraph 0300; 0415
(2016/07/05)
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- Direct synthesis of Z-alkenyl halides through catalytic cross-metathesis
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Olefin metathesis has had a large impact on modern organic chemistry, but important shortcomings remain: for example, the lack of efficient processes that can be used to generate acyclic alkenyl halides. Halo-substituted ruthenium carbene complexes decompose rapidly or deliver low activity and/or minimal stereoselectivity, and our understanding of the corresponding high-oxidation-state systems is limited. Here we show that previously unknown halo-substituted molybdenum alkylidene species are exceptionally reactive and are able to participate in high-yielding olefin metathesis reactions that afford acyclic 1,2-disubstituted Z-alkenyl halides. Transformations are promoted by small amounts of a catalyst that is generated in situ and used with unpurified, commercially available and easy-to-handle liquid 1,2-dihaloethene reagents, and proceed to high conversion at ambient temperature within four hours. We obtain many alkenyl chlorides, bromides and fluorides in up to 91 per cent yield and complete Z selectivity. This method can be used to synthesize biologically active compounds readily and to perform site- and stereoselective fluorination of complex organic molecules.
- Koh, Ming Joo,Nguyen, Thach T.,Zhang, Hanmo,Schrock, Richard R.,Hoveyda, Amir H.
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p. 459 - 465
(2016/04/05)
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- Ultrasonically Assisted Decarboxylative Bromination of α,β-Unsaturated Carboxylic Acids under Vilsmeier-Haack Conditions
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An efficient method for decarboxylative bromination of cinnamic acids (α,β-unsaturated carboxylic acids or 3-arylpropenoic acids) was achieved under relatively mild conditions using Vilsmeier-Haack reagent and KBr in acetonitrile media. Vilsmeier-Haack reagent is prepared by using 1:1 ratio of oxychloride (SOCl2 or POCl3) and DMF under chilled condition. Ultrasonically assisted reactions underwent smoothly with highly significant rate enhancements and afforded bromostyrenes as products in very good yields even though the reactions were too sluggish.
- Kumar, M. Satish,Rajanna,Venkanna,Venkateswarlu,Sudhakar Chary
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p. 642 - 646
(2015/12/26)
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- Tellurium-promoted stereoselective hydrodebromination of 1,1-dibromoalkenes: Synthesis of (: E)-bromoalkenes
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We describe herein an efficient and simple method for the stereoselective hydrodebromination of 1,1-dibromoalkenes by using a catalytic amount of the nucleophilic species of tellurium, generated in situ by the reaction of elemental tellurium with NaBH4. By this methodology, (E)-bromoalkenes were obtained in moderate to excellent yields under mild reaction conditions, without the use of transition metals or base. Furthermore, a high stereoselectivity for the (E)-isomer was observed when 1,1-dibromoarylalkenes were used, thus indicating a promising alternative for future applications in organic synthesis.
- Perin, Gelson,Barcellos, Angelita M.,Peglow, Thiago J.,Nobre, Patrick C.,Cargnelutti, Roberta,Lenard?o, Eder J.,Marini, Francesca,Santi, Claudio
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p. 103657 - 103661
(2016/11/13)
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- A General Copper-Catalyzed Vinylic Halogen Exchange Reaction
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An efficient and general system for the halogen exchange reaction in alkenyl halides has been developed. Upon reaction with catalytic amounts of copper iodide and trans-N,N′-dimethylcyclohexane-1,2-diamine in the presence of tetramethylammonium chloride or bromide, a wide range of easily accessible alkenyl iodides can be smoothly transformed to their far less available chlorinated and brominated derivatives in excellent yields and with full retention of the double bond geometry. This reaction also enables the chlorination of bromoalkenes and could be extended to the use of gem-dibromoalkenes.
- Nitelet, Antoine,Evano, Gwilherm
-
supporting information
p. 1904 - 1907
(2016/05/19)
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- Development of a general copper-catalyzed vinylic Finkelstein reaction—application to the synthesis of the C1–C9 fragment of laingolide B
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An efficient and broadly applicable procedure for the copper-catalyzed vinylic Finkelstein reaction is reported. Using a simple, readily available and cheap catalytic system, a broad range of alkenyl iodides and bromides can be smoothly converted to their lower homologues with high yields and full retention of the double bond geometry. Key features of this vinylic Finkelstein reaction are its broad applicability, enabling the conversion of readily available alkenyl iodides to their less available brominated and chlorinated counterparts, and the mild reaction conditions compatible with a range of highly functionalized substrates. The potential of this vinylic halogen exchange reaction in total synthesis and medicinal chemistry was demonstrated by its successful use for the synthesis of the C1–C9 fragment of laingolide B and for the late-stage modification of drug-like molecules. The extension of this halogen exchange to the acetylenic and allenic Finkelstein reactions is also reported.
- Nitelet, Antoine,Jouvin, Kévin,Evano, Gwilherm
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p. 5972 - 5987
(2016/09/16)
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- Triazole-curcuminoids: A new class of derivatives for 'tuning' curcumin bioactivities?
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Curcumin is a unique blend of pharmacophores responsible for the pleiotropy of this natural pigment. In the present study we have replaced the 1,3-dicarbonyl moiety with a 1,2,3-triazole ring to furnish a new class of triazole-curcuminoids as a possible strategy to generate new compounds with different potency and selectivity compared to curcumin. We obtained a proof-of-principle library of 28 compounds tested for their cytotoxicity (SY-SY5Y and HeLa cells) and for their ability to inhibit NF-κB. Furthermore, we also generated 1,3-dicarbonyl curcuminoids of selected click compounds. Triazole-curcuminoids lost their ability to be Michael's acceptors, yet maintained some of the features of the parent compounds and disclosed new ones. In particular, we found that some compounds were able to inhibit NF-κB without showing cytotoxicity, while others, unlike curcumin, activated NF-κB signalling. This validates the hypothesis that click libraries can be used to investigate the biological activities of curcumin as well as generate analogs with selected features.
- Caprioglio, Diego,Torretta, Simone,Ferrari, Maila,Travelli, Cristina,Grolla, Ambra A.,Condorelli, Fabrizio,Genazzani, Armando A.,Minassi, Alberto
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p. 140 - 152
(2015/12/31)
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- Synthesis of Substituted Quinolizidines via a Gold-Catalyzed Double Cyclization Cascade
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A novel synthesis of quinolizidines by a cationic gold-catalyzed double cyclization cascade has been developed. The reaction was initiated by the gold-catalyzed 6-exo-dig cyclization of ynamides, which was followed by a second cyclization of an enamide intermediate to provide the corresponding quinolizidine derivatives. The utility of this reaction was demonstrated by application to the synthesis of multi-substituted quinolizidines and by the total synthesis of a quinolizidine alkaloid, (±)-lupinine.
- Nonaka, Shiori,Sugimoto, Kenji,Ueda, Hirofumi,Tokuyama, Hidetoshi
-
supporting information
p. 380 - 385
(2016/02/12)
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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
-
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
-
supporting information
p. 15544 - 15548
(2016/12/09)
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- Engaging Alkenyl Halides with Alkylsilicates via Photoredox Dual Catalysis
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Single-electron transmetalation via photoredox/nickel dual catalysis provides the opportunity for the construction of Csp3-Csp2 bonds through the transfer of alkyl radicals under very mild reaction conditions. A general procedure for the cross-coupling of primary and secondary (bis-catecholato)alkylsilicates with alkenyl halides is presented. The developed method allows not only alkenyl bromides and iodides but also previously underexplored alkenyl chlorides to be employed. (Chemical Equation Presented).
- Patel, Niki R.,Kelly, Christopher B.,Jouffroy, Matthieu,Molander, Gary A.
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supporting information
p. 764 - 767
(2016/03/01)
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- The use of BrCCl3-PPh3 in Appel type transformations to esters, O-acyloximes, amides, and acid anhydrides
-
Esters, acyloximes, amides and acid anhydrides have been prepared from the respective carboxylic acids, oximes, amines and alcohols by the use of the reagent combination BrCCl3-PPh3. The reactions obviate the handling acyl halides or more aggressive reagents PCl3, POCl3, or SOCl2. Furthermore, the environmentally hazardous CCl4 used in Appel-type reactions is replaced with BrCCl3, a reagent of less environmental concern.
- Al-Azani, Mariam,al-Sulaibi, Mazen,al Soom, Nuha,Al Jasem, Yosef,Bugenhagen, Bernhard,Al Hindawi, Bassam,Thiemann, Thies
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p. 921 - 932
(2016/08/08)
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- A Convenient Stereoselective Reduction of Gem-Dibromides with a Combination of Dimethyl Phosphite and Potassium Carbonate
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An efficient and highly stereoselective reduction of a gem-dibromocyclopropane to the corresponding monobromocyclopropane under mild reaction conditions was developed using a combination of dimethyl phosphite and potassium carbonate. This reaction provided a simple and practical way for the synthesis of the valuable monobromocyclopropanes and β-monobromoalkenes.
- Zhao, Yalei,Chen, Tieqiao,Wang, Xiang-Bo,Han, Li-Biao
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p. 1820 - 1827
(2015/12/12)
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- Pd-Catalyzed Difluoromethylation of Vinyl Bromides, Triflates, Tosylates, and Nonaflates
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Pd-catalyzed difluoromethylation of di-, tri- or tetra-substituted vinyl bromides, triflates, tosylates and nonaflates under mild conditions is described. The reaction tolerates a wide range of functional groups, such as bromide, chloride, fluoride, ester, amine, nitrile, and protected carbonyl, thus providing a general route for the preparation of difluoromethylated alkenes. Vinyl fantasy: Pd-catalyzed difluoromethylation of di-, tri-, or tetra-substituted vinyl bromides, triflates, tosylates, and nonaflates under mild conditions is described. The reaction tolerates a wide range of functional groups, such as bromide, chloride, fluoride, ester, amine, nitrile, and protected carbonyl, thus providing a general route for the preparation of difluoromethylated alkenes.
- Chang, Dalu,Gu, Yang,Shen, Qilong
-
supporting information
p. 6074 - 6078
(2015/04/14)
-
- Nucleophile-selective cross-coupling reactions with vinyl and alkynyl bromides on a dinucleophilic aromatic substrate
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A nucleophile-selective cross-coupling reaction on an aromatic compound bearing two metal groups, Bpin and SnMe3, has been developed. Previously, only aryl bromides and iodides could be used as electrophilic components, but in this work, the scope could be extended to vinyl and alkynyl bromides as electrophiles. This means that the roles typical in Sonogashira couplings or Heck reactions of the aromatic ring as the dielectrophile coupling to vinyl and alkynyl metal species are reversed, which presents a new tool for organic synthesis. The first nucleophilic site to react is the stannyl group, and subsequently, a Suzuki-Miyaura cross-coupling reaction can take place on the same molecule.
- He, Lu-Ying,Schulz-Senft, Mathias,Thiedemann, Birk,Linshoeft, Julian,Gates, Paul J.,Staubitz, Anne
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supporting information
p. 2498 - 2502
(2015/04/22)
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- Palladium(0)-Catalyzed Methylcyclopropanation of Norbornenes with Vinyl Bromides and Mechanism Study
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An unusual methylcyclopropanation from [2 + 1] cycloadditions of vinyl bromides to norbornenes catalyzed by Pd(OAc)2/PPh3 in the presence of CH3ONa and CH3OH has been established. A methylcyclopropane subunit was installed by a 3-fold domino procedure involving a key protonation course. Preliminary deuterium-labeling studies revealed that the proton came from methyl of CH3OH and also exposed an additional hydrogen/deuterium exchange process. These two proton-concerned reactions were fully chemoselective.
- Mao, Jiangang,Xie, Hujun,Bao, Weiliang
-
supporting information
p. 3678 - 3681
(2015/08/18)
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- Palladium(0)-catalyzed cross-coupling of 1,1-diboronates with vinyl bromides and 1,1-dibromoalkenes
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Palladium-catalyzed cross-coupling reactions of 1,1-diboronates with vinyl bromides and dibromoalkenes were found to afford 1,4-dienes and allenes, respectively. These reactions utilize the high reactivities of both 1,1-diboronates and allylboron intermediates generated in the initial coupling.
- Li, Huan,Zhang, Zhikun,Shangguan, Xianghang,Huang, Shan,Chen, Jun,Zhang, Yan,Wang, Jianbo
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supporting information
p. 11921 - 11925
(2015/01/09)
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- Transition-metal free synthesis of diaryl vinyl selenides: A simple synthetic approach with high selectivity
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A simple, highly efficient synthetic protocol is developed for the synthesis of unsymmetrical diaryl vinyl selenides from diaryldiselenide and β-bromo styrene under transition-metal free conditions in N,N′-dimethyl propylene urea and 130 °C to afford high yields and excellent selectivities. This method provides a new strategy to fabricate a wide variety of important substituted molecular skeletons and an alternative to conventionally used metal salts, additives, and ligands.
- Mohan, Balaji,Hwang, Sori,Woo, Hyunje,Park, Kang Hyun
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supporting information
p. 2699 - 2702
(2014/04/17)
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- Catalytic anti-Markovnikov hydrobromination of alkynes
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We have developed the first catalytic method for anti-Markovnikov hydrobromination of alkynes. The reaction affords terminal E-alkenyl bromides in high yield and with excellent regio- and diastereoselectivity. Both aryl- and alkyl-substituted terminal alkynes can be used as substrates. Furthermore, the reaction conditions are compatible with a wide range of functional groups, including esters, nitriles, epoxides, aryl boronic esters, terminal alkenes, silyl ethers, aryl halides, and alkyl halides. A preliminary study of the reaction mechanism suggests that the hydrobromination reaction involves hydrocupration of an alkyne, followed by the bromination of the alkenyl copper intermediate. This study also suggests that 2-tert-butyl potassium phenoxide functions as a mild catalyst turnover reagent and provides a better understanding of the unique effectiveness of (BrCl2C)2 among brominating reagents.
- Uehling, Mycah R.,Rucker, Richard P.,Lalic, Gojko
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supporting information
p. 8799 - 8803
(2014/07/07)
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- Palladium(0)-catalyzed methylenecyclopropanation of norbornenes with vinyl bromides
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Highly strained methylenecyclopropane derivatives have been achieved via a novel and efficient Pd(0)-catalyzed domino reaction. The formal [2 + 1] cycloaddition reaction of vinyl bromides to norbornenes involves a Heck-type coupling and a C(sp2)-H bond activation.
- Mao, Jiangang,Bao, Weiliang
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supporting information
p. 2646 - 2649
(2014/06/09)
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- Palladium-catalyzed [2+1+1] annulation of norbornenes with (z)-bromostyrenes: Synthesis of bismethylenecyclobutanes via twofold C(sp2)-H bond activation
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The first Pd-catalyzed intermolecular [2+1+1] annulation reaction of (Z)-bromostyrene derivatives and norbornenes has been realized. Bismethylenecyclobutane derivatives were obtained with high yields. The domino coupling reaction involves a double Heck-type coupling process, twofold C(sp2)-H bond activation and formation of three carbon-carbon bonds.
- Mao, Jiangang,Bao, Weiliang
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supporting information
p. 15726 - 15729
(2015/01/08)
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- On the Origin of E/Z Selectivity in the Modified Julia Olefination - Importance of the Elimination Step
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The mechanism and origin of high E selectivity in the modified Julia olefination of aromatic aldehydes have been explored by computational and experimental means. Reversibility of addition and hence selectivity of the formation of sulfinate 5 is very variable and depends on the nature of the sulfone substrate. However, in all cases, elimination occurs through a concerted antiperiplanar and synperiplanar mechanism for sulfinates anti-5 and syn-5, respectively. Both syn and anti diastereomeric pathways thus lead preferentially to the (E)-alkene. Copyright
- Robiette, Raphael,Pospisil, Jiri
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supporting information
p. 836 - 840
(2013/03/29)
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- A green hunsdiecker reaction of cinnamic acids
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Tribromo- and trichloroisocyanuric acids react with cinnamic acids in NaOH/H2O/Et2O at room temperature to produce (E)-2-halostyrenes regioselectively in 25-95percent yield. Mechanism studies using Hammett correlations and DFT (density functional theory) calculations have shown that this reaction has as rate determining step the electrophilic addition of chlorine atom to the double bond.
- Sodre?, Leonardo R.,Esteves, Pierre M.,De Mattos, Marcio C. S.
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p. 212 - 218
(2013/05/08)
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- Formation of quaternary stereogenic centers by copper-catalyzed asymmetric conjugate addition reactions of alkenylaluminums to trisubstituted enones
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Alkenylaluminums undergo asymmetric copper-catalyzed conjugate addition (ACA) to β-substituted enones allowing the formation of stereogenic all-carbon quaternary centers. Phosphinamine-copper complexes proved to be particularly active and selective compared with phosphoramidite ligands. After extensive optimization, high enantioselectivities (up to 96 % ee) were obtained for the addition of alkenylalanes to β-substituted enones. Two strategies for the generation of the requisite alkenylaluminums were explored allowing for the introduction of aryl- and alkyl-substituted alkenyl nucleophiles. Moreover, alkyl-substituted phosphinamine (SimplePhos) ligands were identified for the first time as highly efficient ligands for the Cu-catalyzed ACA. Chiral synthesis made easy: The copper-catalyzed conjugate addition of alkenylaluminum reagents to 3-substituted cyclic enones allows for the formation of all-carbon chiral quaternary centers (see scheme; CuTC=copper(I) thiophene-2-carboxylate). Chiral phosphinamine (SimplePhos) ligands were found to be highly efficient for this transformation.
- Mueller, Daniel,Alexakis, Alexandre
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supporting information
p. 15226 - 15239
(2013/11/06)
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- C-1 alkynylation of N-methyltetrahydroisoquinolines through CDC: A direct access to phenethylisoquinoline alkaloids
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Direct cross-coupling between N-methyltetrahydroisoquinolines and alkynes using CuI-DEAD is presented. It affords the regioselective C-1-alkynylated products in good yield. This regio-selectivity is in contrast to the results reported earlier in the reaction of N,N-dimethylbenzyl amine where the N-methyl alkynylated product was formed exclusively or predominantly. The C-1-substituted propargylic isoquinolines were easily reduced to phenethylisoquinolines with Pd/C. This reaction sequence provides a short route to synthesize methopholine, homolaudanosine and other phenethylisoquinoline alkaloids. Georg Thieme Verlag Stuttgart · New York.
- Singh, Kamal Nain,Singh, Paramjit,Kaur, Amarjit,Singh, Pushpinder
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p. 760 - 764
(2012/07/02)
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- Regioselective copper(I)-catalyzed C-H hydroxylation/C-S coupling: Expedient construction of 2-(styrylthio)phenols
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Regioselective copper(I)-catalyzed C-H hydroxylation/C-S coupling of aryl thiols with vinyl halides was developed. Starting from substituted aryl thiols and vinyl halides, various 2-(styrylthio)phenol derivatives were efficiently prepared. The application of the synthetic methodology to generate the bioactive organic intermediate was also exemplified.
- Xu, Run-Sheng,Yue, Lei,Pan, Yuan-Jiang
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experimental part
p. 5046 - 5052
(2012/08/07)
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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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- Copper-catalyzed asymmetric 1,4-addition of alkenyl alanes to N-substituted-2-3-dehydro-4-piperidones
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Readily available vinyl alanes are used in the Cu-catalyzed asymmetric conjugate addition reaction to N-substituted-2-3-dehydro-4-piperidones. The enhanced reactivity of recently developed and easily prepared phosphine amine ligands in combination with inexpensive Cu(II)naphtenate (CuNp) allows the introduction of a great variety of alkenyl, alkyl, and aryl aluminums in high enantioselectivity.
- Mueller, Daniel,Alexakis, Alexandre
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supporting information; experimental part
p. 1842 - 1845
(2012/06/18)
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- Decarboxylative bromination of cinnamic acids by 2-iodoxybenzoic acid with tetrabutylammonium bromide
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The decarboxylative bromination of cinnamic acids using the hypervalent iodine reagent 2-iodoxybenzoic acid with tetrabutylammonium bromide is described, providing good to excellent yields of bromostyrenes. Bromostyrenes are useful coupling components in a wide range of transition metal-catalysed coupling reactions.
- Han, Jianlei,Wei, Yuping
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experimental part
p. 247 - 248
(2012/09/22)
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