- Sonogashira-Hagihara and Buchwald-Hartwig cross-coupling reactions with sydnone and sydnone imine derived catalysts
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Seven different palladium complexes of sydnones and sydnone imines and a co-catalyst system consisting of lithium sydnone-4-carboxylate and Pd(PPh3)4 catalyzed Sonogashira-Hagihara reactions between (hetero)- aromatic bromides and 2-methylbut-3-yn-2-ol (52 examples, up to 100% yield). The co-catalyst system and a sydnone Pd complex were also tested in Buchwald-Hartwig reactions (9 examples, up to 100% yield). (Equation Presented).
- Lücke, Ana-Luiza,Pruschinski, Lucas,Freese, Tyll,Schmidt, Andreas
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- Synthesis and Utility of 2,2-Dimethyl-2 H-pyrans: Dienes for Sequential Diels-Alder/Retro-Diels-Alder Reactions
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The practical use of 2,2-dimethyl-2H-pyrans as electron-rich dienes in sequential Diels-Alder/retro-Diels-Alder (DA/rDA) domino processes to generate aromatic platforms has been demonstrated. Different polysubstituted alkyl 2-naphthoates have been synthesized by the DA/rDA reaction of benzynes and 2,2-dimethyl-2H-pyrans. The use of other activated alkynes allows the access of substituted alkyl benzoate derivatives.
- Tejedor, David,Díaz-Díaz, Abián,Diana-Rivero, Raquel,Delgado-Hernández, Samuel,García-Tellado, Fernando
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- Palladium(II)-Catalyzed Reaction of Lawsones and Propargyl Carbonates: Construction of 2,3-Furanonaphthoquinones and Evaluation as Potential Indoleamine 2,3-Dioxygenase Inhibitors
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An efficient reaction utilizing propargyl carbonates through Claisen rearrangement to synthesize furanonaphthoquinones is described. The remarkable transformation exhibits excellent functional group tolerance, affording the target furanonaphthoquinones in
- Feng, Xi,Qiu, Xiaqiu,Huang, Huidan,Wang, Jubo,Xu, Xi,Xu, Pengfei,Ge, Ruijia,Liu, Xiaojin,Li, Zhiyu,Bian, Jinlei
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- Synthesis and Photochemistry of a New Photolabile Protecting Group for Propargylic Alcohols
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A new and efficient thiochromenone S,S-dioxide-based photolabile protecting group for propargylic alcohols is described. Robust protection reactions were developed through copper (II)-catalyzed substitution of propargylic alcohols. Subsequent photodeprote
- Ma, Chi,Zhang, Youlai,Zhang, Huan,Li, Junru,Nishiyama, Yasuhiro,Tanimoto, Hiroki,Morimoto, Tsumoru,Kakiuchi, Kiyomi
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- Hollow palladium-cobalt bimetallic nanospheres as an efficient and reusable catalyst for Sonogashira-type reactions
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The synthesis and characterization of hollow Pd-Co bimetallic nanospheres are reported. During Sonogashira-type coupling reactions between aryl halides and terminal alkynes in aqueous medium, these hollow materials exhibited much higher activity than the solid counterpart nanoparticles. Moreover, the catalytic activity could be adjusted via changing the catalyst composition. The enhanced activity was attributed to both the hollow chamber structure and the promotional effect of Co-dopants, which provided more Pd active sites for the reactants. The Royal Society of Chemistry 2010.
- Li, Hui,Zhu, Zhonghong,Liu, Jun,Xie, Songhai,Li, Hexing
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- Efficient synthesis of substituted 3-azabicyclo[3.1.0]hexan-2-ones from 2-iodocyclopropanecarboxamides using a copper-free Sonogashira coupling
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The copper-free Sonogashira coupling between N-substituted cis- 2-iodocyclopropanecarboxamides and terminal aryl-, heteroaryl-alkynes or enynes, followed by 5-exo-dig cyclization of the nitrogen amide onto the carbon-carbon triple bond, provides a remarkably efficient access to a variety of substituted 4-methylene-3-azabicyclo[3.1.0]hexan-2-ones in excellent yields. Protonation of these latter enamides generates bicyclic N-acyliminium ions that can be involved in Pictet-Spengler cyclizations leading to new 3-azabicyclo[3.1.0]hexan-2-ones, possessing a quaternary stereocenter at C4, with high diastereoselectivities. This strategy constitutes an attractive complementary alternative to the classical route that relies on the addition of organometallic reagents to cyclopropyl imides. A copper-free Sonogashira coupling between cis-2-iodocyclopropanecarboxamides and terminal aryl-, heteroaryl-alkynes or enynes followed by 5-exo-dig cyclization provides an efficient access to substituted 4-methylene-3-azabicyclo[3.1.0]hexan-2-ones (see scheme). Protonation of these enamides generates N-acyliminium ions, which can be involved in Pictet-Spengler cyclizations leading to new 3-azabicyclo[3.1.0] hexan-2-ones containing a quaternary stereocenter at C4 with high diastereoselectivities. Copyright
- De Carné-Carnavalet, Beno?t,Archambeau, Alexis,Meyer, Christophe,Cossy, Janine,Folléas, Beno?t,Brayer, Jean-Louis,Demoute, Jean-Pierre
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- Rhodium-catalyzed oxidative coupling of benzoic acids with propargyl alcohols: An efficient access to isocoumarins
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An efficient protocol of Rh(III)-catalyzed oxidative cyclization of benzoic acids with propargyl alcohols to give substituted isocoumarins under mild conditions was reported. A variety of substrates were applied in this reaction in yields up to 89%.
- Luo, Feihua,He, Shuhua,Gou, Quan,Chen, Jinyang,Zhang, mingzhong
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supporting information
(2020/12/29)
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- An Amine-Assisted Ionic Monohydride Mechanism Enables Selective Alkyne cis-Semihydrogenation with Ethanol: From Elementary Steps to Catalysis
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The selective synthesis of Z-alkenes in alkyne semihydrogenation relies on the reactivity difference of the catalysts toward the starting materials and the products. Here we report Z-selective semihydrogenation of alkynes with ethanol via a coordination-induced ionic monohydride mechanism. The EtOH-coordination-driven Cl- dissociation in a pincer Ir(III) hydridochloride complex (NCP)IrHCl (1) forms a cationic monohydride, [(NCP)IrH(EtOH)]+Cl-, that reacts selectively with alkynes over the corresponding Z-alkenes, thereby overcoming competing thermodynamically dominant alkene Z-E isomerization and overreduction. The challenge for establishing a catalytic cycle, however, lies in the alcoholysis step; the reaction of the alkyne insertion product (NCP)IrCl(vinyl) with EtOH does occur, but very slowly. Surprisingly, the alcoholysis does not proceed via direct protonolysis of the Ir-C(vinyl) bond. Instead, mechanistic data are consistent with an anion-involved alcoholysis pathway involving ionization of (NCP)IrCl(vinyl) via EtOH-for-Cl substitution and reversible protonation of Cl- ion with an Ir(III)-bound EtOH, followed by β-H elimination of the ethoxy ligand and C(vinyl)-H reductive elimination. The use of an amine is key to the monohydride mechanism by promoting the alcoholysis. The 1-amine-EtOH catalytic system exhibits an unprecedented level of substrate scope, generality, and compatibility, as demonstrated by Z-selective reduction of all alkyne classes, including challenging enynes and complex polyfunctionalized molecules. Comparison with a cationic monohydride complex bearing a noncoordinating BArF- ion elucidates the beneficial role of the Cl- ion in controlling the stereoselectivity, and comparison between 1-amine-EtOH and 1-NaOtBu-EtOH underscores the fact that this base variable, albeit in catalytic amounts, leads to different mechanisms and consequently different stereoselectivity.
- Huang, Zhidao,Wang, Yulei,Leng, Xuebing,Huang, Zheng
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supporting information
p. 4824 - 4836
(2021/04/07)
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- Ru(ii)-catalyzed allenylation and sequential annulation of: N -tosylbenzamides with propargyl alcohols
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We hereby report Ru(ii)-catalyzed C(sp2)-H allenylation of N-tosylbenzamides to access multi-substituted allenylamides. Furthermore, the allenylamides were converted to the corresponding isoquinolone derivatives via base mediated annulation. The current protocol features low catalyst loading, mild reaction conditions, high functional group compatibility and desired scalability. The unique functionality of the afforded allenes allowed further transformations to expand the practicality of the protocol. This journal is
- Kumar, Shreemoyee,Nair, Akshay M.,Volla, Chandra M. R.
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p. 6280 - 6283
(2021/07/02)
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- Rhodium-Catalyzed Annulation of Phenacyl Ammonium Salts with Propargylic Alcohols via a Sequential Dual C-H and a C-C Bond Activation: Modular Entry to Diverse Isochromenones
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Given their omnipresence in natural products and pharmaceuticals, isochromenone congeners are one of the most privileged scaffolds to synthetic chemists. Disclosed herein is a dual (ortho/meta) C-H and C-C activation of phenacyl ammonium salts (acylammonium as traceless directing group) toward annulation with propargylic alcohols to accomplish rapid access for novel isochromenones by means of rhodium catalysis from readily available starting materials. This operationally simple protocol features broad substrate scope and wide functional group tolerance. Importantly, the protocol circumvents the need of any stoichiometric metal oxidants and proceeds under aerobic conditions.
- Nanubolu, Jagadeesh Babu,Reddy Singam, Maneesh Kumar,Sridhar Reddy, Maddi,Suresh, Vavilapalli,Suri Babu, Undamatla
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supporting information
p. 7888 - 7893
(2021/10/25)
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- Alcohol Dehydrogenases and N-Heterocyclic Carbene Gold(I) Catalysts: Design of a Chemoenzymatic Cascade towards Optically Active β,β-Disubstituted Allylic Alcohols
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The combination of gold(I) and enzyme catalysis is used in a two-step approach, including Meyer–Schuster rearrangement of a series of readily available propargylic alcohols followed by stereoselective bioreduction of the corresponding allylic ketone intermediates, to provide optically pure β,β-disubstituted allylic alcohols. This cascade involves a gold N-heterocyclic carbene and an enzyme, demonstrating the compatibility of both catalyst types in aqueous medium under mild reaction conditions. The combination of [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene][bis(trifluoromethanesulfonyl)-imide]gold(I) (IPrAuNTf2) and a selective alcohol dehydrogenase (ADH-A from Rhodococcus ruber, KRED-P1-A12 or KRED-P3-G09) led to the synthesis of a series of optically active (E)-4-arylpent-3-en-2-ols in good yields (65–86 %). The approach was also extended to various 2-hetarylpent-3-yn-2-ol, hexynol, and butynol derivatives. The use of alcohol dehydrogenases of opposite selectivity led to the production of both allyl alcohol enantiomers (93->99 % ee) for a broad panel of substrates.
- González-Granda, Sergio,Lavandera, Iván,Gotor-Fernández, Vicente
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p. 13945 - 13951
(2021/04/22)
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- Bimetal Cooperatively Catalyzed Arylalkynylation of Alkynylsilanes
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An unprecedented Pd/Rh cooperatively catalyzed arylalkynylation of alkynylsilanes was developed to merge an alkynylidene moiety with benzosilacycle. These silaarenes possess a particular aggregation-induced emission behavior. Mechanistic investigations demonstrate that the relay trimetallic transmetalation plays a pivotal role in governing this transformation.
- Chen, Xing,Li, Mengke,Liu, Zhipeng,Yang, Can,Xie, Haisheng,Hu, Xinwei,Su, Shi-Jian,Jiang, Huanfeng,Zeng, Wei
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supporting information
p. 6724 - 6728
(2021/09/08)
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- Ruthenabenzene: A Robust Precatalyst
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Metallaaromatics constitute a unique class of aromatic compounds where one or more transition metal elements are incorporated into the aromatic system, the parent of which is metallabenzene. One of the main concerns about metallabenzenes generally deals with the structural characterization related to their relative aromaticity compared to the carbon archetype. Transition metal-containing metallabenzenes are also implicated in certain catalytic processes such as alkyne metathesis polymerization; however, these transition metal-based metallaaromatic compounds have not been developed as a catalyst. Herein, we describe an effective strategy to generate diverse arrays of ruthenabenzenes and demonstrated them as an aromatic equivalent of the Grubbs-type ruthenium alkylidene catalysts. These ruthenabenzenes can be prepared via an enyne metathesis and metallotropic [1,3]-shift cascade process to form alkyne-chelated ruthenium alkylidene intermediates followed by spontaneous cycloaromatization. The aromatic nature of these complexes was confirmed by spectroscopic and X-ray crystallographic data, and the mechanistic pathways for the cycloaromatization process were studied by DFT calculations. These ruthenabenzenes display robust catalytic activity for metathesis and other transformations, which illustrates that metallabenzenes are not only compounds of structural and theoretical interests but also are a novel platform for new catalyst development.
- Gupta, Saswata,Su, Siyuan,Zhang, Yu,Liu, Peng,Wink, Donald J.,Lee, Daesung
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supporting information
p. 7490 - 7500
(2021/05/26)
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- Dual Palladium/Copper-Catalyzed anti-Selective Intermolecular Allenylsilylation of Terminal Alkynes: Entry to (E)-Silyl Enallenes
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A palladium-/copper-cocatalyzed three-component trans-allenylsilylation of terminal alkynes with propargyl acetates and PhMe2SiBpin is described, which is driven by the regioselective allenylation of the alkyne with propargyl acetates and then silylation. This method allows the simultaneous incorporation of an allene and silicon across the CC bond and provides a highly chemo-, regio-, and stereoselective alkyne difunctionalization route to the synthesis of valuable (E)-silyl enallenes. The utility of this method is highlighted by late-stage derivatization of bioactive compounds.
- Yang, Liang-Feng,Wang, Qiu-An,Li, Jin-Heng
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p. 6553 - 6557
(2021/09/02)
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- Calcium-Catalyzed Intramolecular Hydroamination-Deacylation Reaction of in situ formed β-Amino Allenes
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We have developed a simple, One-Pot, three-component reaction of tert-propargyl alcohols, primary amines and acyl ketones to synthesize fully substituted pyrroles and pyridine derivatives in good to excellent yields with large substrate diversity. An eco-friendly calcium catalyst catalyzes the reaction to form the key intermediate β-amino allene that undergoes subsequent Thorpe-Ingold effect assisted hydroamination and aromaticity driven deacylation reaction to yield fully substituted five and six-membered azacyclic compounds. (Figure presented.).
- Yaragorla, Srinivasarao,Latha, Dandugula Sneha,Rajesh, Pallava
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supporting information
p. 5486 - 5492
(2021/12/10)
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- Utilizing a copper-free Sonogashira reaction in the synthesis of the leukotriene a4 hydrolase modulator batatasin IV
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Batatasin IV is a dihydrostilbenoid isolated from Chinese yams which was shown to have inhibitory activities against plant growth. Later studies showed that this compound may exhibit anti-inflammatory properties by inhibiting the epoxide hydrolase activity of the leukotriene A4 hydrolase enzyme. To access the dihydrostilbenoid skeleton, a copper-free SPhos-mediated Sonogashira reaction was conceived and the substrate scope was explored. Our results indicate that the reaction can tolerate the presence of free alcohols, aldehydes, nitro groups, and anilinyl groups. However, a substituent with an acidic phenol or carboxylic acid group gave significantly lower yields. Next, a total synthesis of batatasin IV was accomplished in 16% overall yield incorporating the reported copper-free Sonogashira reaction. Finally, we show that batatasin IV inhibits the hydrolysis of alanine p-nitroanilide by leukotriene A4 hydrolase with an IC50 of 91.4 μM.
- Petruncio, Greg,Girgis, Michael,Moummi, Sanae,Jayatilake, Meth,Lee, Kyung Hyeon,Paige, Mikell
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supporting information
(2020/10/27)
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- Fast heck-cassar-sonogashira (hcs) reactions in green solvents
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The replacement of toxic solvents with greener alternatives in Heck-Cassar-Sonogashira (HCS) cross-couplings was investigated. The fine-tuning of the HCS protocol allowed to achieve complete conversions and high speed under mild conditions. N-Hydroxyethylpyrrolidone (HEP) gave the best results. Moreover, the methodology was successfully applied to the synthesis of an intermediate of the anticancer drug Erlotinib, demonstrating the versatility of the new green protocol.
- Cabri, W.,Corbisiero, D.,Daka, A.,Fantoni, T.,Ferrazzano, L.,Martelli, G.,Ricci, A.,Tolomelli, A.,Viola, A.
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supporting information
p. 3969 - 3973
(2020/06/08)
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- Chemoselective Hydroboration of Propargylic Alcohols and Amines Using a Manganese(II) Catalyst
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The first manganese-catalyzed hydroboration of propargylic alcohols and amines as well as internal alkynes is reported. High regio- and stereoselectivity is achieved by applying 2 mol % of a manganese precatalyst based on the readily accessible bis(imino)pyridine ligand and MnCl2 as metal source. Propargylic alcohols and amines, as well as symmetric internal alkynes, were efficiently converted into the corresponding functionalized alkenes, which can serve as important and valuable intermediates for further synthetic applications such as cross-coupling reactions.
- Brzozowska, Aleksandra,Zubar, Viktoriia,Ganardi, Ruth-Christine,Rueping, Magnus
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supporting information
p. 3765 - 3769
(2020/04/15)
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- Br?nsted Acid Promoted Thermal-Ring-Rearrangement of Fluorenopyrans to 2-(1H-Inden-3-yl)-9H-fluoren-3-ols Bearing Two All-Carbon-Quaternary Centres
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4-Aryl-fluorenopyrans bearing quaternary centre at C2 and C6 positions underwent a thermal-ring-rearrangement with a catalytic amount of pTsOH to furnish 2-(1H-inden-3-yl)-9H-fluoren-3-ols with two all carbon-quaternary centres, in which one is retained a
- Jose, K. V. Jovan,Khan, Tabassum,Praveen, Dudam,Rajesh, P.,Yaragorla, Srinivasarao
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supporting information
(2020/04/22)
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- Supramolecular photocatalyst of Palladium (II) Encapsulated within Dendrimer on TiO2 nanoparticles for Photo-induced Suzuki-Miyaura and Sonogashira Cross-Coupling reactions
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In this study, synthesis, characterization and catalytic performance of a novel supramolecular photocatalytic system including palladium (II) encapsulated within amine-terminated poly (triazine-triamine) dendrimer modified TiO2 nanoparticles (Pd (II) [PTATAD] @ TiO2) is presented. The obtained nanodendritic catalyst was characterized by FT-IR, ICP-AES, XPS, EDS, TEM, TGA and UV-DRS. The as-prepared nanodendritic catalyst was shown to be highly active, selective, and recyclable for the Suzuki–Miyaura and Sonogashira cross-coupling of a wide range of aryl halides including electron-rich and electron-poor and even aryl chlorides, affording the corresponding biaryl compounds in good to excellent yields under visible light irradiation. This study shows that visible light irradiation can drive the cross-coupling reactions on the Pd (II) [PTATAD] @ TiO2 under mild reaction conditions (27–30?°C) and no additional additives such as cocatalysts or phosphine ligands. So, we propose that the improved photoactivity predominantly benefits from the synergistic effects of Pd (II) amine-terminated poly (triazine-triamine) dendrimer on TiO2 nanoparticles that cause efficient separation and photogenerated electron–hole pairs and photoredox capability of nanocatalyst which all of these advantages due to the tuning of band gap of catalyst in the visible light region.
- Eskandari, Ameneh,Jafarpour, Maasoumeh,Rezaeifard, Abdolreza,Salimi, Mehri
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- Metal-Free Regioselective Chloroazidation of Internal Alkynes
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A metal-free, room temperature protocol for the regioselective chloroazidation of internal alkynes is disclosed. The reactions of internal alkynes with trimethylsilyl azide (TMSN3) in the presence of 1,3-dichloro-5,5-dimethylhydantoin (DCDMH) afforded the corresponding chloroazidoalkenes in good yields. This reaction has good functional group tolerance and is operationally simple.
- Huang, Bin,Liffert, Raphael,Linden, Anthony,Gademann, Karl
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supporting information
p. 981 - 984
(2019/01/04)
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- Method for preparing large-steric-hindrance electron-deficient organic phosphine ligand compound
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The present invention relates to a novel method for preparing a large-steric-hindrance electron-deficient organic phosphine ligand compound represented by any one of the following formulae, wherein the phosphine is introduced first, the method comprises the following steps: by taking phenylacetylene as a raw material, performing a coupling reaction, and efficiently obtaining the required (1, 1-(dimethyl)-2-substituted phenyl indene (3, 5-bis (trifluoromethyl)) phenyl phosphine (5) by taking phenylacetylene as a raw material through intermediates including 2-methyl-4-phenyl-3-butyne-2-ol, 2, 3-diiodo-1, 1-dimethyl-indene and (1-iodine) indene)-bis (3-bis (3-bis (trifluoromethyl) phenyl phosphine). The novel large-steric-hindrance electron-deficient organic phosphine ligand compound is obtained through a brand-new reaction process. The organic phosphine ligand compound obtained by the invention has the advantages of stable property, stable existence in air, multiple modifiable sites, rich synthetic structure, easily available raw materials and simple synthetic method, and can be used as an important ligand in the field of palladium catalysts.
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Paragraph 0094-0096; 0100-0102; 0106-0108
(2019/12/02)
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- Controllable chemoselectivity in the coupling of bromoalkynes with alcohols under visible-light irradiation without additives: Synthesis of propargyl alcohols and α-ketoesters
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The chemoselectivity of visible-light-induced coupling reactions of bromoalkynes with alcohols can be controlled by simple changes to the reaction atmosphere (N2 or O2). A N2 atmosphere favours propargyl alcohols via a direct C-C coupling process, whereas an O2 atmosphere results in the generation of α-ketoesters through the oxidative CC/C-O coupling pathway.
- Ni, Ke,Meng, Ling-Guo,Ruan, Hongjie,Wang, Lei
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supporting information
p. 8438 - 8441
(2019/07/22)
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- Bi(OTf)3 catalyzed synthesis of acyclic β-sulfanyl ketones via a tandem Meyer-Schuster rearrangement/conjugate addition reaction
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A new strategy to prepare acyclic β-carbonyl thioethers from propargyl alcohols and sulfur nucleophiles is reported. The investigation of the reaction substrates scope indicated that primary 3-aryl propargyl alcohols and thiols underwent the transformation smoothly. The reaction probably proceeded a Bi(OTf)3-catalyzed tandem Meyer-Schuster rearrangement of 3-aryl propargyl alcohol, followed by a thiol Michael conjugate addition of thiols to in situ generated α, β-unsaturated ketones. The method was 100% atom economic, high-yielding, and easy to handle, making it a valuable method for the construction of β-carbonyl sulfides.
- Wang, Yuan,Yin, Yan,Zhang, Qinglin,Pan, Wanyong,Guo, Huifeng,Pei, Keke
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supporting information
p. 2030 - 2034
(2019/07/03)
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- Acid catalysed rearrangement of isobenzofurans to angularly fused phthalides
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An acid catalysed, cascade process for the construction of angularly fused polycyclic phthalides from isobenzofurans under transition metal free conditions has been reported. This process is very general for diverse gem-disubstituted isobenzofuran substrates. Control experiments supported the mechanism as the nucleophilic attack of the carboxylate onto the acid activated furan ring for the simultaneous ring closing-ring opening cascade followed by dehydration. This method serves as a greener alternative for the synthesis of angularly fused polycyclic phthalides.
- Chinta, Bhavani Shankar,Gandhi, Soniya,Baire, Beeraiah
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supporting information
p. 4715 - 4719
(2019/05/24)
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- Regiospecific formal [3 + 2] annulation of: Tert -propargyl alcohols with acyclic 1,3-diketones via the cycloisomerization of homoallenyl ketones
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A one-pot, regiospecific synthesis of dihydrofurans bearing a quaternary centre and tetrasubstituted furans is developed from the formal [3 + 2] annulation of tert-propargyl alcohols and 1,3-diketones under Ca(ii)/DBU conditions. The reaction proceeds through the SN2I mechanism to form homoallenyl ketone and a subsequent cycloisomerization to yield novel and new chemical entities of privileged scaffolds.
- Yaragorla, Srinivasarao,Rajesh
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supporting information
p. 1924 - 1928
(2019/02/20)
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- Visible-light-driven selective alkenyl C-P bond cleavage of allenylphosphine oxides
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An efficient method for highly selective alkenyl C-P bond cleavage, enabled by organic dyes and visible-light irradiation, was developed. This novel protocol involves a highly regioselective radical pathway initiated by singlet oxygen, affording diverse a
- Wei, Kai,Luo, Kai,Liu, Fang,Wu, Lei,Wu, Li-Zhu
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supporting information
p. 1994 - 1998
(2019/03/29)
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- Palladium(II)/Lewis acid cocatalyzed oxidative annulation of 2-alkenylanilines and propargylic esters: An access to benzo[ b]azepines
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An attractive approach to valuable yet synthetically challenging benzo[b]azepines was established via palladium(II)/Lewis acid cocatalyzed oxidative [5 + 2] annulation of readily available 2-alkenylanilines and propargylic esters. The protocol features mild reaction conditions and good functional group tolerance, constituting an array of benzo[b]azepines in yields of 30-75%.
- Qiao, Hong,Zhang, Shengjun,Li, Kangkang,Cao, Zhengqiang,Zeng, Fanlong
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p. 10843 - 10851
(2019/09/12)
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- Flow rhodaelectro-catalyzed alkyne annulations by versatile C-H Activation: Mechanistic support for rhodium(III/IV)
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A flow-metallaelectro-catalyzed C-H activation was realized in terms of robust rhodaelectro-catalyzed alkyne annulations. To this end, a modular electro-flow cell with a porous graphite felt anode was designed to ensure efficient turnover. Thereby, a variety of C-H/N-H functionalizations proved amenable for alkyne annulations with high levels of regioselectivity and functional group tolerance, viable in both an inter- or intramolecular manner. The electro-flow C-H activation allowed easy scale up, while in-operando kinetic analysis was accomplished by online flow-NMR spectroscopy. Mechanistic studies suggest an oxidatively induced reductive elimination pathway on rhodium(III) in an electrocatalytic regime.
- Kong, Wei-Jun,Finger, Lars H.,Messinis, Antonis M.,Kuniyil, Rositha,Oliveira, Jo?o C.A.,Ackermann, Lutz
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supporting information
p. 17198 - 17206
(2019/10/28)
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- Preparation and Reactivation of Heterogeneous Palladium Catalysts and Applications in Sonogashira, Suzuki, and Heck Reactions in Aqueous Media
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A new type of heterogeneous palladium catalyst, PdMgAl-LDH, was facilely prepared by the immobilization of Pd2+ species in the layers of a Mg-Al layered double hydroxide (LDH) with co-precipitation, and then fully characterized by using powder XRD, thermogravimetric differential thermal analysis, TEM, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy techniques. These catalysts can efficiently catalyze copper-free Sonogashira, Suzuki and Heck coupling reactions of various aryl iodides, bromides, and chlorides in aqueous media under phosphine-ligand- and organic-base-free conditions. These catalysts feature easy recovery through simple filtration and could be reused at least six times without a marked loss in activity. Notably, they can be facilely reactivated by a combination of nitrolysis with co-precipitation. The basic LDH skeletons could effectively stabilize the Pd0 species created in situ and donate electron density to the Pd0 center to facilitate the oxidative addition of aryl halides, thus the PdMgAl-LDH catalysts are stable during catalysis.
- Zhang, Sheng-Yan,Yu, Kai,Guo, Yu-Shuang,Mou, Rui-Qi,Lu, Xiao-Fan,Guo, Dian-Shun
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p. 803 - 813
(2018/10/31)
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- Cleavage of C–C and C–O Bonds to Form C–C Bonds: Direct Cross-Coupling between Acetylenic Alcohols and Benzylic Carbonates
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A palladium-catalyzed cross-coupling reaction between C(sp) and C(sp3) centers was achieved in excellent yields via C–C bond cleavage and C–O bond cleavage. This procedure uses relatively stable acetylenic alcohols as reactants instead of unsta
- Mi, Zhiyuan,Tang, Jiahao,Guan, Zhipeng,Shi, Wei,Chen, Hao
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supporting information
p. 4479 - 4482
(2018/09/10)
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- α-Hydroxy Ketones as Masked Ester Donors in Br?nsted Base Catalyzed Conjugate Additions to Nitroalkenes
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The catalyst-controlled enantioselective direct addition reaction of enolizable esters and related carboxylic acid derivatives to π electrophiles remains a difficult synthetic transformation. In this study, the suitability of α-hydroxy ketones as ester equivalents capable of being activated by bifunctional Br?nsted base catalysts in the context of conjugate addition reactions to nitroolefins is demonstrated. The scope of the reaction, which affords the corresponding Michael adducts with very high stereoselectivity (diastereomeric ratio (d.r.) ≥95:5, up to 99 % enantiomeric excess (ee)), and its limitations are explored, as is the aftermath elaboration of adducts into densely functionalized enantioenriched products.
- Olaizola, Iurre,Campano, Teresa E.,Iriarte, Igor,Vera, Silvia,Mielgo, Antonia,García, Jesús M.,Odriozola, José M.,Oiarbide, Mikel,Palomo, Claudio
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supporting information
p. 3893 - 3901
(2018/03/21)
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- Rhodium-Catalyzed Highly Regio- and Enantioselective Hydrogenation of Tetrasubstituted Allenyl Sulfones: An Efficient Access to Chiral Allylic Sulfones
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A highly regio- and enantioselective hydrogenation of challenging tetrasubstituted allenyl sulfones has been developed, affording chiral allylic sulfones in good yields with excellent regio- and enantioselectivities (up to 99 % yield and 99 % ee). This me
- Long, Jiao,Shi, Liyang,Li, Xiong,Lv, Hui,Zhang, Xumu
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supporting information
p. 13248 - 13251
(2018/09/21)
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- Catalyst-Controlled [3 + 2] and [4 + 2] Annulations of Oximes with Propargyl Alcohols: Divergent Access to Indenamines and Isoquinolines
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Rhodium(III)- and iridium(III)-catalyzed C-H activation of oximes and coupling with propargyl alcohols is discussed. Depending on the catalyst, the reaction pathway switched between [3 + 2] and [4 + 2] annulations, thus giving divergent access to indenami
- Gong, Wanchun,Zhou, Zhi,Shi, Jingjing,Wu, Bo,Huang, Biyun,Yi, Wei
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supporting information
p. 182 - 185
(2018/01/17)
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- SeCl2-Mediated Approach Toward Indole-Containing Polysubstituted Selenophenes
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A novel and efficient SeCl2-mediated chalcogenative cyclization strategy toward 3-selenophen-3-yl-1H-indoles from readily available and conveniently substituted propargyl indoles is described. It entails an unprecedented selenirenium-induced 1,
- Martins, Guilherme M.,Back, Davi F.,Kaufman, Teodoro S.,Silveira, Claudio C.
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p. 3252 - 3264
(2018/03/25)
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- Direct Substitution of Secondary and Tertiary Alcohols to Generate Sulfones under Catalyst- and Additive-Free Conditions
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An environmentally benign protocol that affords propargylic sulfones containing highly congested carbon centers from easily accessible alcohols and sulfinic acids with water as the only byproduct is reported. The reaction proceeded via an in situ dehydrative cross-coupling process by taking advantage of the synergetic actions of multiple hydrogen bonds rather than relying on an external catalyst and/or additives to achieve high product distribution.
- Liu, Yanan,Xie, Peizhong,Sun, Zuolian,Wo, Xiangyang,Gao, Cuiqing,Fu, Weishan,Loh, Teck-Peng
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supporting information
p. 5353 - 5356
(2018/09/13)
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- Synthesis of Isoquinolines through IrIII-Catalyzed C–H Activation/Annulation from Benzimidates with Hydroxylisopropylalkynes
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An IrIII-catalyzed cascade reaction consisting of C–H activation/annulation of benzimidates with hydroxylisopropylalkynes is reported. A broad range of isoquinolines has been prepared in one step with good functiona-group tolerance and high eff
- Liu, Mingliang,Gong, Wanchun,You, Erli,Zhang, Haizhen,Shi, Lei,Cao, Weiguo,Shi, Jingjing
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supporting information
p. 4991 - 4995
(2018/10/05)
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- Ca(II)-Mediated Regioselective One-pot Sequential Annulation of Acyclic compounds to Polycyclic Fluorenopyrans
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Herein we report a facile synthesis of tetracyclic fluorenopyrans from simple acyclic reactants, propargyl alcohols and 3-methylpentane-2,4-dione under calcium catalysis. This one-pot, 3-component reaction proceeds through a sequential allene formation, F
- Yaragorla, Srinivasarao,Rajesh,Pareek, Abhishek,Kumar, Ankit
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supporting information
p. 4422 - 4428
(2018/10/20)
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- Anionic N-heterocyclic carbenes derived from sydnone imines such as molsidomine. Trapping reactions with selenium, palladium, and gold
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The sydnone imines Molsidomine and 5-(benzoylimino)-3-(2-methoxyphenyl)-1,2,3-oxadiazolium-2-ide gave anionic N-heterocyclic carbenes on deprotonation at C4 which were trapped as methylated selenium adducts, gold complexes (X-ray analysis) as well as palladium complexes (X-ray analysis). The 13C NMR resonance frequencies of the carbene carbon atom are extremely shifted upfield and appear at δ = 142.1 ppm (Molsidomine carbene) and δ = 159.8 ppm (sydnone imine carbene). The Pd complexes were applied as catalysts in Suzuki-Miyaura and Sonogashira-Hagihara cross-coupling reactions.
- Freese, Tyll,Lücke, Ana-Luiza,Schmidt, Catharina A.S.,Polamo, Mika,Nieger, Martin,Namyslo, Jan C.,Schmidt, Andreas
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p. 5350 - 5357
(2017/08/11)
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- Fe(OTf)3-catalyzed tandem Meyer-Schuster rearrangement/intermolecular hydroamination of 3-aryl propargyl alcohols for the synthesis of acyclic β-Aminoketones
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Fe(OTf)3-catalyzed synthesis of acyclic β-aminoketones from 3-aryl propargyl alcohols and nitrogen nucleophiles were investigated. Results showed that propargyl alcohols without bulky groups α to the hydroxyl group underwent the transformation smoothly. Sulphonamides exhibited the higher reactivity than amides as the nitrogen nucleophiles and the transformation of acyclic β-aminoketones were finished in shorter reaction time and higher yields. Finally, racemic fluoxetine was efficiently accessed with the present reaction as the first step. This novel synthesis of acyclic β-aminoketones probable proceeded a Fe(OTf)3-catalyzed Meyer-Schuster rearrangement of 3-aryl propargyl alcohols, followed by a intermolecular hydroamination between nitrogen nucleophiles and α, β-unsaturated ketones.
- Tao, Ruiheng,Yin, Yan,Duan, Yongbin,Sun, Yuxing,Sun, Yue,Cheng, Fengkai,Pan, Jinpeng,Lu, Cheng,Wang, Yuan
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p. 1762 - 1768
(2017/03/08)
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- Photoinduced Gold-Catalyzed Domino C(sp) Arylation/Oxyarylation of TMS-Terminated Alkynols with Arenediazonium Salts
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A selective and convenient synthesis of tri- and tetrasubstituted α,β-unsaturated ketones, as well as 2,3-diarylbenzofurans has been developed with the aid of light and taking advantage of a cooperative gold/photoredox-catalyzed 2-fold arylation reaction of TMS-terminated alkynols. The reaction of 3-(trimethylsilyl)prop-2-yn-1-ols was competent to generate diarylated α,β-unsaturated ketones; whereas the photoredox sequence involving 2-[(trimethylsilyl)ethynyl]phenol exclusively afforded 2,3-diarylbenzofurans. The reaction of terminal alkynes proceeded in poor yields while the use of bulkier silyl groups, such as TIPS, resulted unproductive. Apparently, the C(sp) arylation reaction is the first event on the domino bis-arylative sequence. These results could be explained through the intermediation of arylgold(III) species and several single electron transfer processes.
- Alcaide, Benito,Almendros, Pedro,Busto, Eduardo,Lázaro-Milla, Carlos
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p. 2177 - 2186
(2017/02/26)
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- Unraveling factors leading to efficient norbornadiene-quadricyclane molecular solar-thermal energy storage systems
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Developing norbornadiene-quadricyclane (NBD-QC) systems for molecular solar-thermal (MOST) energy storage is often a process of trial and error. By studying a series of norbornadienes (NBD-R2) doubly substituted at the C7-position with R = H, M
- Jorner, Kjell,Dreos, Ambra,Emanuelsson, Rikard,El Bakouri, Ouissam,Galván, Ignacio Fdez.,B?rjesson, Karl,Feixas, Ferran,Lindh, Roland,Zietz, Burkhard,Moth-Poulsen, Kasper,Ottosson, Henrik
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supporting information
p. 12369 - 12378
(2017/07/10)
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- Tert-butoxy rare earth/sodium impurity bimetallic complex, as well as preparation method and use thereof
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The invention discloses a tert-butoxy rare earth/sodium hetero-bimetallic complex as well as a preparation method and use thereof. The molecular formula of the tert-butoxy rare earth/sodium hetero-bimetallic complex is LnNa8[OC(CH3)3]10(OH), and Ln repres
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Paragraph 0032-0033
(2017/07/13)
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- Highly Efficient Synthesis of Multi-Substituted Allenes from Propargyl Acetates and Organoaluminum Reagents Mediated by Palladium
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A simple and mild catalytic S N 2′ substitution reaction of propargyl acetates with organoaluminum reagents is reported. The S N 2′ substitution reaction of propargyl acetates with organoaluminum reagents mediated by Pd(PhP 3) 2 Cl 2 (1 mol%)/PPh 3 (2 mol%)/K 2 CO 3 in tetrahydrofuran at 60 °C for 3-4 hours afforded the corresponding multi-substituted allenes in good yields (up to 94%) with high selectivities (up to 99%). The process was simple and easily performed, which offers an efficient method to synthesize the multi-substituted allene derivatives.
- Zhang, Zhen,Shao, Xuebei,Zhang, Gang,Li, Qinghan,Li, Xinying
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p. 3643 - 3653
(2017/08/16)
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- Alkyne Activation by a Porous Silver Coordination Polymer for Heterogeneous Catalysis of Carbon Dioxide Cycloaddition
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The widely studied porous coordination polymers, possessing large pores to adsorb waste carbon dioxide gas and further transform it into valuable chemical products, have been attracting research interest, both industrially and academically. The active silver(I) ions endow the specific alkynophilicity to activate C≡C bonds of alkyne-containing molecules via π activation. Incorporating catalytic Ag metal sites into the porous frameworks represents a promising approach to construct heterogeneous catalysts that cyclize propargylic alcohols with CO2, which is highly desirable for the environmentally benign conversion of carbon dioxide to fine chemicals. We report the preparation of porous coordination polymers (PCPs) with active silver sites and efficient silver-silver bond formation by carefully modifying the coordination geometries of the silver sites. The decentralized silver(I) chains in the porous frameworks enable the efficient conversion of CO2 and derivatives of acetylene to α-alkylidene cyclic carbonates in a heterogeneous manner. X-ray structure analysis reveals two kinds of substrate molecules positioned within the pores of the framework, which correspond to trapping and activated modes through the multiple interactions with the functional Ag chains. The example of tandem conversion of simple alkynes and carbon dioxide to α-alkylidene cyclic carbonates is also presented. The well-positioned catalytic silver(I) sites and the crystalline properties of the frameworks facilitated the structural analyses of the intermediates of each catalytic step, providing knowledge of the synergistic nature of the σ and π activation of C≡C bonds. The successful catalysis of azide-alkyne cycloaddition and synthesis of propargylic alcohols via terminal alkynes could also give another indicator for the activation properties of Ag sites.
- Zhou, Zhen,He, Cheng,Yang, Lu,Wang, Yefei,Liu, Tao,Duan, Chunying
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p. 2248 - 2256
(2017/08/14)
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- Gold-Catalyzed [4+2]- and [3+3]-Annulations of Ynamides with 1-Yn-3-ols to Access Six-Membered Carbocycles and Oxacycles via Three Distinct Cyclizations
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Three distinct strategies for catalytic annulations between ynamides and 1-yn-3-ols are described; the resulting carbo- and heterocycles were produced efficiently in one-pot operations using a gold catalyst. The chemoselectivities of these annulations are controlled by variations of the substituents of the ynamides and the 1-yn-3-ols. This reaction sequence involves initial alkoxylations of ynamides, followed by Claisen rearrangement of propargylic enol ethers, and ends with 6-endo-trig cyclizations of 1-allenyl-5-amide intermediates. Among these cascade annulations, the cyclizations of 5-allenyl-1-amides to yield 5,6-dihydro-2-pyranones and 6-alkylenecyclohex-2-ene-1-carboxamides are unprecedented in the literature. (Figure presented.).
- Giri, Sovan Sundar,Liu, Rai-Shung
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supporting information
p. 3311 - 3318
(2017/09/13)
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- Asymmetric Intermolecular Heck Reaction of Propargylic Acetates and Cycloalkenes to Access Fused Cyclobutenes
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An asymmetric Heck annulation of propargylic acetates with several types of cyclic olefins affords highly strained cyclobutenes in high enantioselectivity.
- Jiao, Zhiwei,Shi, Qi,Zhou, Jianrong Steve
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supporting information
p. 14567 - 14571
(2017/10/23)
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- Palladium-Catalyzed Modular Synthesis of Substituted Piperazines and Related Nitrogen Heterocycles
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We report here a novel method for the modular synthesis of highly substituted piperazines and related bis-nitrogen heterocycles via a palladium-catalyzed cyclization reaction. The process couples two of the carbons of a propargyl unit with various diamine components to provide nitrogen heterocycles in generally good to excellent yields and high regio- and stereochemical control. (Chemical Equation Presented).
- Montgomery, Thomas D.,Rawal, Viresh H.
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supporting information
p. 740 - 743
(2016/03/01)
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- Palladium(II)-Catalyzed Annulation of Alkynes with 2-(Cyanomethyl)phenylboronates Leading to 3,4-Disubstituted 2-Naphthalenamines
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1,2-Bis(diphenylphosphino)ethane (dppe)-ligated palladium(II) complexes catalyze the annulation of internal alkynes with 2-(cyanomethyl)phenylboronates to provide 3,4-disubstituted-2-naphthalenamines in good yields. The annulation reaction proceeds under mild and neutral conditions and requires methanol as an essential solvent. In addition to symmetrical alkynes, unsymmetrical alkynes substituted by aryl, alkyl, and alkynyl groups participate in the annulation to afford the corresponding 2-naphthalenamines with electron-withdrawing sp2- and sp-carbons preferentially located at the C-3 position. Substituents including an alkyl or alkoxy group on the cyanomethyl moiety and a halogen atom on the benzene ring in the boronates are compatible with the reaction conditions. The annulation proceeds through the transmetalation of the palladium(II) complexes with the boronates and alkyne insertion followed by nucleophilic addition of the generated alkenylpalladium(II) species to the intramolecular cyano group. Stoichiometric reactions revealed that the methanol solvent was effective for both transmetalation and catalyst regeneration.
- Tsukamoto, Hirokazu,Ikeda, Taishi,Doi, Takayuki
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p. 1733 - 1745
(2016/03/15)
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- Palladium-Catalyzed Nitration of Meyer-Schuster Intermediates with tBuONO as Nitrogen Source at Ambient Temperature
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A novel domino palladium-catalyzed nitration of Meyer-Schuster intermediates which were generated in situ from propargylic alcohols was developed, by the use of t-BuONO, leading to α-nitro enones in good to excellent yields at room temperature with a broa
- Lin, Yuanguang,Kong, Weiguang,Song, Qiuling
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supporting information
p. 3702 - 3705
(2016/08/16)
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- Synthesis of Polysubstituted 2-Iodoindenes via Iodonium-Induced Cyclization of Arylallenes
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A new chemoselective iodocarbocyclization of allenyl arenes was developed leading to the formation of 2-iodoindenes. In acetonitrile or nitromethane, electrophilic sources of iodine cations react selectively with the C2-C3 double bond of 1-arylallenes to give, after anti nucleophilic attack of the aromatic ring, 2-iodoindene products in high yields. Variations of the allenic skeletons revealed the high 5-endo selectivity and some competitive pathways of cyclization. Postfunctionalization reactions of the carbon-iodine bond, via Pd- and Cu-cross-couplings, gave rise to substituted indenes in good to excellent yields. (Chemical Equation Presented).
- Grandclaudon, Charlotte,Michelet, Véronique,Toullec, Patrick Y.
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supporting information
p. 676 - 679
(2016/03/01)
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- Catalytic α-Allylation of Enones with Alcohols via [Gold(I)]-Mediated [3,3]-Sigmatropic Rearrangement of Propargylic Carboxylates
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The site-selective α-allylic alkylation of enones with alcohols via gold-triggered formation of nucleophilic allenoates by means of [3,3]-sigmatropic rearrangements of propargylic carboxylates is reported. A range of α-alkylated enones is obtained in high yields in the presence of the gold complex [JohnPhosAu(ACN)]SbF6 (2 mol%) as the promoting agent. Examples of allylation/Friedel-Crafts alkylation sequences are also provided, delivering densely functionalized dihydroindenes and dihydrobenzo[7]annulenes in a one-pot procedure in moderate yields. The role of the Br?nsted acidity (i.e., pivalic acid) delivered during the reaction course in assisting the formation of carbocationic intermediates is documented.
- Manoni, Elisabetta,Daka, Mario,Mastandrea, Marco M.,Nisi, Assunta De,Monari, Magda,Bandini, Marco
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supporting information
p. 1404 - 1409
(2016/05/19)
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