- Pd-Catalyzed Coupling of N-Tosylhydrazones with Benzylic Phosphates: Toward the Synthesis of Di- or Tri-Substituted Alkenes
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This study shows that various di- and tri-substituted alkenes with high chemoselectivity were obtained in good to high yields by coupling N-tosylhydrazones (NTHs) with benzylic phosphates as electrophilic partners. The obtained new catalytic system consis
- Zhang, Kena,Provot, Olivier,Alami, Mouad,Tran, Christine,Hamze, Abdallah
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p. 1249 - 1261
(2022/02/07)
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- Heteroleptic Copper-Based Complexes for Energy-Transfer Processes: E → Z Isomerization and Tandem Photocatalytic Sequences
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Energy-transfer processes involving copper complexes are rare. Using an optimized heteroleptic copper complex, Cu(bphen)(XantPhos)BF4, photosensitized E → Z isomerization of olefins is demonstrated. The XantPhos ligand afforded sensitizers with improved catalyst stability, while the bphen ligand lengthened the excited-state lifetime. A series of 25 di- and trisubstituted alkenes underwent photoisomerization, including macrocycles and 1,3-enynes. Cu(bphen)(XantPhos)BF4 could also be employed in a tandem ATRA/photoisomerization process employing arylsulfonyl chlorides, an example of photoisomerization with halide-substituted olefins.
- Cruché, Corentin,Neiderer, William,Collins, Shawn K.
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p. 8829 - 8836
(2021/07/28)
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- Highly Stereoselective Positional Isomerization of Styrenes via Acid-Catalyzed Carbocation Mechanism
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The first transition metal-free highly stereoselective positional isomerization of various α-alkyl styrenes through a carbocation mechanism triggered strategy is developed by using Al(OTf)3 as a hidden Br?nsted acid catalyst, which provides facile access to value-added acyclic tri- and tetra-substituted alkenes in good yields with high stereoselectivity under mild conditions. The practicality of this protocol is further highlighted by the gram-scale synthesis, high stereoselectivity, good functional group tolerance, and simple operation. Mechanistic studies support that Al(OTf)3 acts as a hidden Br?nsted acid catalyst and a carbocation intermediate is formed.
- Hu, Xiao-Si,He, Jun-Xiong,Zhang, Ying,Zhou, Jian,Yu, Jin-Sheng
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supporting information
p. 2227 - 2233
(2021/06/28)
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- Regioselective Synthesis of α-Functional Stilbenes via Precise Control of Rapid cis- trans Isomerization in Flow
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The rapid cis-trans isomerization of α-anionic stilbene was regioselectively controlled by using flow microreactors, and its reaction with various electrophiles was conducted. The reaction time was precisely controlled within milliseconds to seconds at -50 °C to selectively give the cis- or trans-isomer in high yields. This synthetic method in flow was well-applied to synthesize precursors of commercial drug compound, (E)- and (Z)-tamoxifen with high regioselectivity and productivity.
- Lee, Hyune-Jea,Yonekura, Yuya,Kim, Nayoung,Yoshida, Jun-Ichi,Kim, Heejin
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supporting information
p. 2904 - 2910
(2021/05/05)
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- Synthesis of new adamantyl-imine palladium(II) complexes and their application in Mizoroki-Heck and Suzuki-Miyaura C[sbnd]C cross-coupling reactions
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Improving carbon–carbon cross-coupling reactions is an ongoing process and finding the most versatile and stable catalyst precursors has been of great interest. Ligand design has been proven to be important since it is responsible for providing electron density and steric saturation around the metal centre, thus contributing towards the stereo-electronic properties. The adamantyl moiety has been used to generate highly bulky and electron-rich ligands for application in palladium-catalysed cross-coupling reactions. Accordingly, we have prepared some Schiff-base adamantyl ligands (L1-L3) and complexed them with [PdCl2(MeCN)2] to afford the (pre)catalysts C1-C3, which were successfully applied in Mizoroki-Heck and Suzuki-Miyaura carbon–carbon cross-coupling reactions. The cross-coupling reaction products were obtained in good yields using 0.5 mol % Pd catalyst loading. C2 and C3 showed remarkable activity in the Mizoroki-Heck coupling reactions involving substrates with substituents on the olefin and aryl halide (including 4-Cl, 4-CH3, -CO2Me and -CO2Et). We also, observed that the Suzuki-Miyaura cross-coupling system was active towards challenging activated and deactivated aryl chlorides, with to up 70% conversions recorded. The mercury poisoning tests conducted revealed that the catalysts act as homogenous molecular active species in the Mizoroki-Heck reactions and act as both homogenous and heterogeneous catalysts in the Suzuki-Miyaura cross-coupling reactions.
- Makhubela, Banothile C. E.,Matsheku, Asanda C.,Maumela, Munaka C.
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- Remote sp2C-H Carboxylation via Catalytic 1,4-Ni Migration with CO2
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A remote catalytic reductive sp2 C-H carboxylation of arenes with CO2 (1 bar) via 1,4-Ni migration is disclosed. This protocol constitutes the first catalytic 1,4-Ni migration reported to date, thus offering new vistas in the Ni-catalyzed reductive coupling arena while providing an unconventional new platform for incorporating electrophilic sites at remote sp2 C-H linkages.
- B?rjesson, Marino,Duan, Yaya,Janssen-Müller, Daniel,Martin, Ruben,Sahoo, Basudev,Wang, Xueqiang
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supporting information
p. 16234 - 16239
(2020/10/09)
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- Nickel-Catalyzed Allylmethylation of Alkynes with Allylic Alcohols and AlMe3: Facile Access to Skipped Dienes and Trienes
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We present herein an unprecedented allylative dicarbofunctionalization of alkynes with allylic alcohols. This simple catalytic procedure utilizes commercially available Ni(COD)2, triphenylphosphine, and inexpensive reagents, and delivers valuable skipped dienes and trienes with an all-carbon tetrasubstituted alkene unit in a highly stereoselective fashion. Preliminary mechanistic studies support the reaction pathway of allylnickelation followed by transmetalation in this dicarbofunctionalization of alkynes.
- Li, Jincan,Li, Wanfang,Yu, Shun,Zhao, Yu
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p. 14404 - 14408
(2020/07/04)
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- Promising new catalytic properties of a Co (II)-carboxamide complex and its derived Co3O4 nanoparticles for the Mizoroki-Heck and the Epoxidation reactions
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The new Co(II) - carboxamide complex (1) and Co3O4 nanoparticles (2), by way of thermal decomposition of (1) have been efficiently synthesised in the environment-friendly. X-ray diffraction reveals a slightly distorted octahedral coordination of cobalt (four nitrogens and two oxygens) in (1) and regular octahedral or tetrahedral ones (oxygens only) in (2). The investigation of (1) and (2) in the Mizoroki-Heck and epoxidation of alkens reactions showed them both to be powerful, green and inexpensive catalysts.
- Kiani, Mahsa,Bagherzadeh, Mojtaba,Meghdadi, Soraia,Fadaei-Tirani, Farzaneh,Babaie, Maryam,Schenk-Jo?, Kurt
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- Synthesis of α-methylstilbenes using an aqueous Wittig methodology and application toward the development of potent human aromatase inhibitors
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The development of aqueous Wittig methodology for the synthesis of α-methylstilbenes using tripropylphosphine-derived phosphonium salts is described. The Wittig olefination reaction was high yielding and allowed isolation of stilbenes by simple filtration and washing with water. The novel phosphonium salts employed were accessed via a highly efficient, regioselective addition of hydrogen bromide to styrenes. Application of the α-methylstilbenes toward the synthesis of a collection of stilbenoid-triazoles is reported and their inhibition of CYP450 19A1 (aromatase) investigated. The overall structure-activity profile provided additional evidence on the aryl halide-ketone bioisostere hypothesis and identified 6c as a potent inhibitor of aromatase in vitro (Ki = 8 nM).
- Nielsen, Alexander J.,Raez-Villanueva, Sergio,Crankshaw, Denis J.,Holloway, Alison C.,McNulty, James
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supporting information
p. 1395 - 1398
(2019/04/03)
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- Dipalladium(I) complexes of ortho- and para-functionalized 1,3-bis(aryl)triazenide ligands: Synthesis, structure and catalytic activity
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The synthesis and characterization of a series dipalladium(I) complexes of formulae [Pd{1-[2′-(methoxycarbonyl)phenyl]-3-[4′-X-phenyl]triazenide}]2 [X = F (4), Cl (5), Br (6)] are reported. The crystal structure of complex 4 was determined by X-ray diffraction studies. The previously reported dipalladium(I) 1–3 as well as the new complexes 4–6 were used as catalysts in the Heck and Suzuki couplings of different p-substituted bromobenzenes.
- Correa-Ayala, Erick,Campos-Alvarado, Carlos,Chávez, Daniel,Hernández-Ortega, Simón,Morales-Morales, David,Miranda-Soto, Valentín,Parra-Hake, Miguel
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supporting information
p. 130 - 138
(2019/03/12)
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- Synthesis of Polyethylene with In-Chain α,β-Unsaturated Ketone and Isolated Ketone Units: Pd-Catalyzed Ring-Opening Copolymerization of Cyclopropenone with Ethylene
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Although various functionalized units can be incorporated into polyolefins by transition metal catalyzed coordination copolymerizations of nonfunctionalized olefins with polar functional monomers, the incorporated functional units are largely limited to a C1 unit from either CO or C2 units from vinyl monomers. Reported here is the Pd-catalyzed copolymerization of ethylene with cyclopropenone, leading to incorporation of C3 units with functional groups, α,β-unsaturated ketones, in the chain. Coordination-insertion of the carbonyl group and ring opening of the strained three-membered ring are proposed as the key steps in the mechanism. Under different reaction conditions an isolated ketone structure was afforded as the major carbonyl unit, and could be generated by the copolymerization of ethylene with CO formed in situ from cyclopropenone.
- Wang, Xiaoming,Seidel, Falk William,Nozaki, Kyoko
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supporting information
p. 12955 - 12959
(2019/08/21)
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- Nickel-Catalyzed Arylboration of Alkenylarenes: Synthesis of Boron-Substituted Quaternary Carbons and Regiodivergent Reactions
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A method for the construction of boron-substituted quaternary carbons or diarylquaternary carbons by arylboration of highly substituted alkenylarenes is presented. A wide range of alkenes and arylbromides can participate in this reaction thus allowing for a diverse assortment of products to be prepared. In addition, a solvent dependent regiodivergent arylboration of 1,2-disubstituted alkenylarenes is presented, thus greatly increasing the scope of products that can be accessed.
- Chen, Liang-An,Lear, Alan R.,Gao, Pin,Brown, M. Kevin
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supporting information
p. 10956 - 10960
(2019/07/08)
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- Acceptorless dehydrogenative construction of CN and CC bonds through catalytic aza-Wittig and Wittig reactions in the presence of an air-stable ruthenium pincer complex
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The construction of CN bonds was achieved by the dehydrogenative coupling of alcohol and azide via aza-Wittig type reaction. The reaction is catalyzed by an acridine-derived ruthenium pincer complex and does not use any oxidant. The present protocol offers a wide substrate scope, including aliphatic, aryl or heteroaryl alcohol/azides. This expeditious protocol was successfully applied to construct a CC bond directly from alcohol via dehydrogenative Wittig reaction. Furthermore, the synthesis of structurally important pyrrolo[1,4]benzodiazepine derivatives was also achieved by this methodology.
- Biswas, Nandita,Das, Kalicharan,Sardar, Bitan,Srimani, DIpankar
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p. 6501 - 6512
(2019/05/24)
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- Conversion of Carbonyl Compounds to Olefins via Enolate Intermediate
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A general and efficient protocol to synthesize substituted olefins from carbonyl compounds via nickel catalyzed C—O activation of enolates was developed. Besides ketones, aldehydes were also suitable substrates for the presented catalytic system to produce di- or tri- substituted olefins. It is worth noting that this approach exhibited good tolerance to highly reactive tertiary alcohols, which could not survive in other reported routes for converting carbonyl compounds to olefins. This method also showed good regio- and stereo-selectivity for olefin products. Preliminary mechanistic studies indicated that the reaction was accomplished through nickel catalyzed C—O activation of enolates, thus offering helpful contribution to current enol chemistry.
- Cao, Zhi-Chao,Xu, Pei-Lin,Luo, Qin-Yu,Li, Xiao-Lei,Yu, Da-Gang,Fang, Huayi,Shi, Zhang-Jie
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supporting information
p. 781 - 785
(2019/06/24)
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- Olefination with Sulfonyl Halides and Esters: E-Selective Synthesis of Alkenes from Semistabilized Carbanion Precursors
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Carbanions of sulfonyl halides and activated sulfonates add to carbonyl compounds, and so-formed aldol-type adducts spontaneously fragment into olefins. This transformation mimics the one-pot Julia olefination with (hetero)aryl sulfones, but the mechanism of fragmentation involves a four-membered intermediate, typical for reactivity of phosphorus reagents. Moreover, in contrast to the reactions of sulfones, sulfonates of fluorinated alcohols (TFE and HFI) produce byproducts that are easily removed during workup. In our report, we focus on reactions of unstabilized and semistabilized carbanion precursors: alkylsulfonates, and allyl- and benzylsulfonates, respectively. In particular for semistabilized systems, olefins were synthesized as predominant E isomers in good yields. The presented studies reveal that optimal reaction conditions, including the type of base and alcohol groups of the sulfonates, are different depending on stabilization of the carbanion precursors and structure of the carbonyl substrates. The practical synthetic guide is supplemented with a discussion of the mechanism, based on reactivity studies of intermediates and identification of side-products.
- Górski, Bartosz,Basiak, Dariusz,Talko, Alicja,Basak, Tymoteusz,Mazurek, Tomasz,Barbasiewicz, Micha?
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supporting information
p. 1774 - 1784
(2018/04/27)
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- Oxidative cross-coupling of allyl(trimethyl)silanes with aryl boronic acids by palladium catalysis
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The first oxidative cross-coupling of allylsilanes with aryl boronic acids has been developed by palladium catalysis. The reaction between β-substituted allyl(trimethyl)silanes and a wide range of aryl boronic acids afforded allylarenes in moderate to good yields and excellent selectivity. On the basis of experimental results and literature reports, it was suggested that the reaction might start from transmetalation of aryl boronic acid with AgOAc followed by transmetalation with Pd(II) to give an arylpalladium acetate complex as a key intermediate. This intermediate underwent either electrophilic addition/desilylation or transmetalation with allylsilane and subsequent reductive elimination to give the final product.
- Zhou, Zhibing,Hou, Zhen-Lin,Yang, Fan,Yao, Bo
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p. 7228 - 7236
(2018/11/03)
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- Radical Cation Cyclopropanations via Chromium Photooxidative Catalysis
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The chromium photocatalyzed cyclopropanation of diazo reagents with electron-rich alkenes is described. The transformation occurs under mild conditions and features specific distinctions from traditional diazo-based cyclopropanations (e.g., avoiding β-hydride elimination, chemoselectivity considerations, etc.). The reaction appears to work most effectively using chromium catalysis, and a number of decorated cyclopropanes can be accessed in generally good yields.
- Sarabia, Francisco J.,Ferreira, Eric M.
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supporting information
p. 2865 - 2868
(2017/06/07)
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- Influence of the methyl group at C=C bridging bond of stilbene on the longest wavelength maximum in ultraviolet absorption spectra
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The compounds stilbenes XArCH=CHArY(XSBY) and 1,2-diphenylpropylenes XArC(Me)=CHArY(XSMBY) have bridging groups CH=CH and C(CH3)=CH, respectively, in which the C(CH3)=CH has a side-group CH3 at the carbon-carbon double bond. A series of XSMBY were synthesized, and their longest wavelength maximum λmax (nm) in ultraviolet absorption spectra were measured in this work. We investigated the change regularity of the νmax (cm-1, νmax?=?1/λmax) of XSMBY and compared it with that of XSBY. The results indicate that (1) there is no good linear relationship between the νmax of XSMBY and that of XSBY. (2) Because of the influence of the side-group CH3, in case of the same couple of groups X and Y, the λmax of XSMBY is shorter than that of XSBY, that is, it has a blue shift. (3) The cross-interaction between the side-group CH3 and Y has an important effect on the νmax of XSMBY, while the cross-interaction between the side-group CH3 and X has a little effect on the νmax and can be ignored. (4) The specific cross-interaction between X and Y has important effect on the νmax of XSMBY, whereas it has no important effect on the νmax of XSBY.
- Zhang, Yanxiu,Cao, Chao-Tun,Zhang, Jingyuan,Cao, Chenzhong
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- Highly-phosphorescent tungsten(0) carbonyl pyridyl-imidazole complexes as photosensitisers
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Photoluminescence data are reported for two W(CO)4L complexes (L = 2-(1H-imidazol-2-yl)pyridine and 2-(2′-pyridyl)benzimidazole) in room-temperature solutions. The bidentate ligands consist of a pyridine and an imidazole moiety connected by a C-C bond. The complexes have been found to exhibit enhanced phosphorescence from the metal-to-ligand charge transfer (MLCT) excited state with quantum yields in the order of 10-3, almost two orders of magnitude higher than those reported for W(CO)4(diimine) complexes. One of the complexes W(CO)4(2-(2′-pyridyl)benzimidazole) can serve as an efficient visible-light photosensitiser for the isomerisation of aromatic alkenes with efficiency comparable to and even exceeding that of the well-studied ruthenium tris-bipyridine complex, Ru(bpy)Cl2.
- Lee, Jia Jin,Yap, Chew Pheng,Chwee, Tsz Sian,Fan, Wai Yip
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p. 11008 - 11012
(2017/08/30)
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- A New Mode of Operation of Pd-NHC Systems Studied in a Catalytic Mizoroki-Heck Reaction
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Metal complexes bearing N-heterocyclic carbene (NHC) ligands are typically considered the system of choice for homogeneous catalysis with well-defined molecular active species due to their stable metal-ligand framework. A detailed study involving 19 different Pd-NHC complexes with imidazolium, benzimidazolium, and triazolium ligands has been carried out in the present work and revealed a new mode of operation of metal-NHC systems. The catalytic activity of the studied Pd-NHC systems is predominantly determined by the cleavage of the metal-NHC bond, while the catalyst performance is strongly affected by the stabilization of in situ formed metal clusters. In the present study, the formation of Pd nanoparticles was observed from a broad range of metal complexes with NHC ligands under standard Mizoroki-Heck reaction conditions. A mechanistic analysis revealed two different pathways to connect Pd-NHC complexes to "cocktail"-type catalysis: (i) reductive elimination from a Pd(II) intermediate and the release of NHC-containing byproducts and (ii) dissociation of NHC ligands from Pd intermediates. Metal-NHC systems are ubiquitously applied in modern organic synthesis and catalysis, while the new mode of operation revealed in the present study guides catalyst design and opens a variety of novel opportunities. As shown by experimental studies and theoretical calculations, metal clusters and nanoparticles can be readily formed from M-NHC complexes after formation of new M-C or M-H bonds followed by C-NHC or H-NHC coupling. Thus, a combination of a classical molecular mode of operation and a novel cocktail-type mode of operation, described in the present study, may be anticipated as an intrinsic feature of M-NHC catalytic systems.
- Astakhov, Alexander V.,Khazipov, Oleg V.,Chernenko, Andrey Yu.,Pasyukov, Dmitry V.,Kashin, Alexey S.,Gordeev, Evgeniy G.,Khrustalev, Victor N.,Chernyshev, Victor M.,Ananikov, Valentine P.
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supporting information
p. 1981 - 1992
(2017/06/14)
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- Nickel-catalyzed synthesis of (E)-olefins from benzylic alcohol derivatives and arylacetonitriles via C-O activation
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An efficient Ni-catalyzed synthesis of (E)-olefins using the readily available benzylic alcohol derivatives and arylacetonitriles is described. This transformation should proceed via a tandem process involving nickel-catalyzed cross coupling via C-O activation and subsequent stereoselective E2 elimination.
- Xiao, Jing,Yang, Jia,Chen, Tieqiao,Han, Li-Biao
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supporting information
p. 2157 - 2160
(2016/02/05)
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- Hydrophenylation of internal alkynes with boronic acids catalysed by a Ni-Zn hydroxy double salt-intercalated anionic rhodium(III) complex
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[Rh(OH)6]3- intercalated Ni-Zn mixed basic salt (Rh/NiZn) acts as an efficient catalyst for the hydrophenylation of internal alkynes with arylboronic acids under mild conditions. The turnover number per Rh site approached 740 in the reaction between 4-octyne and phenylboronic acid. The catalytic monomeric Rh(iii) complex is stabilised within the NiZn interlayers, attributable to a strong electrostatic interaction, promoting its re-use.
- Hara, Takayoshi,Fujita, Nozomi,Ichikuni, Nobuyuki,Wilson, Karen,Lee, Adam F.,Shimazu, Shogo
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p. 863 - 868
(2016/02/18)
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- Microwave role in the thermally induced SRN1 reaction for α-arylation of ketones
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The coupling between iodobenzene and the enolate anion of acetophenone is accelerated by microwave irradiation. This increase in reaction rate is only ascribed to thermal effects. The coupling reaction gave the corresponding substitution product 1,2-di-phenylethanone in a 50% yield when microwave irradiation was applied between 15-60 s according to the intensity of the pulse. Moreover, this reaction is effective in a temperature window of 70-120 °C. The presence of ionic and dipolar species is not involved in the initiation process as molecular radiators. The excess of tBuOK in the reaction medium may also act as an electron donor helping to generate radicals when the solution temperature increases to 70 °C. This journal is
- Caminos, Daniel A.,Garro, Alexis D.,Soria-Castro, Silvia M.,Pe?é?ory, Alicia B.
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p. 20058 - 20065
(2015/03/30)
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- 1,1′-methylene-3,3′-bis[(N -(tert -butyl)imidazol-2-ylidene] and Its effect in palladium-catalyzed C-C coupling
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A catalytic system utilizing a chelate carbene ligand containing bulk tert-butyl groups is described for palladium-catalyzed Heck and Suzuki coupling reactions. The Heck reaction focused on the coupling of different aryl bromides with mono- and 1,1-disubstituted olefins while the Suzuki reaction involved the coupling of aryl bromides and phenylboronic acid to afford the corresponding biphenyls. The catalyst system performs well with low Pd(OAc)2 levels (0.025 mol% Pd). In all cases with monosubstituted olefins, the trans-configured products were obtained, while the results of Heck reaction of 1,1-disubstituted olefins exhibited a high selectivity favoring the terminal product.
- Nadri, Shirin,Rafiee, Ezzat,Jamali, Sirous,Joshaghani, Mohammad
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supporting information
p. 619 - 624
(2015/03/14)
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- General Olefin Synthesis by the Palladium-Catalyzed Heck Reaction of Amides: Sterically Controlled Chemoselective N-C Activation
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Metal-catalyzed reactions of amides proceeding via metal insertion into the N-CO bond are severely underdeveloped due to resonance stabilization of the amide bond. Herein we report the first Heck reaction of amides proceeding via highly chemoselective N-CO cleavage catalyzed by Pd0 utilizing amide bond ground-state destabilization. Conceptually, this transformation provides access to a myriad of metal-catalyzed transformations of amides via metal insertion/decarbonylation.
- Meng, Guangrong,Szostak, Michal
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supporting information
p. 14518 - 14522
(2016/01/25)
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- Arylation of alkynes over hydrotalcite docked Rh-m-TPPTC complex
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Rh-m-TPPTC complex was successful immobilized onto a hydrotalcite Zn-Al to convert selectively in aqueous media both the symmetric and nonsymmetric alkynes into functionalized alkenes, with boronic acids. The complex preserved its activity after the ionic exchange, leading to excellent results (~87%) for the symmetric alkynes and also for the non-symmetrical alkynes (up to 99%).
- Nea?u, Florentina,Ciobanu, M?d?lina,?toflea, Laura E.,Frunz?, Ligia,Parvulescu, Vasile I.,Michelet, Véronique
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p. 155 - 162
(2015/03/30)
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- Carboncarbon bond forming reactions: Application of covalently anchored 2,4,6-triallyloxy-1,3,5-triazine (TAT) Pd(II) complex over modified surface of SBA-15 to Heck, Suzuki, Sonogashira and Hiyama cross coupling reactions
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A highly active SBA-15-TAT-Pd(II) catalyst was synthesized from organofunctionalized SBA-15 and 2,4,6-triallyloxy-1,3,5-triazine. The catalyst was employed in carrying out Heck, "copper-free" Sonogashira, Suzuki and Hiyama cross coupling reactions. Under the optimized conditions the catalyst displays excellent catalytic activity in delivering the desired products in good to excellent yields. The catalytic system exhibited superior activity regarding the time taken for the completion of reaction, isolation, Pd loading (0.62 mmol%) and yields of products as compared to the earlier reported heterogeneous SBA-15 anchored Pd catalysts. The catalyst could be recycled and reused for five times without any appreciable loss of catalytic activity.
- Singh, Chandani,Jawade, Kiran,Sharma, Priti,Singh, Anand P.,Kumar, Pradeep
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- One-pot multistep synthesis of trisubstituted alkenes from N -tosylhydrazones and alcohols
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A one-pot procedure for the synthesis of trisubstituted alkenes from N-tosylhydrazones and alcohols is reported. This procedure combines the aerobic oxidation reaction and Wittig reaction in one pot, which avoids using of environmentally toxic oxidants and isolation of the intermediates. The simple procedure makes it very attractive for the synthesis of trisubstituted alkenes when alcohols are used as starting materials. A variety of trisubstituted alkenes as well as trifluoromethyl-substituted alkenes were obtained in moderate to good yields (up to 84%) with good E-selectivity (up to 99%). Georg Thieme Verlag Stuttgart.New York.
- Sha, Qiang,Wei, Yunyang
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p. 2353 - 2361
(2014/11/08)
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- Construction of polyaromatics via photocyclization of 2-(fur-3-yl) ethenylarenes, using a 3-furyl group as an isopropenyl equivalent synthon
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The construction of different types of substituted arenes was demonstrated through the photocyclization of 2-(fur-3-yl)ethenylarenes using a 3-furyl group as an isopropenyl equivalent synthon in the photocyclization reaction. The furan portion of the photocyclization intermediate could be fragmented via a base-induced elimination reaction to yield a series of substituted polyaromatics, including naphthalene, benzofuran, benzothiophene, phenanthrene, phenalene, acenaphthene, and triphenylene. Using different reagents, this method made it possible to introduce methyl or 2-hydroxyethyl groups as substituents at specific positions in these arenes.
- Chen, Ying-Zhe,Ni, Ching-Wen,Teng, Fu-Lin,Ding, Yi-Shun,Lee, Tunng-Hsien,Ho, Jinn-Hsuan
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p. 1748 - 1762
(2014/03/21)
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- METHODS FOR PHOSPHINE OXIDE REDUCTION IN CATALYTIC WITTIG REACTIONS
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A method for increasing the rate of phosphine oxide reduction, preferably during a Wittig reaction comprising use of an acid additive is provided. A room temperature catalytic Wittig reaction (CWR) the rate of reduction of the phosphine oxide is increased due to the addition of the acid additive is described. Furthermore, the extension of the CWR to semi-stabilized and non-stabilized ylides has been accomplished by utilization of a masked base and/or ylide-tuning.
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Page/Page column 71; 72
(2014/09/29)
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- Efficient synthetic photocyclization for phenacenes using a continuous flow reactor
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The continuous flow reaction technique has been applied to the photocyclization of 1,2-diarylethenes, the so-called Mallory reaction, to afford phenacenes in high chemical yields and efficiencies (114-288mg h-1). The present technique will allow us to produce several grams of phenacenes at a time.
- Okamoto, Hideki,Takane, Takamitsu,Gohda, Shin,Kubozono, Yoshihiro,Sato, Kaori,Yamaji, Minoru,Satake, Kyosuke
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supporting information
p. 994 - 996
(2014/07/22)
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- Capture of in situ generated diazo compounds or copper carbenoids by triphenylphosphine: Selective synthesis of trans-alkenes and unsymmetric azines via reaction of aldehydes with ketone-derived N-tosylhydrazones
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Copper(II) acetylacetonate-catalyzed Wittig olefination reactions of aldehydes with ketone-derived N-tosylhydrazones are reported. A series of tosylhydrazones was investigated and our results showed that the carbon number of the alkyl chain influences the E-selecivity of the alkenes greatly. Alkenes could be obtained in moderate yields and excellent E-selectivity when the carbon numbers were up to two. Under metal-free conditions, triphenylphosphine was able to capture the in situ generated diazo compounds and the corresponding unsymmetrical azines were formed in good yields.
- Sha, Qiang,Ling, Yifei,Wang, Wenyong,Wei, Yunyang
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supporting information
p. 2145 - 2150
(2013/10/01)
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- An operationally simple approach to (E)-α-halo vinyl sulfides and their applications for accessing stereodefined trisubstituted alkenes
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An operationally simple and practical protocol for the synthesis of (E)-α-halo vinyl sulfides has been achieved via a highly regio- and stereoselective hydrohalogenation of alkynyl thioethers using lithium halides in HOAc or propionic acid at room temperature. It permits the formation of (E)-α-chloro and (E)-α-bromo vinyl sulfides in satisfactory yields with good to excellent stereoselectivities. Moreover, this work results in a new method for the assembly of stereodefined (E)- or (Z)-trisubstituted alkenes featuring the first coupling of the C-X bond of (E)-α-halo vinyl sulfides followed by a subsequent Ni-catalyzed coupling of the C-S bond with Grignard reagents. The Royal Society of Chemistry 2013.
- Yang, Zhaozhen,Chen, Xiaoyi,Kong, Wei,Xia, Siyuan,Zheng, Renwei,Luo, Fang,Zhu, Gangguo
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p. 2175 - 2185
(2013/04/10)
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- Iron-catalysed tandem cross-dehydrogenative coupling (CDC) of terminal allylic C(sp3) to C(sp2) of styrene and benzoannulation in the synthesis of polysubstituted naphthalenes
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A novel iron-catalysed tandem cross-dehydrogenative coupling and benzoannulation process was developed for the synthesis of biologically and synthetically important polysubstituted naphthalene derivatives from simple 1,2-aryl-propenes and styrenes in moderate to good yields. The Royal Society of Chemistry 2012.
- Liu, Hua,Cao, Li,Sun, Jia,Fossey, John S.,Deng, Wei-Ping
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supporting information; scheme or table
p. 2674 - 2676
(2012/04/04)
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- The ligand and base-free Pd-catalyzed oxidative Heck reaction of arylboronic acids and olefins
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Highly effective Pd-catalyzed Heck-type oxidative couplings between arylboronic acids and terminal olefins were reported. It is noteworthy that such reactions could be carried out in the absence of the base and the ligand.
- Sun, Peng,Zhu, Yan,Yang, Hailong,Yan, Hong,Lu, Linhua,Zhang, Xiang,Mao, Jincheng
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scheme or table
p. 4512 - 4515
(2012/07/14)
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- Catalytic conversion of alcohols over alumina-zirconia mixed oxides: Reactivity and selectivity
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The amorphous and crystalline mixed 25, 50 and 75 wt.% Al2O 3-ZrO2 composites were prepared by means of sol-gel method using aluminum iso-propoxide and zirconyl nitrate precursors. Physicochemical properties were determined using XRD, BET, NH3-TPD, TGA, SEM, and FT-IR spectroscopy. Catalytic activity and selectivity were investigated for the dehydration of 2-octanol and 1,2-diphenyl-2-propanol (DPP). Al 75Zr25 composite is more selective than other forms for the conversion of 2-octanol. The selectivity of DPP for 1-alkene formation was increased over Al25Zr75 catalyst. The crystalline 50 wt.% catalyst dehydrated tertiary alcohol (DPP) selectively in the presence of 2-octanol. The amorphous 50 wt.% catalyst dehydrated DPP predominately to 1-alkene isomer. The crystalline catalyst favored the formation of E-2-alkene.
- Dabbagh, Hossein A.,Zamani, Mehdi
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experimental part
p. 141 - 148
(2012/02/15)
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- Cyclization reaction for the synthesis of polysubstituted naphthalenes in the presence of Au(I) precatalysts
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Au(I)-catalyzed cyclization of alkenyl carbonyl compounds leading to a variety of substituted naphthalenes has been developed. This process exploits a dual function of the Au(I) catalyst: (1) the oxophilic nature of the Au(I) catalyst, counterintuitive to the π-acidic reactivities generally associated with Au catalysts, and (2) olefin isomerization supported by the outcome of isotope scrambling experiments. It cannot be completely excluded that TfOH is a true operative catalyst in this protocol. In view of the practicality, the unnecessity of isomerically pure starting material in this reaction is particularly attractive and valuable.
- Jagdale, Arun R.,Park, Jong Hyub,Youn, So Won
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experimental part
p. 7204 - 7215
(2011/10/17)
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- Heck reactions catalyzed by Pd(0)-PVP nanoparticles under conventional and microwave heating
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Pd(0) nanoparticles stabilized by polyvinylpyrrolidone (Pd-PVP) with a diameter of 3-6 nm in ethanol catalyzed Heck coupling of iodobenzene with different alkenes under microwave heating. Products were obtained in good yields (62-99%) and good selectivity to the E-isomers. Microwave heating proved to be superior to conventional heating, providing products in higher yields and selectivities in short times (12 min).
- Martins, Daniela De L.,Alvarez, Heiddy M.,Aguiar, Lúcia C.S.,Antunes, Octavio A.C.
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experimental part
p. 47 - 53
(2012/04/11)
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- Effects of vacuum and calcination temperature on the structure, texture, reactivity, and selectivity of alumina: Experimental and DFT studies
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The effects of vacuum and/or calcination temperature on the structure and texture of alumina were investigated using XRD, SEM, BET, DTG and FT-IR. Elucidation of the observed reactivity and selectivitythe catalyst was carried out via elimination reaction of secondary (2-octanol) and tertiary (1,2-diphenyl-2-propanol, DPP) alcohols. The mechanism of (R)-, (S)-2-octanol and (R)-, (S)-DPP dehydration(1 0 0) and (1 1 0) surfaces of alumina was modeled using density functional theory (DFT).
- Dabbagh, Hossein A.,Taban, Keivan,Zamani, Mehdi
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scheme or table
p. 55 - 68
(2010/10/01)
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- Impact on hydrogenation catalytic cycle of the R groups Cyclic feature in "r-SMS-Phos"
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A series of R-SMS-Phos ligands was evaluated in the Rh(I)-catalyzed hydrogenation of a set of olefins showing a marked influence of the cyclic nature and structure of the R groups. Overall, cPen- and Cy-SMS-Phos performed efficiently, while Ph- and Bn-SMS-Phos exhibited slower kinetics and furnished lower ees also compared with C6F5CH2-SMS-Phos. The Rh(I)-(Cy-SMS-Phos) catalyst was screened under mild conditions displaying excellent enantioselectivities and high TOFs. Cases of catalysis under catalyst or substrate control were identified.
- Zupancic, Borut,Mohar, Barbara,Stephan, Michel
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supporting information; experimental part
p. 3022 - 3025
(2010/08/19)
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- Lanthanum tricyanide-catalyzed acyl silane-ketone benzoin additions and kinetic resolution of resultant α-silyloxyketones
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We report the full account of our efforts on the lanthanum tricyanide-catalyzed acyl silane-ketone benzoin reaction. The reaction exhibits a wide scope in both acyl silane (aryl, alkyl) and ketone (aryl-alkyl, alkyl-alkyl, aryl-aryl, alkenyl-alkyl, alkynyl-alkyl) coupling partners. The diastereoselectivity of the reaction has been examined in both cyclic and acyclic systems. Cyclohexanones give products arising from equatorial attack by the acyl silane. The diastereoselectivity of acyl silane addition to acyclic α-hydroxy ketones can be controlled by varying the protecting group to obtain either Felkin-Ahn or chelation control. The resultant α-silyloxyketone products can be resolved with selectivity factors from 10 to 15 by subjecting racemic ketone benzoin products to CBS reduction.
- Tarr, James C.,Johnson, Jeffrey S.
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supporting information; scheme or table
p. 3317 - 3325
(2010/08/05)
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- Lewis acid promoted carbon - Carbon double-bond formation via organozinc reagents and carbonyl compounds
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(Chemical Equation Presented) Using cheap and readily available AlCl3 as Lewis acid, functionalized aldehydes react with organozinc reagents to give (E)-alkenes stereoselectively in high yields. 2009 American Chemical Society.
- Peng, Zhi-Yong,Ma, Fang-Fang,Zhu, Lv-Feng,Xie, Xiao-Min,Zhang, Zhaoguo
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supporting information; experimental part
p. 6855 - 6858
(2009/12/31)
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- Hydroxypropyl-a-cyclodextrin-capped palladium nanoparticles: active scaffolds for efficient carbon-carbon bond forming cross-couplings in water
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A new approach for the preparation of palladium nanoparticles in water from a renewable source, 2-hydroxypropyl-a-cyclodextrin (a-HPCD), which acts both as a reductant and capping agent, is presented. The palladium nanoparticles were characterized by using dynamic light scattering (DLS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), which revealed the formation of spherical particles in the size range of 2-7 nm. Further analysis by Fourier-transform infrared spectroscopy (FT-IR) and 1H NMR did not show covalent bonds between cyclodextrins and palladium nanoparticles, suggesting that a-HPCD is only physically adsorbed on the nanoparticle surface, presumably through hydrophobic interactions which limit the mutual coalescence of nanoclusters. The catalytic activity was tested in Suzuki, Heck and Sonogashira reactions in neat water, providing good yields and selectivities of coupling products under very low Pd loadings (0.5-0.01 mol%). Remarkably, the nanocatalyst showed significant stability hence the aqueous phase remained active for four subsequent runs. The combination of a binding site for substrates (the HPCD cavity) and a reactive centre (Pd core) provides a potential to explore functional catalysis in aqueous medium.
- Senra, Jaqueline D.,Malta, Luiz Fernando B.,Da Costa, Marcelo E. H. M.,Michel, Ricardo C.,Aguiar, Lucia C. S.,Simas, Alessandro B. C.,Antunes
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supporting information; experimental part
p. 2411 - 2422
(2009/12/28)
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- Selective arylation of 1,1-disubstituted olefins using a biphenyl-based phosphine in Heck coupling reactions
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The biphenyl-based phosphine, 2-diphenylphosphino-2′-methylbiphenyl is an effective ligand for palladium-catalyzed terminal arylation of 1,1-disubstituted olefins with aryl bromides in DMF and K2CO3 as base. The yields of products are independent of the electronic properties of the aryl bromides, however, the nature of the olefin has a major effect.
- Nadri, Shirin,Joshaghani, Mohammad,Rafiee, Ezzat
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experimental part
p. 5470 - 5473
(2010/01/11)
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- Rhodium-catalyzed coupling of 2-silylphenylboronic acids with alkynes leading to benzosiloles: Catalytic cleavage of the carbon-silicon bond in trialkylsilyl groups
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(Chemical Equation Presented) The reaction of 2-(trimethylsilyl) phenylboronic acid with alkynes in the presence of a rhodium catalyst affords benzosilole derivatives. The arylvinylrhodium intermediate undergoes formal substitution at a silicon center, resulting in the cleavage of a robust silicon-methyl bond in the trimethylsilyl group.
- Tobisu, Mamoru,Onoe, Masahiro,Kita, Yusuke,Chatani, Naoto
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supporting information; experimental part
p. 7506 - 7507
(2009/10/17)
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- Iron-catalyzed carbolithiation of alkynes having no heteroatoms
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Alkyl- and aryllithium compounds were found to add to alkynes having no heteroatoms in the presence of an iron or iron-copper catalyst to give various trisubstituted vinyllithium compounds.
- Shirakawa, Eiji,Ikeda, Daiji,Ozawa, Tsubasa,Watanabe, Shogo,Hayashi, Tamio
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supporting information; experimental part
p. 1885 - 1887
(2009/10/17)
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- Titanacyclobutenes or titanium vinyl carbene complexes? Reactivity of organotitanium species generated by the reaction of γ-chloroallyl sulfides with a titanocene(II) reagent
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The reactivity of the organotitanium species generated by the reductive titanation of γ-chloroallyl sulfides with the titanocene(II) reagent [Cp2Ti{P(OEt)3}2] was studied. The organotitanium species formed from α-monosubstituted γ-chloroallyl sulfides reacted with 1,5-diphenylpentan-3-one and styrene to produce conjugated dienes and vinyl cyclopropanes as major products, thus suggesting the formation of vinyl carbene complexes as intermediates. On the contrary, the organotitanium species generated from acyclic β,γ-disubstituted γ-chloroallyl sulfides revealed titanacyclobutene-like reactivity, and their reaction with 1,5-diphenylpentan-3-one produced homoallyl alcohols. These organotitanium species did not react with styrene, but did react with dichlorophenylphosphine to afford phosphacyclobutenes. In the case of β-monosubstituted, γ-monosubstituted, and α,γ- disubstituted γ-chloroallyl sulfides, the organotitanium species reacted with both 1,5-diphenylpentan-3-one and styrene. The former reaction produced homoallyl alcohols and the latter gave vinyl cyclopropanes or unconjugated dienes. These results suggest that titanacyclobutenes and/or titanium vinyl carbene complexes are produced by the reductive titanation of γ-chloroallyl sulfides depending on their substitution patterns.
- Shono, Tomohiro,Kurashige, Rie,Mukaiyama, Ryo,Tsubouchi, Akira,Takeda, Takeshi
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p. 4074 - 4080
(2008/02/08)
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- The reactivity of epoxides with lithium 2,2,6,6-tetramethylpiperidide in combination with organolithiums or grignard reagents
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(Chemical Equation Presented) The scope and limitations of lithium 2,2,6,6-tetramethylpiperidide (LTMP)-modified reductive alkylation of epoxides is detailed. A variety of organolithiums are added to terminal and 2,2-disubstituted epoxides in the presence of LTMP to generate alkenes in a completely regio- and highly stereoselective manner. Arylated alkenes, dienes, allylsilanes, and enynes are accessed using this procedure. The methodology is applied in the synthesis of the roller leaf moth pheromone, (3E,5Z)-dodecadienyl acetate. The corresponding reaction without LTMP has also been examined, and a study using deuterated epoxides provides insight into the mechanism. In the presence of LTMP, Grignard reagents are also shown to produce E-alkenes directly from epoxides.
- Hodgson, David M.,Fleming, Matthew J.,Stanway, Steven J.
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p. 4763 - 4773
(2008/02/04)
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- Chromium-catalyzed arylmagnesiation of alkynes
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Equation presented Arylmagnesiation of unfunctionalized alkynes in the presence of catalytic amounts of chromium(II) chloride and pivalic acid proceeds with high stereoselectivity. The alkenylmagnesium intermediate reacts with various electrophiles to afford the corresponding tetrasubstituted olefins in good yields.
- Murakami, Kei,Ohmiya, Hirohisa,Yorimitsu, Hideki,Oshima, Koichiro
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p. 1569 - 1571
(2008/02/03)
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- Novel alkylidenating agents via the α lithiation of monoalkyl group 4 metal derivatives: Methylidene-metal complexes and their active lithiated precursors
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The interaction of the Group 4 metal chlorides, MCl4, where M = Ti, Zr, Hf, with two equiv. of methyllithium at -78 °C in toluene has led to the corresponding methylidene-metal complex, H2C=MCl2, possibly complexed with LiCl. That this complex was stable to at least -40 °C was demonstrated by adding chemical trapping agents at this temperature: 1) benzophenone was quantitatively converted into 1,1-diphenylethylene when M = Ti or Zr; with the Hf analogue, a 1:3 mixture of 1,1-diphenylethylene and 1,1-diphenylethanol was produced; 2) propiophenone reacted with the methylidene complex to yield 2-phenyl-1-butene, 38% (M = Ti) or 25% (M = Zr), with the majority of the propiophenone being recovered (the unreacted ketone is attributed to enolate salt formation competing with the methylidenation); 3) diphenylacetylene reacted with H2C=TiCl2 by cycloaddition in 50% yield, ultimately to give a 1:1 mixture of α-methyl-cis-stilbene and α-methyl-trans-stilbene; and finally 4) norbomene was polymerized in a ROMP process by either the methylidenetitanium or methylidene-zirconium complex, but the titanium catalyst exhibited higher activity. The stability of such methylidene complexes proved to be highly temperature- and solvent-dependent: 1) the methylidene complex in toluene was no longer detectable by chemical trapping when the reaction mixture was warmed to 0 °C or above; 2) the generation of the methylidene complex in THF was uniformly unsuccessful even at -78 °C or above. From these observations this study concludes that in toluene the free methylidene complex, H2C=MCl 2, is not present but rather the agent is still bonded to LiCl. At higher temperatures in toluene or even at -78 °C in THF, the LiCl dissociates from such complexation and the free methylidene dimerizes to [Cl2M-CH2]2, as is known in the case of Cp 2Ti=CH2. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Eisch, John J.,Adeosun, Adetenu A.
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p. 993 - 997
(2007/10/03)
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