- Photochemistry of chromium arene tricarbonyl complexes with tethered pyridinyl and propenyl groups: Investigations of the effect of ring size on chelate formation, structure, and linkage isomerization
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Chromium arene tricarbonyl complexes with tethered pyridinyl groups [Cr{η6-C6H5(CH2) n(2-Py)}(CO)3] (4-6) (2-Py = 2-pyridinyl, n = 1-3, respectively) were synthesized and irradiated to form the chelates [Cr{η6-C6H5(CH2) n(2-Py)-κN}(CO)2] (7-9). Studies examined the effect of ring size and structure on chromophore λmax, stability, and photosensitivity, which are factors important for photochromes based on linkage isomerization of tethered functional groups. The studies also include [Cr{η6-C6H5CH(2-Py)CH2CH=CH 2}(CO)3] (3), which has a bifunctional tether of propenyl and pyridinyl groups, and irradiation produces the linkage isomers [Cr{η6-C6H5(CH(2-Py)CH2CH= CH2)-κN}(CO)2] (1) and [Cr{η6-C 6H5(CH(2-Py)CH2CH=CH2) (η2-CH=CH2)}(CO)2] (2). X-ray crystal structures for 7-9 show that the dihedral angle between the coordinated pyridinyl groups and the phenyl-chromium centroid increases from 1 to 73 (n = 1-3, respectively). The experimental and TDDFT computed optical changes accompanying an increase in the dihedral angle are modest and not monotonic for 7-9 due to structural changes inherent in the chelate rings. An increase in Cr-N bond lengths and decrease in their bond energies were observed experimentally and computationally for the series of 7-9. The quantum yields for formation of the five-, six-, and seven-membered chelate rings during the conversion of 4-6 to 7-9, respectively, were within experimental error for that observed for conversion of 10 [Cr{η6-C6H6}(CO) 3] with free pyridine to 11 [Cr{η6-C6H 6}(C5H5N-κN)(CO)2], indicating that the product-determining step precedes chelation. The enthalpies for chelation of 4-6 to 7-9 were determined independently by photoacoustic calorimetry and DFT computations. The computationally derived mechanism for thermal isomerization of 1 to 2 indicates that the transition state is a dissociative interchange with a free energy of activation of 27.9 kcal mol -1 (1 → 2), a result consistent with an experimentally bistable photochrome. The results indicate which tether properties are important for optimizing photochrome performance.
- Duke, Charles B.,Letterman, Roger G.,Johnson, Jermaine O.,Barr, James W.,Hu, Songnan,Ross, Charles R.,Webster, Charles Edwin,Burkey, Theodore J.
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Read Online
- CpRhIII-Catalyzed Arylation of C(sp3) Bonds
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The first CpRhIII-catalyzed arylation of unactivated C(sp3) bonds is presented. The unactivated primary C(sp3) bond of 2-alkylpyridines can be activated by RhIII and further reacts with triarylboroxines to efficiently build new C(sp3)-aryl bonds. The methodology also provides a facile and efficient synthesis of unsymmetrical triarylmethanes by RhIII-catalyzed C(sp3) arylation of diarylmethanes. Unactivated! The unactivated primary C(sp3) bond of 2-alkylpyridines can be activated by RhIII and then react with triarylboroxines to efficiently build new C(sp3)-aryl bonds (see scheme, DG=directing group, FG=functional group). The methodology also provides a facile and efficient synthesis of unsymmetrical triarylmethanes by RhIII-catalyzed C(sp3) arylation.
- Wang, Xiaoming,Yu, Da-Gang,Glorius, Frank
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Read Online
- An improved method for aromatic hydroxylation with heteroaromatic oxides
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Photolysis of the boron trifluoride complex of pyridine-N-oxide in benzene gives a higher yield of phenol than photolysis of pyridine-N-oxide alone; with some intramolecular models, intramolecular hydroxylation can be achieved.
- Serra-Errante, Guido,Sammes, Peter G.
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Read Online
- Reduction of Electron-Deficient Alkenes Enabled by a Photoinduced Hydrogen Atom Transfer
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Direct hydrogen atom transfer from a photoredox-generated Hantzsch ester radical cation to electron-deficient alkenes has enabled the development of an efficient formal hydrogenation under mild, operationally simple conditions. The HAT-driven mechanism is supported by experimental and computational studies. The reaction is applied to a variety of cinnamate derivatives and related structures, irrespective of the presence of electron-donating or electron-withdrawing substituents in the aromatic ring and with good functional group compatibility. (Figure presented.).
- Larionova, Natalia A.,Ondozabal, Jun Miyatake,Cambeiro, Xacobe C.
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supporting information
p. 558 - 564
(2020/12/07)
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- C2-selective alkylation of pyridines by rhodium–aluminum complexes
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A C2- and mono-selective alkylation of various pyridines and azines with unactivated alkenes and vinylarenes using a heterobimetallic Rh–Al catalyst is reported. The use of aliphatic alkenes exclusively affords the linear alkylation products, while vinylarenes mainly afford branched alkylation products. The details of the reaction mechanism are revealed by DFT calculations: the reductive elimination of the products is rate-determining, which is consistent with the experimental results. The origin of the linear/branched selectivity is elucidated based on deformation/interaction analysis.
- Aso, Koki,Hara, Naofumi,Li, Qiao-Zhi,Nakao, Yoshiaki,Sakaki, Shigeyoshi
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supporting information
(2021/08/06)
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- Compound containing carbon-silicon bond and application thereof
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The invention discloses a compound containing a carbon-silicon bond and application of the compound in construction of the carbon-carbon bond. The invention provides an application of a compound containing the carbon-silicon bond as shown in a formula I or a formula I' in a chemical reaction for constructing the carbon-carbon bond, wherein one carbon in the carbon-carbon bond is from carbon connected with silicon in the compound containing the carbon-silicon bond. According to the preparation method, the compound containing the carbon-silicon bond is used for providing a carbon free radical, and the carbon free radical can directly react with carbon provided in another molecule under a mild condition to construct the carbon-carbon bond; the preparation method is wider in substrate application range, is suitable for functional group activated C and carbon free radical substrates, and is also suitable for unactivated C-H bond substrates.
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Paragraph 0402-0405
(2020/09/08)
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- Aqueous phase semihydrogenation of alkynes over Ni-Fe bimetallic catalysts
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Bimetallic Ni-Fe catalysts (Ni/Fe, 1?:?1, 1?:?3, and 3?:?1) are synthesized and explored for their catalytic activity in semihydrogenation of internal alkynes using H2 gas in water-ethanol solution. Our findings revealed that over the Ni1Fe3 catalyst a high diastereoselectivity for Z-alkenes with a high conversion for a wide range of internal alkynes can be achieved at moderate reaction temperature (40 °C). Notably, the selectivity for the Z-alkenes is enhanced in the presence of n-butyl amine as an additive. Deuterium labeling experiments evidenced that H2 gas becomes dissociated homolytically over the catalyst surface to hydrogenate alkynes to alkenes. Synthesized catalysts were successfully characterized by HR-TEM, SEM, XPS, EDS, P-XRD and H2-TPD.
- Awasthi, Mahendra K.,Barman, Sudipta Roy,Behrens, Silke,Rai, Rohit K.,Singh, Sanjay K.,Singh, Vipin K.
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p. 4968 - 4980
(2020/08/19)
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- Iron-catalysed alkylation of 2-methyl and 4-methyl azaarenes with alcoholsviaC-H bond activation
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The first Fe-catalysed alkylation of 2-methyl and 4-methyl-azaarenes with a series of alkyl and hetero-aryl alcohols is reported (>39 examples and up to 95% yield). Multi-functionalisation of pyrazines and synthesis of anti-malarial drug (±) Angustureine significantly broaden the scope of this methodology. Preliminary mechanistic investigation, deuterium labeling and kinetic experiments including trapping of the enamine intermediate1a'are of special importance.
- Banerjee, Debasis,Bera, Sourajit,Kabadwal, Lalit Mohan
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supporting information
p. 4777 - 4780
(2020/05/13)
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- An Annelated Mesoionic Carbene (MIC) Based Ru(II) Catalyst for Chemo- And Stereoselective Semihydrogenation of Internal and Terminal Alkynes
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The catalytic utility of [RuL1(CO)2I2] (1), containing an annelated π-conjugated imidazo-naphthyridine-based mesoionic carbene (MIC) ligand (L1), is evaluated for E-selective alkyne semihydrogenation. The precatalyst 1, in combination with 2 equiv of AgBArF, semihydrogenates a broad range of internal alkynes with molecular hydrogen (5 bar) in water. (E)-Alkenes are accessed in high yields, and a number of reducible functional groups are tolerated. A chelate MIC ligand and two cis carbonyls provide a well-defined platform at the Ru center for hydrogenation and isomerization. The loss of two iodides and the presence of two carbonyls render the Ru center electron deficient and thus the formation of metal vinylidenes with terminal alkynes is avoided. This is leveraged for the semihydrogenation of terminal alkynes by the same catalytic system in isopropyl alcohol. Reaction profile, isomerization, kinetic, and DFT studies reveal initial alkyne hydrogenation to a (Z)-alkene, which further isomerizes to an (E)-alkene via metal-catalyzed Z → E isomerization.
- Bera, Jitendra K.,Choudhury, Joyanta,Das, Shubhajit,Dutta, Indranil,Pati, Swapan K.,Saha, Sayantani,Yadav, Suman
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p. 3212 - 3223
(2020/10/02)
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- Palladium acetate-catalyzed one-pot synthesis of mono- And disubstitued pyridines
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A Pd-catalyzed one-pot synthesis of mono- and disubstituted pyridines was developed. The substituted pyridines were obtained from ketones or an aldehyde and 1,3-diaminopropane using a combination of catalytic Pd(OAc)2 and Cu(OAc)2. High-concentration reaction conditions enabled this catalytic reaction to be acid-free.
- Mikami, Shunya,Toyota, Masahiro
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p. 1315 - 1321
(2019/08/01)
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- A heterocyclic methyl compound dehydration C - alkylation method
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The invention discloses a dehydration C-alkylation method for a heterocyclic methyl compound. According to the method, alcohol is used as an alkylation reagent and undergoes dehydration C-alkylation with the heterocyclic methyl compound without presence of a catalyst so as to synthesize an alkylated heterocyclic compound; meanwhile, alcohol and the heterocyclic methyl compound can be directly subjected to dehydration C-methyl alkylation reaction at methyl position in the presence of air and alkali, wherein the reaction temperature is 100 to 180 DEG C; the reaction time is 6 to 60 hours; the reaction solvent is an organic solvent; and a byproduct is water. According to the method, cheap, easily and widely available and stable alcohol with low toxicity is used as the alkylation agent; no catalyst is used; and the alkylated compound is directly synthesized via the dehydration C-alkylation reaction in the presence of air and alkali. The method provided by the invention has low demand for reaction conditions, a wide application range and certain research and industrial application prospects.
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Paragraph 0119-0122
(2018/09/21)
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- Nickel-catalysed alkylation of C(sp3)-H bonds with alcohols: direct access to functionalised N-heteroaromatics
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The first base-metal catalysed coupling of primary alcohols with methyl-N-heteroaromatics is reported. The use of an earth abundant and nonprecious NiBr2/L1 system enables access to a series of C(sp3)-alkylated N-heteroaromatics. Mechanistic studies have established the participation of a hydrogen-borrowing strategy for α-alkylation.
- Vellakkaran, Mari,Das, Jagadish,Bera, Sourajit,Banerjee, Debasis
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supporting information
p. 12369 - 12372
(2018/11/20)
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- Manganese-Catalyzed Kumada Cross-Coupling Reactions of Aliphatic Grignard Reagents with N-Heterocyclic Chlorides
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Herein we report the use of manganese(II) chloride for the catalytic generation of C(sp 2)-C(sp 3) bonds via Kumada cross-coupling. Rapid and selective formation of 2-alkylated N-heterocyclic complexes were observed in high yields with use of 3 mol% MnCl 2 THF 1.6 and under ambient reaction conditions (21 °C, 15 min to 20 h). Manganese-catalyzed cross-coupling is tolerant toward both electron-donating and electron-withdrawing functional groups in the 5-position of the pyridine ring, with the latter resulting in an increased reaction rate and a decrease in the amount of nucleophile required. The use of this biologically and environmentally benign metal salt as a catalyst for C-C bond formation highlights its potential as a catalyst for the late-stage functionalization of pharmaceutically active N-heterocyclic molecules (e.g., pyridine, pyrazine).
- Petel, Brittney E.,Purak, Merjema,Matson, Ellen M.
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supporting information
p. 1700 - 1706
(2018/07/13)
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- Rhodium Complexes Bearing PAlP Pincer Ligands
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We report rhodium complexes bearing PAlP pincer ligands with an X-type aluminyl moiety. IR spectroscopy and single-crystal X-ray diffraction analysis of a carbonyl complex exhibit the considerable σ-donating ability of the aluminyl ligand, whose Lewis acidity is confirmed through coordination of pyridine to the aluminum center. The X-type PAlP-Rh complexes catalyze C2-selective monoalkylation of pyridine with alkenes.
- Hara, Naofumi,Saito, Teruhiko,Semba, Kazuhiko,Kuriakose, Nishamol,Zheng, Hong,Sakaki, Shigeyoshi,Nakao, Yoshiaki
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supporting information
p. 7070 - 7073
(2018/06/01)
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- Semireduction of Alkynes Using Formic Acid with Reusable Pd-Catalysts
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The treatment of PdCl2 with K2CO3 and HCO2H in dioxane gives black precipitates, which are an effective catalyst for the semireduction of alkynes to alkenes using formic acid as a reductant. Even 0.05 mol % Pd promoted the reduction reaction of tolane in high yield with high selectivity.
- Iwasaki, Riku,Tanaka, Eikichi,Ichihashi, Toshinari,Idemoto, Yasushi,Endo, Kohei
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p. 13574 - 13579
(2018/11/02)
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- Copper-catalyzed cross-coupling of aryl-, primary alkyl-, and secondary alkylboranes with heteroaryl bromides
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A method for the Cu-catalyzed cross-coupling of both aryl and alkylboranes with aryl bromides is described. The method employs an inexpensive Cu-catalyst and functions for a variety of heterocyclic as well as electron deficient aryl bromides. In addition, aryl iodides of varying substitution patterns and electronic properties work well.
- Bergmann, Allison M.,Oldham, Adam M.,You, Wei,Brown, M. Kevin
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supporting information
p. 5381 - 5384
(2018/06/01)
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- Ligand-Free RuCl3-Catalyzed Alkylation of Methylazaarenes with Alcohols
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RuCl3 efficiently catalyzes the alkylation of methylquinolines, methylpyridines, 2-methyl-benzooxazoles, and 2-methyl-quinoxalines with alkyl- or aryl-alcohols as alkylating agents. This synthetically useful and atom economical transformation does not require additional ligands. The mechanistic study indicated the alkylation reaction underwent a stepwise transfer hydrogenation, aldol condensation, and hydrogenation reaction pathway.
- Feng, Tong-Yu,Li, Hong-Xi,Young, David James,Lang, Jian-Ping
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p. 4113 - 4120
(2017/04/28)
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- Thermal Rearrangement of Sulfamoyl Azides: Reactivity and Mechanistic Study
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The rearrangement of sulfamoyl azides under thermal conditions to form a C-C bond while breaking two C-N bonds is reported. Mechanistic study shows that this reaction goes through a Curtius-type rearrangement to form a 1,1-diazene, then which rearranges possibly through both a concerted rearrangement process and a stepwise radical process. This rearrangement could be used in the synthesis of complex biologically active molecules, such as sterols, and piperine derivatives.
- Zou, Xiaodong,Zou, Jiaqi,Yang, Lizheng,Li, Guigen,Lu, Hongjian
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p. 4677 - 4688
(2017/05/12)
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- Iron pincer complex catalyzed, environmentally benign, E-selective semi-hydrogenation of alkynes
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Ironing out hydrogenation: For the first time, an iron catalyst provided chemo- and stereo-selective semi-hydrogenation of alkynes to E-alkenes. This efficient, atom-economical reaction is catalyzed by a novel acridine-based PNP iron pincer catalyst and exhibits excellent functional group tolerance under mild, neutral, environmentally benign reaction conditions. Copyright
- Srimani, Dipankar,Diskin-Posner, Yael,Ben-David, Yehoshoa,Milstein, David
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supporting information
p. 14131 - 14134
(2014/01/06)
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- Iridium-catalyzed alkylation of methylquinolines with alcohols
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Iridium-catalyzed alkylation of methylquinolines at the methyl substituent was achieved using alcohols as alkylating agents. The reaction proceeded through a transfer hydrogenation pathway from the alcohol to the Ir complex, affording an aldehyde and Ir-H species, followed by base-assisted aldol condensation and hydrogenation. This method provides an atom-economical and convenient route to alkylquinolines from easily accessible methylquinolines.
- Obora, Yasushi,Ogawa, Shinji,Yamamoto, Nobuyuki
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p. 9429 - 9433,5
(2012/12/12)
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- Ruthenium-catalyzed conversion of sp3 C-O bonds in ethers to C-C bonds using triarylboroxines
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Catalytic conversion of unreactive sp3 C-O bonds in alkyl ethers to C-C bonds is described. Alkyl ethers bearing 2- or 4-pyridyl groups were coupled with triarylboroxines in the presence of a ruthenium catalyst. Triarylboroxines bearing a variety of functional groups including electron-withdrawing and -donating groups can be used for the reaction. No additional base was required for the coupling with the organoboron reagents, and base-sensitive groups can be tolerated. The reaction is considered to proceed via dehydroalkoxylation followed by addition of triarylboroxines to form C-C bonds.
- Ogiwara, Yohei,Kochi, Takuya,Kakiuchi, Fumitoshi
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p. 3254 - 3257
(2011/08/02)
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- Direct synthesis of water-tolerant alkyl indium reagents and their application in palladium-catalyzed couplings with aryl halides
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A direct result: Alkyl indium reagents are synthesized by the insertion of indium into alkyl halide mediated by CuCl. The synthetic utility of these reagents is demonstrated by their palladium-catalyzed coupling with aryl halides (see scheme). The reagents are compatible with various functional groups, and this makes the protocol generally useful in organic synthesis. DMA=N,N-dimethylacetamide, TBS=tert-butyldimethylsilyl.
- Shen, Zhi-Liang,Goh, Kelvin Kau Kiat,Yang, Yong-Sheng,Lai, Yin-Chang,Wong, Colin Hong An,Cheong, Hao-Lun,Loh, Teck-Peng
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supporting information; experimental part
p. 511 - 514
(2011/03/17)
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- Scope and limitations of the Minisci reaction for the synthesis of aza-heterocycles
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Attempts to prepare several classes of aza-heterocycles by application of the Minisci radical cyclisation reaction are described. Competing β-scission, hydrolytic cleavage and lactonisation reactions were found to be major hurdles to adopting this strategy for the synthesis of such targets.
- Burgin, Ryan N.,Jones, Simon,Tarbit
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scheme or table
p. 6772 - 6774
(2010/04/27)
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- Reductive metalation of 1,2-diaryl-substituted ethenes: Synthetic applications
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Reduction of 1,2-diaryl-substituted ethenes with Na metal in dry THF allowed easy access to a variety of 1,2-diaryl-1,2-disodiumethanes. These diorganometallic intermediates were elaborated into the corresponding 1,2-diarylethanes (aqueous work up), or cycloalkylated with 1,3- dichloropropanes. The last reaction led to a highly diastereoselective synthesis of trans-1,2-diaryl-substituted cyclopentanes.
- Azzena, Ugo,Dettori, Giovanna,Lubinu, Caterina,Mannu, Alberto,Pisano, Luisa
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p. 8663 - 8668
(2007/10/03)
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- Evidence of a borderline region between E1cb and E2 elimination reaction mechanisms: A combined experimental and theoretical study of systems activated by the pyridine ring
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We report a combined experimental and theoretical study to characterize the mechanism of base-induced β-elimination reactions in systems activated by the pyridyl ring, with halogen leaving groups. The systems investigated represent borderline cases, where it is uncertain whether the reaction proceeds via a carbanion intermediate (E1cb, AxhDH + DN) or via the concerted loss of a proton and the halide (E2, AND EDN) upon base attack. Experimentally, the Taft correlation for H/D exchange, in OD-/D2O with noneliminating substrates (1-methyl-2-(2-Xethyl)pyridinium iodide), is used to predict the expected values of the rate constants for the elimination reactions with N-methylated substrates and F, Cl, Br as the leaving group. The comparison indicates an E1cb irreversible mechanism with F, but the deviation observed with Cl and Br does not allow a conclusive assignment. The theoretical calculations show that for the N-methylated substrate with a fluoride leaving group the elimination proceeds via formation of a moderately stable carbanion. No stable anionic intermediate is instead found when the leaving group is Cl or Br, as well as for any of the nonmethylated species, indicating a concerted elimination. The methylated substrate with Cl shows however only a moderate increase in reactivity compared to the fluorinated substrate, despite the change in mechanism. Very interestingly, our analysis of the computed two-dimensional potential energy surface for the reaction with a F leaving group indeed evidences the lack of a net distinction between the E1cb and E2 reaction paths, which appear to merge smoothly into each other in these borderline cases.
- Alunni, Sergio,De Angelis, Filippo,Ottavi, Laura,Papavasileiou, Magdalini,Tarantelli, Francesco
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p. 15151 - 15160
(2007/10/03)
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- New studies of Rh-catalyzed addition of boronic acids under basic conditions in aqueous medium
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Rh-catalyzed C-C bond formation in neat water under basic conditions has been efficiently performed. The addition of various boronic acids to styrene, 2-vinylpyridine, and cyclic α,β-unsaturated ketones has been realized with high selectivity and yield. We have shown that m-TPPTC (tris(m-carboxyphenyl)phosphane trilithium salt) exhibited a higher reactivity compared to TPPTS. These couplings could also be conducted very efficiently under basic and phosphaneless conditions to give functionalized aryl derivatives. The benefits of the additional anionic ligand m-TPPTC lied in the successful recycling experiments of 1,4-addition of phenylboronic acid to cyclohexenone, with no loss of the water-soluble catalyst.
- Amengual, Rémi,Michelet, Véronique,Genêt, Jean-Pierre
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p. 5905 - 5908
(2007/10/03)
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- Synthesis of pyridine and isoquinoline derivatives by the palladium-catalyzed cyclization of olefinic ketone O-pentafluorobenzoyloximes
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Pyridines and isoquinolines are synthesized from olefinic ketone O-pentafluorobenzoyloximes by treatment with a catalytic amount of Pd(PPh3)4 in the presence of (n-Bu)4NCl and triethylamine.
- Tsutsui, Hironori,Narasaka, Koichi
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p. 526 - 527
(2007/10/03)
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- Mechanistic studies of the ring opening reactions of [1,2,3]triazolo[1,5-a]pyridines
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A mechanism with radical intervention is proposed for the opening of the triazole ring in [1,2,3] triazolo[1,5-a]pyridines which results in the production of 2- or 2,6-disubstituted pyridines.
- Abarca, Belen,Ballesteros, Rafael,Rodrigo, Gemma,Jones, Gurnos,Veciana, Jaume,Vidal-Gancedo, Jose
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p. 9785 - 9790
(2007/10/03)
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- A Convenient Palladium-Catalyzed Coupling Approach to 2,5-Disubstituted Pyridines
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2,5-Dibromopyridine has been found to undergo a regioselective palladium-catalyzed coupling reaction with terminal acetylenes and arylzinc halides to give the corresponding 2-alkynyl-5-bromo- and 2-aryl-5-bromopyridines, respectively, in 70percent-90percent isolated yields.To complement this chemistry, the triflate derived from 2-methyl-5-pyridinol was found to participate in a palladium-catalyzed reaction with terminal acetylenes leading to the corresponding 5-alkynyl-2-methylpyridines.These intermediates can be further manipulated to afford a broad range of 2,5-disubstituted pyridines.
- Tilley, Jefferson W.,Zawoiski, Sonja
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p. 386 - 390
(2007/10/02)
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- FLASH VACUUM PYROLYSIS OF α-TOLUENESULFONYL AZIDE
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The flash vacuum pyrolysis of α-toluenesulfonyl azide (1) gave bibenzyl (2), 2-(β-phenethyl)pyridine (3), and 2,1-benzisothiazole 2,2-dioxide (4); an authentic sample of the latter was prepared from 2-bromo-α-toluenesulfonamide and potassium amide in liquid ammonia.FVP of benzenesulfonyl azide using benzene as carrier gas gave some diphenylamine, but not in the absence of benzene.
- Abramovitch, Rudolph A.,Harder, Raymond R.,Holcomb, William D.
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p. 2327 - 2330
(2007/10/02)
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- PHOTOCHEMICAL GENERATION OF ALIPHATIC RADICALS FROM BENZOPHENONE OXIME ESTERS: SIMPLE SYNTHESIS OF ALKYLBENZENES AND ALKYLPYRIDINES
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Photolysis of benzophenone oxime esters, prepared with aliphatic carboxylic acids and benzophenone oxime, in benzene and pyridine generates various primary, secondary and tertiary aliphatic radicals selectively, and corresponding alkylbenzenes and alkylpyridines are produced in good yields, respectively.
- Hasebe, Masato,Tsuchiya, Takashi
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p. 3239 - 3242
(2007/10/02)
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- A Convenient Method for the Regioselective Synthesis of 4-Alkyl(aryl)pyridines Using Pyridinium Salts
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RCu.BF3 reacted with 1-ethocycarbonylpyridinium chloride at the 4-position with almost complete regioselectivity (>99percent) to afford the corresponding 1,4-dihydropyridine derivatives in high yields (81-94percent).The dihydropyridines were oxidized by oxygen to give 4-alkyl(aryl)pyridines (38-68percent).Grignard reagents also reacted with 1-t-butyldimethylsilylpyridinium triflate with almost complete regioselectivity (>99percent) to afford the corresponding 1,4-dihydropyridines, which were easily oxidized to give 4-substituted pyridines in higher yields than above (58-70percent).
- Akiba, Kin-ya,Iseki, Yuji,Wada, Makoto
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p. 1994 - 1999
(2007/10/02)
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- FLASH VACUUM PYROLYSIS OF 2-PICOLINE N-OXIDE. FORMATION OF 2-PICOLYL RADICAL
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The flash vacuum pyrolysis of 2-picoline N-oxide was found to give 2-picoline, pyridine, 2-vinylpyridine, bis(2-pyridyl)methane, and 1,2-bis(2-pyridyl)ethane.From the mechanistic consideration of the formation of these products, intermediacy of 2-picolyl radical (i.e., 2-pyridylmethyl radical) is strongly suggested.Keywords: flash vacuum pyrolysis; thermolysis; picoline N-oxides; heterocycles; radical reaction; radical coupling; picolyl radical; pyridylmethyl radical
- Ohsawa, Akio,Kawaguchi, Takayuki,Igeta, Hiroshi
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p. 1481 - 1483
(2007/10/02)
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