- Isopropylation of naphthalene by isopropyl alcohol over USY catalyst: An investigation in the high-pressure fixed-bed flow reactor
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Catalytic performances of USY, H-mordenite, dealuminated H-mordenite, and H-MCM-22 zeolite catalysts in the isopropylation of naphthalene by isopropyl alcohol with decalin or cyclohexane as a solvent were compared in a high-pressure fixed-bed flow reactor. For the USY catalyst, reaction conditions, such as reaction temperature and pressure, reactant ratio and space velocity, and solvent concentration and type, were controlled to investigate in detail the effect of reaction conditions on the catalytic activity. Over H-mordenite, it was found that 2,6-diisopropylnaphthalene (2,6-DIPN) could be selectively synthesized with a 2,6-/2,7-DIPN ratio of 2.46, and dealumination could enhance not only the selectivity of 2,6-DIPN, with a 2,6-/2,7-DIPN ratio of 2.67, but also the conversion of naphthalene, which was 27.4%, three times as high as that over the unmodified one at 6 h of reaction time on stream. However, neither the H-mordenite or the dealuminated one were catalytically stable and the selectivity of DIPN was at a very low level of less than 12%. In contrast, over the USY catalyst, a high and stable conversion of about 90%, a high selectivity of DIPN of more than 40%, and a considerable 2,6-/2,7-DIPN ratio of 1.46 could be achieved by adjusting the reaction conditions, although no shape selectivity was observed on USY. On the other hand, only a low 2,6-/2,7-DIPN ratio of 0.47 with a low conversion of about 30% was revealed over H-MCM-22, which indicates that the reaction takes place on the external surface of this zeolite. An attempt has been made to explain the catalytic activity, selectivity, and stability in relation to the zeolite structures, product properties, and reaction conditions.
- Wang, Jun,Park, Jung-Nam,Park, Yong-Ki,Lee, Chul Wee
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- Shape-selective synthesis of 2,6-diisopropylnaphthalene on H-mordenite catalysts
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To finally dispel any doubts on the shape-selective formation of 2,6-diisopropylnaphthalene (2,6-DIPN) over H-MOR zeolites, naphthalene alkylation was carried out over high-silica H-MOR catalysts with propylene or isopropanol as an alkylating agent and with or without cyclohexane as a solvent. Isomeric composition of DIPN's, determined by one-dimensional GC analysis, was additionally confirmed with advanced two-dimensional GC × GC. Our results proved beyond any doubt shape-selective formation of 2,6-DIPN over these H-MOR catalysts from naphthalene and propylene and without cyclohexane as a solvent. The DIPN mixture contained 60-64% 2,6-DIPN, and the ratio of 2,6-DIPN/2,7-DIPN was in the range 2.5-2.8. We also showed that shape-selective formation of 2,6-DIPN over H-MOR catalyst was depressed by using isopropanol instead of propylene and in the presence of cyclohexane.
- Brzozowski, Robert,Buijs, Wim
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- Dialkylation of naphthalene with isopropanol over H3PO 4/MCM-41 Catalysts for the environmentally friendly synthesis of 2,6-dialkylnaphthalene
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AlMCM-41 materials with SiO2/Al2O3 molar ratios 20, 70, 110, 150, 200, and Si-MCM-41 were synthesized following standard procedures, and loaded with different amounts of H3PO4. The catalysts were well
- Ghiaci,Aghabarari,Rives,Vicente,Sobrados,Sanz
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- Bidentate Lewis acid catalyzed inverse-electron-demand Diels-Alder reaction for the selective functionalization of aldehydes
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The inverse-electron-demand Diels-Alder (IEDDA) reaction catalyzed by a bidentate Lewis acid was applied to enamines generated in situ from aldehydes. In general, a high functional group tolerance has been observed. Side reactions during the enamine forming step can limit the yield of the desired naphthalene. For citronellal as substrate, the initial intermediate after the catalyzed IEDDA reaction was trapped by an intramolecular Diels-Alder reaction to furnish a tricyclic compound. This scaffold represents the framework of natural products such as valerianoids A-C or the patchouli alcohol. Georg Thieme Verlag Stuttgart New York.
- Schweighauser, Luca,Bodoky, Ina,Kessler, Simon N.,Haeussinger, Daniel,Wegner, Hermann A.
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- Mechanistic Study of Domino Processes Involving the Bidentate Lewis Acid Catalyzed Inverse Electron-Demand Diels?Alder Reaction
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The detailed understanding of mechanisms is the basis to design new reactions. Herein, we studied the domino bidentate Lewis acid catalyzed inverse electron-demand Diels?Alder (IEDDA) reaction developed in our laboratory computationally as well as by synthetic experiments, to characterize different pathways. A quinodimethane intermediate was identified as key structure, which is the basis for all subsequent transformations: Elimination to an aromatic naphthalene, rearrangement to a dihydroaminonaphthalene and a photo-induced ring opening. These insights allow to optimize the reaction conditions, such as catalytic utilization of amine, as well as to advance new reactions in the future.
- Strauss, Marcel A.,Kohrs, Daniel,Ruhl, Julia,Wegner, Hermann A.
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- Shape-selective diisopropylation of naphthalene in H-Mordenite: Myth or reality?
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Selective diisopropylation of naphthalene to 2,6-diisopropylnaphthalene is a challenging goal in sustainable catalysis. Ultrastable Y and H-Mordenite zeolites are the best catalysts reported in the literature with respect to 2,6-diisopropylnaphthalene selectivity. It is generally accepted that in the case of H-Mordenite, shape-selectivity is responsible for the observed 2,6-diisopropylnaphthalene selectivity, while on Ultrastable Y-zeolite, the observed selectivity reflects the internal thermodynamic equilibrium of positional isomers. Revisiting both the experimental and the computational work in this field now leads to the conclusion that shape-selectivity of whatever kind can be ruled out in the case of H-Mordenite. H-Mordenite catalysts produce usually a kinetically controlled mixture of diisopropylnaphthalene isomers which can shift to the direction of a thermodynamical distribution at high reaction temperatures or over more active catalysts.
- Bouvier, Christophe,Buijs, Wim,Gascon, Jorge,Kapteijn, Freek,Gagea, Bogdan C.,Jacobs, Pierre A.,Martens, Johan A.
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- Isopropylation of naphthalene by isopropanol over conventional and Zn- and Fe-modified USY zeolites
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Catalytic performances of USY, MOR, and BEA zeolites were compared for the isopropylation of naphthalene by isopropyl alcohol in a high-pressure, fixed-bed reactor. The USY catalyst showed a high conversion of 86% and good stability but a low 2,6-/2,7-DIPN shape selectivity ratio of 0.94. In contrast, over the MOR catalyst, 2,6-DIPN was selectively synthesized with a high 2,6-/2,7-DIPN ratio of 1.75, but low naphthalene conversions and fast deactivation of the catalyst were observed. The USY catalyst was modified by Zn and Fe using the wet impregnation method to enhance the selectivity for 2,6-DIPN. The highest conversion (~95%) and selectivity for 2,6-DIPN (~20%) were achieved with 4% Zn/USY catalyst. It appeared that small metal oxide islands formed in the USY pores to decrease the effective pore size and thus render it mildly shape-selective. Zn loading also decreased the number of strong acid sites responsible for coke formation and increased the number of weak acid sites. The high conversion and stability of Zn-modified catalysts were ascribed to the presence of a suitable admixture of weak and strong acid sites with less coke deposition. The Fe-modified USY catalysts were less effective because the modification increased the number of the strong acid sites.
- Banu, Marimuthu,Lee, Young Hye,Magesh, Ganesan,Lee, Jae Sung
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- An Amine Group Transfer Reaction Driven by Aromaticity
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A stereoselective domino inverse electron-demand Diels-Alder/amine group transfer reaction catalyzed by a bidentate Lewis acid provides 1-amino-1,2-dihydronaphthalenes, a core structure in many bioactive compounds. A concerted mechanism is proposed based on experimental studies as well as DFT computations demonstrating a new general reactivity scheme. The broad scope of the reaction was evaluated by variation of all three starting compounds, phthalazines, aldehydes, and amines. Scalability was demonstrated by a gram scale reaction without diminished yield.
- Ahles, Sebastian,G?tz, Silas,Schweighauser, Luca,Brodsky, Mirko,Kessler, Simon N.,Heindl, Andreas H.,Wegner, Hermann A.
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- Disproportionation of isopropylnaphthalene on zeolite catalysts
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Disproportionation of isopropylnaphthalene (IPN) was tested over H-mordenite, HY, H-beta zeolites and over amorphous aluminosilicate in the range of 150-300°C. High β,β-selectivity in diisopropylnaphthalene (DIPN) product obtained over zeolites was observed. However, the 2,6-DIPN/2,7-DIPN mole ratio was dependent on the pore structure of the applied zeolite and on the temperature. Over H-mordenites 2,6-DIPN was the most preferred isomer, whereas 2,7-DIPN was favored over HY and H-beta zeolites. Such disproportion in isomer predominating in the DIPN product can be explained by a bimolecular mechanism of disproportionation. Due to the zeolite pore architecture the bent transition-state complex, leading to 2,7-DIPN (HY and H-beta) or more linear, leading to 2,6-DIPN (H-mordenite), was preferred. At high temperatures the monomolecular disproportionation mechanism (dealkylation realkylation) dominated and concealed (simultaneously with side reactions) the shape-selectivity effect. As a result the 2,6-DIPN/2,7-DIPN mole ratio in the product approached equilibrium value.
- Brzozowski, Robert,Skupinski, Wincenty
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- Zeolite pore entrance effect on shape selectivity in naphthalene isopropylation
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Naphthalene alkylation with propylene was studied over various large-pore zeolites and also over amorphous aluminosilicate catalysts. Isomeric distribution of isopropylnaphthalenes (IPN) and diisopropylnaphthalenes (DIPN) were compared at different temperatures. The shape-selectivity effect that occurred in the entrances to the pores could be responsible for high α-selectivity in monoisopropylation and 1NR-selectivity in diisopropylation observed in the naphthalene alkylation over wide pore zeolites. The product was then relatively rich in 1-IPN, 1,3-DIPN, and 1,4-DIPN. This type of shape selectivity suppressed other shape-selectivity effects, e.g., high β-selectivity of reactions occurring inside channels or cavities of the zeolite. High concentration of TIPN in alkylation products could be explained superbly with the help of catalysis in pore entrances. The explanation of such results was proposed to be a specific shape-selectivity effect of alkylation reaction occurring in the entrances to the pores of zeolite.
- Brzozowski,Skupinski
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- Comparison of the catalytic performance of the metal substituted cage type mesoporous silica catalysts in the alkylation of naphthalene
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Alkylation of naphthalene with propylene to diisopropylnaphthalenes (DIPN) for the use as a high-quality solvent was carried out over mesoporous AlSBA-1, GaSBA-1 and FeSBA-1 catalysts. The AlSBA-1 and GaSBA-1 catalysts were very active in alkylation while the FeSBA-1 samples, although initially active, deactivated quickly. Activity of the SBA-1 catalysts increased with the amount of Al, Ga or Fe incorporation into the silica framework. Regardless of the alkylation activity, all SBA-1 catalysts showed rather low isomerization activity and as a result low 2,6-DIPN selectivity was observed. The AlSBA-1 and GaSBA-1 catalysts proved to be promising for DIPN solvent synthesis due to their high alkylation activity and stability together with low 2,6-DIPN selectivity.
- Brzozowski, Robert,Vinu, Ajayan,Gil, Barbara
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- Factors affecting the selection of products from a photochemically generated singlet biradical
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The chemistries of a monoradical of the ultrafast "radical-clock" type and a structurally related singlet biradical, generated by Norrish type II photochemistry, are compared. The monoradical is found to undergo the characteristic ring-opening reaction of its class at about 1010 s-1 at room temperature. However, the singlet biradical shows no evidence of the analogous ring-opening reaction. The contrasting chemistry is traced not to a fundamental difference in electronic structure of the two intermediates, but rather to a steric interaction that the biradical alone would have to suffer during the ring opening. Although the magnitude of the steric hindrance is small (estimated 15-20 kJ mol-1), it is enough to shut down the reaction, because the biradical has other facile product-forming reactions available. The Royal Society of Chemistry 2005.
- Broyles, David A.,Carpenter, Barry K.
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- Reductive activation and hydrofunctionalization of olefins by multiphoton tandem photoredox catalysis
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The conversion of olefin feedstocks to architecturally complex alkanes represents an important strategy in the expedient generation of valuable molecules for the chemical and life sciences. Synthetic approaches are reliant on the electrophilic activation of unactivated olefins, necessitating functionalization with nucleophiles. However, the reductive functionalization of unactivated and less activated olefins with electrophiles remains an ongoing challenge in synthetic chemistry. Here, we report the nucleophilic activation of inert styrenes through a photoinduced direct single electron reduction to the corresponding nucleophilic radical anion. Central to this approach is the multiphoton tandem photoredox cycle of the iridium photocatalyst [Ir(ppy)2(dtbbpy)] PF6, which triggers in situ formation of a high-energy photoreductant that selectively reduces styrene olefinic π bonds to radical anions without stoichiometric reductants or dissolving metals. This mild strategy enables the chemoselective reduction and hydrofunctionalization of styrenes to furnish valuable alkane and tertiary alcohol derivatives. Mechanistic studies support the formation of a styrene olefinic radical anion intermediate and a Birch-type reduction involving two sequential single electron transfers. Overall, this complementary mode of olefin activation achieves the hydrofunctionalization of less activated alkenes with electrophiles, adding value to abundant olefins as valuable building blocks in modern synthetic protocols.
- Czyz, Milena L.,Taylor, Mitchell S.,Horngren, Tyra H.,Polyzos, Anastasios
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p. 5472 - 5480
(2021/06/01)
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- Ambient Hydrogenation and Deuteration of Alkenes Using a Nanostructured Ni-Core–Shell Catalyst
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A general protocol for the selective hydrogenation and deuteration of a variety of alkenes is presented. Key to success for these reactions is the use of a specific nickel-graphitic shell-based core–shell-structured catalyst, which is conveniently prepared by impregnation and subsequent calcination of nickel nitrate on carbon at 450 °C under argon. Applying this nanostructured catalyst, both terminal and internal alkenes, which are of industrial and commercial importance, were selectively hydrogenated and deuterated at ambient conditions (room temperature, using 1 bar hydrogen or 1 bar deuterium), giving access to the corresponding alkanes and deuterium-labeled alkanes in good to excellent yields. The synthetic utility and practicability of this Ni-based hydrogenation protocol is demonstrated by gram-scale reactions as well as efficient catalyst recycling experiments.
- Beller, Matthias,Feng, Lu,Gao, Jie,Jackstell, Ralf,Jagadeesh, Rajenahally V.,Liu, Yuefeng,Ma, Rui
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supporting information
p. 18591 - 18598
(2021/06/28)
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- Synthesis of renewable alkylated naphthalenes with benzaldehyde and angelica lactone
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Herein, we report a new route for the synthesis of renewable alkylated naphthalenes (ANs) with benzaldehyde and angelica lactone, two platform compounds that can be derived from lignocellulose.
- Cong, Yu,Li, Guangyi,Li, Ning,Wang, Aiqin,Wang, Ran,Wang, Xiaodong,Xu, Jilei,Zhang, Tao
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supporting information
p. 5474 - 5480
(2021/08/16)
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- Chemoselective Deoxygenation of 2° Benzylic Alcohols through a Sequence of Formylation and B(C6F5)3-Catalyzed Reduction
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A sequence of formylation and B(C6F5)3-catalyzed reduction of the resulting formate with Et3SiH enables the chemoselective deoxygenation of secondary benzylic alcohols. Primary benzylic and tertiary non-benzylic alcohols are not reduced by this protocol. The formyl group fulfills a double role as activator and self-sacrificing protecting group. The deoxygenation of these formates is fast and can be carried out in the presence of other potentially reducible groups. Neighboring-group participation was found in the deoxygenation of certain diol motifs.
- Oestreich, Martin,Richter, Sven C.
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supporting information
p. 2103 - 2106
(2021/07/22)
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- Method for synthesizing 2-isopropylnaphthalene
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The invention discloses a method for synthesizing 2-isopropylnaphthalene, and belongs to the technical field of organic synthesis application. Naphthalene is preheated to serve as a fluid A, an alkylation reagent serves as a fluid B, a chloroaluminate ionic liquid serves as a fluid C, and the three fluids are synchronously fed into a micro-reactor; the fluids A, B and C react in the micro-reactoraccording to a certain molar ratio at a controlled flow rate, and the 2-isopropylnaphthalene product is obtained after a discharged liquid is treated. The method is simple and convenient to operate, does not use an organic solvent, and is safe, controllable and environment-friendly in process, the catalyst is easy to separate, the naphthalene conversion rate is 100%, the selectivity of the product2-isopropylnaphthalene is 98% or above, and the 2-isopropylnaphthalene product can be continuously produced.
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Paragraph 0041-0046; 0049-0072; 0079-0084; 0091-0110
(2020/05/02)
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- Pd-Catalyzed Alkylation of (Iso)quinolines and Arenes: 2-Acylpyridine Compounds as Alkylation Reagents
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The first Pd-catalyzed alkylation of (iso)quinolines and arenes is reported. The readily available and bench-stable 2-acylpyridine compounds were used as an alkylation reagent to form the structurally versatile alkylated (iso)quinolines and arenes. The method affords a convenient pathway for the introduction of alkyl groups into organic molecules.
- Wu, Qingsong,Han, Shuaijun,Ren, Xiaoxiao,Lu, Hongtao,Li, Jingya,Zou, Dapeng,Wu, Yangjie,Wu, Yusheng
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supporting information
p. 6345 - 6348
(2018/10/20)
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- Hydride Reduction by a Sodium Hydride-Iodide Composite
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Sodium hydride (NaH) is widely used as a Br?nsted base in chemical synthesis and reacts with various Br?nsted acids, whereas it rarely behaves as a reducing reagent through delivery of the hydride to polar π electrophiles. This study presents a series of reduction reactions of nitriles, amides, and imines as enabled by NaH in the presence of LiI or NaI. This remarkably simple protocol endows NaH with unprecedented and unique hydride-donor chemical reactivity.
- Too, Pei Chui,Chan, Guo Hao,Tnay, Ya Lin,Hirao, Hajime,Chiba, Shunsuke
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supporting information
p. 3719 - 3723
(2016/03/26)
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- Nickel-catalyzed alkylative cross-coupling of anisoles with grignard reagents via C-O bond activation
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We report nickel-catalyzed cross-coupling of methoxyarenes with alkylmagnesium halides, in which a methoxy group is eliminated. A wide range of alkyl groups, including those bearing β-hydrogens, can be introduced directly at the ipso position of anisole derivatives. We demonstrate that the robustness of a methoxy group allows this alkylation protocol to be used to synthesize elaborate molecules by combining it with traditional cross-coupling reactions or oxidative transformation. The success of this method is dependent on the use of alkylmagnesium iodides, but not chlorides or bromides, which highlights the importance of the halide used in developing catalytic reactions using Grignard reagents.
- Tobisu, Mamoru,Takahira, Tsuyoshi,Morioka, Toshifumi,Chatani, Naoto
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supporting information
p. 6711 - 6714
(2016/06/14)
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- Lewis Acid Assisted Nickel-Catalyzed Cross-Coupling of Aryl Methyl Ethers by C-O Bond-Cleaving Alkylation: Prevention of Undesired β-Hydride Elimination
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In the presence of trialkylaluminum reagents, diverse aryl methyl ethers can be transformed into valuable products by C-O bond-cleaving alkylation, for the first time without the limiting β-hydride elimination. This new nickel-catalyzed dealkoxylative alkylation method enables powerful orthogonal synthetic strategies for the transformation of a variety of naturally occurring and easily accessible anisole derivatives. The directing and/or activating properties of aromatic methoxy groups are utilized first, before they are replaced by alkyl chains in a subsequent coupling process.
- Liu, Xiangqian,Hsiao, Chien-Chi,Kalvet, Indrek,Leiendecker, Matthias,Guo, Lin,Schoenebeck, Franziska,Rueping, Magnus
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supporting information
p. 6093 - 6098
(2016/05/19)
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- Nickel-Catalyzed Cross-Coupling of Organolithium Reagents with (Hetero)Aryl Electrophiles
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Nickel-catalyzed selective cross-coupling of aromatic electrophiles (bromides, chlorides, fluorides and methyl ethers) with organolithium reagents is presented. The use of a commercially available nickel N-heterocyclic carbene (NHC) complex allows the reaction with a variety of (hetero)aryllithium compounds, including those prepared via metal-halogen exchange or direct metallation, whereas a commercially available electron-rich nickel-bisphosphine complex smoothly converts alkyllithium species into the corresponding coupled product. These reactions proceed rapidly (1 h) under mild conditions (room temperature) while avoiding the undesired formation of reduced or homocoupled products. Nickel-catalyzed cross-coupling of aromatic electrophiles with organolithium reagents is presented. The use of a commercially available nickel N-heterocyclic carbene complex allows reaction with a variety of (hetero)aryllithium compounds, whereas a commercially available electron-rich nickel bisphosphine complex smoothly converts alkyllithium species into the corresponding coupled product.
- Heijnen, Dorus,Gualtierotti, Jean-Baptiste,Hornillos, Valentín,Feringa, Ben L.
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supporting information
p. 3991 - 3995
(2016/03/16)
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- Palladium-catalysed direct cross-coupling of secondary alkyllithium reagents
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Palladium-catalysed cross-coupling of secondary C(sp3) organometallic reagents has been a long-standing challenge in organic synthesis, due to the problems associated with undesired isomerisation or the formation of reduction products. Based on our recently developed catalytic C-C bond formation with organolithium reagents, herein we present a Pd-catalysed cross-coupling of secondary alkyllithium reagents with aryl and alkenyl bromides. The reaction proceeds at room temperature and on short timescales with high selectivity and yields. This methodology is also applicable to hindered aryl bromides, which are a major challenge in the field of metal catalysed cross-coupling reactions.
- Vila, Carlos,Giannerini, Massimo,Hornillos, Valentin,Fananas-Mastral, Martin,Feringa, Ben L.
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p. 1361 - 1367
(2014/03/21)
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- Shape-selective isopropylation of aromatic hydrocarbons over h-mordenite in supercritical carbon dioxide medium
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The isopropylation of aromatic hydrocarbons isobutylbenzene (IBB), naphthalene (NP), and biphenyl (BP) was examined over H-mordenite (MOR), H-β (BEA), and H-Y (FAU) zeolites in supercritical carbon dioxide (sc-CO2) medium. MOR was only selective for the formation of the least bulky 4-isobutylcumene (4-IBC) in the isopropylation of IBB. In particular, the catalytic activity and selectivity for 4-IBC were enhanced by the dealumination of MOR; MOR with 110 of SiO2/Al2O3 ratio rendered the highest performance; however, the catalytic activity was decreased by further dealumination. Thermogravimetric analyses confirmed the reduction of coke formation on the catalysts in sc-CO2 medium, preventing the deactivation of MOR. Shape-selective formation of the least bulky isomers, 2,6- diisopropylnaphthalene (2,6-DIPN) and 4,4′-diisopropylbiphenyl (4,4′-DIPB), was also observed in the isopropylation of NP and BP over MOR in sc-CO2. sc-CO2 works as an efficient medium to access and/or replace substrates and their products to/from acidic sites in the MOR channels. In particular, the removal of coke precursors from acidic sites on the zeolite is enhanced by the sc-CO2 medium, resulting in decreased coke formation.
- Laha, Subhash Chandra,Naiki, Hiroaki,Komura, Kenichi,Sugi, Yoshihiro
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supporting information; body text
p. 1283 - 1290
(2012/01/31)
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- Conformationally gated fragmentations and rearrangements promoted by interception of the bergman cyclization through intramolecular H-abstraction: A possible mechanism of auto-resistance to natural enediyne antibiotics?
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A variety of fragmentations and rearrangements can follow Bergman cyclization in enediynes equipped with acetal rings mimicking the carbohydrate moiety of natural enediyne antibiotics of the esperamicine and calchiamicine families. In the first step of all these processes, intramolecular H-atom abstraction efficiently intercepts the p-benzyne product of the Bergman cyclization through a six-membered TS and transforms the p-benzyne into a new more stable radical. Depending on the substitution pattern and reaction conditions, this radical follows four alternative paths: (a) abstraction of an external hydrogen atom, (b) O-neophyl rearrangement which transposes O- and C-atoms of the substituent, (c) fragmentation of the O-C bond in the acetal ring, or (d) fragmentation with elimination of the appended acetal moiety as a whole. Experiments with varying concentrations of external H-atom donor (1,4-cyclohexadiene) were performed to gain further insight into the competition between intermolecular H-abstraction and the fragmentations. The Thorpe-Ingold effect in gem-dimethyl substituted enediynes enhances the efficiency of fragmentation to the extent where it cannot be prevented even by a large excess of external H-atom donor. These processes provide insight into a possible mechanism of unusual fragmentation of esperamicin A1 upon its Bergman cycloaromatization and lay foundation for a new approach for the conformational control of reactivity of these natural antitumor antibiotics. Such an approach, in conjunction with supramolecular constraints, may provide a plausible mechanism for resistance to enediyne antibiotics by the enediyne-producing microorganisms.
- Baroudi, Abdulkader,Mauldin, Justin,Alabugin, Igor V.
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supporting information; experimental part
p. 967 - 979
(2010/03/31)
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- The alkylation of naphthalene over one-dimensional fourteen-membered ring zeolites. the influence of zeolite structure and alkylating agent on the selectivity for dialkylnaphthalenes
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The alkylation, i.e., isopropylation, s-butylation, and t-butylation, of naphthalene (NP) was examined over one-dimensional fourteen-membered (14-MR) zeolites: CIT-5 (CF1), UTD-1 (DON), and SSZ-53 (SFH), and compared to the results over H-mordenite (MOR)
- Sugi, Yoshihiro,Maekawa, Hiroyoshi,Naiki, Hiroaki,Komura, Kenichi,Kubota, Yoshihiro
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experimental part
p. 1166 - 1174
(2009/05/06)
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- Direct benzylic alkylation via Ni-catalyzed selective benzylic sp 3 C-O activation
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This article demonstrates the first cross coupling of benzyl ether with Grignard reagents via Ni-catalyzed benzylic sp3 C-O activation with high efficiency and excellent chemoselectivity. Benzylic sp3 C-O and aryl sp2 C-O were differentiated, controlled by ligands. Copyright
- Guan, Bing-Tao,Xiang, Shi-Kai,Wang, Bi-Qin,Sun, Zuo-Peng,Wang, Yang,Zhao, Ke-Qing,Shi, Zhang-Jie
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p. 3268 - 3269
(2008/10/09)
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- Lewis acid-catalyzed [4 + 2] benzannulation between enynal units and enols or enol ethers: Novel synthetic tools for polysubstituted aromatic compounds including indole and benzofuran derivatives
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The reaction of enynals 1, including o-(alkynyl)benzaldehydes, and carbonyl compounds 2, such as aldehydes and ketones, in the presence of a catalytic amount of AuBr3 in 1,4-dioxane at 100 °C gave the functionalized aromatic compounds 3 in high yields. Similarly, the AuBr3-catalyzed reactions of 1 with acetal compounds 5 afforded the corresponding aromatic compounds 3 in good yields. On the other hand, when the reaction was carried out in the presence of a catalytic amount of Cu(NTf2)2 and 1 equiv of H2O in (CH2Cl)2 at 100 °C, the decarbonylated naphthalene products 4 were obtained selectively over 3. Benzofused heteroaromatic compounds, such as indole derivatives 13 and benzofuran derivatives 15, were also synthesized by using the present benzannulation methodology.
- Asao, Naoki,Aikawa, Haruo
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p. 5249 - 5253
(2007/10/03)
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- Highly efficient Pd-catalyzed carbonylative cross-coupling reactions with tetraorganoindates
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Tetraorganoindates, which were prepared easily from the reaction of 1 equiv of InCl3 with 4 equiv of organometallics, could be employed as effective nucleophilic cross-coupling partners in Pd-catalyzed carbonylative cross-coupling reactions with a variety of organic electrophiles. The present method gave unsymmetrical ketones and 1,4-diacylbenzenes in good yields with highly efficient transfer of almost all the organic groups attached to the indium under a carbon monoxide atmosphere in THF at 60 °C.
- Lee, Sung Wook,Lee, Kooyeon,Seomoon, Dong,Kim, Sundae,Kim, Hyunseok,Kim, Hyun,Shim, Eunkyong,Lee, Miae,Lee, Seokju,Kim, Misook,Lee, Phil Ho
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p. 4852 - 4855
(2007/10/03)
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- Rutheniun-catalyzed cycloisomerization of o-(ethynyl)phenylalkenes to diene derivatives via skeletal rearrangement
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Treatment of a series of 2′,2′-disubstituted (oethynyl)styrenes with TpRu(PPh3)(CH3CN)2PF6 (10 mol %) in benzene (80°C, 12-18 h) efficiently gave 2-alkenyl-1H-indene derivatives. This catalytic reaction represents an atypical enyne cycloisomerization with skeletal rearrangement of starting enyne, where the C=C bond is completely cleaved and inserted by the terminal alkynyl carbon. The reaction mechanism was elucidated by a series of deuterium and 13C labeling experiments, as well as by changing the substituents at the phenyl moieties. The mechanism is proposed to involve the following key steps: 5-endo-dig cyclization of ruthenium-vinylidene intermediate, a nonclassical ion formation, and the "methylenecyclopropane-trimethylenemethane" rearrangement.
- Madhushaw, Reniguntala J.,Lo, Ching-Yu,Hwang, Chun-Wei,Su, Ming-Der,Shen, Hung-Chin,Pal, Sitaram,Shaikh, Isak R.,Liu, Rai-Shung
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p. 15560 - 15565
(2007/10/03)
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- AuBr3-catalyzed [4 + 2] benzannulation between an enynal unit and enol
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The reaction of enynals 1, including o-alkynylbenzaldehydes, and carbonyl compounds 2 in the presence of a catalytic amount of AuBr3 in 1,4-dioxane at 100 °C gave the functionalized aromatic compounds 3 in high yields. The AuBr3-catalyzed formal [4 + 2] benzannulation proceeds most probably through the coordination of the triple bond of 1 to AuBr3, the formation of a pyrylium auric ate complex via the nucleophilic addition of the carbonyl oxygen atom, the reverse electron demand-type Diels-Alder addition of the enols, derived from 2, to the auric ate complex, and subsequent dehydration and bond rearrangement. Similarly, the AuBr3-catalyzed reactions of 1 with acetal compounds afforded the corresponding aromatic compounds in good yields. Copyright
- Asao, Naoki,Aikawa, Haruo,Yamamoto, Yoshinori
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p. 7458 - 7459
(2007/10/03)
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- Study of regioselective dialkylation of napthalene in the presence of reusable zeolite catalysts
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Highly regioselective dialkylation of naphthalene using various alkylating agents can be achieved over zeolite catalysts. For example, the tert-butylation of naphthalene (1) using tert-butanol in cyclohexane over a dealuminated H-Mordenite (HM) zeolite has been optimised to give a 60% yield of 2,6-di-tert-butylnaphthalene (3) with a 2,6/2,7 ratio of over 50. This has been achieved by varying the reaction time, temperature, solvent, pressure, amount of tert-butanol, solvent and catalyst, Si/Al ratio of the catalyst, and the mode of addition. The zeolites can be easily regenerated by heating and reused.
- Smith, Keith,Roberts, Simon D.,El-Hiti, Gamal A.
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p. 1552 - 1559
(2007/10/03)
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- Friedel-crafts alkylation and acylation in the absence of solvent
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A short and efficient synthetic route, for alkylation and acylation of aromatic compounds in the absence of solvent is developed. According to the reaction system and conditions used, different alkyl-, and acyl arenes are obtained in moderate to good yields. The structures are assigned by 1H and 13C NMR spectroscopy.
- Ghiaci,Asghari
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p. 2213 - 2220
(2007/10/03)
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- Kinetics and Regioselectivity of the Autoxidation of o-Substituted Isopropyl Aromatics
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The relative chain propagation constants and the regioselectivities of the oxidations of o-cymene and 2-isopropyl-1,4-dimethylbenzene were determined by competitive oxidations of the hydrocarbons with cumene.As expected, the reactivity of the tertiary C-H bond of the isopropyl group is considerably decreased by o-methyl groups.Also in α-isopropylnaphthalene a considerable decrease in the reactivity of the tertiary C-H bond takes place.The decrease of the chain propagation constants effects a decrease of the oxidabilities of o-substituted isopropyl aromatics.In the case of the methyl isopropyl benzenes the increase of the chain termination constants by primary peroxy radicals must also be taken into consideration.This results in a decrease of the oxidabilities which can be observed even in p-cymene (in comparison with cumene).
- Heinze, Antje,Lauterbach, Gerlinde,Pritzkow, Wilhelm,Schmidt-Renner, Wolfgang,Voerckel, Volkmar,Zewegsuren, Nansadyn
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p. 439 - 446
(2007/10/02)
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- Acylation of naphthalenes
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Naphthalene substituted in the 2- or β-position with an electron-donating substituent can be acylated with high regioselectivity in the 6-position by using an acylating agent in substantially anhydrous hydrogen fluoride which functions both as catalyst and solvent.
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