- Preparation of 1,3,5-tris(aminomethyl)-2,4,6-triethylbenzene from two versatile 1,3,5-tri(halosubstituted) 2,4,6-triethylbenzene derivatives
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The use of 1,3,5-tris(aminomethyl)-2,4,6-triethylbenzene and the intermediates 1,3,5-tris(halomethyl)-2,4,6-triethylbenzene (halo = bromo and chloro) compounds, have been utilized as scaffolds for many molecular receptors. We report here for the first time a detailed practical synthetic procedure, starting from benzene, and in four straightforward steps, to prepare 1,3,5-tris(aminomethyl)-2,4,6-triethylbenzene, a very versatile molecular scaffold. The added advantage is the limited chromatography in the purification procedure. Georg Thieme Verlag Stuttgart.
- Wallace, Karl J.,Hanes, Robert,Anslyn, Eric,Morey, Jeroni,Kilway, Kathleen V.,Siegel, Jay
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- Supramolecular Alloys from Fluorinated Hybrid Tri4Di6 Imine Cages
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To create innovative materials, efficient control and engineering of pore sizes and their characteristics, crystallinity and stability is required. Eight hybrid Tri4Di6 imine cages with a tunable degree of fluorination and one fully fluorinated Tri4Di6 imine cage are investigated. Although the fluorinated and the non-fluorinated building blocks used herein differ vastly in reactivity, it was possible to gain control over the outcome of the self-assembly process, by carefully controlling the feed ratio. This represents the first hybrid material based on fluorinated/hydrogenated porous organic cages (POCs). These cages with unlimited miscibility in the solid state were obtained as highly crystalline samples after recrystallization and even showed retention of the crystal lattice, forming alloys. All mixtures and the fully fluorinated Tri4Di6 imine cage were analyzed by MALDI-MS, single-crystal XRD, powder XRD and in regard to thermal stability (TGA).
- Kunde, Tom,Pausch, Tobias,Schmidt, Bernd M.
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- Regioselective synthesis of 1,3,5-substituted benzenes via the InCl 3/2-iodophenol-catalyzed cyclotrimerization of alkynes
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A novel indium(III)-catalyzed cyclotrimerization of alkynes in the presence of 2-iodophenol gave 1,3,5-substituted benzenes in excellent yields with complete regioselectivity. The reaction condition is tolerant to air, and atom economical, in accordance with the concept of modern green chemistry. This method provides a rapid and efficient access to 1,3,5-substituted benzenes.
- Xu, Yan-Li,Pan, Ying-Ming,Wu, Qiang,Wang, Heng-Shan,Liu, Pei-Zhen
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- Guaiacol demethoxylation catalyzed by Re2O7 in ethanol
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Re2O7 is used to convert guaiacol in alcohols at 280–320 °C. In ethanol, guaiacol is deoxygenated and alkylated, and the major products are phenol and alkylphenols (including ethylphenol, diethylphenol, diisopropylphenol, di-tert-butylphenol and 2,6-di-tert-butyl-4-ethylphenol), accounting for 97 mol% of all products after 6 hour reaction at 320 °C. Both catechol and phenol are the intermediates of guaiacol demethoxylation. Among the substituents, ethyl is directly provided by ethanol while isopropyl and tert-butyl are formed by the addition of methyl to ethyl step by step. In addition, Re2O7 has negligible activity for the saturation of benzene ring so it does not cause considerable over-consumption of reductant. The actual catalyst for guaiacol demethoxylation is likely a ReIV?VI species.
- Yan, Fei,Sang, Yushuai,Bai, Yunfei,Wu, Kai,Cui, Kai,Wen, Zhe,Mai, Fuhang,Ma, Zewei,Yu, Linhao,Chen, Hong,Li, Yongdan
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p. 231 - 237
(2019/08/12)
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- Unraveling the Homologation Reaction Sequence of the Zeolite-Catalyzed Ethanol-to-Hydrocarbons Process
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Although industrialized, the mechanism for catalytic upgrading of bioethanol over solid-acid catalysts (that is, the ethanol-to-hydrocarbons (ETH) reaction) has not yet been fully resolved. Moreover, mechanistic understanding of the ETH reaction relies heavily on its well-known “sister-reaction” the methanol-to-hydrocarbons (MTH) process. However, the MTH process possesses a C1-entity reactant and cannot, therefore, shed any light on the homologation reaction sequence. The reaction and deactivation mechanism of the zeolite H-ZSM-5-catalyzed ETH process was elucidated using a combination of complementary solid-state NMR and operando UV/Vis diffuse reflectance spectroscopy, coupled with on-line mass spectrometry. This approach establishes the existence of a homologation reaction sequence through analysis of the pattern of the identified reactive and deactivated species. Furthermore, and in contrast to the MTH process, the deficiency of any olefinic-hydrocarbon pool species (that is, the olefin cycle) during the ETH process is also noted.
- Chowdhury, Abhishek Dutta,Lucini Paioni, Alessandra,Whiting, Gareth T.,Fu, Donglong,Baldus, Marc,Weckhuysen, Bert M.
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supporting information
p. 3908 - 3912
(2019/02/20)
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- Synthesis, characterization and application of MCM-22 zeolites via a conventional HMI route and temperature-controlled phase transfer hydrothermal synthesis
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With less environmental and economical impact, temperature-controlled phase transfer hydrothermal synthesis of MWW zeolites was realized with hexamethyleneimine as a structure-directing agent and aniline as a structure-promoting agent. MCM-22 zeolite, synthesized via temperature-controlled phase transfer hydrothermal synthesis, is nearly identical concerning chemical composition and structure, and possesses nearly identical properties with respect to porosity, Si/Al ratio, thermal behavior and catalytic activity at 200°C, compared with that made from conventional synthesis with hexamethyleneimine as the only template.
- Xing, Enhui,Shi, Yanchun,Xie, Wenhua,Zhang, Fengmei,Mu, Xuhong,Shu, Xingtian
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p. 8514 - 8522
(2015/03/05)
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- Silica-supported tripod triarylphosphines: Application to palladium-catalyzed borylation of chloroarenes
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Silica-supported tripod triarylphosphines that have a Ph3Ptype core tripodally immobilized on a silica surface enabled the Pd-catalyzed borylation of chloroarenes with bis(pinacolato)diboron under mild conditions. The immobilization in tripod was crucial for the excellent performance of the Ph3P-based ligands.
- Iwai, Tomohiro,Harada, Tomoya,Tanaka, Ryotaro,Sawamura, Masaya
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supporting information
p. 584 - 586
(2014/05/20)
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- An efficient approach to the cyclotrimerisation of alkynes: Solvent-free synthesis of 1,3,5-trisubstituted benzenes using p-toluenesulfonic acid monohydrate
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An environmentally friendly, efficient method for transforming alkynes into substituted benzenes catalyzed by p-toluenesulfonic acid monohydrate (p-TsOH·H2O) under solvent-free conditions has been developed, which conforms to the principles of "green" chemistry and overcomes the shortcomings of previous methods for the synthesis of substituted benzenes. The reaction is quite general and provides good to excellent yields. ARKAT-USA, Inc.
- Gao, Qi,Bao, Fang-Ping,Feng, Xiao-Jing,Pan, Ying-Ming,Wang, Heng-Shan,Li, Dian-Peng
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- Isopropylamino and isobutylamino groups as recognition sites for carbohydrates: Acyclic receptors with enhanced binding affinity toward β-galactosides
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Binding motifs observed in the crystal structures of protein-carbohydrate complexes, in particular the participation of the isopropyl/isobutyl side chain of valine/leucine in the formation of van der Waals contacts, have inspired the design of new artificial carbohydrate receptors. The new compounds, containing a trisubstituted triethylbenzene core, were expected to recognize sugar molecules through a combination of NH→O and OH→N hydrogen bonds, CH→π interactions, and numerous van der Waals contacts. 1H NMR spectroscopic titrations in competitive and noncompetitive media, as well as binding studies in two-phase systems, such as dissolution of solid carbohydrates in apolar media and phase transfer of sugars from aqueous into organic solvents, revealed effective recognition of neutral carbohydrates and β- vs α-anomer binding preferences in the recognition o' glycosides as well as significantly increased binding affinity of the receptors toward β-galactoside in comparison with the previously described receptors.
- Mazik, Monika,Sonnenberg, Claudia
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scheme or table
p. 6416 - 6423
(2010/12/20)
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- Molybdenum(III) chloride-tetrahydrothiophene (tht) complexes in the catalytic polymerization and cyclotrimerization of alkynes: Structures and reactivities of the possible intermediates [MoCl3(tht)2(PhC≡CR)] (R = Me or Et)
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The binuclear complexes [Mo2Cl6(tht)3] (both the C2r and Cs isomers, tht = tetrahydrothiophene) have been found to be active catalysts for the selective polymerization and cyclotrimerization of a variety of alkynes. The mononuclear complex [MoCl3(tht)3] shows similar behaviour, leading to the postulate that the active species in all cases is mononuclear. Two unique molybdenum(III) alkyne complexes, [MoCl3(tht)2L] (L = PhC≡CMe or PhC≡CEt) have been isolated and structurally characterized. The structural parameters for these complexes suggest that the alkynes behave as four-electron donors. These complexes are also catalytically active, and the alkyne L is incorporated into the product cyclotrimers and polymers suggesting they are the first intermediates in the formation of active catalysts from the original thioether complexes.
- Boorman, P. Michael,Wang, Meiping,Parvez, Masood
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p. 4533 - 4542
(2007/10/03)
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- Flash photolysis study of a Friedel-Crafts alkylation. Reaction of the photogenerated 9-fluorenyl cation with aromatic compounds
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A combination of flash photolysis and product analysis is employed to investigate the reaction of aromatic compounds (ArH) with the 9-fluorenyl cation (Fl+) photogenerated from 9-fluorenol in 1,1,1,3,3,3-hexafluoroisopropyl alcohol (HFIP).The availability of the photochemical route to Fl+ means that the reaction of benzylic-type cation with ArH can be directly followed by flash photolysis.An additional feature with electron-rich ArH is that the cyclohexadienyl cation is observed to grow as Fl+ decays.Thus both cationic intermediates of a Friedel-Crafts alkylation are observed in the same experiment.The formation of the cyclohexadienyl cation is demonstrated to be reversible, or at least quasi-reversible, with the kinetic analysis furnishing absolute rate constants for the formation of this cation as well as for its loss of H+ and Fl+.Values of kH:kD for benzene:benzene and toluene:toluene are ca. 1.5 and demonstrate that Fl+ addition is at least partly reversible with these compounds as well.The Hammett ρ+ value obtained for a series of the less electron-rich ArH is -8, indicative of a transition state with considerable cyclohexadienyl cation character.Anisole shows a negative deviation from from Hammett correlation line, explained by the addition of Fl+ to ArH becoming encounter-controlled.This behaviour is dramatically illustrated in a comparison of data for Fl+ and Br2.For the less electron-rich ArH, rate constants for the two electrophiles are parallel.However, from m-xylene through pentamethylbenzene, the rate with Fl+ is unchanged, while the rate with Br2 increases over 1000-fold.The concept of encounter control with Fl+ is strongly supported by the absolute rate constants, which for the electron-rich ArH are all in the range 1-2 E9 dm3 mol-1 s-1, a magnitude typical of diffusion-controlled reactions.The electron-rich ArH also show no intermolecular selectivity since their reactions are encounter-controlled, but have a high intramolecular selectivity.It is suggested that a factor influencing the latter is the reversibility of formation of the cyclohexadienyl cation from the encounter complex.
- McClelland, Robert A.,Cozens, Frances L.,Li, Jianhui,Steenken, Steen
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p. 1531 - 1544
(2007/10/03)
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- Hemicarcerands that encapsulate hydrocarbons with molecular weights greater than two hundred
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Syntheses are reported for the globe-shaped hemicarcerands 1 and 2 composed of two rigid bowl-like units (polar caps) attached to one another at their rims through four OCH2C≡CC≡CCH2O units (equatorial spacers). Eight pendant CH3(CH2)4 groups in 1 and C6H5CH2CH2 groups in 2 attached in assemblies of four to each polar cap render the hosts soluble in organic solvents. The important shell-closing reactions 2Ar(OCH2C≡CH)4 + [O] → Ar(OCH2C≡CC≡CCH2O)4Ar went in 5-8% yields in pyridine-O2-Cu(OAc)2 to give a hemicarcerand free of pyridine. The higher solubility of 1 (compared to that of 2) in organic solvents led to an examination of its binding properties. By heating 1 dissolved either in potential guests or in 1,3,5-[(CH3)3C]3C6H3 (too large to enter 1) containing dissolved potential guests at 80-140 °C for 2-7 days, 1:1 hemicarceplexes mixed with the empty host were isolated in those cases when the potential guests were just small enough to enter the host's portals at high temperatures but large enough not to depart during isolation as stable solids. Thus, constrictive bonding played a large role in kinetic stabilization of the hemicarceplexes. The 1H NMR spectra of both the host and the guest were markedly modified upon complexation. The half-lives in hours of representative complexes dissolved in CDCl3 at 25 °C were as follows: 1·1,3,5-[(CH3)2CH]3C6H 3, 1628; 1·1,3,5-Et3C6H3, 960; 1·4-Et[2.2]paracyclophane, 24; 1·1,3-dimethyladamantane, 13.5; 1-[3.3]paracyclophane, 13; 1·tetradehydro[2.2]paracyclophane, 11; 1·[2.2]paracyclophane, 5; 1·4,12-dihydroxy[2.2]paracyclophane, 4; and 1·[2.3]paracyclphane, 0.5. Complexes of smaller guests such as CHCl3, ferrocene, adamantane, and 1,3,5-trimethylbenzene were unstable to room-temperature isolation conditions. Larger guests such as [3.4]paracyclophane and 4,12-dinitro[2.2]paracyclophane did not enter the portals of 1 at temperatures under which host 1 was stable, whereas smaller guests such as CH2Cl2 and pyridine entered and departed the host at 25 °C rapidly on the NMR time scale. Catalytic reduction (H2, PdC) of the eight acetylenic bonds of 1 produced an empty host of much more flexible structure, 3, whose binding properties have not yet been examined.
- Cram, Donald J.,Jaeger, Ralf,Deshayes, Kurt
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p. 10111 - 10116
(2007/10/02)
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- Synthesis and Reactions of Some Crowded Triorganylbismuthines
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Bismuth trichloride reacts smoothly with mesityl- and 2,4,6-triisopropylphenylmagnesium bromides in boiling tetrahydrofuran to form the corresponding trialkylbismuthines in good yields, white a similar reaction with 2,4,6-triisopropylphenylmagnesium bromide halts a diarylation stage, giving chlorobis(2,4,6-triisopropylphenyl)bismuthine as the sole product.Several crowded alkyl-, alkenyl-, and alkynyldiarylbismuthines have been prepared from the above diarylchlorobismuthine through the reaction with an appropriate organolithium reagent.
- Matano, Yoshihiro,Kinoshita, Masamichi,Suzuki, Hitomi
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p. 3504 - 3506
(2007/10/02)
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- Flash Vacuum Pyrolysis of o-Alkylaryl- and Arylalkylchloroboranes. - Synthesis of Benzoannulated Boracycloalkenes
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The dichloroorganylboranes chosen as pyrolytic starting materials were synthesized upon treatment of the corresponding triorganylboroxines and aryltrimethylsilanes (giving 3, 4) or the tetraorganylstannanes (giving 9-12, 17-20) with boron trichloride.At 700 deg C the flash vacuum pyrolysis of the dichloro(2-ethylphenyl)boranes 10 and 4 led to 1-boraindanes 21 and 22 selectively.The dichloro-2-tolylborane (9), the B-dimethylamino derivative, and mesitylboranes like 3 were completely stable upon pyrolysis.Pyrolyzing the isopropylphenylborane 12 1,5-elimination exclusively took place yielding 26, while pyrolysis of propylphenylborane 11 led to a mixture of boraindane 29 and boratetraline 30.To exclude such competitive reactions, some arylalkyldichloroboranes were pyrolyzed.At 750 deg C dichloro(2-methylbenzyl)borane (18) exclusively yielded oligomeric 2-chloro-2-boraindane (31).At 950 deg C even the pyrolysis of benzyldichloroborane (17) succeeded in a 1,4-elimination reaction yielding the eight-membered 2H-benzoborete dimer 34.The inversion barrier of 34 is ΔG(excit.)228 = 10.3 kcal mol-1, determined by NMR spectroscopy.The pyrolysis of the next-higher homologous dichloroorganylborane 19 yielded a boraindane 21 and a noncyclic diorganylborane 38 by a dehydroboration/hydroboration pathway.Both reaction types also took place when pyrolyzing dichloroborane (20): cyclization under formation of a five-membered ring system 39, formed upon attack of an aromatic C-H bond exclusively, and formation of an open-chain chlorodiorganylborane 40.
- Schacht, Wolfgang,Kaufmann, Dieter
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p. 1331 - 1338
(2007/10/02)
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- Migrations in Oxidations of Mesidine
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The oxidation of mesidine in methanolic media by ferricyanide, dichromate, and persulfate afforded an anil 4 containing a shifted methoxymethyl group in addition to the principal anil 3 formed by oxidative dealkylation.Possible intermediates 6, 7, and 8 were prepared and oxidized to the product anils.Oxidations of related anilines 9, 10, and 13 did not parallel those of mesidine but afforded analogues of 3.There is significant spectral evidence for anils with alkyl shifts but little for anils analogous to 4.
- Goldstein, Stephen L.,McNelis, Edward
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p. 1613 - 1620
(2007/10/02)
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- Studies in Trifluoromethanesulfonic Acid. 3. Kinetics and Mechanism of Transalkylation Reactions
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Rates of disproportionation of ethylbenzene and m-diethylbenzene have been measured in the solvent trifluoromethanesulfonic acid (triflic acid).Ethylbenzene disproportionates very rapidly, whereas m-diethylbenzene reacts at a conveniently measurable rate.The reactions obey first-order kinetics over a wide range of concentration, and the results are interpreted as involving ethyl transfer to the triflate anion followed by alkylation via the ethyl triflate formed.
- Bakoss, H. J.,Roberts, R. M. G.,Sadri, A. R.
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p. 4053 - 4055
(2007/10/02)
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- Alkyltrifluoromethanesulphonates as alkylating reagents for aromatic compounds
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Methyl and ethyl trifluoromethanesulphonates (' triflates '), prepared by conventional routes involving either trifluoromethanesulphonic acid (' triflic acid ') or its anhydride, contain traces of triflic acid as an impurity, which catalyse their alkylation reactions with aromatic compounds. Pure methyl triflate, obtained from reaction between CH3l and CFS03Ag, does not alkylate p-cymene after several hours at 100 °C. Pure ethyl triflate, prepared by a similar method, is thermally less stable under these conditions, and alkylation takes place only after long induction periods during which some breakdown to triflic acid occurs. With aromatic substrates such as p-cymene or mesitylene the onset of alkylation is followed rapidly by the formation of isomerisation and disproportionation products. Benzyl triflate, prepared from PhCH2Br and CF3SO3Ag, alkylates p-cymene even at room temperature. The strong Lewis acids SbF5 and AlCl3 similarly catalyse alkylation reactions of methyl and ethyl triflates, but BF3, FeCl3, and SnCl4 are much less effective.
- Booth, Brian L.,Haszeldine, Robert N.,Laali, Khosrow
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p. 2887 - 2893
(2007/10/02)
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