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Novel approach towards Al-rich AFI for catalytic application
A new germanosilicate structural analogue of AFI zeolite (Ge-AFI) was hydrothermally synthesized. One- and two-step alumination of the Ge-AFI zeolites were used to modify their structure and acidic properties traced using XRD, N2 adsorption, ICP-OES, 27Al NMR, and FTIR spectroscopy. Two-step aluminated sample (deGe-Al-AFI) provided a higher Al content, stronger acid sites and a higher micropore volume than one-step aluminated sample (Al-AFI). Extensive evaluation of the catalytic performance of these AFI zeolites compared with reference conventional zeolite catalysts for alkylation of toluene with isopropyl alcohol showed that deGe-Al-AFI exhibited relatively high toluene conversion and selectivity to valuable p-cymene due to the optimized textural and acidic properties.
Zhou, Yong,?ilková, Nadě?da,Shamzhy, Mariya,Avadhut, Yamini,Hartmann, Martin,?ejka, Ji?í,Opanasenko, Maksym
p. 62 - 68
(2019)
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Electrophilic Aromatic Substitution. 9. A Kinetic Study of the Friedel-Crafts Isopropylation Reaction in Nitromethane
The kinetics of the aluminum chloride catalyzed reaction between isopropyl chloride and benzene or toluene were determined in solvent nitromethane by using vacuum-line techniques.The reaction at 25 deg C was first order in isopropyl chloride and in aromatic hydrocarbon and first order in initial catalyst concentration.Noncompetitive results are kT/kB = 2.0 +/- 0.7 with the following toluene product isomer distribution: percent ortho, 45.3 +/- 1.5; percent meta, 22.7 +/- 1.1; percent para, 32.0 +/- 1.0.For competitive runs kT/kB was 2.3 +/- 0.1 with the same isomer distribution.Rate constants at 25, 15, 0, -15, and -27 deg C yielded Ea = 78 +/- 4 kJ/mol, ΔH = 76 +/- 4 kJ/mol, Δ = -13 +/- 14 J/mol deg.The results are consistent with a ? complex-like transition state and a predominantly ionic mechanism.
DeHaan, Franklin P.,Delker, Gerald L.,Covey, William D.,Ahn, Jeffrey,Cowan, Robert L.,et al.
p. 1587 - 1590
(1986)
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Catalytic Property of Calcined Iron Sulfate Treated with Hydrogen Chloride in Alkylation of Toluene and Benzene with Alkyl Chlorides
Alkylation was carried out at room temperature over catalysts prepared by calcination of FeSO4, Fe2O3, and Fe(OH)3 in the air at various temperatures and subsequent exposure to HCl at room temperature for 20 min.The FeSO4-HCl catalysts heat-treated at 700 and 750 deg C showed very high activity and selectivity, the other catalysts except for the sulfate treated at 800 deg C being almost inactive.The FeSO4(700 deg C)-HCl catalyst was found to consist of FeCl3 and α-Fe2O3 by means of Moessbauer effect, the absorption peak areas being 14 and 86percent for portions of iron based on the chloride and oxide, respectively.The results of DTA and TGA experiments suggest that the coordinate bond of water molecule on FeCl3 of the FeSO4(700 deg C)-HCl catalyst is stronger than that on FeCl3 of the FeSO4 (600, 800, and 900 deg C)-HCl and commercial FeCl3.The FeSO4(700 deg C)-HCl catalyst showed a much higher activity than pure FeCl3.The iron(III) chloride formed by reaction of HCl and α-Fe2O3 obtained by thermal decomposition of the sulfate at 700 or 750 deg C was found to be a very strong Lewis acid catalyst.
Arata, Kazushi,Hino, Makoto,Yabe, Katsumasa
p. 6 - 9
(1980)
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Continuous, ionic liquid-catalysed propylation of toluene in a liquid-liquid biphasic reaction mode using a loop reactor concept
Acidic ionic liquids of the type [cation] [bis(trifluoromethanesulfonyl) imide anion]/aluminium trichloride {[cation] [(CF3SO 2)2N]/AlCl3} have been applied to realise for the first time a continuous Friedel-Crafts alkylation reaction in liquid-liquid biphasic reaction mode using a loop reactor concept. Exemplified for the continuous propylation of toluene we have proved that the acidic catalyst layer is successfully immobilised over at least 18 h in the loop reactor. After 8 h time-on-stream, a steady state has been reached followed by at least 10 h time-on-stream without any loss of activity or change in selectivity. Our results reveal the high potential of this class of acidic ionic liquids in continuous arene functionalisation reactions.
Ladnak, Viktor,Hofmann, Norbert,Brausen, Nicole,Wasserscheid, Peter
p. 719 - 726
(2007)
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The Acidic Property and Catalytic Activity of MoO3-SiO2-Al2O3
The ternary oxide system MoO3-SiO2-Al2O3 was prepared by coprecipitation method.The pH of coprecipitation has been varied from pH = 2 to pH = 8 and its effect on the acidic properties of the ternary oxide acidic system was studied by butylamine titration.The MoO3-SiO2-Al2O3 prepared from highly acidic solution has low acid strength.The total acid amount of the ternary oxide decreased considerably at higher pH (>6) of coprecipitation.It was found that the total acid amount of MoO3-SiO2-Al2O3 containing 9.7 percent (by weight) of MoO3 and silica to alumina molar ratio 16.6 is very high compared with that of SiO2-Al2O3 of the same silica to alumina molar ratio.The acid strength of SiO2-Al2O3 is reduced by the incorporation of MoO3.Increase in calcination temperature increased the acid strength.The catalytic activity of MoO3-SiO2-Al2O3 was found to be very high for the alkylation of toluene with 2-propanol.The products are found to be o-cymene, p-cymene, and three isomers of diisopropyltoluenes.Reaction temperature >200 deg C, higher liquid hourly space velocity, and higher alcohol content in the feed decreased the total conversion of 2-propanol to isopropyltoluenes.The acidic property and catalytic activity of MoO3-SiO2-Al2O3 are not considerably reduced up to four successive regeneration cycles.
Sabu, Kuzhunellil Raghavan Pillai,Rao, Kalur Vijayachandra C.,Nair, Chandrathil Govindan Ramacha.
p. 1926 - 1932
(1991)
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Alkylation of Toluene with 2-Propanol over Titania-Silica-Alumina Catalysts
The alkylating activity of titania supported on silica-alumina has been reported earlier (V.G.Kumar, T.S.Shoba, and K.V.C.Rao, Tetrahedron Lett., 26, 3281 (1985)).Further investigations to synthesize such a catalyst with optimum alkylation activity resulted in the coprecipitation of the catalyst from a solution of pH 4-the test reaction selected being the alkylation of toluene with 2-propanol in a fixed bed tubular reactor.The product mixtures at different reaction times are analyzed to have a view on the variation of yields of different alkylated products with reaction time.The alkylated products are o-cymene, p-cymene, and diisopropyltoluenes (DIT).The presence of titania exerts a synergistic effect upon the alkylating activity of silica-alumina.Also the catalytic activity is governed by the physical caracteristics of the catalyst like surface area and porosity.The trend of para-rich isomer distribution observed in the product mixture is attributed to the steric factors.It has been observed that o-cymene is formed at a constant rate whereas p-cymene formation decreased with reaction time.Increased formation of diisopropyltoluenes are observed with the passing of reaction time.Alkylation studies in the temperature range 165-240 degC have been done to find the effect of reaction temperature on the product distribution.Thus a decrease in the ortho to para molar ratio with increase in reaction temperature and increased formation of diisopropyltoluenes at lower temperatures are observed.No considerable reduction in the alkylation activity has been noticed up to five regeneration cycles.
Rao, K. V. C.,Sabu, K. R.,Nair, C. G. R.
p. 2657 - 2661
(1989)
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Condon
p. 2265
(1948)
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Simons,Hart
p. 979
(1947)
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Condon
p. 3544
(1949)
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Identification by GC-MS of cymene isomers and 3,7,7-trimethylcyclohepta-1, 3,5-triene in essential oils
Retention indices of cymene isomers published in popular GC-MS atlases were found to be erroneous by analyzing synthetic samples. The following retention indices (RI) were found using a nonpolar phase (diphenyl: dimethylpolysiloxane, 5:95) for four essential-oil components with indistinguishable mass spectra: 3,7,7-trimethylcyclohepta-1,3,5-triene (RI = 970), m-cymene (RI = 1022), p-cymene (RI = 1024), and o-cymene (RI = 1039). The relative distributions of these compounds were evaluated based on the analysis of about 1000 essential oils. Simple methods were given for preparing standard mixtures of isomeric compounds for identification by GC-MS.
Romanenko,Tkachev
p. 699 - 701
(2006)
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Production of p -cymene from crude sulphate turpentine with commercial zeolite catalyst using a continuous fixed bed reactor
Crude sulphate turpentine (CST), containing -pinene, 3-carene, other terpene isomers, and organic sulphur compounds, was used as feedstock in the production of cymenes with commercial zeolite catalysts. The catalysts used were not sensitive to sulphur, and the desulphurisation step was not needed prior to cymene synthesis. The experiments were performed in a continuous fixed bed reactor. Promising results were obtained after initial optimization at temperatures close to 300 °C with faujasite Y zeolite under 5 bar N2 pressure. Cymenes were produced with 54% yields from model compound -pinene and with 28% yields from CST. The mechanistic route of the reaction can be divided into three steps: (1) ring opening, (2) rearrangement, and (3) dehydrogenation. The final step in the formation of p-cymene can occur via dehydrogenation or disproportion; here the effect of reaction conditions and catalyst plays a crucial role.
Linnekoski, Juha A.,Asikainen, Martta,Heikkinen, Harri,Kaila, Reetta K.,R?s?nen, Jari,Laitinen, Antero,Harlin, Ali
p. 1468 - 1475
(2014)
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Facile fabrication of aluminum-promoted vanadium phosphate: A highly active heterogeneous catalyst for isopropylation of toluene to cymene
Vanadium phosphate is well known as a heterogeneous catalyst in gas phase oxidation reactions. To date, there has been little interest in carrying out liquid-phase reactions with vanadium phosphate as catalyst. Herein, we report the catalytic activity of vanadium phosphate and aluminum-promoted vanadium phosphate toward liquid-phase isopropylation of toluene to cymene. The catalysts were unambiguously characterized by X-ray diffraction, N2 adsorption-desorption, FT-IR technique, UV-vis DRS, and FE-SEM. The total acid sites were estimated by an NH3 TPD analyzer. XPS was used as a powerful tool to know the electronic environment of the catalysts. The optimization of the reaction was carried out by varying temperature from 75 to 150 °C and molar ratio (toluene: isopropanol) from 1:1-1:3. Under optimum reaction conditions, 5 wt.% aluminum-promoted vanadium phosphate showed 90% conversion with 85% selectivity to p-cymene.
Behera, Gobinda Chandra,Parida,Das
p. 190 - 198
(2012)
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Alkylation of Toluene with Isopropanol on Lantanum Modified ZSM-5 Zeolite
Abstract: The effect of lanthanum concentration on the physicochemical and catalyticproperties of HZSM-5 zeolite in a reaction of toluene alkylation withisopropanol was studied in a temperature range of 250–350°C. Based on the dataobtained by X-ray diffraction analysis, low-temperature nitrogen adsorption (BETmethod), and IR spectroscopy, it was shown that an increase in lanthanumconcentration in HZSM-5 from 1.0 wt % to 7.0 wt % reduces both the specificsurface area and the pore volume of the zeolite despite the retention of itscrystalline structure. This also results in redistribution of acid sites,specifically decreases the concentration of strong Br?nsted acid sites (B) andincreases that of moderate Lewis acid sites (L), thus decreasing the B/L ratiofrom 3.53 to 0.20. All these occurrences have a crucial effect on theselectivity of reaction products and, in particular, on the p-isopropyl toluene (4-IPT) selectivity. Maximumselectivity, making up 72.4%, is achieved by a zeolite containing 5.0 wt %lanthanum at a B/L ratio of 0.25.
Abdullaeva,Voskressenskii,Akhmedova,Mamedov
p. 190 - 197
(2020/12/17)

Halogen-Bridged Methylnaphthyl Palladium Dimers as Versatile Catalyst Precursors in Coupling Reactions
Halogen-bridged methylnaphthyl (MeNAP) palladium dimers are presented as multipurpose Pd-precursors, ideally suited for catalytic method development and preparative organic synthesis. By simply mixing with phosphine or carbene ligands, they are in situ converted into well-defined monoligated complexes. Their catalytic performance was benchmarked against state-of-the-art systems in challenging Buchwald–Hartwig, Heck, Suzuki and Negishi couplings, and ketone arylations. Their use enabled record-setting activities, beyond those achievable by optimization of the ligand alone. The MeNAP catalysts permit syntheses of tetra-ortho-substituted arenes and bulky anilines in near-quantitative yields at room temperature, allow mono-arylations of small ketones, and enable so far elusive cross-couplings of secondary alkyl boronic acids with aryl chlorides.
Doppiu, Angelino,Goo?en, Lukas J.,Hu, Zhiyong,Pirkl, Nico,Sivendran, Nardana
supporting information
p. 25151 - 25160
(2021/10/19)

Mechanistic Interrogation of Co/Ni-Dual Catalyzed Hydroarylation
Cobalt/nickel-dual catalyzed hydroarylation of terminal olefins with iodoarenes builds complexity from readily available starting materials, with a high preference for the Markovnikov (branched) product. Here, we advance a mechanistic model of this reaction through the use of reaction progress kinetic analysis (RPKA), radical clock experiments, and stoichiometric studies. Through exclusion of competing hypotheses, we conclude that the reaction proceeds through an unprecedented alkylcobalt to nickel direct transmetalation. Demonstration of catalytic alkene prefunctionalization, via spectroscopic observation of an organocobalt species, distinguishes this Csp2-Csp3 cross-coupling method from a conventional transmetalation process, which employs a stoichiometric organometallic nucleophile, and from a bimetallic oxidative addition of an organohalide across nickel, described by radical scission and subsequent alkyl radical capture at a second nickel center. A refined understanding of the reaction leads to an optimized hydroarylation procedure that excludes exogenous oxidant, demonstrating that the transmetalation is net redox neutral. Catalytic alkene prefunctionalization by cobalt and engagement with nickel catalytic cycles through direct transmetalation provides a new platform to merge these two rich areas of chemistry in preparatively useful ways.
Shevick, Sophia L.,Obradors, Carla,Shenvi, Ryan A.
supporting information
p. 12056 - 12068
(2018/09/27)

Three-dimensional 10-ring zeolites: The activities in toluene alkylation and disproportionation
Three-dimensional 10-ring zeolites TUN, IMF, -SVR, MFI and MEL were investigated as for their acid properties, adsorption of 2,2-dimethylbutane and in toluene disproportionation and its alkylation with isopropyl alcohol. The results were compared against zeolite?SFV, the structure of which consists mainly of MEL zeolite with some additional 12-ring channel system. With exception of -SVR synthesized with high Si/Al ratio, all other zeolites provided Si/Al ratios in a narrow region. Novel zeolites TUN, IMF, and -SVR exhibited higher conversions than MFI and MEL in toluene alkylation. TUN and IMF were substantially more active in toluene disproportionation indicating less diffusion restrictions of channel structure on the disproportionation reaction.?SFV showed a similar catalytic behavior to MEL with much lower selectivity to p-xylene and p-cymene. This could indicate that both toluene disproportionation and alkylation proceed in reaction space of?SFV being similar to those of MFI and MEL.?SFV and TUN exhibited much faster adsorption of 2,2-dimethylbutane than MFI, MEL, IMF, and -SVR. It was concluded that the presence of some larger transport pores in?SFV than in other zeolites is responsible for fast adsorption of 2,2-dimethylbutane and transport of products resulting in a low selectivity to p-xylene and p-cymene.
Kub?, Martin,?ilková, Nadě?da,Zones, Stacey I.,Chen, Cong-Yan,Al-Khattaf, Sulaiman,?ejka, Ji?í
p. 97 - 106
(2015/10/29)

Heterogeneous Catalytic Hydroarylation of Olefins at a Nanoscopic Aluminum Chlorofluoride
We report on hydroarylation reactions of arenes with olefins under very mild conditions catalyzed heterogeneously by aluminum chlorofluoride (ACF; AlClxF3?x, x≈0.05–0.25). The reactions of benzene and toluene with ethylene or propylene proceed with high conversions to afford various alkylated arenes. For cyclohexene and 1-hexene, the reactions require higher temperatures and the conversions are lower. ACF also catalyzes the hydroarylation of 1,3,5-trifluorobenzene and pentafluorobenzene with ethylene and propylene. The alkylations of arenes with non-fluorinated olefins resemble typical Friedel–Crafts chemistry to give rise to Markovnikov regioselectivity. The reaction of CF3CH=CH2 with benzene proceeds with anti-Markovnikov regioselectivity to give the fluorinated olefin PhCHCH=CF2 and the alkylation product PhCH2CH2CF3 as products of C?F and C?H activation.
Calvo, Beatriz,Wuttke, Jan,Braun, Thomas,Kemnitz, Erhard
p. 1945 - 1950
(2016/07/06)

Efficient synthesis of sterically hindered arenes bearing acyclic secondary alkyl groups by suzuki-miyaura cross-couplings
Bulky P,P-O ligands were designed to inhibit isomerization and reduction side reactions during the cross coupling between sterically hindered aryl halides and alkylboronic acids. Suzuki-Miyaura cross-couplings between di-ortho-substituted aryl bromides and acyclic secondary alkylboronic acids have been achieved with high yields. The method has also enabled the preparation of ortho-alkoxy di-ortho-substituted arenes bearing isopropyl groups in excellent yields. The utility of the synthetic method has been demonstrated in a late-stage modification of estrone and in the application to a new synthetic route toward gossypol. No side reaction: The shown bulky P,P-O ligands (right) successfully inhibit isomerization and reduction side reactions of the cross-coupling of sterically hindered substrates such as di-ortho-substituted aryl bromides with acyclic secondary alkylboronic acids. The method also allows the preparation of ortho-alkoxy di-ortho-substituted isopropyl arenes in excellent yields.
Li, Chengxi,Chen, Tianyu,Li, Bowen,Xiao, Guolan,Tang, Wenjun
supporting information
p. 3792 - 3796
(2015/03/18)

Reaction routes in catalytic reforming of poly(3-hydroxybutyrate) into renewable hydrocarbon oil
Poly(3-hydroxybutyrate) or PHB is an energy storage material of microbial organisms and can be reformed into hydrocarbon oils rich with aromatic compounds. This work investigated the main reaction routes from PHB to the key intermediates and final hydrocarbons. The main sequential reactions under catalysis of phosphoric acid at moderate temperatures (200-230 °C) consist of: (1) decomposition of PHB into crotonic acid, a major monomeric intermediate, (2) deoxygenation of crotonic acid, and (3) combination of the deoxygenated molecules. The oxygen in PHB is removed as CO2 and H2O in stage (2), involving decarboxylation and ketonization of crotonic acid. The main aromatic compounds are formed in stage (3) from propylene and 2,3-dimethyl-2-cyclopenten-1-one as two key intermediates, the former from decarboxylation and the latter from ketonization of crotonic acid. The reaction routes reveal that the formation of aromatics is affected to a great extent by the concentrations of phosphoric acid and water in the reaction, which can be used to control the composition of hydrocarbon oil.
Kang, Shimin,Yu, Jian
p. 30005 - 30013
(2015/05/13)

Design and performance of supported Lewis acid catalysts derived from metal contaminated biomass for Friedel-Crafts alkylation and acylation
The main goal of this work was to prove the interest of metal hyperaccumulator plants in supported Lewis acid catalysis. Friedel-Crafts alkylation and acylation reveal the great catalytic activity of different plant extracts. This approach is a green solution with chemical benefits including high yield, excellent regioselectivity, small amounts of catalyst, mild conditions and concrete perspectives towards the depletion of mineral resources. The results also constitute an incentive for the development of phytoextraction programs on metal-bearing soils.
Losfeld, Guillaume,Escande, Vincent,Vidal De La Blache, Paul,L'Huillier, Laurent,Grison, Claude
experimental part
p. 111 - 116
(2012/09/08)

Microwave-assisted silica-supported aluminum chloride-catalyzed Friedel-Crafts alkylation
Microwave irradiation is a popular method in organic synthesis to achieve high yields in shorter reaction times. This decreases total 'man-hours' in a synthetic setting. Another technique used in organic chemistry to decrease manual manipulations, is solid support reagents. The benefits of this approach is that upon completion of a reaction, a simple filtration can be performed which expedites the work-up and also produces less organic waste. Friedel-Crafts alkylation has been explored using microwave chemistry as well as with solid-supported reagents. In comparison with traditional heating, as well as with AlCl3, superior yields were observed with silica-gel bound aluminum chloride (Si-AlClx) when microwave irradiated for only 5 min.
Zupp, Laurine R.,Campanella, Veronica L.,Rudzinski, Diandra M.,Beland, Franois,Priefer, Ronny
p. 5343 - 5346
(2012/10/30)

Selective reduction of biomass by hydriodic acid and its in situ regeneration from iodine by metal/hydrogen
HI returns: Hydroiodic acid is a highly selective reducing reagent for a wide variety of substrates. Its application is limited by the formation of iodine and the difficulty in reconverting that iodione back to HI in situ. We report the facile conversion of I2 to HI by metal-catalyzed hydrogenation in the presence of water, and demonstrate the utility of this process in the conversion of fructose to 5-methyfurfural and glycerol to 2-iodopropane. Copyright
Yang, Weiran,Grochowski, Matthew R.,Sen, Ayusman
scheme or table
p. 1218 - 1222
(2012/09/08)

Influence of mesoporous materials containing ZSM-5 on alkylation and cracking reactions
In order to increase the yield of cymene in alkylation of toluene with isopropanol, ZSM-5 zeolite units were incorporated into a mesostructured material. The catalysts were characterized by X-ray diffraction, TGA, SEM, NH3 temperature-programmed desorption and FTIR of pyridine adsorption. XRD analysis indicated that a structurally well ordered cubic MCM-48 aluminosilicate was successfully assembled from ZSM-5 zeolite seeds. The ZSM-5/MCM-48 catalyst exhibited significantly improved toluene conversion and yield of cymene product for toluene isopropylation. Catalytic tests show that the ZSM-5/MCM-48 composite material exhibits high catalytic activity compared with the conventional Y-zeolite for catalytic cracking of 1,3,5- triisopropylbenzene (TIPB). The exceptional catalytic performance of ZSM-5/MCM-48 catalyst in cracking and alkylation reaction was attributed to the easier access of active sites provided by the mesopores for both reactant and larger product molecules. The apparent activation energies for the cracking of 1,3,5-TIPB over ZSM-5/MCM-48 catalyst were found to decrease as follows: E C/CM-3 (tertiary cracking) > E C/CM-4 (disproportionation) > E C/CM-2 (secondary cracking) > E C/CM-1 (primary cracking).
Odedairo,Balasamy,Al-Khattaf
experimental part
p. 21 - 36
(2011/10/05)

Vapor phase alkylation of toluene using various alcohols over H 3PO4/MCM-41 catalyst: Influence of reaction parameters on selectivity and conversion
A mesoporous MCM-41 molecular sieve material with a molar ratio of SiO 2/Al2 O3 = 70 and loaded with H3 PO4 was used as a catalyst for the alkylation of toluene, using various alcohols, namely methanol, iso-propanol, and tert-butanol, as alkylating agents. Para-alkylated toluene was the predominant product, formation of which was enhanced by moderate temperature, low amounts of the alkylating agents in the feed, and high carrier gas flow rate. Time on stream was found to exert a profound effect on the selectivity and conversion to the different products. TUeBITAK.
Abbaspourrad, Alireza,Kalbasi, Roozbeh Javad,Zamani, Farzad
experimental part
p. 875 - 885
(2011/08/06)

Cross-coupling reactions through the intramolecular activation of Alkyl(triorgano)silanes
(Figure Presented) Cross-Si-ing the Jordan: Cross-coupling reactions of 2-(2-hydroxyprop-2-yl)phenylsubstituted alkylsilanes with a variety of aryl halides proceed in the presence of palladium and copper catalysts. The use of K3PO4 base allows for highly chemoselective alkyl coupling with both primary and secondary alkyl groups (Alk).
Nakao, Yoshiaki,Takeda, Masahide,Matsumoto, Takuya,Hiyama, Tamejiro
supporting information; scheme or table
p. 4447 - 4450
(2010/08/19)

Chlorine borrowing: An efficient method for an easier use of alcohols as alkylation agents
Chlorine functionalised tin dioxide nanoparticles proved able to partially convert alcohols into the corresponding chlorides, which act as alkylation agents with an increased electrophilicity, as evidenced on ether formation and Friedel-Crafts reactions.
Makowski, Philippe,Rothe, Regina,Thomas, Arne,Niederberger, Markus,Goettmann, Frederic
scheme or table
p. 34 - 37
(2010/04/22)

Regioselective arene functionalization: Simple substitution of carboxylate by alkyl groups
Arenes with various alkyl side-chains were synthesized in high yields and excellent regioselectivities. Starting from toluic and naphthoic acids, the carboxylate group was conveniently substituted by alkyl halides by Birch reduction and subsequent decarbonylation. The method is characterized by inexpensive starting materials and reagents, and methylation of arenes was realized. Besides simple alkyl substituents, the scope of arene functionalization was extended by benzyl, fluoro, amino, and ester groups. We were able to control the alkylation of 1-naphthoic acid during Birch reduction by the addition of tert-butanol. This allowed the regioselective synthesis of mono and bis-substituted naphthalenes from the same starting material.
Krueger, Tobias,Vorndran, Katja,Linker, Torsten
experimental part
p. 12082 - 12091
(2010/05/17)

Intermolecular hydroarylation of unactivated olefins catalyzed by homogeneous platinum complexes
Designing catalysts: The five-coordinate platinum(IV) complex A and the platinum(II) trans complex B act as precatalysts for the hydroarylation of unactivated olefins. The catalytic cycle features an aryl-olefin insertion at PtII and a C-H bond activation of the arene solvent as key steps. The Pt II cis complex C has been observed in hydroarylation reactions of ethylene with benzene.
Luedtke, Avery T.,Goldberg, Karen I.
supporting information; experimental part
p. 7694 - 7696
(2009/04/11)

Catalytic activity of the VIII group metals in the hydrogenation and isomerization of α- And β-pinenes
The kinetic regularities of the liquid-phase hydrogenation and isomerization of α- and β-pinenes over the Pd/C, Ru/C, Rh/C, Pt/C, and Ir/C catalysts were studied at temperatures ranging from 20 to 100 °C and at hydrogen pressures of 1-11 bar using n-octane as the solvent. The hydrogenation and isomerization of α- and β-pinenes occur simultaneously on the Ru/C, Rh/C, Pt/C, and Ir/C catalysts, and the reaction mixture contains the products of double bond hydrogenation, viz., cis- and trans-pinanes. The Ru, Rh, and Pd metals have a higher catalytic activity in β-pinene isomerization than Ir and Pt. Among the VIII Group metals studied, the Pd-based catalyst has the highest catalytic activity in double bond isomerization of α- and β-pinenes. The general scheme of the mechanism of hydrogenation and isomerization of α- and β-pinenes on the Pd/C catalyst was proposed.
Deliy,Simakova
body text
p. 2056 - 2064
(2010/05/02)

Efficient cross-coupling of secondary alkyltrifluoroborates with aryl chlorides-reaction discovery using parallel microscale experimentation
Microscale parallel experimentation was used to discover three catalyst systems capable of coupling secondary organotrifluoroborates with sterically and electronically demanding aryl chlorides and bromides. The ensuing results represent the first comprehensive study of alkylboron coupling to aryl chlorides and, in particular, using secondary alkylboron partners. A ligand-dependent β-hydride elimination/reinsertion mechanism was implicated in the cross-coupling of more hindered substrates, leading to isomeric mixtures of coupled products in some cases. Copyright
Dreher, Spencer D.,Dormer, Peter G.,Sandrock, Deidre L.,Molander, Gary A.
supporting information; body text
p. 9257 - 9259
(2009/02/02)

Catalytic ring-attachment isomerization and dealkylation of diethylbenzenes over halide clusters of group 5 and group 6 transition metals
A molybdenum halide cluster, (H3O)2[(Mo 6Cl8)Cl6]·6H2O, possessing an octahedral metal framework was used as a catalyst in a gas flow reactor under 1 atm of hydrogen. On reaction of p-diethylbenzene, dehydrogenation to ethylstyrene proceeded selectively at 300°C. At 400°C, mutual interconversion of o-, m-, and p-diethylbenzenes proceeded selectively. The ethyl group migrated by an intramolecular 1,2-shift mechanism without yielding disproportionation products. Niobium and tungsten chloride clusters with the same metal framework were also active catalysts for the isomerization of p-diethylbenzene. All the reactions resulted in appreciable yields of dealkylation products. The catalytic activity for isomerization can be ascribed to acid sites on the cluster surface, and the catalytic activity for dealkylation, to the metallic nature of the framework metal.
Kamiguchi, Satoshi,Kondo, Kunihiko,Kodomari, Mitsuo,Chihara, Teiji
p. 54 - 63
(2007/10/03)

Simple two-step ipso substitution of aromatic carboxylic acids by alkyl halides
Methyl-substituted arenes can be synthesized with high regioselectivity in only two steps through formal exchange of an aromatic carboxylic acid function with an alkyl substituent. The results obtained with toluic acid illustrate that good to very good yields can be obtained from inexpensive reagents (see scheme).
Vorndran, Katja,Linker, Torsten
p. 2489 - 2491
(2007/10/03)

Contributions of enthalpy and entropy factors to isomerization equilibrium of isopropyl- and cyclohexylbenzenes
Experimental and theoretical data on the liquid-phase equilibrium of the positional isomerization of isopropyl- and cyclohexylbenzenes are analyzed in detail. Contributions of the enthalpy and entropy factors to the equilibrium constants of the ortho-meta and para-meta transformations are estimated.
Nesterova,Pimerzin,Krasnykh
p. 1884 - 1890
(2007/10/03)

Thermal degradation of terpenes: Camphene, Δ3-carene, limonene, and α-terpinene
Emissions from wood dryers have been of some concern for a number of years, and recent policy changes by the Environmental Protection Agency have placed emphasis upon the gaseous emissions that lead to the formation of particulate matter as small as 2.5 μm diameter. In this qualitative study, camphene, Δ3-carene, limonene, and α-terpinene were thermally degraded in the presence of air to determine the number and kind of oxidative degradation products that might be expected under drying conditions used in processing wood products. Various chromatographic methods were used to isolate the products for proof of structure by NMR and/or GC-MS. The degradation products resulted from dehydrogenations, epoxidations, double bond cleavages, allylic oxidations, and rearrangements. A number of compounds not previously associated with the thermal degradation of these terpenes were identified. Emissions from wood dryers have been of some concern for a number of years, and recent policy changes by the Environmental Protection Agency have placed emphasis upon the gaseous emissions that lead to the formation of particulate matter as small as 2.5 μm diameter. In this qualitative study, camphene, Δ3-carene, limonene, and α-terpinene were thermally degraded in the presence of air to determine the number and kind of oxidative degradation products that might be expected under drying conditions used in processing wood products. Various chromatographic methods were used to isolate the products for proof of structure by NMR and/or GC-MS. The degradation products resulted from dehydrogenations, epoxidations, double bond cleavages, allylic oxidations, and rearrangements. A number of compounds not previously associated with the thermal degradation of these terpenes were identified.
Mcgraw, Gerald W.,Hemingway, Richard W.,Ingram Jr., Leonard L.,Canady, Catherine S.,Mcgraw, William B.
p. 4029 - 4033
(2007/10/03)

Indium trichloride catalyzed reductive Friedel-Crafts alkylation of aromatics using carbonyl compounds
Reductive Friedel-Crafts alkylation of aromatics with aldehydes or ketones using chlorodimethylsilane as a hydride source was effectively promoted by a catalytic amount of indium trichloride, whereas a popular type of Friedel-Crafts catalysts showed less effect.
Miyai, Takashi,Onishi, Yoshiyuki,Baba, Akio
p. 6291 - 6294
(2007/10/03)

Regio- und diastereoselektive Photooxygenierung chiraler 2,5-Cyclohexadien-1-carbonsaeuren
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Linker, Torsten,Froehlich, Lothar
p. 2064 - 2066
(2007/10/02)

Nitration of Isopropylpyrenes. Strained Models for Protonation and Transfer-Nitration in the Condensed Phase
Protic mono- and dinitration of 1,3,5,7,9-pentaisopropylpyrene (1) occurred at the available α positions to give 2 and 3.Despite steric crowding, 2 and 3 did not exhibit a torsional barrier to i-Pr rotation at ambient temperatures; however, buttressing of the peri i-Pr groups was evident (1H NMR, UV, and force field energy minimizations).Persistent (dihydroxyiminium)pyrenium dications 2a+2 and 3a+2 were formed by low temperature protonation of 2 and 3 with CF3SO3H (TfOH)/SO2 or with FSO3H/SO2.Intramolecular cyclization of the nitro group of 2a+2 gave the rearranged pyrenium ion 2c+. 1 reacted with NO2+BF4- in acetonitrile solvent to give two pyrenium ions stable at rt, viz. the Wheland intermediate of α-nitration 2b+2 and the (dihydroxyiminium)pyrenium dication 2a+2; the latter was also the predominant pyrenium ion formed in the reaction of 1 with NO+BF4- in acetonitrile.Reaction of 1 with NO2+BF4- in chloroform solvent gave α-nitration products and a persistent radical cation RC.The simultaneous presence of α-nitration products and a persistent pyrenium RC was also observed in the reaction of 1 with NO+BF4- in chloroform, where broader NMR line widths and a stronger ESR signal suggested more extensive oxidation.Protic and aprotic nitrations of 1,3,6,8-tetraisopropylpyrene (10) occurred at the αβ positions; a minor addition product (26) was also found.A mixture of isomeric dinitropyrenes was obtained in NO2+ nitration of 1-isopropylpyrene (13).In line with low temperature protonation studies, aprotic nitrations of 2-isopropyl- and 4-isopropylpyrenes occurred predominantly at the α positions.The crowded pyrenium ion of 3 and 2 transfer nitrate to aromatics (toluene, mesitylene, benzene) under mild conditions in competition with a more facile transalkylation.
Laali, Kenneth Khosrow,Liang, Tze-Ming,Hansen, Poul Erik
p. 2658 - 2667
(2007/10/02)

A Comparative Study on the Acidic Properties and Catalytic Activities of TiO2, SiO2, Al2O3, SiO2-Al2O3, SiO2-TiO2, Al2O3-TiO2, and TiO2-SiO2-Al2O3
Investigations are carried out to have a systematic comparison of the acidic properties and catalytic activities of single oxide TiO2, SiO2, Al2O3, their binary oxides and the ternary oxide TiO2-SiO2-Al2O3.The acidity distributions are measured by using butylamine titration technique and the test reactions selected for the catalytic activity measurements are alkylation of toluene with 2-propanol and the dehydration of 2-propanol.The single oxides have only low acid strength and are not at all active in catalyzing the alkylation reaction, but are marginally active in the dehydration of 2-propanol.However the binary oxides SiO2-TiO2 and Al2O3-TiO2 of 10percent by weight of TiO2 are found to contain very strong sites H0 = -8.2 and are highly active catalysts in both the test reactions.But TiO2-SiO2-Al2O3 of 10percent by weight TiO2 showed the highest acid amount and the highest activity in the alkylation and dehydration reactions compared to the binary oxides.The acid amount and the catalytic activity of the ternary oxide increased with the increase of TiO2 content upto 50 molpercent of TiO2 and then decreased.The ternary oxide containing 80 molpercent of TiO2 is rich in weak acid sites.The increase of TiO2 content does not affect the selectivity.
Sabu, Kuzhunellil Raghavan Pillai,Rao, Kalur Vijayachandra C.
p. 1920 - 1925
(2007/10/02)

Diverse photochemistry of sterically congested α-arylacetophenones: ground-state conformational control of reactivity
The effects of α and ortho substituents on the photoreactivity of various α-(o-tolyl)- and α-mesitylacetophenones have been measured. In general, both types of substitution lower the efficiency of cyclization to 2-indanol derivatives in solution. 1,3-Rearrangement of an α-mesityl group to group to form enol ethers and α-cleavage to radicals compete to various degrees, in some cases becoming dominant. Quenching studies in solution show that all three reactions occur from the same n,π* triplet state; α-substitution lowers rate constants for δ-hydrogen abstraction and increases those for α-cleavage and 1,3-rearrangement. X-ray crystal analysis and MMX calculations both show that any additional substitution at the α-carbon of α-aryl (phenyl, tolyl, or mesityl) ketones favors conformers in which the α-aryl group have rotated 120° away from eclipsing the carbonyl. In agreement with this, α-phenyl and α-(o-tolyl) ketones undergo γ-hydrogen abstraction (Norrish type II reaction) with rate constants almost as large as those of the nonarylated ketones. NMR line-broadening studies show that, in most of the α-mesityl ketones, the rate constants for rotation around the mesityl-α-carbon bond (104-106 s-1) are much slower than triplet decay. The same is true for rotations around the carbonyl-α-carbon bond in the α-arylisobutyrophenones. Considered of the spectroscopic evidence, triplet lifetimes, and calculated rotational barriers indicates that ground-state conformational preferences determine which excited-state reactions can occur in most of these ketones. Many of the ketones that cyclize in low yield in solution do so in much higher yield when irradiated as solids, presumably because α-cleavage to radicals becomes mostly revertible. The solid-state reactivity demonstrates that hydrogen abstraction can occur from what are supposedly nonideal geometries; in particular, large values (60-70°) for the dihedral angle and rate constants for hydrogen abstraction in solution plane of the carbonyl π system. The relationship between this angle and rate constants for hydrogen abstraction in solution is discussed. Rate constants for α-cleavage reveal the separate influences of steric congestion and conjugation of the developing benzyl radicals. The 1,3-aryl migration to oxygen appears to arise from initial CT complexation of the α-aryl to the carbonyl; subsequent bonding of oxygen to the benzene ring apparently relieves steric congestion. The 50:50 initial mixture of Z and E enol ethers suggests that the rearrangement is adiabatic, generating enol ether in its twisted triplet state. A large enhancement of indanol yields by alcoholic solvents is suggested to involve protonation of the same CT complex.
Wagner, Peter J.,Zhou, Boli,Hasegawa, Tadashi,Ward, Donald L.
p. 9640 - 9654
(2007/10/02)

Mechanism of the Cyclopropane "Walk" Rearrangement: Syntheses and Properties of 2-Diazopropane-Arene Adducts; a Regiospecific N2 Elimination
The synthesis and the thermal and photochemical behavior of 2-diazopropane adducts of toluene 1a, m-xylene 1b,c, and Dewar benzene 2a,b are reported.At 60 deg C the thermal N2 elimination of the specifically deuterated compound 1c proceeds regiospecifically leading to 1,7,7-trimethyl-5-(trideuteriomethyl)-1,3,5-cycloheptatriene (12c), whereas the photolysis of 1c sensitized by benzophenone yields both regioisomeric cycloheptatrienes 12c and 13c in a 51:49 ratio.This finding excludes the symmetrical diradical 3c as an intermediate in the thermal N2 elimination of 1c and suggests a novel pericyclic process for it.The formation of both regioisomeric cycloheptatrienes 25b and 25c in a 74:26 ratio in the thermolysis of the diazopropane-tetradeuterio Dewar benzene adduct 2b indicates that in this case a multi-step N2 elimination passing through the diradical intermediate 3e competes with the concerted process.According to force-field calculations the course of the N2 elimination in 1a-e might be controlled by the conformational equilibrium A B.
Klaerner, Frank-Gerrit,Glock, Volker,Hemmes, Jan-Luiken
p. 1869 - 1879
(2007/10/02)

A comparative study of gas phase aromatic desilylation and detertbutylation by charged electrophiles
Aromatic desilylation and detertbutylation by CH5+, C2H5+, i-C3H7+, and t-C4H9+ ions have been studied in the gas phase by mass spectrometric and radiolytic techniques.The higher rate of desilylation than of dealkylation in traced to the step involving the formation of ipso arenium ions, protonated at the ring carbon bearing the SiMe3 or the CMe3 substituent.The latter has been shown by ab initio calculations at the SCFSTO-3G level to selectively depress the basicity of the ipso position, hence the stability of the corresponding arenium ion relative to its protomers, e.g. the basicity of the ipso position of PhCMe3 is lower by ca. 11 kcal mol-1 than of the para position.The SiMe3 group has no comparable effect, very close basicities being computed for the para and the ipso position of PhSiMe3.The different effects of the CMe3 and SiMe3 groups are traced to electronic and steric factors.
Cacace, Fulvio,Crestoni, M. Elisa,Petris, Giulia De,Fornarini, Simonetta,Grandinetti, Felice
p. 3099 - 3107
(2007/10/02)

BORON, ALUMINUM, AND GALLIUM TRIS(TRIFLUOROMETHANESULFONATE) (TRIFLATE): EFFECTIVE NEW FRIEDEL-CRAFTS CATALYSTS.
Boron, aluminum, and gallium tris(trifluoromethanesulfonate) (triflate) were prepared from the corresponding chlorides (bromides) and triflic acid. The group IIIA triflates were isolated in pure form and fully characterized (elemental analysis, molecular weight, and NMR and IR spectroscopy). Boron tris(triflate) is a monomeric, relatively volatile compound left bracket mp 43-45 degree C, bp 68-73 degree C (0. 5 Torr) right bracket , whereas aluminum and gallium triflate are associated, high-melting associated solids. Boron, aluminum, and gallium tris(triflate) are efficient new Friedel-Crafts catalysts as shown in alkylation, isomerization, and acylation reactions. Alkylation of benzene and toluene with methyl, ethyl, isopropyl, and tert-butyl halides (fluoride, chloride, and bromide) were carried out with boron, aluminum, and gallium tris(triflate) as catalyst in CH//2Cl//2 and CH//3NO//2 solvent at room temperature.
Olah,Farooq,Morteza,Farnia,Olah
p. 2560 - 2565
(2007/10/02)

Competitive concerted and stepwise addition of free arylium ions to propane in the gas phase
Labelled tolylium ions from the decay of ring-multitritiated toluene have been allowed to react with propane in the gas phase, at pressures ranging from 20 to 744 Torr, yielding isomeric propyltoluenes as the major addition products. The relative composition of the n- versus iso-propyltoluenes (σp:σs 3.2-4.7) is found to depend appreciably upon the total pressure of the system and the presence of added bases (NH 3 or CH3OH). Pressure and base effects on the isomeric distribution of both n- and iso-propyltoluenes are also investigated. The results are consistent with a reaction pattern involving preliminary formation of an electrostatic adduct, wherein fast hydride-ion transfer from a secondary C-H bond of C3H8 to the arylium ion takes place. The same mechanism does not seem operative when the first interaction occurs between the tolylium ions and a primary C-H bond of the substrate. The behaviour of isomeric tolylium ions towards propane is discussed and compared with related studies involving unsubstituted phenylium ions. A mechanistic model is proposed for both reactions, which accounts for the apparent discrepancy between the indiscriminate affinity of arylium ions for any kind of substrate and their 'abnormally' high site selectivities.
Angelini, Giancarlo,Sparapani, Cinzia,Speranza, Maurizio
p. 1393 - 1400
(2007/10/02)

ORIENTATION IN METHYLATION AND PHENYLATION OF ALKYLBENZENES BY CATIONS GENERATED BY THE NUCLEAR CHEMICAL METHOD
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Sinotova, E. N.,Krylov, E. N.
p. 1042 - 1049
(2007/10/02)

Kinetics and Regioselectivity of the Autoxidation of o-Substituted Isopropyl Aromatics
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
p. 439 - 446
(2007/10/02)

STUDIES OF COMPOUNDS IN THE MENTHANE SERIES. XIX. SYNTHESIS AND PROPERTIES OF TRANS-o-4-MENTHEN-8-OL AND STEREOISOMERIC o-5-METHEN-8-OLS
Trans-o-4-Menthen-8-ol and cis- and trans-o-5-menthen-8-ols have been prepared via the Diels-Alder reactions of 1,3-butadiene with crotonaldehyde in the presence of boron trifluoride etherate, and piperylene with methyl acrylate, respectively.The dehydration reactions of these alcohols have been studied in the presence of acetic anhydride and potassium bisulfate; the latter reagent demonstrates a high reaction selectivity.
Bazyl'chik, V. V.,Fedorov, P. I.,Klyuev, N. A.,Dank, E. Kh.
p. 1320 - 1327
(2007/10/02)

STUDIES OF COMPOUNDS IN THE MENTHANE SERIES. XVIII. VAPOR PHASE ISOMERIZATION OF o-1,4-MENTHADIENE IN THE PRESENCE OF DIATOMACEOUS EARTH
Vapor phase isomerization of o-1,4-menthadiene in the presence of diatomaceous earth results in deprotonation of the 1,2 and 4,5 positions to give an equilibrium mixture of o-menthadienes containing both endo- and exocyclic double bonds; the skeletal rearrangement products, 2-isopropyl-3-ethylidene-1-cyclopentene and 4-isopropyl-3-ethylidene-1-cyclopentene, are also formed. o-Menthadienes also undergo dehydrogenation to give o-cumene, and disproportionation to give a mixture of o-cumene and o-menthenes.The dehydrogenation process predominates as the temperature is increased.
Bazyl'chik, V.V.,Fedorov, P.I.,Skakovskii, E.D.,Klyuev, N.A.
p. 1316 - 1319
(2007/10/02)

Preparation, Pyrolysis, and Photolysis of Three Sterically Crowded Alkenes, 3,3,3',3',5,5,5',5'-Octamethyl-3,3',5,5'-tetrahydro-4,4'-bi(4H-pyrazolylidene) 2,2,4,4-Tetramethyl-3-(3,3,5,5-tetramethyl-3,5-dihydro-4H-pyrazol-4-ylidene)-thietane 1,1-Dioxide and 2,2,2',2',4,4,4',4'-Octameth...
Photolysis and pyrolysis of the title compounds involve a stepwise elimination of nitrogen and/or sulphur dioxide and reactions which can be interpreted in terms of a series of trimethylenemethane (TMM) biradical intermediates.However, the photosensitised photolysis of the bi(pyrazolylidene) (11) give products indicative of an elimination of both nitrogens and the generation of a tetramethylene-ethane (TME) biradical intermediate.New synthesis of a number of highly sterically crowded alkenes including 2,2,4,4-tetramethyl-3-(3,3,5,5-tetramethyl-3,4-dihydro-4H-pyrazol-4-ylidene)thietane 1,1-dioxide (12) and 2,2,2',2',4,4,4',4'-octamethyl-3,3'-bithietanylidene 1,1,1',1'-tetraoxide (13), are described.Flash vacuum pyrolysis (f.v.p) of 3,3,3',3',5,5,5',5'-octamethyl-3,3'-5,5'-tetrahydro-4,4'-bi(4H-pyrazolylidene) (11) at 400 deg C gives 3,3,5,5-tetramethyl-4-(2,2,3,3-tetramethylcyclopropylidene)-3,5-dihydro-4H-pyrazole (21), at ca. 400 deg C 1-isopropylidene-2,2,4,4,5,5-hexamethylspiropentane (22), and at ca. 580 deg C a ca. 5:1 mixture of 4-isopropyl-3-isopropylidene-2,5-dimethylhexa-1,4-diene (23) and 2-(2,3-dimethylbut-1-en-3-yl)-1-isopropyl-3,3-dimethylcyclopropene (27).Above 700 deg C a complex mixture of aromatic products and low molecular weight hydrocarbons is produced which includes ethane, ethylene, propene, isobutane, and isobutene, p-xylene, o-cumene and probably m-cumene, and 2,5-dimethylisopropylbenzene.F.v.p. of the dihydropyrazole sulphone (12) gives initially 2,2,4,4-tetramethyl-3-(2,2,3,3,-tetramethylcyclopropylidene)thietane 1,1-dioxide (41) and at higher temperatures similar mixtures to those obtained from the bipyrazolylidene (11).Similar results were also obtained for the f.v.p. of the bis-sulphone (13).Photolysis of the bipyrazolylidene (11) gave initially the dihydropyrazole (21) and then a 48:52 mixture of the spiro compound (22) and 2,2,2',2',3,3,3',3'-octamethylbicyclopropylidene (42).Photolysis of the dihydropyrazole sulphone (12) gave 2,2,4,4-tetramethyl-3-(2,2,3,3-tetramethylcyclopropylidene)thietane 1,1-dioxide (41).Benzophenone-sensitised photolysis of the bipyrazolylidene (11) gave 1,2-di-isopropylidene-3,3,4,4-tetramethylcyclobutane (32).
Bushby, Richard J.,Mann, Stephen,Jesudason, Malini, V.
p. 2457 - 2464
(2007/10/02)

FRIEDEL-CRAFTS ALKYLATION OF ANISOLE AND ITS COMPARISON WITH TOLUENE. PREDOMINANT ORTHO-PARA SUBSTITUTION UNDER KINETIC CONDITIONS AND THE EFFECT OF THERMODYNAMIC ISOMERIZATIONS
The AlCl3 and BF3, as well as 65percent HPF6, catalyzed Friedel-Crafts alkylation of anisole with alkyl halides and alkohols was investigated.The alkylation of anisole with lower catalyst concentrations under mild conditions shows predominant ortho/para directing effect generally with a ratio of c.a. 2:1, with the amount of meta isomer uniformly less than 3percent.With "swamping" catalyst conditions the amount of meta substitution in methylation and ethylation can substantially increase.The isomer distribution in tert-butylation changes with time due to rapid ortho-para interconversion.Consequently, the AlCl3-catalyzed isomerization of isomeric alkylanisoles was also studied.In case of tert-butylanisoles, the ortho isomer shows relatively rapid conversion into para followed by much slower isomerization to meta.The para and meta isomers show isomerization to meta-para mixtures.Isomerization of ethyl-, isopropyl-, and benzylanisoles is generally slow whereas methylanisoles do not isomerize.Comparing results of the alkylation of anisole with toluene leads to the conclusion that the latter are readily affected by concurrent (and in some cases consecutive) isomerization.As the barrier for isomerization in the benzenium ion intermediates of the alkylations is higher in the case of CH3O- than CH3-substituted systems, anisole tends to give the kinetically controlled ortho-para alkylation products and the amount of meta isomer is low.Study of alkylation of 3,5-di- and 2,4,6-trideuterated toluene and anisole and comparing retained deuterium contents with isomer distributions shows that alkylated product formation in case of toluene, but not of anisole, is proceeded by intramolecular, 1,2-alkyl, and hydrogen-deuterium shifting resulting also in increased meta substitution.This effect is most predominant in methylation and ethylation where the alkyl shifts are intramolecular but not in tert-butylation and benzylation, where alkyl transfer is intermolecular.Isopropylation is intermediate in nature.No simple selectivity-reactivity relationship is indicated in the studied alkylation reactions.As shown in benzylations with increasingly electron-donating and -withdrawing substituted benzyl chlorides overall rate (i.e., substrate selectivity) and isomer distributions (i.e., regioselectivity) are not determined in the same step as significantly decreased substrate selectivity is not accompanied by loss of positional selectivity.Previously reported alkylations showing high degree of meta substitution therefore, must have been affected by thermodynamically controlled rearrangement processes, including intramolecular alkyl and hydrogen shifts in the arenium ion intermediates of the alkylation reactions.These are to be differentiated from possible subsequent product isomerizations.Under predominantly kinetic conditions anisole as well as toluene are substantially ortho-para directing in alkylations, as in other electrophilic aromatic substitutions.
Olah, George A.,Olah, Judith A.,Ohyama, Toshiyuki
p. 5284 - 5290
(2007/10/02)

INVESTIGATION OF COMPOUNDS OF THE MENTHANE SERIES. XVI. REDUCTION OF o- AND p-ISOPROPENYLTOLUENES WITH CALCIUM HEXAAMMONIATE
In the reduction of o- and p-isopropenyltoluenes with calcium hexaammoniate in the presence of protic and aprotic solvents 1,2-addition of hydrogen mostly occurs with the formation of o- and p-cymenes and o- and p-menthatrienes, which under the reaction conditions give the products from 1,2- and 1,4-addition of hydrogen.
Bazyl'chik, V. V.
p. 1847 - 1851
(2007/10/02)

GAS PHASE ISOPROPYLATION OF AROMATIC HYDROCARBONS. FLUORINE AND METHYL SUBSTITUENT EFFECTS ON REACTIVITY AND ORIENTATION.
The isopropylation of substituted benzenes by s-C3H7+ cations is studied to evaluate the directive effects of fluorine, methyl group and their combinations as ring substituents in the gas-phase aromatic substitution.
Attina, Marina,Petris, Giulia de,Giacomello, Pierluigi
p. 3525 - 3528
(2007/10/02)

INVESTIGATION OF COMPOUNDS IN THE o-MENTHANE SERIES XI. ISOMERIZATION TRANSFORMATIONS OF o-1,4-MENTHADIENES
Under the conditions of base catalysis under the influence of potassium tert-butoxide in dimethyl sulfoxide and lithium and calcium amides o-1,4-menthadiene forms equilibrium mixtures of o-1,3-menthadiene, o-1,5-menthadiene, and the skeletal rearrangement product 1-isopropyl-5-ethylidenecyclopentene.In the presence of NaX and KX zeolites competing dehydrogenation and disproportionation of the hydrogen occur in o-1,4-menthadiene with the formation of a mixture of o-menthenes and o-cymene.With increase in temperature the dehydration process becomes determining.With acid catalysis the transformation of o-1,4-menthadiene into 1-isopropyl-5-ethylidenecyclopentene and dehydration to o-cymene are the mainpaths.
Bazyl'chik, V. V.,Fedorov, P. I.
p. 1221 - 1227
(2007/10/02)

Electrophilic aromatic substitution. Part 24. The nitration of isopropylbenzene, 2- and 4-isopropyltoluene, 1-chloro-4-isopropylbenzene, 4-isopropylanisole, and 2-bromotoluene: Nitrodeisopropylation
The kinetics and products of nitration in aqueous sulphuric acid of the title compounds have been studied. 4-Isopropyl-phenol and -anisole are nitrated at or near the encounter rate. In 65-79% H2SO4 2-isopropyltoluene suffers ca. 25% ipso-attack; the only fate of W iPri (ipso-Wheland intermediate) is nitrodeisopropylation. From 4-isopropyltoluene WiPri is also nitrodeisopropylated, but some 1,2-nitro-migration may occur. From the same compound WiMe may be captured by water, rearrange, or give 4-methylacetophenone; a mechanism is proposed for the formation of the last compound. Nitrodeisopropylation occurs without the assistance of water. With 4-isopropylanisole, demethoxylation and nitrodeisopropylation are consequences of the formation of WiPri. The results are consistent with increasing attack at C-4 with increasing acidity, loss of isopropyl without assistance from water, and decomposition of the unobserved intermediate, 4-isopropyl-4-nitrocyclohexa-2,5-dienone, by two processes. One, acid-catalysed process gives 4-nitrophenol and possibly 4-isopropyl-2-nitrophenol. The other, probably radical, process gives 4-isopropyl-2-nitrophenol. In contrast to 4-bromotoluene, 2-bromotoluene is not nitrodebrominated.
Manglik, Ajay K.,Moodie, Roy B.,Schofield, Kenneth,Tobin, Geoffrey D.,Coombes, Robert G.,Hadjigeorgiou, Panicos
p. 1606 - 1616
(2007/10/02)