- Catalysis by 12-Heteropolymolybdic Acid. II. Friedel-Crafts-type Reaction of Aromatic Compounds
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12-Heteropolymolybdic acid, a heteropolyacid of Keggin-structure, behaves as an effective catalyst of the Friedel-Crafts-type reactions for aromatic compounds, such as alkylation by benzyl chloride and t-butyl chloride, acylation by acetyl chloride, and sulfonylation by tosyl chloride.The catalyst mainly gives para-substiuted products for phenol and anisole.The reactions proceed via carbocation-generation mechanism brought about by the strong Broensted acid.
- Nomiya, Kenji,Sugaya, Yoshio,Sasa, Sadayoshi,Miwa, Makoto
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Read Online
- S,O-Ligand-Promoted Pd-Catalyzed C?H Olefination of Anisole Derivatives
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The C?H olefination of substituted anisole derivatives by a Pd/S,O-ligand catalyst is reported. The reaction proceeds under mild conditions with a broad range of substituted aryl ethers bearing both electron donating and withdrawing substituents at ortho,
- Fernández-Ibá?ez, M. ángeles,Jia, Wen-Liang,Sukowski, Verena,van Borselen, Manuela,van Diest, Rianne
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supporting information
p. 4132 - 4135
(2021/08/24)
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- An N-heterocyclic carbene-based nickel catalyst for the Kumada–Tamao–Corriu coupling of aryl bromides and tertiary alkyl Grignard reagents
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In this study, nickel-catalyzed coupling reactions between arylhalides and tert-alkyl Grignard reagents were developed. Our original bicyclic NHC ligands reduced the formation of isomerized products, and we found that NMP as a co-solvent suppressed the reduction process. Under the optimal conditions we developed, the catalyst loading was lowered to 0.5?mol?%, and catalyst loading using ortho-substituted aryl bromides was also applicable at the level of 2.0?mol?%.
- Ando, Shin,Mawatari, Mai,Matsunaga, Hirofumi,Ishizuka, Tadao
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supporting information
p. 3287 - 3290
(2016/07/11)
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- Palladium-Catalyzed, tert-Butyllithium-Mediated Dimerization of Aryl Halides and Its Application in the Atropselective Total Synthesis of Mastigophorene A
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A palladium-catalyzed direct synthesis of symmetric biaryl compounds from aryl halides in the presence of tBuLi is described. In situ lithium-halogen exchange generates the corresponding aryl lithium reagent, which undergoes a homocoupling reaction with a second molecule of the aryl halide in the presence of the palladium catalyst (1 mol %). The reaction takes place at room temperature, is fast (1 h), and affords the corresponding biaryl compounds in good to excellent yields. The application of the method is demonstrated in an efficient asymmetric total synthesis of mastigophorene A. The chiral biaryl axis is constructed with an atropselectivity of 9:1 owing to catalyst-induced remote point-to-axial chirality transfer. It takes two: A palladium-catalyzed direct homocoupling of aryl halides in the presence of tBuLi enabled the synthesis of even tetra-ortho-substituted symmetric biaryl compounds in high yield (see scheme). The method was applied to the asymmetric synthesis of mastigophorene A in just eight steps through straightforward enantioselective installation of the benzylic quaternary stereocenter and highly diastereoselective homocoupling.
- Buter, Jeffrey,Heijnen, Dorus,Vila, Carlos,Hornillos, Valentín,Otten, Edwin,Giannerini, Massimo,Minnaard, Adriaan J.,Feringa, Ben L.
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supporting information
p. 3620 - 3624
(2016/03/23)
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- NOVEL AND SPECIFIC INHIBITORS OF CYTOCHROME P450 26 RETINOIC ACID HYDROLASE
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The present disclosure is generally directed to compositions and methods for treating diseases that are ameliorated by the inhibition of CYP26 mediated retinoic acid metabolism.
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Page/Page column 58; 59
(2015/03/13)
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- Phase-transfer and other types of catalysis with cyclopropenium ions
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Abstract This work establishes the cyclopropenium ion as a viable platform for efficient phase-transfer catalysis of a diverse range of organic transformations. The amenability of these catalysts to large-scale synthesis and structural modification is demonstrated. Evaluation of the molecular structure of an optimal catalyst reveals some unique structural features of these systems. Finally, a discussion of electronic charge distribution underscores an important consideration for catalyst design. Aromatic ions: Tris(dialkylamino)cyclopropenium ions are shown to be effective carbocationic phase-transfer catalysts for a variety of mainstay transformations. The cyclopropenium platform is shown to be modular and accessible on scale. An X-ray structure and electron-density map revealed some unique features of this architecture (see scheme).
- Bandar, Jeffrey S.,Tanaset, Anont,Lambert, Tristan H.
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supporting information
p. 7365 - 7368
(2015/05/13)
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- New catalyst system for producing polyethylene copolymers in a high temperature solution polymerization process
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Catalyst system for producing ethylene copolymers in a high temperature solution process, the catalyst system comprising (i) a metallocene complex of formula (I) wherein M is Hf or Zr X is a sigma ligand L is a bridge of the formula -SiR72
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- Bridged metallocene catalysts
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A solid, particulate catalyst comprising: (i) a complex of formula (I) wherein M is zirconium or hafnium; each X is a sigma ligand; L is a divalent bridge selected from —R′2C—, —R′2C—CR′2—, —R′2Si—, —R′2Si—SiR′2—, —R′2Ge—, wherein each R′ is independently a hydrogen atom, C1-C20-hydrocarbyl, tri(C1-C20-alkyl)silyl, C6-C20-aryl, C7-C20-arylalkyl or C7-C20-alkylaryl; each R1 is a C4-C20 hydrocarbyl radical branched at the β-atom to the cyclopentadienyl ring, optionally containing one or more heteroatoms belonging to groups 14-16, or is a C3-C20 hydrocarbyl radical branched at the β-atom to the cyclopentadienyl ring where the β-atom is an Si-atom; each R18 is a C1-C20 hydrocarbyl radical optionally containing one or more heteroatoms belonging to groups 14-16; each R4 is a hydrogen atom or a C1-6-hydrocarbyl radical; each W is a 5 or 6 membered aryl or heteroaryl ring wherein each atom of said ring is optionally substituted with at least one R5 group; each R5 is the same or different and is a C1-C20 hydrocarbyl radical optionally containing one or more heteroatoms belonging to groups 14-16; and optionally two adjacent R5 groups taken together can form a further mono or multicyclic ring condensed to W optionally substituted by one or two groups R5; and each R7 is a C1-C20 hydrocarbyl radical; and (ii) a cocatalyst, preferably comprising an organometallic compound of a Group 13 metal.
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(2015/07/22)
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- Indium(III) triflate - A catalyst for greener aromatic alkylation reactions
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An environmentally friendly method for alkylating aromatic compounds with simple alcohols in the presence of a catalytic amount of indium(III) triflate is reported. Ionic liquids are used as solvents and energy-efficient heating is provided by microwave radiation. Good yields are obtained with benzyl, secondary, and tertiary alcohols. Simple primary alcohols are not effective alkylating agents under these conditions. With tertiary alcohols, activated aromatic compounds such as toluene and anisole must be used to obtain good yields. The catalyst, which is immobilized in a water-insoluble ionic liquid, can be easily recycled without significant loss of activity.
- Mack, Ryan,Askins, Grant,Lowry, Jacob,Hurley, Nathan,Reeves, Perry C.
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p. 1262 - 1265
(2014/01/06)
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- Properties and reactivity of zinc-folded sheet mesoporous materials
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Mesoporous material incorporating zinc with different Si/Zn ratios = 95, 65, and 20 have been synthesized by intercalating kanemite using cetyltrimethylammonium bromide as the intercalating agent and zinc nitrate. The resulting materials were characterized by different techniques such as: inductively coupled plasma technique, XRD, Brunauer-Emmett-Teller, and a temperature-programmed-desorption of pyridine. The catalytic performance was studied in the vapor phase tert-butylation of anisole with tert-butanol at different temperatures under atmospheric pressure. The results indicate that Zn-FSM-16 (20) was found to be more active than its relatives. The major products are found to be 4-tert-butyl anisole (4-TBA), 2-tert-butyl anisole (2-TBA) and 2,4 di-tert-butyl-anisole (2,4-DTBA).
- Laribi,Chenouf,Bachari,Hamani
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p. 1771 - 1780
(2013/07/05)
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- Synthesis and stereochemical properties of "extended" biphenols bridged by ortho-, meta-, and para-phenylene spacers
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A series of isomeric biphenols based on para- (1), meta- (2), and ortho- (3) terphenyl backbones was synthesized. Suzuki cross-coupling methodology was employed for the construction of the terphenyl backbone of their methyl-protected precursors (respectiv
- Gruza, Mariusz M.,Chambron, Jean-Claude,Espinosa, Enrique,Aubert, Emmanuel
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experimental part
p. 6318 - 6327
(2011/02/28)
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- BICYCLIC COMPOUNDS USEFUL AS CATHEPSIN S INBHIBITORS
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Compounds of formula (I), wherein R1, R2, R3, Ra and E are are defined within, and pharmaceutically acceptable salts, solvates, hydrates and N-oxides thereof having utility in the treatment of disorders mediated by cathepsin S.
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(2010/11/29)
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- METALLOCENE COMPOUNDS
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A bridged metallocene compound of formula (I) wherein: M is a transition metal; X, is a hydrogen atom, a halogen atom, or a hydrocarbon group optionally containing heteroatoms; L is a divalent bridging group; R1 is a linear C1-C
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Page/Page column 30
(2008/06/13)
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- Contra-Friedel-Crafts tert-butylation of substituted aromatic rings via directed metallation and sulfinylation
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Directed metallation and sulfinylation yields sulfoxides which undergo ipso nucleophilic aromatic substitution with tertiary and secondary alkyllithiums, giving aromatic rings bearing alkyl groups generally incompatible with directed metallation methods and with regioselectivity complementary with classical Friedel-Crafts substitution. The Royal Society of Chemistry 2006.
- Clayden, Jonathan,Stimson, Christopher C.,Keenan, Martine
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p. 1393 - 1394
(2008/02/03)
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- CATHEPSIN S INHIBITORS
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Compounds of the formula (I) where R1 is C1-C4 straight or branched alkyl, optionally substituted with up to three substituents selected from halo and hydroxy; R2 is halo, hydroxy, methyloxy, or C1-C2 alkyl, which alkyl is optionally substituted with up to three halogens or an hydroxy or a methyloxy; D is - C3-C7 alkylene-, thereby defining a cycloalkyl ring; E is -C(=O)-, -S(=O)m-, -NRdS(=O)m-, -NRaC(=O)-, -OC(=O)-, R3 is an optionally substituted carbocyclic or heterocyclic ring R10 is H, ORc, SRc or together with the gem H is =O or (ORc)2; Ra is independently selected from H, C1-C4 alkyl; have utility in the inhibition of cathepsin S and are thus useful pharmaceuticals against disorders such as autoimmune disorders and chronic pain.
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Page/Page column 92-93
(2010/11/08)
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- Heterocyclic derivatives for the treatment of cancer and other proliferative diseases
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The invention relates to certain heterocyclic compounds useful for the treatment of cancer and other diseases, having the Formula (I): wherein: (a) m is an integer 0 or 1; (b) R12 is an alkyl, a substituted alkyl, a cycloalkyl, a substituted cycloalkyl, a heterocyclic, a substituted heterocyclic, a heteroaryl, a substituted heteroaryl, an aryl or a substituted aryl residue; (c) Ar3 is an aryl, a substituted aryl, a heteroaryl or a substituted heteroaryl residue; (d) Ar4 is an aryl, a substituted aryl, a heteroaryl or a substituted heteroaryl residue; (e) R5 is hydrogen, hydroxy, alkyl or substituted alkyl; (f) - - - - - represents a bond present or absent; and (g) W, X, Y and Z are independently or together C(O)—, C(S), S, O, or NH; or a pharmaceutically acceptable salt thereof.
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- Electrophilic Aromatic Alkylation by Hydroperoxides. Competition between Ionic and Radical Mechanisms with Phenols
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Tertiary hydroperoxides have been utilized for the electrophilic alkylation of activated aromatic substrates, particularly phenols and phenol ethers. Cumyl (1) and tert-butyl (2) hydroperoxides have shown a greatly different behavior as concerns the catalysis and the regioselectivity. The best catalyst for 1 is TiCl4, which is completely inactive with 2. With the latter an effective catalyst is FeCl3, which, however, can give rise to a combination of electrophilic and radical reactions with alkyl phenols. 2,2′-Dihydroxy-3,3′-di-tert-butyl-5,5′-dimethyldiphenyl is obtained in high yields from p-cresol.
- Liguori, Lucia,Bjorsvik, Hans-Rene,Fontana, Francesca,Bosco, Dino,Galimberti, Laura,Minisci, Francesco
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p. 8812 - 8815
(2007/10/03)
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- Pentaalkylguanidines as etherification and esterification catalysts
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Several pentaalkylguanidines have been prepared and found to be superior catalysts for the preparation of aryl and aralkyl ethers from carbonates and for the methylation of phenols with dimethylcarbonate.They also act as effective catalysts for esterification of acids with alkyl chloroformates but not for the acetylation of tertiary alcohols with acetic anhydride.
- Barcelo, Gerard,Grenouillat, Denis,Senet, Jean-Pierre,Sennyey, Gerard
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p. 1839 - 1848
(2007/10/02)
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- Enhancement of the Resonance Interaction of Out-of-Plane Methoxy Groups By Ortho Substituents in Crowded Anisoles
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The 17O and 13C NMR chemical shifts of substituted anisoles provide evidence that the resonance interaction of methoxy groups which are perpendicular to the aromatic ring in crowded anisoles is influenced, to varying degrees, by ortho substituents.Enhance
- Schuster, Ingeborg I.,Parvez, Masood,Freyer, Alan J.
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p. 5819 - 5825
(2007/10/02)
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- Methylation of Alcohols and Phenols Adsorbed on Silica Gel with Diazomethane
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Alcohols and phenols adsorbed on silica gel react with diazomethane and quantitatively afford the corresponding methyl ethers.Alumina and titanium dioxide are also effective adsorbents for the reaction.
- Ogawa, Haruo,Hagiwara, Toshikazu,Chihara, Teiji,Teratani, Shousuke,Taya, Kazuo
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p. 627 - 630
(2007/10/02)
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- Methylation of Alcohols, Phenols, and Carboxylic Acids, and Selective Monomethylation of Diols and Dicarboxylic Acids with Dimethyl Sulfate by Use of Alumina
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Alcohols in cyclohexane give their methyl ethers in high yields by the use of a combination of dimethyl sulfate and alumina.Some diols and dicarboxylic acids adsorbed on alumina react with dimethyl sulfate and produce the corresponding monomethyl ethers and esters in high selectivities.
- Ogawa, Haruo,Ichimura, Youko,Chihara, Teiji,Teratani, Shousuke,Taya, Kazuo
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p. 2481 - 2484
(2007/10/02)
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- FRIEDEL-CRAFTS ALKYLATION OF ANISOLE AND ITS COMPARISON WITH TOLUENE. PREDOMINANT ORTHO-PARA SUBSTITUTION UNDER KINETIC CONDITIONS AND THE EFFECT OF THERMODYNAMIC ISOMERIZATIONS
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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
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p. 5284 - 5290
(2007/10/02)
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- Silica Gel as an Effective Catalyst for the Alkylation of Phenols and Some Heterocyclic Compounds
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In the presence of silica gel, the reaction of phenol with t-BuBr was examined under a variety of conditions and it was found that silica gel is an effective catalyst for the alkylation.As a result of this work 2-tert-butyl-, 2,6-di-tert-butyl-, and 2,4,6-tri-tert-butylphenols, all of which are hard to obtain directly by the Friedel-Crafts process, could be prepared easily by this one-step reaction.Several other alkyl halides were also used in this reaction.The alkylations of some heterocyclic aromatic compounds which cannot be alkylated by the conventional Friedel-Crafts method were also succesfully performed by this reaction.
- Kamitori, Yasuhiro,Hojo, Masaru,Masuda, Ryoichi,Izumi, Tatsuo,Tsukamoto, Shuichi
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p. 4161 - 4165
(2007/10/02)
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- Molecular Orbital Calculations and 13C NMR Studies To Explain a Regiospecific Demethylation of 3-Alkyl-1,2-dimethoxybenzenes
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This study was performed to explain a regiospecific demethylation of 3-alkyl-1,2-dimethoxybenzenes.PRDDO-MO calculations show that the low-energy conformation of the carbon of a methoxy group having two ortho neighbors on a benzene ring is located out of the plane of the aromatic ring, whereas a methoxy group with only one ortho neighbor executes restricted rotation in the plane of the ring.The carbon portion of the methoxy group is turned away from the neighboring substituent.These calculations also show that the atomic charge on the oxygen atom in the former caseexceeds that in the latter.The carbon of a methoxy group with two ortho neighbors yields 13C NMR T1 relaxation times longer than those with only one ortho neighbor, also suggesting that the methoxy group with two ortho neighbors is crowded out of the plane of the aromatic ring. 13C NMR chemical shifts of these ortho-substituted methoxybenzenes did not correlate well with shifts predicted from published additive parameters; this again suggests an unusual methoxy group orientation and distribution of electrons.The forced rotation of a methoxy group out of the plane of the benzene ring diminishes the release of electrons from the methoxy group to the benzene ring.The resulting higher atomic charge on the oxygen and the orientation of the oxygen orbitals facilitate complexation with Lewis acids and methoxy group cleavage.
- Jardon, Phillip W.,Vickery, Euin H.,Pahler, Leon F.,Pourahmady, Naser,Mains, Gilbert J.,Eisenbraun, Edmund J.
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p. 2130 - 2135
(2007/10/02)
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