- Photoactivatable aggregation-induced emission of triphenylmethanol
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Triphenylmethanol (TPOH) is a non-fluorescent compound. Interestingly, after UV irradiation at 254 nm, TPOH showed a strong blue fluorescence on a solid surface. Moreover, the fluorescence can be quenched by UV irradiation at 365 nm, making the photoactiv
- Zheng, Yue,Zheng, Xiaokun,Xiang, Yu,Tong, Aijun
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Read Online
- Observation of Radical Rebound in a Mononuclear Nonheme Iron Model Complex
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A nonheme iron(III) terminal methoxide complex, [FeIII(N3PyO2Ph)(OCH3)]ClO4, was synthesized. Reaction of this complex with the triphenylmethyl radical (Ph3C?) leads to formation of Ph
- Pangia, Thomas M.,Davies, Casey G.,Prendergast, Joshua R.,Gordon, Jesse B.,Siegler, Maxime A.,Jameson, Guy N. L.,Goldberg, David P.
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Read Online
- On the Mechanism of the Cleavage Reaction of (Methylthio)methyl Ether with Triphenylmethyl Cation
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The cleavage reaction of a (methylthio)methyl (MTM) ether with triphenylmethyl cation was not initiated by the previously proposed hydride abstraction with triphenylmethyl cation but promoted by the coordination of triphenylmethyl cation as a Lewis acid to the sulfur atom in the MTM group.
- Niwa, Haruki,Miyachi, Yasuyoshi
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Read Online
- Mechanistic Investigation of Oxygen Rebound in a Mononuclear Nonheme Iron Complex
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An iron(III) methoxide complex reacts with para-substituted triarylmethyl radicals to give iron(II) and methoxyether products. Second-order rate constants for the radical derivatives were obtained. Hammett and Marcus plots suggest the radical transfer rea
- Pangia, Thomas M.,Yadav, Vishal,Gérard, Emilie F.,Lin, Yen-Ting,De Visser, Sam P.,Jameson, Guy N. L.,Goldberg, David P.
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supporting information
p. 9557 - 9561
(2019/08/26)
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- Selective reaction of benzyl alcohols with HI gas: Iodination, reduction, and indane ring formations
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Reactions of benzyl alcohols with HI in solvent-free conditions were examined. Three types of reactions (iodination, reduction, and ring formation) occurred depending on the degree of crowding around the benzyl position and the benzylic stabilization of substrates. Results also showed that the ring formation to give indanes proceeded efficiently when HI was used, and that compounds with electron-rich aromatic rings gave indane derivatives in good yields.
- Matsumoto, Shoji,Naito, Masafumi,Oseki, Takehisa,Akazome, Motohiro,Otani, Yasuhiko
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p. 7254 - 7259
(2017/11/24)
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- In(III) triflate-catalyzed detritylation and glycosylation by solvent-free ball milling
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A highly efficient In(III) triflate-assisted method for the detritylation of O-trityl derivatives of carbohydrates, phenols, and alcohols using solvent-free mechanochemical method is described. In the case of carbohydrates, further reaction in the presence of an acceptor sugar leads to highly efficient glycosylation in the same pot resulting in the formation of the desired glycoside-product in very high yields. The method was applied successfully to the synthesis of a combinatorial library of galactose-based (1,6)-linked cyclohexa-, hepta-, and octasaccharides on gram scale.
- Kumar, Vajinder,Yadav, Narender,Kartha, K.P. Ravindranathan
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- Efficient assembly of α-aryl and α-vinyl nitriles via iron-catalyzed ether bond activation
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A novel and practical method for the synthesis of diverse α-aryl and α-vinyl nitriles was developed via an iron-catalyzed sp3 C-O ether bond cleavage with C-C bond formation in the reaction of π-activated ethers with TMSCN.
- Fan, Xiaohui,Guo, Kun,Guan, Yong-Hong,Fu, Lin-An,Cui, Xiao-Meng,Lv, Hao,Zhu, Hong-Bo
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supporting information
p. 1068 - 1071
(2014/02/14)
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- Iron-catalyzed π-activated C-O ether bond cleavage with C-C and C-H bond formation
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A novel and efficient allylic alkylation reaction between π-activated ethers and allylsilane was realized under mild conditions through iron(III)-catalyzed C sp 3-O ether bond cleavage. The present protocol provides an attractive approach for the construction of sp3-sp3 C-C bonds and can be potentially applied for the selective reduction of benzyl and allyl ethers to their corresponding hydrocarbon compounds by using triethylsilane as a hydride-transfer reagent. A mild, economical, and environmentally friendly method for the construction of C sp 3-C sp 3 bonds through iron-catalyzed π-activated C-O ether bond cleavage is developed. In addition, this catalytic system can be used for the selective reduction of benzylic and allylic C-O ether bonds to C-H bonds. Copyright
- Fan, Xiaohui,Cui, Xiao-Meng,Guan, Yong-Hong,Fu, Lin-An,Lv, Hao,Guo, Kun,Zhu, Hong-Bo
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supporting information
p. 498 - 501
(2014/02/14)
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- Efficient assembly of α-aryl and α-vinyl nitriles via iron-catalyzed ether bond activation
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A novel and practical method for the synthesis of diverse α-aryl and α-vinyl nitriles was developed via an iron-catalyzed sp3 C-O ether bond cleavage with C-C bond formation in the reaction of π-activated ethers with TMSCN.
- Fan, Xiaohui,Guo, Kun,Guan, Yong-Hong,Fu, Lin-An,Cui, Xiao-Meng,Lv, Hao,Zhu, Hong-Bo
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supporting information
p. 1068 - 1071
(2015/02/18)
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- Iron-Catalyzed π-Activated C-O Ether Bond Cleavage with C-C and C-H Bond Formation
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A novel and efficient allylic alkylation reaction between π-activated ethers and allylsilane was realized under mild conditions through iron(III)-catalyzed C sp 3-O ether bond cleavage. The present protocol provides an attractive approach for the construction of sp3-sp3 C-C bonds and can be potentially applied for the selective reduction of benzyl and allyl ethers to their corresponding hydrocarbon compounds by using triethylsilane as a hydride-transfer reagent.
- Fan, Xiaohui,Cui, Xiao-Meng,Guan, Yong-Hong,Fu, Lin-An,Lv, Hao,Guo, Kun,Zhu, Hong-Bo
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supporting information
p. 498 - 501
(2015/10/05)
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- Structural and solvent effects on the C-S bond cleavage in aryl triphenylmethyl sulfide radical cations
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Steady-state and laser flash photolysis (LFP) studies of a series of aryl triphenylmethyl sulfides [1, 3,4-(CH3O)2-C 6H3SC(C6H5)3; 2, 4-CH3O-C6H4SC(C6H5) 3; 3, 4-CH3-C6H4SC(C 6H5)3; 4, C6H5SC(C 6H5)3; and 5, 4-Br-C6H 4SC(C6H5)3] has been carried out in the presence of N-methoxyphenanthridinium hexafluorophosphate in CH 3CN, CH2Cl2, CH2Cl 2/CH3CN, and CH2Cl2/CH3OH mixtures. Products deriving from the C-S bond cleavage in the radical cations 1?+-5?+ have been observed in the steady-state photolysis experiments. Time-resolved LFP showed first-order decay of the radical cations accompanied by formation of the triphenylmethyl cation. A significant decrease of the C-S bond cleavage rate constants was observed by increasing the electron-donating power of the arylsulfenyl substituent, that is, by increasing the stability of the radical cations. DFT calculations showed that, in 2?+ and 3?+, charge and spin densities are mainly localized in the ArS group. In the TS of the C-S bond cleavage an increase of the positive charge in the trityl moiety and of the spin density on the ArS group is observed. The higher delocalization of the charge in the TS as compared to the initial state is probably at the origin of the observation that the C-S bond cleavage rates decrease by increasing the polarity of the solvent.
- Del Giacco, Tiziana,Lanzalunga, Osvaldo,Mazzonna, Marco,Mencarelli, Paolo
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p. 1843 - 1852
(2012/04/23)
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- Carbonate, acetate and phenolate phosphonium salts as catalysts in transesterification reactions for the synthesis of non-symmetric dialkyl carbonates
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Methyl trioctylphosphonium methyl carbonate [P8881] +[MeOCO2]- was prepared by the alkylation of trioctyl phosphine with the non-toxic dimethyl carbonate. This salt was a convenient source to synthesize different ionic liquids where the methyl trioctylphosphonium cation was coupled to weakly basic anions such as bicarbonate, acetate, and phenolate. At 90-220 °C, all these compounds [P8881]+X-; X = MeOCO2; HOCO 2; AcO; PhO were excellent organocatalysts for the transesterification of dimethyl and diethyl carbonate with primary and secondary alcohols, including benzyl alcohol, cyclopentanol, cyclohexanol, and the rather sterically hindered menthol. Conditions were optimized to operate with very low catalyst loadings up to 1 mol% and to obtain non-symmetric dialkyl carbonates (ROCO2R′; R = Me, Et) with selectivity up to 99% and isolated yields >90%. The catalytic performance of the investigated ionic liquids was discussed through a cooperative mechanism of simultaneous activation of both electrophilic and nucleophilic reactants.
- Selva, Maurizio,Noe, Marco,Perosa, Alvise,Gottardo, Marina
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experimental part
p. 6569 - 6578
(2012/09/08)
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- An efficient synthesis of tert-butyl ethers/esters of alcohols/amino acids using methyl tert-butyl ether
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A facile synthesis of a wide variety of tert-butyl ethers and tert-butyl ester derivatives under mild conditions is described. Alcohols etherified with tert-butyl methyl ether as tert-butyl source and solvent, in the presence of sulfuric acid. Many amino acid tert-butyl esters have been synthesized by this procedure. The reaction is simple, inexpensive, easily scaled up, and proceeds without observable racemization. A green method was developed for the deprotection of this group using Amberlite resin IR 120-H as catalyst.
- Mallesha,Prahlada Rao,Suhas,Channe Gowda
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experimental part
p. 641 - 645
(2012/02/15)
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- Synthesis, pharmacokinetics, and pharmacodynamics studies of valsartan peptide derivatives
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In order to increase the intestinal permeability of valsartan, 14 esters and peptide derivatives of valsartan were chemically synthesized and their absorption characteristics were described. All derivatives were stable and could be better absorbed into th
- Wu, Chun,Hu, Yanpeng,Li, Qianbin,He, Limei,Chen, Jun,Cheng, Zeneng,Li, Yuanjian,Hu, Gaoyun
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experimental part
p. 393 - 400
(2012/08/07)
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- Method for activation and recycling of trityl resins
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This note describes a rapid and mild strategy for the loading of alcohols and anilines onto a polystyrene triphenylmethyl (trityl) resin. High loadings were obtained in a matter of minutes by treating resin-bound trityl chloride with triethyloxonium tetrafluoroborate followed by alcohols or anilines. Yields were comparable or better than known literature methods. Recycling of the recovered resin was also possible using the developed method.
- Redwan, Itedale Namro,Gr?tli, Morten
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experimental part
p. 7071 - 7075
(2015/02/20)
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- Indium(i)-catalyzed alkyl-allyl coupling between ethers and an allylborane
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An efficient method for alkyl-allyl cross-coupling between ethers and a 9-BBN-derived allylborane catalyzed by indium(i) triflate has been developed. The allylborane proved to be essential to obtain the desired products in high yields. The reaction displayed good substrate scope including high functional group tolerance. The Royal Society of Chemistry 2011.
- Dao, Hai Thanh,Schneider, Uwe,Kobayashi, Shu
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supporting information; experimental part
p. 692 - 694
(2011/03/22)
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- Radiofluorinated pyrimidine-2,4,6-triones as molecular probes for noninvasive MMP-targeted imaging
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Matrix metalloproteinases (MMPs) are zinc- and calcium-dependent endopeptidases. Representing a subfamily of the metzincin superfamily, MMPs are involved in the proteolytic degradation of components of the extracellular matrix. Unregulated MMP expression,
- Breyholz, Hans-Joerg,Wagner, Stefan,Faust, Andreas,Riemann, Burkhard,Hoeltke, Carsten,Hermann, Sven,Schober, Otmar,Schaefers, Michael,Kopka, Klaus
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experimental part
p. 777 - 789
(2011/01/05)
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- Total syntheses of (+)-tedanolide and (+)-13-deoxytedanolide
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Convergent total syntheses of the potent cytotoxins (+)-tedanolide (1) and (+)-13-deoxytedanolide (2) are described. The carbon framework of these compounds was assembled via a stereoselective aldol reaction that unifies the C(1)-C(12) ketone fragment 5 with a C(13)-C(23) aldehyde fragment 6 (for 13-deoxytedanolide) or 52 (for tedanolide). Multiple obstacles were encountered en route to (+)-1 and (+)-2 that required very careful selection and orchestration of the stereochemistry and functionality of key intermediates. Chief among these issues was the remarkable stability and lack of reactivity of hemiketals 33b and 34 that prevented the tedanolide synthesis from being completed from aldol 4. Key to the successful completion of the tedanolide synthesis was the observation that the 13-deoxy hemiketal 36 could be oxidized to C(11, 15)-diketone 38 en route to 13-deoxytedanolide. This led to the decision to pursue the tedanolide synthesis via C(15)-(S)-epimers, since this stereochemical change would destabilize the hemiketal that plagued the attempted synthesis of tedanolide via C(15)-(R) intermediates. However, use of C(15)-(S)-configured intermediates required that the side-chain epoxide be introduced very late in the synthesis, owing to the ease with which the C(15)-(S)-OH cyclized onto the epoxide of intermediate 50.
- Dunetz, Joshua R.,Julian, Lisa D.,Newcom, Jason S.,Roush, William R.
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supporting information; experimental part
p. 16407 - 16416
(2009/05/08)
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- Concerning the synthesis of the tedanolide C(13)-C(23) fragment via anti-aldol reaction
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Synthesis of C(13)-C(23) aldehyde 4, an Important Intermediate In a planned total synthesis of tedanolide, Is described. The stereoselectivity of the key anti-aldol reaction of aldehyde 5 and ketone 6 (en route to 4) perfectly tracks the enantiomeric purity of 5. It is demonstrated that aldehyde 24, a precursor of 5, undergoes facile epimerization during a Swern oxidation and stabilized ylide olefination sequence.
- Dunetz, Joshua R.,Roush, William R.
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supporting information; experimental part
p. 2059 - 2062
(2009/04/18)
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- PROCESS FOR PRODUCING BIPHENYL-TETRAZOLE COMPOUNDS
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A process for producing biphenyl-tetrazole compounds in pure form by deprotecting compounds of the following formula (II): proposes to use acids in an alcohol-ketone-water mixture and/or a mixture of alcohol-alcohol-keton-water to remove the Ph3C-protecting group.
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Page/Page column 9
(2008/06/13)
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- Palladium-catalyzed DYKAT of butadiene monoepoxide: Enantioselective total synthesis of (+)-DMDP, (-)-bulgecinine, and (+)-broussonetine G
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Palladium catalyzed asymmetric allylic alkylation reaction of an amine with two equivalents of butadiene monoxide allows for the expedient synthesis of trans- and cis-2,5-dihydropyrroles. The versatility of these chiral synthons towards the synthesis of a wide variety of iminosugar natural products was demonstrated with the short and high yielding asymmetric syntheses of (+)-DMDP, and (-)-bulgecinine. In addition, the first total synthesis of (+)-broussonetine G, a potent glycosidase inhibitor, is described along with the assignment of its relative and absolute stereochemical configuration.
- Trost, Barry M.,Horne, Daniel B.,Woltering, Michael J.
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p. 6607 - 6620
(2008/09/16)
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- A METHOD OF REMOVING THE TRIPHENYLMETHANE PROTECTING GROUP
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A method of removing the triphenylmethane protecting group from 1-triphenylmethyl-5-(4'-subst. methyl-1,1‘-biphenyl-2-yl)-1H-tetrazoles of general formula I wherein R represents the groups of formulae and where R1, R2 and R3 can be H, a halogen, an unbranched or branched C1-C5 alkyl, C1-C5 hydroxyalkyl, Cl-C5 alkoxy, C1-C5 alkoxymethyl or benzyl, or wherein R2 and R3 can form together a saturated or unsaturated C5-C7 ring, optionally an unsubstituted or substituted aromatic ring, is carried out by solvolysis in a simple anhydrous Cl to C5 alcohol in a neutral or slightly basic medium. The method is suitable for the preparation of drugs, such as the potassium salts of losartan, irbesartan or valsartan or candesartan cilexetil.
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Page/Page column 15
(2008/06/13)
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- Decarboxylative photooxygenation of arylacetic acids by using mercuric oxide
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A new method for decarboxylative photooxygenation of arylacetic acids is developed by using light sensitive HgO in MeCN-MeOH which leads to aldehydes and ketones in high yield through trapping of benzylic radical intermediates by dioxygen.
- Habibi, Mohammad H.,Farhadi, Saeid
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p. 296 - 297
(2007/10/03)
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- Lewis acid-catalyzed three-component condensation reactions of aldehydes, alkoxysilanes, and allenylsilanes: Synthesis of α-propargyl ethers
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Lewis acid-catalyzed reaction of acetals with allenylsilanes and the three-component reactions of aldehydes, alkoxysilanes, and allenylsilanes are described. Both reactions are strongly dependent on the substituent at the α-position of allenylsilanes. Allenylsilanes having bulky substituents such as the tert-butyl and isopropyl groups result in the corresponding α-propargyl ethers in high yields, whereas allenylsilanes having the methyl and ethyl groups afford not only the corresponding α-propargyl ethers in low yield but also cyclopropyl ketones and α,β-unsaturated ketones as by-products.
- Niimi, Lui,Hiraoka, Shuichi,Yokozawa, Tsutomu
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p. 245 - 252
(2007/10/03)
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- Tetrazoles: XLIV. Synthesis and chemical properties of 5-substituted 2-triphenylmethyltetrazoles
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Tritylation of tetrazole and its 5-substituted derivatives with triphenylmethyl chloride under conditions of phase-transfer catalysis regioselectively yields the corresponding 5-substituted 2-trityltetrazoles which can be used to protect N-H bonds in nitrogen-containing heterocycles and O-H bonds in primary alcohols. Thermolysis of 2-trityltetrazoles in benzonitrile leads to 3,6-disubstituted 1,2,4,5-tetrazines. Thermal transformation of the same compounds in dodecane follows a radically different mechanism, resulting in formation of difficultly accessible 8,8-diphenylheptafulvenes. The structure of the latter was proved by X-ray analysis.
- Myznikov,Artamonova,Bel'skii,Stash,Skvortsov,Koldobskii
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p. 1360 - 1369
(2007/10/03)
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- Transetherification of allylic and benzylic ethers in the presence of ferric ion
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Alcoholysis of allylic, secondary and tertiary benzylic ethers is proceeded efficiently in the presence of catalytic amounts of ferric ion as anhydrous FeCl3 and Fe(ClO4)3.
- Salehi, Peyman,Irandoost, Mohsen,Seddighi, Behnam,Kargar Behbahani, Farahnaz,Tahmasebi, Daryush Poor
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p. 1743 - 1747
(2007/10/03)
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- Improved procedure for the synthesis of methyl ethers from alcohols
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Alcohols can be conveniently converted to the corresponding methyl ethers with methyl iodide in the presence of KOH under solvent-free conditions.
- Rao, H. Surya Prakash,Senthilkumar,Reddy, D. Srinivasa,Mehta, Goverdhan
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p. 260 - 263
(2007/10/03)
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- Macrocyclic bisindolylmaleimides: Synthesis by inter- and intramolecular alkylation
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Macrocyclic bisindolylmaleimides 1-4 have been identified as competitive reversible inhibitors of PKC β1 and β2 and are being advanced to the clinic for evaluation as a treatment of retinopathy associated with diabetic complications. Highly convergent and stereoselective syntheses of 1-4 have been developed. The key synthetic step involves intermolecular alkylation of symmetrical bisindolylmaleimide 9 with chiral bisalkylating agent 8c and is amenable to the preparation of multikilogram quantities of these compounds. The synthetic sequence to 1, the most active the compound, proceeds in 11 steps and 26% overall yield (> 98% ee) from (R)-1-chloro-2,3-propanediol. No chromatographic purifications are required throughout the process and the final product is isolated in >97% purity after crystallization from DMF/MeOH. Synthesis of 1-4 by intramolecular alkylation proved less efficient, requiring 17 steps and affording 1-4 in lower overall yields of 6.0-8.5%.
- Faul, Margaret M.,Winneroski, Leonard L.,Krumrich, Christine A.,Sullivan, Kevin A.,Gillig, James R.,Neel, David A.,Rito, Christopher J.,Jirousek, Michael R.
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p. 1961 - 1973
(2007/10/03)
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- Selective and efficient alcoholyses of allylic, secondary- and tertiary benzylic alcohols in the presence of iron(III)
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An efficient and selective method for the conversion of allylic, secondary- and tertiary benzylic alcohols into their corresponding ethers in the presence of iron(III) as FeCl3 and Fe(ClO4)3 under solvolytic condition is d
- Salehi, Peyman,Iranpoor, Nasser,Behbahani, Farahnaz Kargar
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p. 943 - 948
(2007/10/03)
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- On the mechanism of alcoholysis of allylic and benzylic alcohols and of epoxides in the presence of ceric ammonium nitrate
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The methanolysis of allylic alcohols, benzylic tertiary alcohols and epoxides in the presence of a catalytic amount of ceric ammonium nitrate (CAN) is shown to be catalysed by protons generated from the oxidation of methanol. This reaction is also catalysed by Lewis acids.
- Chapuzet, Jean-Marc,Beauchemin, Sophie,Daoust, Benoit,Lessard, Jean
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p. 4175 - 4180
(2007/10/03)
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- Alcoholyses and acetolyses of allylic and tertiary benzylic alcohols catalyzed by 2,3-dichloro-5,6-dicyanobenzoquinone
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Allylic and tertiary benzylic alcohols can be converted into their corresponding ethers and acetates selectively and efficiently in the presence of catalytic amounts of 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ).
- Iranpoor,Mottaghinejad
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p. 2253 - 2260
(2007/10/02)
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- Catalytic and Efficient Cleavage of Allylic and Tertiary Benzylic Ethers and Esters with Ce(IV)
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The reaction of cerium(IV) as ceric ammonium nitrate (CAN) with a variety of allylic and tertiary benzylic ethers and esters has been examined in different alcohols and acetic acid under catalytic and mild conditions.Experiments have been conducted to elu
- Iranpoor, Nasser,Mottaghinejad, Enayatolah
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p. 7299 - 7306
(2007/10/02)
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- Cerium(IV), as a selective and efficient catalyst for alcoholyses of allylic and tertiary benzylic alcohols
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An efficient and selective method is described for the catalytic conversion of allylic, and tertiary benzylic alcohols into their corresponding ethers in the presence of Ce(IV) under solvolytic and non- solvolytic conditions.
- Iranpoor, Nasser,Mothaghineghad, Enayatholah
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p. 1859 - 1870
(2007/10/02)
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- Efficient synthesis of azetidine through N-trityl- or N- dimethoxytritylazetidines starting from 3-amino-1-propanol or 3- halopropylamine hydrohalides
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Efficient synthetic routes for the preparation of azetidine starting from commercially available 3-amino-1-propanol or 3-halopropylamine hydrohalides are reported. First, the appropriate N-trityl- or N-dimethoxytrityl protected tosyloxy- or halopropylamines were prepared. These precursors were then cyclized into the N-trityl- or N-dimethoxytritylazetidines. The N-protecting groups were removed in the presence of perchloric acid giving the hydrogen perchlorate salt of azetidine. The latter compound was transformed into its free base using a strong base under anhydrous conditions. The relatively expensive 4,4'-dimethoxytrityl chloride and less expensive trityl chloride used in these synthetic procedures were recycled in good yields. Azetidine hydrogenperchlorate can be used to prepare N-substituted azetidines without the need to isolate the free azetidine.
- Huszthy,Bradshaw,Krakowiak,Wang,Dalley
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p. 1197 - 1207
(2007/10/02)
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- The Reaction of Triphenylmethyl Halides with Triphenylphosphine in Cumene and tert-Butylbenzene
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Reactions of triphenylmethyl bromide and chloride with triphenylphosphine at elevated temperatures under argon furnish mixtures of the reductive dehalogenation product triphenylmethane and the tele substitution products 2a or 2b, the ratio of the products depending on the reaction conditions.The formation of triphenylmethane indicates that the reaction is, at least partly, initiated by halophilic attack or by single-electron transfer (SET) from the phosphine .The resulting triphenylmethanide anions or triphenylmethyl radicals would then be converted into triphenylmethane by proton or hydrogen abstraction or recombine with their phosphorus containing co-products to yield the tele substitution products .The latter could, at least partly, also be formed via eqn. (1a).Exclusive operation of the SET initiated mechanisms of formation of both products has been proved by combination of trapping studies with molecular oxygen and proof of the absence of triphenylmethanide anions from the reaction mixture.
- Huszthy, Peter,Kajtar-Peredy, Maria,Lempert, Karoly,Hegedues-Vajda, Judit
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p. 347 - 354
(2007/10/02)
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- Photolysis of 1,1,1,2-Tetraarylalkanes in the Presence of 1,4-Dicyanobenzene. A Photochemical C-C Bond Cleavage Reaction of Radical Cations in Solution
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Irradiation of acetonitrile-methanol (1:1) solutions of 1,1,1,2-tetraarylalkanes or 1,1,1-triphenyl-2-methoxyethane containing 1,4-dicyanobenzene led to the formation of triarylmethane and triarylmethyl methyl ethers in good yields.This C-C bond cleavage reaction is thought to proceed via a radical cation intermediate.
- Shi, Min,Okamoto, Yoshiki,Takamuku, Setsuo
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p. 1831 - 1840
(2007/10/02)
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- Electroorganic Synthesis Using Organometals. 2. Reductive Dehalogenation of Halides with Carbonylferrates Derived from Pentacarbonyliron(0) and Cathodically-Generated Methoxide Ion
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A stoichiometry for the reductive dehalogenation of an organic halide with carbonylferrates was established: One mol of the halide was quantitatively reduced with the carbonylferrates derived from 0.2 mol of pentacarbonyl iron(0) and 2 mol of cathodically-generated tetramethylammonium methoxide.The dehalogenation was also examined using a variety of halides under the stoichiometric reaction conditions.
- Hashiba, Shigeto,Fuchigami, Toshio,Tsutomu, Nonaka
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p. 2424 - 2426
(2007/10/02)
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- RADICAL-ANIONS OF AROMATIC COMPOUNDS. VIII. EFFECT OF THE NATURE OF IONIC ASSOCIATION ON THE RATIO OF THE NUCLEOPHILIC AND ELECTRON-DONATING CHARACTERISTICS OF THE BENZOPHENONE RADICAL-ANION IN REACTIONS WITH N,N,N-TRIMETHYLPHENYLAMMONIUM PERCHLORATE
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In reaction with N,N,N-trimethylphenylammonium perchlorate in THF the potassium, sodium, and lithium salts of the benzophenone radical-anion exibit dual reactivity, acting both as nucleophiles (an SN process) and as electron donors (an ET process).Decrease in the radius of the counterion, increase in the polarity of the solvent (hexamethylphosphorotriamide), and the use of dibenzo-18-crown-6 ether lead to an increase in the ratio of the rates wET/wSN.The effects of increase in the radius of the counterion and the polarity of the solvent and also the use of the crown ether in terms of the SN process are characterized by an increase in the yields of the products from O-methylation of the benzophenone radical-anion compared with C-methylation.During the reaction in hexamethylphosphorotriamide the nature of the counterion has practically no effect on the ratio the products for each of the raction paths.
- Bil'kis, I. I.,Selivanov, B. A.,Shteingarts, V. D.
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p. 709 - 719
(2007/10/02)
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- RADICAL-ANIONS OF AROMATIC COMPOUNDS. V. EFFECT OF THE STRUCTURE OF THE ELECTROPHILE ON THE RATIO OF THE ELECTRON-DONATING AND NUCLEOPHILIC CHARACTERISTICS OF THE BENZOPHENONE RADICAL-ANION IN REACTIONS WITH N,N,N-TRIMETHYLARYLAMMONIUM PERCHLORATES
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In reaction with N,N,N-trimethylammonium perchlorates in THF the potassium salt of the benzophenone radical-anion exhibits dual reactivity, acting both as nucleophile (as SN process) and as a one-electron reducing agent (an ET process).The effect of the structure of the aryl fragment of the ammonium salt on the ratio of the rates WET/WSN is determined by the higher sensitivity of the electron transfer rate to the effect of this factor compared with nucleophilic substitution and varies in the following order: p-Methoxyphenyl p-tolyl m-tolyl phenyl m-methoxyphenyl p-biphenylyl m-chlorophenyl 1-naphthyl.I t was found that the structure of the aryl fragment of the ammonium salt has a significant effect on the regioselectivity of the methylation of the benzophenone radical-anion.
- Selivanov, B. A.,Bil'kis, I. I.,Varand, V. L.,Shteingarts, V. D.
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p. 865 - 877
(2007/10/02)
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- Single-electron-transfer-initiated Thermal Reactions of Arylmethyl Halides. Part 11. The Reaction of Trityl Halides with Sodium Methoxide in 2,2-Dimethoxypropane
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Trityl chloride (1a) and bromide (1b) furnish with sodium methoxide in 2,2-dimethoxypropane, in addition to several minor products, mixtures of the substitution products methyl trityl ether (1c) and p-methoxytriphenylmethane (2a), and of the reduction products triphenylmethane (1f) and p-diphenylmethyltritylbenzene (3a) which are the products of competing SN and single-electron transfer-initiated processes.Compound (1c) is suggested to be formed via two successive SN' processes rather than by either the SN1 or Sn2 mechanisms which are both disfavoured under the experimental conditions applied.
- Huszthy, Peter,Lempert, Karoly,Simig, Gyula
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p. 1323 - 1330
(2007/10/02)
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- The Protecting-Directing Role of the Trityl Group in Syntheses of Pyrrole Derivatives: Efficient Preparations of 1-H-Pyrrole-3-carboxylic Acid and 3-Acyl, 3-Amino, and 3-Bromo-1-tritylpyrroles
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Trifluoroacetylation, formylation, and bromination of 1-tritylpyrrile occur regioselectively at the 3-position in high yields.Quantitative hydrolysis of the 3-trifluoroacetyl derivative and removal of the trityl group from the resulting acid with sodium in liquid ammonia furnishes a new, short, high-yielding synthessis of the simple 1-H-pyrrole-3-carboxylic acid. 1-Tritylpyrrole-3-carboxylic acid has been converted efficiently into 3-aminopyrroles via Curtius rearrangement of the derived azide: 3-amino-1-tritylpyrrole appears to exist in solution exclusively as its imino-Δ4-pyrroline tautomer. 1-H-3-t-Butyloxycarbonylaminopyrrole udergoes trifluoroacetylation regioselectively at the 2-position.Metallation of 1-tritylpyrrole with butyl-lithium in hexamethylphosphoric triamide gives rise to the unexpected products 9-phenylfluorene, 1-methoxycarbonylpyrrole and methyl triphenylmethylacetate (after work-up of the lithio-intermediates with carbon dioxide and methylation of the resulting acids).
- Chadwick, Derek J.,Hodgson, Simon T.
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- RADICAL-ANIONS OF AROMATIC COMPOUNDS. IV. N,N,N-TRIMETHYLPHENYLAMMONIUM PERCHLORATE - A MODEL REAGENT FOR THE INVESTIGATION OF FACTORS DETERMINING THE RATIO OF THE NUCLEOPHILIC AND ELECTRON-DONATING CHARACTERISTICS OF THE BENZOPHENONE RADICAL-ANION IN REACTIONS WITH ELECTROPHILES
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In reaction with N,N,N-trimethylphenylammonium perchlorate in tetrahydrofuran the potassium salt of the benzophenone radical-anion exhibits dual reactivity, acting both as nucleophile and as electron donor.From the ratio of products corresponding to methylation and phenylation of the potassium salt of the benzophenone radical-anion it was found that the ratio of the reaction rates of the latter in these two directions amounts to approximately 3 : 2.It was concluded that N,N,N-trimethylphenylammonium perchlorate and its derivatives can be used as models for investigating the effect of various factors on the ratio of the nucleophilic and electron-donating characteristics of the benzophenone radical-anion in reactions with electrophilic reagents.
- Selivanov, B. A.,Bil'kis, I. I.,Danilov, I. S.,Shteingarts, V. D.
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p. 1888 - 1896
(2007/10/02)
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- The Reduction of Triarylcarbenium Ions by Alcohols: Simple Hydride Transfer or Concerted Breakdown of ortho-Adducts?
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Reduction of tris-(4-methoxyphenyl)methyl chloride (2) by refluxing methanol to tris-(4-methoxyphenyl)methane (3) is, as shown by 2H labelling, accompanied by exchange of methoxy-groups between solvent and substrate.This exchange reaction appears to be th
- Huszthy, Peter,Lempert, Karoly,Simig, Gyula,Tamas, Jozsef
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p. 1671 - 1674
(2007/10/02)
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- EFFETS DE CRYPTANDS ET ACTIVATION DE BASES-Va ACTION DES HYDRURES ALCALINS SUR LES ACIDES FAIBLES-II. ALKYLATION DES ANIONS OBTENUS
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Phenoxides, alkoxides and potassium amidates generated by KH in THF or benzene at room temperature are easily alkylated in the presence of catalytic quantities of crytand, without affecting addition-elimination ratios.Thus, Williamson and Gabriel syntheses, as well as the alkylation of secondary amines, occur readily in mild conditions.
- Pasquini, M. A.,Goaller, R. Le,Pierre, J.L.
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p. 1223 - 1226
(2007/10/02)
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