- A novel synthesis of tolunitriles by selective ammoxidation
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A new approach to synthesize tolunitriles is reported. Tolunitriles can be prepared by selective ammoxidation of methylbenzyl chlorides prepared by chloromethylation of toluene. The total yields can reach 83% and the selectivity of tolunitriles is almost 100%. This approach provides a new path for preparing alkylbenzonitriles and other aromatic nitriles.
- Xie, Guangyong,Zhang, Aiqing,Huang, Chi
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- Microwave assisted solid additive effects in simple dry chlorination reactions with n-chlorosuccinimide
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Solid additives participate in the dry microwave assisted chlorination reaction of N-chlorosuccinimide with the xylenes affecting both yields and chemoselectivities. Total yields can be increased up to nine times for simple alkylaromatics and chemoselectivities can be altered according to the desired ring or α-side chlorination product by choosing the appropriate additive. We believe that in these reactions the solid additives play a very important role by increasing yields and affecting chemoselectivities, as well as behaving as microwave energy absorbers that consequently aid the transfer of heat to the active reagents.
- Bucos, Madalina,Villalonga-Barber, Carolina,Micha-Screttas, Maria,Steele, Barry R.,Screttas, Constantinos G.,Heropoulos, Georgios A.
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- Regiospecific chlorination of xylenes using K-10 montmorrillonite clay
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Regiospecific chlorination of xylenes has been developed by employing NCS as a reagent and K-10 montmorrillonite clay as a solid support. Copyright Taylor & Francis Group, LLC.
- Thirumamagal,Narayanasamy, Sureshbabu,Venkatesan
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- Facile synthesis of hypercrosslinked resin via photochlorination of p-xylene and succedent alkylation polymerization
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A combination of photochlorination of p-xylene and succedent Friedel-Crafts alkylation polymerization was firstly used in the preparation of the hypercrosslinked adsorptive resin. The data of GC-MS and GC showed that a series of chlorizates were produced when p-xylene was photochlorinated. Hypercrosslinked resins could be synthesized by copolymerization, self-polymerization of chlorizates or post crosslinking reaction. The chemical structure and micromorphology of the porous resins were characterized by BET, FT-IR, SEM and elementary analysis (EA). The results showed that the novel adsorptive resins possess high BET surface near to 1038 m2/g and large pore volumes range from 0.5 to 1.2 cm3/g.
- Bai, Ling Ling,Zhou, Yong Hao,Wang, Xiu Li,Yuan, Si Guo,Wu, Xian Li
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- Photocatalytic activation of N-chloro compounds for the chlorination of arenes
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Photoredox catalysis activates N-chloramines and N-chloro-succinimide (NCS) for the electrophilic chlorination of arenes. The photooxidation of the nitrogen atom to a radical cation induces a positive polarization on the chlorine atom, which results in a higher reactivity in electrophilic aromatic chlorination reactions.
- Hering, Thea,K?nig, Burkhard
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- Efficient synthesis of tolunitriles by selective ammoxidation
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Tolunitriles have been efficiently synthesized by selective ammoxidation of methylbenzyl chlorides prepared with chlorination of xylenes. In comparison with ammoxidation of xylenes themselves, the reaction temperature of ammoxidation of methylbenzyl chlorides has been lowered more than 100°C and the selectivity forming mono-nitriles is almost 100%.
- Xie, Guangyong,Zheng, Qiong,Huang, Chi,Chen, Yuanyin
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- Mechanism of solvolysis of substituted benzyl chlorides in aqueous ethanol
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The mechanism of solvolyses of activated ortho-, meta- and para-substituted benzyl chlorides in aqueous ethanol has been studied by using the Hammett-Brown and Yukawa-Tsuno treatments as well as by correlating logarithms of solvolysis rate constants with relative stabilities of corresponding benzyl carbocations in water calculated at the IEFPCM-M06–2X/6-311+G(3df,3pd) level of theory. Benzyl chlorides containing strong conjugative electron-donors in the para-position solvolyze by the SN1 mechanism, whereas other activated benzyl chlorides solvolyze by the SN2 mechanism via loose transition states.
- Denegri, Bernard,Mati?, Mirela,Va?ko, Monika
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supporting information
(2021/11/22)
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- Structure-guided optimization of 1H-imidazole-2-carboxylic acid derivatives affording potent VIM-Type metallo-β-lactamase inhibitors
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Production of metallo-β-lactamases (MBLs) in bacterial pathogens is an important cause of resistance to the ‘last-resort’ carbapenem antibiotics. Development of effective MBL inhibitors to reverse carbapenem resistance in Gram-negative bacteria is still needed. We herein report X-ray structure-guided optimization of 1H-imidazole-2-carboxylic acid (ICA) derivatives by considering how to engage with the active-site flexible loops and improve penetration into Gram-negative bacteria. Structure-activity relationship studies revealed the importance of appropriate substituents at ICA 1-position to achieve potent inhibition to class B1 MBLs, particularly the Verona Integron-encoded MBLs (VIMs), mainly by involving ingenious interactions with the flexible active site loops as observed by crystallographic analyses. Of the tested ICA inhibitors, 55 displayed potent synergistic antibacterial activity with meropenem against engineered Escherichia coli strains and even intractable clinically isolated Pseudomonas aeruginosa producing VIM-2 MBL. The morphologic and internal structural changes of bacterial cells after treatment further demonstrated that 55 crossed the outer membrane and reversed the activity of meropenem. Moreover, 55 showed good pharmacokinetic and safety profile in vivo, which could be a potential candidate for combating VIM-mediated Gram-negative carbapenem resistance.
- Yan, Yu-Hang,Li, Wenfang,Chen, Wei,Li, Chao,Zhu, Kai-Rong,Deng, Ji,Dai, Qing-Qing,Yang, Ling-Ling,Wang, Zhenling,Li, Guo-Bo
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- Nickel catalyzed deoxygenative cross-coupling of benzyl alcohols with aryl-bromides
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A nickel-catalyzed cross-electrophile coupling of benzyl alcohols with aromatic bromides has been developed. This deoxygenative cross-coupling occurs under mild reaction conditions at ambient temperature affording diarylmethanes, or 1,3-diarylpropenes from benzyl allyl alcohols. The system demonstrated good chemoselectivity tolerating an assortment of reactive functional groups.
- Kumar Chenniappan, Vinoth,Peck, Devin,Rahaim, Ronald
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- N -Hydroxyphthalimide/benzoquinone-catalyzed chlorination of hydrocarbon C-H bond using N -chlorosuccinimide
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The direct chlorination of C-H bonds has received considerable attention in recent years. In this work, a metal-free protocol for hydrocarbon C-H bond chlorination with commercially available N-chlorosuccinimide (NCS) catalyzed by N-hydroxyphthalimide (NHPI) with 2,3-dicyano-5,6-dichlorobenzoquinone (DDQ) functioning as an external radical initiator is presented. Aliphatic and benzylic substituents and also heteroaromatic ones were found to be well tolerated. Both the experiments and theoretical analysis indicate that the reaction goes through a process wherein NHPI functions as a catalyst rather than as an initiator. On the other hand, the hydrogen abstraction of the C-H bond conducted by a PINO species rather than the highly reactive N-centered radicals rationalizes the high chemoselectivity of the monochlorination obtained by this protocol as the latter is reactive towards the C(sp3)-H bonds of the monochlorides. The present results could hold promise for further development of a nitroxy-radical system for the highly selective functionalization of the aliphatic and benzylic hydrocarbon C-H.
- Li, Zi-Hao,Fiser, Béla,Jiang, Biao-Lin,Li, Jian-Wei,Xu, Bao-Hua,Zhang, Suo-Jiang
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supporting information
p. 3403 - 3408
(2019/04/01)
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- α-Diimine-Niobium Complex-Catalyzed Deoxychlorination of Benzyl Ethers with Silicon Tetrachloride
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α-Diimine niobium complexes serve as catalysts for deoxygenation of benzyl ethers by silicon tetrachloride (SiCl4) to cleanly give two equivalents of the corresponding benzyl chlorides, where SiCl4 has the dual function of oxygen scavenger and chloride source with the formation of a silyl ether or silica as the only byproduct. The reaction mechanism has two successive trans-etherification steps that are mediated by the niobium catalyst, first forming one equivalent of benzyl chloride along with the corresponding silyl ether intermediate that undergoes the same reaction pathway to give the second equivalent of benzyl chloride and silyl ether.
- Parker, Bernard F.,Hosoya, Hiromu,Arnold, John,Tsurugi, Hayato,Mashima, Kazushi
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supporting information
p. 12825 - 12831
(2019/10/19)
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- Revisiting the Perfluorinated Trityl Cation
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Although ultimately not isolable for X-ray structural characterization, the free perfluorinated trityl cation was shown to be observable in neat triflic acid, which represents milder conditions than previous reports of this cation in “magic acid” or oleum. A triflate-bound species could be generated in organic solvents using stoichiometric amounts of triflic acid and was shown to be synthetically viable for hydride abstraction from Et3SiH. It was demonstrated that the para-position on the -C6F5 rings is the primary point of attack for decomposition of the cation.
- Delany, Eoghan G.,Kaur, Satnam,Cummings, Steven,Basse, Kristoffer,Wilson, David J. D.,Dutton, Jason L.
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p. 5298 - 5302
(2019/03/11)
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- Ferric(III) Chloride Catalyzed Halogenation Reaction of Alcohols and Carboxylic Acids Using α,α-Dichlorodiphenylmethane
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A new method for chlorination of alcohols and carboxylic acids, using α,α-dichlorodiphenylmethane as the chlorinating agent and FeCl3 as the catalyst, was developed. The method enables conversions of various alcohols and carboxylic acids to their corresponding alkyl and acyl chlorides in high yields under mild conditions. Particulary interesting is the observation that the respective alkyl bromides and iodides can be generated from alcohols when either LiBr or LiI are present in the reaction mixtures.
- Lee, Chang-Hee,Lee, Soo-Min,Min, Byul-Hana,Kim, Dong-Su,Jun, Chul-Ho
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supporting information
p. 2468 - 2471
(2018/04/25)
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- Mild Aliphatic and Benzylic Hydrocarbon C-H Bond Chlorination Using Trichloroisocyanuric Acid
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We present the controlled monochlorination of aliphatic and benzylic hydrocarbons with only 1 equiv of substrate at 25-30 °C using N-hydroxyphthalimide (NHPI) as radical initiator and commercially available trichloroisocyanuric acid (TCCA) as the chlorine source. Catalytic amounts of CBr4 reduced the reaction times considerably due to the formation of chain-carrying ·CBr3 radicals. Benzylic C-H chlorination affords moderate to good yields for arenes carrying electron-withdrawing (50-85%) or weakly electron-donating groups (31-73%); cyclic aliphatic substrates provide low yields (24-38%). The products could be synthesized on a gram scale followed by simple purification via distillation. We report the first direct side-chain chlorination of 3-methylbenzoate affording methyl 3-(chloromethyl)benzoate, which is an important building block for the synthesis of vasodilator taprostene.
- Combe, Sascha H.,Hosseini, Abolfazl,Parra, Alejandro,Schreiner, Peter R.
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p. 2407 - 2413
(2017/03/11)
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- Formamides as Lewis Base Catalysts in SNReactions—Efficient Transformation of Alcohols into Chlorides, Amines, and Ethers
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A simple formamide catalyst facilitates the efficient transformation of alcohols into alkyl chlorides with benzoyl chloride as the sole reagent. These nucleophilic substitutions proceed through iminium-activated alcohols as intermediates. The novel method, which can be even performed under solvent-free conditions, is distinguished by an excellent functional group tolerance, scalability (>100 g) and waste-balance (E-factor down to 2). Chiral substrates are converted with excellent levels of stereochemical inversion (99 %→≥95 % ee). In a practical one-pot procedure, the primary formed chlorides can be further transformed into amines, azides, ethers, sulfides, and nitriles. The value of the method was demonstrated in straightforward syntheses of the drugs rac-Clopidogrel and S-Fendiline.
- Huy, Peter H.,Motsch, Sebastian,Kappler, Sarah M.
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supporting information
p. 10145 - 10149
(2016/08/16)
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- Direct halogenation of alcohols with halosilanes under catalyst- and organic solvent-free reaction conditions
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A chemoselective method for the direct halogenation of different types of alcohols with halosilanes under catalyst- and solvent-free reaction conditions (SFRC) is reported. Various primary, secondary and tertiary benzyl alcohols and tertiary alkyl alcohols were directly transformed to the corresponding benzyl and alkyl halides, respectively, using chlorotrimethylsilane (TMSCl) and bromotrimethylsilane (TMSBr).
- Ajvazi, Njomza,Stavber, Stojan
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supporting information
p. 2430 - 2433
(2016/05/19)
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- Improved Halogenation of Methyl Aromatics and Methyl Heteroaromatics: Unexpected Reactivity of Tetrahalogeno-diphenylglycolurils
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1,3,4,6-Tetrachloro (TCDGU) and 1,3,4,6-tetrabromo-3α,6α-diphenylglycolurils smooth halogen oxidizers have been exploited in a new direction as reagents for free radical substitution toward some N-halosuccinimide nonreactive bis-heterocycles. An unexpected selectivity and reactivity were observed with methyl benzenes, methyl heterocycles, and methyl-bis-heterocycles of interest. A chemometric study has been performed to optimize five independent factors of the chlorination reaction with TCDGU. The predictive model was established either for the halogenation conversion and the ratio of monochlorination.
- Moretti, Florian,Poisson, Guillaume,Marsura, Alain
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p. 173 - 183
(2016/05/19)
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- Iron catalyzed halogenation of benzylic aldehydes and ketones
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A simple and efficient iron-catalyzed method for chlorination of aromatic carbonyl compounds is reported. By using 4-10 mol% Fe(iii) oxo acetate catalyst, prepared by solid state atmospheric oxidation of Fe(ii) acetate, in combination with triethylsilane and chlorotrimethylsilane, hydrosilylation of benzylic carbonyl compounds with subsequent chlorination is achieved within a few hours at room temperature. This new method is mild and rapid compared to the conventional two step approach involving reduction and chlorination reactions in separate stages. Development of synthetic methodology is also supplemented here by kinetic investigation of the reaction mechanism, which supports the tentative mechanisms suggested previously for similar reactions. This journal is
- Savela, Risto,W?rn?, Johan,Murzin, Dmitry Yu.,Leino, Reko
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p. 2406 - 2417
(2015/04/14)
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- Sulfite formation versus chlorination of benzyl alcohols with thionyl chloride
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Recently, we have reported the photolytic decay of a library of para-substituted dibenzylic sulfites in a Srinivasan-Griffin-Rayonet photochemical reactor. In an attempt to synthesize the complete library for that study we discovered that bis(p-methoxybenzyl) sulfite and bis(p-phenoxybenzyl) sulfite could not be formed and only their corresponding benzyl chlorides were synthesized. Thus, sulfite formation versus chlorination of a range of para-substituted benzyl alcohols with thionyl chloride was investigated. Sulfite formation was observed to be parabolically related to Swain and Lupton's Field ?-values while chloride formation was found to be linearly related to Swain and Lupton's Field ?-values.
- Rodriguez, Deana A.,Priefer, Ronny
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p. 3045 - 3048
(2014/05/20)
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- An experimental and theoretical study on imidazolium-based ionic liquid promoted chloromethylation of aromatic hydrocarbons
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The chloromethylation of aromatic hydrocarbons proceeded efficiently using the reusable imidazolium-based ionic liquid as promoter. Mild reaction conditions, enhanced rates, improved yields, recyclability of ionic liquids, and reagents' reactivity which is different from that in conventional organic solvents are the remarkable features observed in ionic liquids. The ionic liquids were recycled in three subsequent runs with no decrease in activity. In addition, the results of calculations with the Gaussian 98 suite of program are in good accordance with the experimental outcomes.
- Wang, Yun,Xi, Yanli
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p. 2196 - 2199
(2014/03/21)
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- Silver-catalyzed decarboxylative chlorination of aliphatic carboxylic acids
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Decarboxylative halogenation of carboxylic acids, the Hunsdiecker reaction, is one of the fundamental functional group transformations in organic chemistry. As the initial method requires the preparations of strictly anhydrous silver carboxylates, several modifications have been developed to simplify the procedures. However, these methods suffer from the use of highly toxic reagents, harsh reaction conditions, or limited scope of application. In addition, none is catalytic for aliphatic carboxylic acids. In this Article, we report the first catalytic Hunsdiecker reaction of aliphatic carboxylic acids. Thus, with the catalysis of Ag(Phen)2OTf, the reactions of carboxylic acids with t-butyl hypochlorite afforded the corresponding chlorodecarboxylation products in high yields under mild conditions. This method is not only efficient and general, but also chemoselective. Moreover, it exhibits remarkable functional group compatibility, making it of more practical value in organic synthesis. The mechanism of single electron transfer followed by chlorine atom transfer is proposed for the catalytic chlorodecarboxylation.
- Wang, Zhentao,Zhu, Lin,Yin, Feng,Su, Zhongquan,Li, Zhaodong,Li, Chaozhong
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experimental part
p. 4258 - 4263
(2012/04/10)
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- Treatment of alcohols with tosyl chloride does not always lead to the formation of tosylates
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Treatment of substituted benzyl alcohols with tosyl chloride resulted in the formation of the corresponding chlorides, not the usual tosylates. A series of experiments demonstrated that it was possible to predict whether chlorination or tosylation would occur for substituted benzyl alcohols and pyridine methanols. Treatment of electron withdrawing group-substituted benzyl alcohols with tosyl chloride gave the corresponding chlorides in moderate yields under mild conditions, which provided a simple way to directly prepare chlorides from alcohols.
- Ding, Rui,He, Yong,Wang, Xiao,Xu, Jingli,Chen, Yurong,Feng, Man,Qi, Chuanmin
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experimental part
p. 5665 - 5673
(2011/09/20)
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- Pd-catalyzed cyanation of benzyl chlorides with nontoxic K 4[Fe(CN)6]
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Non-toxic K4[Fe(CN)6] was demonstrated to be effective as a green cyanating agent for the cyanation of alkyl halides using PPh3/Pd(OAc)2 as a catalyst system. The presented method allowed a series of benzyl chlorides to be smoothly cyanated in up to 88% yield. In order to avoid or suppress the deactivation of the catalyst, the reaction was required to be performed in a stringent inert ambiance.
- Ren, Yunlai,Yan, Mengjie,Zhao, Shuang,Sun, Yanpei,Wang, Jianji,Yin, Weiping,Liu, Zhifei
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supporting information; body text
p. 5107 - 5109
(2011/10/05)
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- An inexpensive and convenient procedure for chloromethylation of aromatic hydrocarbons by phase transfer catalysis in aqueous media
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Reaction of aromatic hydrocarbons catalyzed by a novel catalytic system consisting of zinc chloride, acetic acid, sulfuric acid and PEG-800 in aqueous media under PTC conditions results in chloromethylation in good to excellent yield.
- Hu, Yu Lin,Lu, Ming,Ge, Qiang,Wang, Peng Cheng,Zhang, Sheng Bin,Lu, Ting Ting
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experimental part
p. 97 - 102
(2010/08/05)
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- NOVEL PROTEIN TYROSINE PHOSPHATASE - IB INHIBITORS
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The present invention relates to the novel compounds of the general formula (I), wherein the symbols are same as described in specification, their pharmaceutically acceptable salts, their tautomeric forms, their stereoisomers, pharmaceutical compositions containing them, to process and intermediates for the preparation of the above said compounds, having the utility of these compounds in medicine and to methods for their therapeutic use, and their use in the treatment of diabetes and related diseases.
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- NOVEL PROTEIN TYROSINE PHOSPHATASE - IB INHIBITORS
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The present invention relates to the novel compounds of the general formula (I), wherein the symbols are same as described in specification, their pharmaceutically acceptable salts, pharmaceutical compositions containing them, to process and intermediates for the preparation of the above said compounds, having the utility of these compounds in medicine and to methods for their therapeutic use, and their use in the treatment of metabolic disorders.
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- Identification of alkylarene chloromethylation products using gas-chromatographic retention indices
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Gas-chromatographic retention indices on standard nonpolar polydimethylsiloxane stationary phases allow identification of products formed by known organic reactions even without using mass-spectrometric data. The efficiency of this approach was demonstrated by the example of identification of previously uncharacterized chloromethyl derivatives of alkylarenes, including structural isomers of compounds containing several chloromethyl groups, directly in reaction mixtures. Chromatographic analysis of such reaction mixtures allows identification of positional isomers of the starting alkylarenes even when they are present simultaneously. The retention indices were determined for the first time for more than 50 alkyl-(chloromethyl)arenes, by-products of chloromethylation, and chloromethyl derivatives of the simplest alkyl phenyl ketones. Nauka/Interperiodica 2007.
- Zenkevich,Makarov
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p. 611 - 619
(2008/03/18)
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- [emim]BF4-promoted chloromethylation of aromatic hydrocarbons
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The chloromethylation of aromatic hydrocarbons proceeded efficiently using the reusable ionic liquid [emim]BF4 as promoter. The reactions were completed in 5 h at 70°C with good yields and easy workup. Copyright Taylor & Francis Group, LLC.
- Wang, Yun,Shang, Zhi-Cai,Wu, Tian-Xing
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p. 3053 - 3059
(2007/10/03)
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- Indium-catalyzed direct chlorination of alcohols using chlorodimethylsilane-benzil as a selective and mild system
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The InCl3-catalyzed reaction of alcohols with chlorodimethylsilane (HSiMe2Cl) in the presence of benzil gave the corresponding organic chlorides under mild conditions. Benzil significantly changes the reaction course because the reducing product through dehydroxyhydration was obtained in the absence of benzil. The secondary or tertiary alcohols were effectively chlorinated. The substrates bearing acid-sensitive functional groups were also applied to this system. The highly selective chlorination of the tertiary site was observed in the competitive reaction between tertiary and primary alcohols. The highly coordinated hydrosilane generated from benzil and HSiMe2Cl is an important intermediate. Copyright
- Yasuda, Makoto,Yamasaki, Satoshi,Onishi, Yoshiyuki,Baba, Akio
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p. 7186 - 7187
(2007/10/03)
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- Silica Chloride (SiO2-Cl), a New Heterogeneous Reagent, for the Selective and Efficient Conversion of Benzylic Alcohols to Their Corresponding Chlorides and Iodides
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Structurally different benzylic alcohols were efficiently converted to their corresponding chlorides by silica chloride (SiO2-Cl) in CHCl3 at room temperature. Silica chloride is also able to convert benzylic alcohols to their iodides in the presence of NaI in a mixture of CH3CN/CHCl3 in excellent yields.
- Firouzabadi, Habib,Iranpoor, Naser,Karimi, Babak,Hazarkhani, Hassan
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p. 3671 - 3677
(2007/10/03)
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- A duality of mechanisms for the fragmentation of substituted benzyloxychlorocarbenes
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Substituted benzyloxychlorocarbenes (X-PhCH2OCCl) were generated photochemically at 25 °C in dichloroethane from appropriate diazirine precursors. Fragmentations of the carbenes produced were determined by laser flash photolysis. The data (X, kfrag in s-1) were: p-Me, 2.6 × 105; p-Ph, 8.3 × 104; H, 6.0 × 104; p-Cl, 5.2 × 104; m-Cl, 1.3 × 105; p-F3C, 2.1 × 106; p-O2N, 6.3 × 106. A Hammett correlation of log kfrag versus σ+ was parabolic. The curvature was taken to imply the gradual change of the fragmentation mechanism from predominantly heterolytic for X-PhCH2CCl with electron-donating X (with developing positive charge on the benzylic carbon in the transition state) to predominantly homolytic for carbenes with electron-withdrawing X. This idea was supported by computational studies. Copyright
- Moss, Robert A.,Ma, Yan,Sauers, Ronald R.
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p. 13968 - 13969
(2007/10/03)
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- A simple and efficient iodination of alcohols on polymer-supported triphenylphosphine
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A simple, mild, and high-yielding procedure for the iodination of allylic, benzylic, and other primary alcohols using a combination of iodine and imidazole on polymer-supported triphenyl phosphine is described.
- Anilkumar, Gopinathan,Nambu, Hisanori,Kita, Yasuyuki
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p. 190 - 191
(2013/09/06)
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- Oxidation of benzylsilanes and benzyltins by oxovanadium(V) compound and molecular oxygen
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Benzylsilane and benzyltin compounds were oxidized by oxovanadium(V) compound under an oxygen atmosphere to afford the corresponding aromatic aldehydes (ketones) and/or carboxylic acids. In the reaction of benzyltins, oxovanadium(V) compound can be reduce
- Hirao, Toshikazu,Morimoto, Chihiro,Takada, Takashi,Sakurai, Hidehiro
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p. 5073 - 5079
(2007/10/03)
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- Interpretation of retention indices in gas chromatography for establishing structures of isomeric products of alkylarenes radical chlorination
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By an example of previously uncharacterized products obtained by alkylarenes radical chlorination was demonstrated that combination of various interpretation methods applied to the retention indices (RI) in the gas chromatography on the standard nonpolar phases (comparison of RI of products and initial compounds, characteristics of succession of the chromatographic elution of the structural isomers with the use of estimation of molecular dynamic parameters, application of the additive schemes to RI calculation, and using of structural analogy CH3?Cl for testing the results obtained) permitted unambiguous identification of the structure even without data of mass spectrometry.
- Zenkevich
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p. 270 - 280
(2007/10/03)
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- Oxidation of benzyltins by oxovanadium(V) compound and molecular oxygen
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Benzyltin compounds were oxidized by oxovanadium(V) compound under an oxygen atmosphere to afford the corresponding aromatic aldehydes (ketone) and/or carboxylic acids.
- Hirao, Toshikazu,Morimoto, Chihiro,Takada, Takashi,Sakurai, Hidehiro
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p. 1961 - 1963
(2007/10/03)
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- Reactions of benzyl methyl substituted-benzyl phosphites with tert- butyl hypochlorite: 'Balanced TS' validating reactivity/selectivity principle
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Reactions of a series of several benzyl methyl substituted-benzyl phosphites with tert-butyl hypochlorite were investigated. The reactions produced phosphates, isobutene, alkyl chlorides, and benzyl chlorides via phosphonium chlorides as intermediates. Fu
- Kim, Sung Soo,Zhu, Yu,Oh, In Seok,Lim, Chang Gyeong
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p. 836 - 842
(2007/10/03)
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- Gas-phase substituent effects in highly electron-deficient systems. II. stabilities of 1-aryl-2,2,2-trifluoroethyl cations based on chloride-transfer equilibria
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The relative stabilities of 1-aryl-2,2,2-trifluoroethyl cations were determined based on the chloride ion-transfer equilibria in the gas phase. An application of the Yukawa-Tsuno equation to this substituent effect on the equilibrium constants gave a remarkably larger r+ of 1.53 and a ρ of-10.6, supporting our previous conclusion that the highly electron-deficient benzylic carbocation systems are characterized by extremely high resonance demands. This r+ value, furthermore, conformed a linear relationship between the r+ value and the relative stability of the unsubstituted member of the respective benzylic carbocations, clearly demonstrating a continuous spectrum of varying resonance demands characteristic of the stabilities of carbocations. The π-delocalization of the positive charge into the aryl π-system increases with the destabilization of a carbocation by the α-substituent(s) linked to the central carbon. In addition, the r + value of 1.53 for 1-aryl-2,2,2-trifluoroethyl cations was found to be in complete agreement with that for the solvolysis of 1-aryl-2,2,2- trifluoroethyl tosylates in 80% aq acetone. This reveals that the r+ value observed for this solvolysis must be the intrinsic resonance demand of a highly electron-deficient cationic transition state in the SN 1 ionizing process. The identity of the r+ value was consistent with our previous observation for other benzylic carbocation systems, indicating that the degree of the π-delocalization of the positive charge is identical between the cationic transition state and an intermediate cation for all benzylic systems, which cover a wide range of reactivity and stability of the carbocation. This leads us to the conclusion that the geometry of the transition state in the ionizing process of the SN1 solvolysis, which is a highly endothermic reaction, closely resembles the high-energy product, an intermediate cation.
- Mishima, Masaaki,Inoue, Hiroki,Fujio, Mizue,Tsuno, Yuho
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p. 1163 - 1169
(2007/10/03)
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- Electrophilic Aromatic Substitution. 13.1 Kinetics and Spectroscopy of the Chloromethylation of Benzene and Toluene with Methoxyacetyl Chloride or Chloromethyl Methyl Ether and Aluminum Chloride in Nitromethane or Tin Tetrachloride in Dichloromethane. the Methoxymethyl Cation as a Remarkably Selective Common Electrophile
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Vacuum line kinetics studies have been made of the reaction in nitromethane between benzene and/or toluene, methoxyacetyl chloride (MAC), and AlCl3 to produce benzyl or xylyl chlorides, CO, and a CH3OH- AlCl3 complex. For both arenes, the rate law appears to be R = (k3/[AlCl3]0) [AlCl3]2-[MAC]. When chloromethyl methyl ether (CMME) is substituted for MAC, a similar rate law is obtained. Both chloromethylation reactions yielded similar, large kT/kB ratios (500-600) and similar product isomer distributions with low meta percentages (~0.4) which suggest CH3OCH2+ or the CH3OCH2+Al2Cl7 - ion pair as a common, remarkably selective, electrophile. The kinetics of MAC decomposition to CMME and CO in the presence of AlCl3 yielded the rate law R = k2[AlCl3]0[MAC]. Here AlCl3 is a catalyst (no CH3OH is formed), and thus the rate law is equivalent to the chloromethylation rate law. All three reactions have comparable reactivities, which is consistent with rate-determining production of the electrophile. Kinetics studies of benzene or toluene with SnCl4 and MAC or CMME in dichloromethane were also completed. With MAC and benzene the rate law is R = k3[SnCl4]0[MAC][benzene] and with toluene R = k2[SnCl4]0[MAC]. MAC decomposition, again followed by CO production, was unaffected by the presence of either aromatic and obeyed the rate law R = k2′ [SnCl4]0[MAC] where k2 ≈ k2′ Chloromethylation with CMME followed the rate law R = k3[SnCl4]0[CMME][arene] for benzene and toluene and produced a kT/kB ratio and product isomer distributions very similar to those determined with AlCl3 in nitromethane, further supporting a common electrophile. Low-temperature 13C and 119Sn FT-NMR and Raman spectroscopic studies suggest the existence of a weak 1:1 adduct between MAC and SnCl4 of the type RCXO → SnCl4, with electron donation to the metal through carboxy oxygen. Finally, an explanation is provided for the range of chloromethylation kT/kB values and product isomer percentages published in the literature.
- Dehaan, Franklin P.,Djaputra, Markus,Grinstaff, Mark W.,Kaufman, Craig R.,Keithly, James C.,Kumar, Amit,Kuwayama, Mark K.,Dale Macknet,Na, Jim,Patel, Bimal R.,Pinkerton, Michael J.,Tidwell, Jeffrey H.,Villahermosa, Randy M.
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p. 2694 - 2703
(2007/10/03)
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- New applications of tungsten hexachloride (WCl6) in organic synthesis. Halo-de-hydroxylation and dihalo-de-oxo-bisubstitution reactions
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Tungsten hexachloride (WCl6) has been used for the halo-de-hydroxylation and dihalo-de-oxo-bisubstitution reactions of benzylic alcohols, benzaldehydes, acyloins, and epoxides to their chlorides, gem-dichlorides, vic-trichlorides, and vic-dichlorides respectively.
- Firouzabadi, Habib,Shiriny, Farhad
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p. 14929 - 14936
(2007/10/03)
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- Homolytic fragmentations of benzyl methyl substituted-benzyl carbinyloxy radicals and the related reactions: Limitations of the Leffler-Hammond postulate and reactivity/selectivity principle
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Photolyses of benzyl methyl substituted-benzyl carbinyl hypochlorites produced the corresponding carbinyloxy radicals, which undergo fragmentations. Oxidations of 1-aryl-2,3-diphenylpropan-2-ols by ceric ammonium nitrate also proceeded through quite simil
- Kim, Sung Soo,Kim, Hong Rae,Kim, Hong Bae,Youn, Sang Jun,Kim, Chul Jae
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p. 2754 - 2758
(2007/10/02)
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- Selective Cross Coupling via Oxovanadium(V)-Induced Oxidative Desilylation of Benzylic Silanes
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Benzylic silanes bearing an electron-donating group at the ortho- or para-position underwent the oxovanadium(V)-induced one-electron oxidative desilylation due to low ionization potential, which was applied to the intermolecular regioselective coupling with allylic silanes or silyl enol ether.
- Hirao, Toshikazu,Fujii, Takashi,Ohshiro, Yoshiki
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p. 8005 - 8008
(2007/10/02)
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- Photolysis of (Arylmethyl)triphenylphosphonium Salts. Substituent, Counterion, and Solvent Effects on Reaction Products
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Quaternary (arylmethyl)phosphonium salts of the general formula ArCH2-PR3(+)Y(-) (Ar = substituted phenyl or 1-naphthyl; R = phenyl, ferrocenyl, or butyl; Y(-) = BF4(-) or halide) have been photolyzed in acetonitrile or in methanol.Photolysis involved the cleavage of the P-CH2 bond and the products derived from both, the arylmethyl radical and the carbocation, were formed.The proportion of the radical- and carbocation-derived products was determined as a function of substituents in group Ar, of groups R, counterions Y(-), and the solvent.For the nonoxidizable counterion (BF4(-), the proposed mechanism of the reaction involves initial homolysis, followed by the escape of the radical products from a solvent cage, or by the electron transfer from carbon to phosphorus, yielding the corresponding arylmethyl carbocation.The latter can either react with the solvent to form the observed carbocation-derived product or can undergo recombination with the tertiary phosphine formed to yield the starting phosphonium ion.Some indication of the "inverted substituent effect" resulting from the inhibition of single electron transfer from an easily oxidized radical was obtained.For the oxidizable counterions (halides), an additional pathway is suggested, that involves electron transfer from the anion, yielding the arylmethyl radical and the phosphine, thus decreasing the ionic/radical products ratio.
- Imrie, C.,Modro, T. A.,Rohwer, E. R.,Wagener, C. C. P.
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p. 5643 - 5649
(2007/10/02)
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- N-NITROSOHYDROXYLAMINES I. ACETOLYSIS AND ACID-CATALYZED HYDROLYSIS OF N,O-DIBENZYL-N-NITROSOHYDROXYLAMINES. REACTION WITH POTASSIUM t-BUTOXIDE
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The major products of the hydrolysis of N,O-dibenzyl-N-nitrosohydroxylamines (3) are the denitrosated parent hydroxylamines (6); under more forcing conditions, products of the further hydrolysis of 6 are obtained.Acetolysis in acetic acid gives the benzyl acetates derived from both N- and O-substituents.With potassium tert-butoxide, the major path is abstraction of an O-benzyl hydrogen followed by fragmentation to the aldehyde and the benzyldiazotate ion.Possible mechanisms for the formation of the products are discussed.
- Kano, Kunio,Anselme, Jean-Pierre
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p. 10075 - 10086
(2007/10/02)
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- Halogenative Allylation and Reduction of Aromatic Acetals by Double Substitution of Alkoxyl Groups in Acetal
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In the presence of excessive amount of acetyl halide along with a catalytic amount of tin(II) halide, aromatic acetals react with allyltrimethylsilane or triethylsilane to give α-allylbenzyl halides or benzyl halides, respectively, in good to excellent yields.
- Oriyama, Takeshi,Iwanami, Katsuyuki,Tsukamoto, Kazuhisa,Ichimura, Yuichi,Koga, Gen
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p. 1410 - 1412
(2007/10/02)
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- REACTIVITY OF 3,6-DIMETHOXY-3,6-DIMETHYLCYCLOHEXA-1,4-DIENE: NUCLEAR VERSUS BENZYLIC NUCLEOPHILIC SUBSTITUTION
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The treatment of cis/trans-3,6-dimethoxy-3,6-dimethylcyclohexa-1,4-diene (ca. 1/1 mixture; easily prepared electrochemically in multigram scale from p-xylene) under acidic conditions (acetic, trifluoroacetic, sulfuric, or a Lewis acid) yields almost exclusively 2-methoxy-1,4-dimethylbenzene 4, through a trasposition reaction.The use of aqueous hydrochloric or hydrofluoric acid gives 2,5-dimethylphenol 12, and with hydrogen chloride a mixture of 2- and α-chloro-p-xylene (13, 14) is isolated.Different oxygen-, nitrogen-, and sulfur-containing nucleophiles (alcohols,thiols, or hydrazoic acid) react with 3 under acid catalysis giving the corresponding products resulting from a nuclear or/ and benzylic substitution on p-xylene (15 - 20).The reaction of compound 3 with organolithium reagents affords exclusively benzylic products 21 in a regiospecific manner.In all cases the mixtures of isomers are separated by column chromatography.The lithiation of compound 3 with lithium powder or lithium naphthalenide fails, giving p-xylene.A probable mechanism is proposed for the studied reactions.
- Alonso, Francisco,Barba, Isidoro,Yus, Miguel
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p. 2069 - 2080
(2007/10/02)
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- Versatility of Zeolites as Catalysts for Ring or Side-Chain Aromatic Chlorinations by Sulfuryl Chloride
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Zeolites catalyze chlorination of aromatics by sulfuryl chloride SO2Cl2.It is possible by an appropriate choice of the catalyst to effect at will, with very high selectivity, either the ring or the side-chain chlorination.Zeolite ZF520 is the choice catalyst for the former, because of its high Broensted acidity.Zeolite NaX (13X) is a fine catalyst for the latter, free-radical chlorination; the reaction is best effected in the presence of a light source; the catalyst can be reused many times with no loss in activity.Both reaction modes, the ionic (ring chlorination)and the radical (side-chain substitution), are likely to occur outside of the channel network in the microporous solid.The effects of various experimental factors - such as the nature of the solvent, the reaction time and temperature, the Broensted acidity of the solid support, the presence of radical inhibitors, and the quantity of catalysts - were investigated.The procedures resulting from this study are very easy to implement in practice and are quite effective.
- Delaude, Lionel,Laszlo, Pierre
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p. 5260 - 5269
(2007/10/02)
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- CATALYTIC ACTIVITY OF TRIVALENT LANTHANIDE SALTS IN THE CHLOROMETHYLATION OF AROMATIC COMPOUNDS
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A study was carried out on the electrophilic substitution reactions in benzene and toluene by the action of ClCH2OCH3 in the presence of trivalent lanthanide salts, LnCl3, where Ln = Ce, Dy, Er, and Sm(O3SCF3)3 as the catalysts, at room temperature over 24 h.These lanthanide salts display the properties of weak but hard Lewis acids.The raection proceeds exclusively by chloromethylation with the subsequent formation of diarylmethanes.
- Davydov, D. V.,Vinogradov, S. A.,Beletskaya, I. P.
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p. 627 - 628
(2007/10/02)
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- An E.S.R. Investigation of Radical Cations Formed in Friedel-Crafts Reactions
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The present study deals with the detection and identification of radical cations produced in a Friedel-Crafts alkylating system, with benzene, toluene, or ethylbenzene, and an alkyl chloride.Our results indicate that the observed e.s.r. spectra are due to polycyclic aromatic radical cations formed from the parent hydrocarbons.It is suggested that benzyl halides produced in the Friedel-Crafts alkylating reaction undergo Scholl self-condensation to give polycyclic aromatic hydrocarbons, which are converted into the corresponding polycyclic aromatic radical cations in the presence of aluminium chloride.
- Wang, Hanqing,Kispert, Lowell. D.,Sang, Hong
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p. 1463 - 1470
(2007/10/02)
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- Amino Acids, 9 - Reactions of 5-Oxoproline Derivatives with Phosphorus Pentachloride - Synthesis of Chloro-pyrrole-2-carboxylic Acid Derivatives
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N-Benzyl-4,5-dichloro-1H-pyrrole-2-carboxylic esters 6 are formed from N-benzyl-5-oxoproline esters 5 and PCl5 via differently chlorinated intermediates.The N-benzhydryl- L-3 and N-acyl-5-oxoproline esters L-4, on the other hand, suffer cleavage of the N-substituent in the course of this reaction sequence to give L-4,4,5-trichloro-3,4-dihydro-2H-pyrrole-2-carboxylic esters 18, which are dehydrohalogenated in the presence of base, yielding 4,5-dichloro-1H-pyrrole-2-carboxylic esters 20.These reactions provide the best access to 4,5-dichloro-1H-pyrrole-2-carboxylic acid derivatives which, in turn, can serve as precursors in the synthesis of pyoluteorin type compounds.
- Effenberger, Franz,Mueller, Wolfgang,Isak, Heinz
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