- 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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- Ir-Catalyzed Asymmetric and Regioselective Hydrogenation of Cyclic Allylsilanes and Generation of Quaternary Stereocenters via the Hosomi-Sakurai Allylation
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A number of cyclic dienes containing the allylsilane moiety were prepared by a Birch reduction and subjected to iridium-catalyzed regioselective and asymmetric hydrogenation, which provided chiral allylsilanes in high conversion and enantiomeric excess (up to 99 % ee). The compounds were successively used in the Hosomi–Sakurai allylation with various aldehydes employing TiCl4 as Lewis acid, providing adducts with two additional stereogenic centers in excellent diastereoselectivity.
- Rabten, Wangchuk,Margarita, Cristiana,Eriksson, Lars,Andersson, Pher G.
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supporting information
p. 1681 - 1685
(2018/01/05)
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- Aromatic cation activation: Nucleophilic substitution of alcohols and carboxylic acids
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A new method for the nucleophilic substitution of alcohols and carboxylic acids using aromatic tropylium cation activation has been developed. This article reports the use of chloro tropylium chloride for the rapid generation of alkyl halides and acyl chlorides under very mild reaction conditions. It demonstrates, for the first time, the synthetic potential of tropylium cations in promoting chemical transformations.
- Nguyen, Thanh V.,Bekensir, Alp
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supporting information
p. 1720 - 1723
(2014/04/17)
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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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- 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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- 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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- Synthesis, pharmacological evaluation, and molecular modeling studies of novel peptidic CAAX analogues as farnesyl-protein-transferase inhibitors
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Fifteen analogues of the C-terminal CA1A2X motif were synthesized and evaluated for their inhibition potency against farnesyltransferase (FTase). Replacement of the A2 residue by phenylalanine or tyrosine-derived analogues, in which a different number of methyl groups were introduced on the aromatic ring, resulted in compounds less active than the reference compound CVFM against FTase except for compounds I and VI (IC50 = 1 μM and 2.5 μM, respectively) that were comparable to CVFM and compound IV (IC50 = 0.1 μM), which was 6-fold more active than the reference compound. Because pseudopeptidic derivatives I-IX were inactive in the cellular assays, the N-formyl- and methyl-ester derivatives (compounds X-XV) were synthesized and tested on different cell lines, showing, in some cases, activity and appreciable selectivity against transformed cells. To rationalize the obtained results, molecular modeling experiments were carried out suggesting the molecular basis of FTase inhibition by these products.
- Santagada, Vincenzo,Caliendo, Giuseppe,Severino, Beatrice,Lavecchia, Antonio,Perissutti, Elisa,Fiorino, Ferdinando,Zampella, Angela,Sepe, Valentina,Califano, Daniela,Santelli, Giovanni,Novellino, Ettore
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p. 1882 - 1890
(2007/10/03)
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- Synthesis and molecular structures of zirconium and hafnium complexes bearing dimethylsilandiyl-bis-2,4,6-trimethylindenyl and dimethylsilandiyl-bis- 2-methyl-4,6-diisopropylindenyl ligands
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Zirconium and hafnium ansa-complexes containing 2,4,6-trialkyl-substituted indenyl fragments were synthesized and unambiguously characterized. Mixtures of rac- and meso-Me2Si(2-Me-4,6-R2C9H 3-η5)2MCl2, where R = Me, i-Pr and M = Zr, Hf, were obtained by a treatment of MCl4 by dilithium salts of the respective bis(2,4,6-trialkylindenyl)dimethylsilanes in toluene. Alternatively, better yields of the same complexes can be obtained by the reaction between metal tetrachlorides and indenyl-tin derivatives gave the desired ansa-metallocenes. All rac- and meso-complexes of Zr and Hf were isolated in an analytically pure form, and six of these ansa-metallocenes were characterized by X-ray crystal structure analysis.
- Izmer, Vyacheslav V.,Sorokin, Denis A.,Kuz'Mina, Lyudmila G.,Churakov, Andrei V.,Howard, Judith A.K.,Voskoboynikov, Alexander Z.
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p. 1067 - 1079
(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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- Aromatic Spiranes XX [1]: Syntheses of Dimethylsubstituted 2-Carboxymethyl-indan-1-ones and Benzylchlorides as Synthones for Syntheses of di- to tetramethylsubstituted Spirobiindandiones
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The isomeric dimethyl methylbenzoates 5, obtained from the bromides via Grignard reactions with dimethylcarbonate, were reduced with LiAlH4 to the hydroxymethyl derivatives 6. The latter were then transformed both to the benzylchlorides 7 (with SOCl2) and to the aldehydes 8 (with pyridinium chlorochromate). Knoevenagel-Doebner reaction of 8 afforded the acrylic acids 9 which (after hydrogenation to 11) were cyclized to the desired indanones 12 with polyphosphoric acid. On the other hand, 12c and 12e were prepared from dimethyl 3-chloropropiophenone (14) by warming with sulfuric acid. After NaH-catalyzed reaction with dimethylcarbonate, the indanones 12 gave the ketoesters 15 which then could be hydrogenated to the indanes 16. All reactions proceeded with satisfactory to excellent yields (60-90%).
- Neudeck
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p. 185 - 200
(2007/10/03)
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- ALKALOIDS OF Nitraria schoberi. STRUCTURE OF NITRARAINE
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The dehydration of nitraraine leads to the formation of 1-(2',6'-dimethylbenzyl)-β-carboline, together with other products.Several isomeric 1-(dimethylbenzyl)-β-carbolines have been synthesized for comparison.The products of acylation, hydrogenation, and oxidation of the alkaloid nitraraine have been studied.The results obtained have shown its structure as (+/-)-16-hydroxymethylyohimb-16-ene.
- Ibragimov, A. A.,Yunusov, S. Yu.
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p. 502 - 509
(2007/10/02)
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- ARYLMETHYL ISOCYANATES
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Chloromethyl isocyanate reacts readily with aromatic hydrocarbons in the presence of anhydrous ferric chloride or other catalysts of the Friedel-Crafts reaction with the formation of arylmethyl isocyanates.The latter add alcohols and amines readily, being converted into the corresponding substituted urethanes and ureas.When heated in the presence of catalytic amounts of 1,3-dimethylphosphol-3-ene they give substituted carbodiimides.
- Kozhushko, B. N.,Lomakina, A. V.,Paliichuk, Yu. A.,Shokol, V. A.
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p. 654 - 660
(2007/10/02)
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- New Approach to the Mechanism of the Reaction between Benzyl Grignard Reagents and Carbonyl Compounds
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The reaction of the magnesium chloride with ketones can lead to the formation of ortho alcohols 4, normal alcohols 3, or enolates.We propose a mechanism for the reaction whose first step, as in the case of aldehydes, is a reversible attack of the ketone at the ortho position of the benzylic Grignard reagent, which can then lead to the formation of the normal alcohol and/or enolate.The fact that benzylmagnesium chloride reacts with cyclobutanone to give a diol analogous to that obtained in reactions with aldehydes, while its reaction with 1,1,1-trifluoro-2-propanone does not give a diol, leads us to propose an interpretation involving steric effects in the rearrangement alkoxide.In the case of ketones, these steric interactions generally prevent the Prins-type reaction leading to diols.
- Bernardon, Claude,Deberly, Alain
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p. 463 - 468
(2007/10/02)
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