- Thiourea-Mediated Halogenation of Alcohols
-
The halogenation of alcohols under mild conditions expedited by the presence of substoichiometric amounts of thiourea additives is presented. The amount of thiourea added dictates the pathway of the reaction, which may diverge from the desired halogenation reaction toward oxidation of the alcohol, in the absence of thiourea, or toward starting material recovery when excess thiourea is used. Both bromination and chlorination were highly efficient for primary, secondary, tertiary, and benzyl alcohols and tolerate a broad range of functional groups. Detailed electron paramagnetic resonance (EPR) studies, isotopic labeling, and other control experiments suggest a radical-based mechanism. The fact that the reaction is carried out at ambient conditions, uses ubiquitous and inexpensive reagents, boasts a wide scope, and can be made highly atom economic, makes this new methodology a very appealing option for this archetypical organic reaction.
- Mohite, Amar R.,Phatake, Ravindra S.,Dubey, Pooja,Agbaria, Mohamed,Shames, Alexander I.,Lemcoff, N. Gabriel,Reany, Ofer
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p. 12901 - 12911
(2020/11/26)
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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)
-
- 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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- A preparation method of the Pcad (by machine translation)
-
The invention discloses a method for preparing chlorobenzaldehyde, monochlorotoluene to raw materials under the action of catalyst with chlorine to produce substitution reaction to obtain the mixture of chlorine phenmethyl chlorine and chlorine benzal chloride. To chlorine phenmethyl chlorine and chlorine benzal chloride mixture under the action of catalyst through hydrolytic reaction and air catalytic oxidation reaction to obtain the Pcad. The invention through the action of a catalyst reduces the reaction temperature of the substitution reaction, improves the selectivity of the substitution reaction, by hydrolysis reaction and air way of combining the catalytic oxidation reaction to improve the yield of chlorobenzaldehyde, through catalyst applied mechanically mode to reduce the hydrolysis reaction of the waste water. (by machine translation)
- -
-
Paragraph 0066-0068; 0077-0079
(2019/05/08)
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- NMP-mediated chlorination of aliphatic alcohols with aryl sulfonyl chloride for the synthesis of alkyl chlorides
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NMP-mediated chlorination of aliphatic alcohols has been developed for the synthesis of alkyl chlorides. This facile, efficient and practical approach used simple and readily available aryl sulfonyl chlorides as the chlorination reagent for the construction of C–Cl bond in good to excellent yields with mild conditions and broad substrate scope.
- Zheng, Dagui,Mao, Liu-Liang,Zhu, Xian-Hong,Zhou, An-Xi
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supporting information
p. 2793 - 2800
(2018/11/06)
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- Systematic Evaluation of Sulfoxides as Catalysts in Nucleophilic Substitutions of Alcohols
-
Herein, a method for the nucleophilic substitution (SN) of benzyl alcohols yielding chloro alkanes is introduced that relies on aromatic sulfoxides as Lewis base catalysts (down to 1.5 mol-%) and benzoyl chloride (BzCl) as reagent. A systematic screening of various sulfoxides and other sulfinyl containing Lewis bases afforded (2-methoxyphenyl)methyl sulfoxide as optimal catalyst. In contrast to reported formamide catalysts, sulfoxides also enable the application of plain acetyl chloride (AcCl) as reagent. In addition, it was demonstrated that weakly electrophilic carboxylic acid chlorides like BzCl promote Pummerer rearrangement of sulfoxides already at room temperature. This side-reaction also provided the explanation, why sulfoxide catalyzed SN-reactions of alcohols do not allow the effective production of aliphatic and electron deficient chloro alkanes. Comparison experiments provided further insight into the reaction mechanism.
- Motsch, Sebastian,Schütz, Christian,Huy, Peter H.
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supporting information
p. 4541 - 4547
(2018/09/13)
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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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- Highly selective halogenation of unactivated C(sp3)-H with NaX under co-catalysis of visible light and Ag@AgX
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The direct selective halogenation of unactivated C(sp3)-H bonds into C-halogen bonds was achieved using a nano Ag/AgCl catalyst at RT under visible light or LED irradiation in the presence of an aqueous solution of NaX/HX as a halide source, in air. The halogenation of hydrocarbons provided mono-halide substituted products with 95% selectivity and yields higher than 90%, with the chlorination of toluene being 81%, far higher than the 40% conversion using dichlorine. Mechanistic studies demonstrated that the reaction is a free radical process using blue light (450-500 nm), with visible light being the most effective light source. Irradiation is proposed to cause AgCl bonding electrons to become excited and electron transfer from chloride ions induces chlorine radical formation which drives the substitution reaction. The reaction provides a potentially valuable method for the direct chlorination of saturated hydrocarbons.
- Liu, Shouxin,Zhang, Qi,Tian, Xia,Fan, Shiming,Huang, Jing,Whiting, Andrew
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p. 4729 - 4737
(2018/10/23)
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- SNAr catalysis enhanced by an aromatic donor-acceptor interaction; Facile access to chlorinated polyfluoroarenes
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Selective catalytic SNAr reaction of polyfluoroaryl C-F bonds with chloride is shown. Stoichiometric TMSCl makes the reaction exergonic and allows catalysis, which involves ground state elevation of chloride, aromatic donor-acceptor interactions, and stabilization of the Meisenheimer complex. Traditional cross-coupling of the products is now possible and demonstrates the utility.
- Senaweera, Sameera,Weaver, Jimmie D.
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p. 7545 - 7548
(2017/07/12)
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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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- PROCESS FOR THE PREPARATION OF ORGANIC HALIDES
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The present invention provides a halo-de-carboxylation process for the preparation of organic chlorides, organic bromides and mixtures thereof, from their corresponding carboxylic acids, using a chlorinating agent selected from trichloroisocyanuric acid (TCCA), dichloroisocyanuric acid (DCCA), or combination thereof, and a brominating agent.
- -
-
Paragraph 00163
(2017/08/01)
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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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- Method for preparing chlorohydrocarbons from alcohols by using aryl sulfonyl chloride as chlorination agent
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The invention provides a method for preparing chlorohydrocarbons from alcohols by using aryl sulfonyl chloride as a chlorination agent. The method comprises the following steps: heating alcohols and aryl sulfonyl chloride in N,N-dialkyl substituted amide to react for 30 minutes, cooling the reaction product to room temperature, adding dichloromethane and water, carrying out extraction and skimming, washing the organic layer with saturated saline water, drying with anhydrous sodium sulfate, steaming to remove the solvent, and carrying out further separation and purification to obtain the chlorohydrocarbons. The method has the characteristics of cheap and accessible chlorination agent, simple technical process, short reaction time and the like, can obtain high reaction under the condition that the aryl sulfonyl chloride consumption is approximate to the stoichiometric quality, and can remove the reaction byproduct aryl sulfonic acid from the reaction mixture.
- -
-
Paragraph 0011; 0012; 0016
(2017/01/17)
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- METHOD OF CONVERTING ALCOHOL TO HALIDE
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The present invention relates to a method of converting an alcohol into a corresponding halide. This method comprises reacting the alcohol with an optionally substituted aromatic carboxylic acid halide in presence of an N-substituted formamide to replace a hydroxyl group of the alcohol by a halogen atom. The present invention also relates to a method of converting an alcohol into a corresponding substitution product. The second method comprises: (a) performing the method of the invention of converting an alcohol into the corresponding halide; and (b) reacting the corresponding halide with a nucleophile to convert the halide into the nucleophilic substitution product.
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Page/Page column 96
(2017/01/02)
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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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- A Visible-Light-Induced α-H Chlorination of Alkylarenes with Inorganic Chloride under NanoAg@AgCl
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An efficient, photocatalytic chlorination of alkylarene α-H groups using NaCl/HCl as a chlorine source has been developed, which involves a radical mechanism under visible-light (including sunlight) conditions. A chlorine radical is proposed to be formed by an electron transfer from chloride ion to O2 in air through the bandgap hole of the semiconductor AgCl. The chlorination protocol is characterized by its use of natural sunlight or other visible light, mild conditions, cheap source of chlorine, green solvent, and high selectivity. The yield of benzylchloride is 95 % with a toluene conversion as high as 40 %, which rivals traditional chlorination methods.
- Liu, Shouxin,Zhang, Qi,Li, Huiying,Yang, Yihua,Tian, Xia,Whiting, Andrew
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supporting information
p. 9671 - 9675
(2015/06/30)
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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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- DMSO-catalyzed chlorination of alcohols using N-phenylbenzimidoyl chloride
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N-phenylbenzimidoyl chloride has been demonstrated as an efficient chlorination reagent catalyzed by dimethyl sulfoxide (DMSO) in conversion of alcohols to corresponding chlorides. The reaction conditions were mild, and most of the substrates gave satisfactory yields. The configuration inversion of the chlorination was proved using optically active phenyl alcohols. The amount of DMSO can be as low as 0.001 eq without reducing the efficiency of the chlorination. A plausible mechanism for the reaction was proposed and proved by experiments. The reaction is stereoselective and potentially chemoselective among primary benzyl alcohols, secondary benzyl alcohols, and unactivated aliphatic alcohols.
- Wang, Qiang,Xu, Jian,Xu, Zhou-Qing,Yan, Ji-Dan
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p. 2071 - 2076
(2013/06/05)
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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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- Efficient organic transformations mediated by ZrOCl28H 2O in Water
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Operationally simple and environmentally benign methods for some organic transformations comprising reductive coupling of sulfonyl chlorides, chemoselective deoxygenation of sulfoxides, and halogenation of alcohols mediated by ZrOCl28H2O/MX in water have been developed.
- Jafarpour, Maasoumeh,Rezaeifard, Abdolreza,Heidari, Mahdieh
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experimental part
p. 1470 - 1482
(2011/10/05)
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- Anti-prion activities and drug-like potential of functionalized quinacrine analogs with basic phenyl residues at the 9-amino position
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In this paper, we report the synthesis and cell-based anti-prion activity of quinacrine analogs derived by replacing the basic alkyl side chain of quinacrine with 4-(4-methylpiperazin-I-yl)phenyl, (1-benzylpiperidin-4-yl) and their structural variants. Several promising analogs were found that have a more favorable anti-prion profile than quinacrine in terms of potency and activity across different prion-infected murine cell models. They also exhibited greater binding affinities for a human prion protein fragment (hPrP121-231) than quinacrine, and had permeabilities on the PAMPA-BBB assay that fall within the range of CNS permeant candidates. When evaluated on bidirectional assays on a Pgp overexpressing cell line, one analog was less susceptible to Pgp efflux activity compared to quinacrine. Taken together, the results point to an important role for the substituted 9-amino side chain attached to the acridine, tetrahydroacridine and quinoline scaffolds. The nature of this side chain influenced cell-based potency, PAMPA permeability and binding affinity to hPrP121-231.
- Nguyen, Thuy,Sakasegawa, Yuji,Doh-Ura, Katsumi,Go, Mei-Lin
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experimental part
p. 2917 - 2929
(2011/07/08)
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- Boron difluoride acetylacetonate sulfenyl(selenyl) halides
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By cleavage of disulfide and diselenide derivatives of the boron difluoride acetylacetonate the previously unknown sulfenyl(selenyl) chlorides and bromides were prepared. It was shown that these compounds could be involved into the substitution and addition reactions characteristic of sulfenyl(selenyl) halides. Pleiades Publishing, Ltd., 2010.
- Svistunova,Shapkin,Zyazeva
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body text
p. 2430 - 2437
(2011/04/16)
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- Synthesis and biological evaluation of 3,4-diaryl-5-aminoisoxazole derivatives
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A series of cis-restricted 3,4-diaryl-5-aminoisoxazoles have been synthesized and evaluated for their biological activities. Among them, compound 11a and 13a displayed potent cytotoxic activities in vitro against five human cancer cell lines with IC50 values in the low micromolar range and two compounds inhibited tubulin polymerization with IC50 value of 1.8, and 2.1 μM, respectively, similar to that of CA-4. Compound 13a could arrest at the G2/M phase of the cell cycle at the concentration of 0.1 and 1.0 μM and induce apoptosis at 0.1-1.0 μM.
- Liu, Tao,Dong, Xiaowu,Xue, Na,Wu, Rui,He, Qiaojun,Yang, Bo,Hu, Yongzhou
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scheme or table
p. 6279 - 6285
(2011/02/24)
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- A highly chemoselective and rapid chlorination of benzyl alcohols under neutral conditions
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A rapid and highly selective chlorination method has been developed using 2,4,6-trichloro-1,3,5-triazine (TCT) catalyzed by dimethyl sulfoxide. The reactions take 10 to 40 minutes, and the yields are almost quantitative. The neutral reaction conditions are compatible with substrates bearing acid-labile functional groups. Both competitive intramolecular and intermolecular reactions for benzyl alcohols in the presence of aliphatic alcohols indicate high selectivity. The procedure has been successfully used in the selective chlorination of gastrodin, a clinically used neuromedicine. This procedure represents a useful new tool in organic and medicinal chemistry. Georg Thieme Verlag Stuttgart.
- Sun, Lili,Peng, Guisheng,Niu, Hongmei,Wang, Qiang,Li, Chunbao
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experimental part
p. 3919 - 3924
(2009/05/26)
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- Direct halogenation of alcohols and their derivatives with tert-Butyl halides in the ionic liquid [pmIm]Br under sonication conditions - A novel, efficient and green methodology
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A novel halogenating reagent system for direct halogenation of alcohols has been developed. tert-Butyl bromide, chloride and iodide in combination with the ionic liquid [pmIm]Br have been found to convert alcohols into the corresponding bromides, chlorides and iodides under sonication conditions (or heating) in good yields. Although a variety of primary and secondary alcohols participated in this reaction without any difficulty, tertiary alcohols remained inert. Several alcohol derivatives such as OTMS, OTBDMS, OAc, OTS and OTHP are also transformed into the corresponding halides in one-pot fashion by this procedure. A plausible rationale for this transformation is also presented. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Ranu, Brindaban C.,Jana, Ranjan
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p. 755 - 758
(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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- Cyclopentanoindoles, compositions containing such compounds and methods of treatment
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Substituted cyclopentanoindole derivatives are antagonists of prostaglandins, and as such are useful for the treatment of prostaglandin mediated diseases.
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- Direct conversion of carbonyl compounds into organic halides: Indium(III) hydroxide-catalyzed deoxygenative halogenation using chlorodimethylsilane
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The reaction of carbonyls and chlorodimethylsilane was effectively catalyzed by indium(III) hydroxide and afforded the corresponding deoxygenative chlorination products, in which the carbonyl carbon accepted two nucleophiles (H and Cl) with releasing oxygen. Only In(OH)3 catalyzed the reaction, and typical Lewis acids such as TiCl4, AlCl3, and BF3·OEt2 showed no catalytic activity. The reaction mechanism of this deoxygenative chlorination includes initial hydrosilylation followed by chlorination. Other nucleophiles such as allyl or iodine were available for this methodology. The moderate Lewis acidity of indium catalyst enabled chemoselective reaction, and therefore ester, nitro, cyano, or halogen groups were not affected during the reaction course. Copyright
- Onishi, Yoshiyuki,Ogawa, Daigo,Yasuda, Makoto,Baba, Akio
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p. 13690 - 13691
(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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- Chlorination of aromatic compounds with chlorous acid under non-aqueous conditions
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The non-aqueous solution of chlorous acid is a versatile chlorinating agent for aromatic compounds, e.g. alkylbenzenes, anisoles, and acetanililides. It is also an effective chlorine-substitute for the conversion of aryl bromides into aryl chlorides under mild conditions. The stoichiometry of the chlorination reaction is ArH+3HOClO→ArCl+2ClO2+2H2O, and the mode of dissociation of chlorous acid in dichloromethanc is 3HOClO→HOCl+2ClO2+H2O.
- Muathen, Hussni A.
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p. 1493 - 1497
(2007/10/03)
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- Synthesis and antiparasitic and antitumor activity of 2,4-diamino-6- (arylmethyl)-5,6,7,8-tetrahydroquinazoline analogues of piritrexim
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Nineteen previously undescribed 2,4-diamino-6-(arylmethyl)-5,6,7,8- tetrahydroquinazolines (5a-m, 10-12) were synthesized as part of a larger effort to assess the therapeutic potential of lipophilic dihydrofolate reductase (DHFR) inhibitors against opportunistic infections of AIDS. Condensation of appropriately substituted (arylmethyl)triphenylphosphoranes with 4,4-ethylenedioxycyclohexanone, followed by hydrogenation (H2/Pd-C) and acidolysis, yielded the corresponding 4-(arylmethyl)cyclohexanones, which were then condensed with cyanoguanidine to form the tetrahydroquinazolines. Three simple 2,4-diamino-6-alkyl-5,6,7,8-tetrahydroquinazoline model compounds (9a-c) were also prepared in one step from commercially available 4-alkylcyclohexanones by this method. Enzyme inhibition assays against rat liver DHFR, Pneumocystis carinii DHFR, and the bifunctional DHFR-TS enzyme from Toxoplasma gondii were carried out, and the selectivity ratios IC50(rat)/IC50(P. carinii) and IC50(rat)/IC50(T. gondii) were compared. The three most potent inhibitors of P. carinii DHFR were the 2,5- dimethoxybenzyl (5j), 3,4-dimethoxybenzyl (5k), and 3,4,5-trimethoxybenzyl (51) analogues, with IC50 values of 0.057, 0.10, and 0.091 μM, respectively. The remaining compounds generally had IC50 values in the 0.1- 1.0 μM range. However all the compounds were more potent against the rat liver enzyme than the P. carinii enzyme and thus were nonselective. The T. gondii enzyme was always more sensitive than the P. carinii enzyme, with most of the analogues giving IC50 values of 0.01-0.1 μM. Moderate 5-10-fold selectivity for T. gondii versus rat liver DHFR was observed with five compounds, the best combination of potency and selectivity being achieved with the 2-methoxybenzyl analogue 5d, which had an IC50 of 0.014 μM and a selectivity ratio of 8.6. One compound (51) was tested for antiproliferative activity against P. carinii trophozoites in culture at a concentration of 10 μg/mL and was found to completely suppress growth over 7 days. The suppressive effect of 51 was the same as that of trimethoprim (10 μg/mL) + sulfamethoxazole (250 μg/mL), a standard clinical combination for the treatment of P. carinii pneumonia in AIDS patients. Four compounds (5a,h,k,l) were tested against T. gondii tachyzoites in culture and were found to have a potency (IC50 = 0.1-0.5 μM) similar to that of pyrimethamine (IC50 = 0.69 μM), a standard clinical agent for the treatment of cerebral toxoplasmosis in AIDS patients. Compound 5h was also active against T. gondii infection in mice when given qdx8 by peritoneal injection at doses ranging from 62.5 (initial dose) to 25 mg/kg. Survival was prolonged to the same degree as with 25 mg/kg clindamycin, another widely used drug against toxoplasmosis. Three compounds (5j-l) were tested for antiproliferative activity against human tumor cells in culture. Among the 25 cell lines in the National Cancer Institute panel for which data were confirmed in two independent experiments, the IC50 for at least two of these compounds was 50 of 50 was 0.01 μM.
- Rosowsky, Andre,Papoulis, Andrew T.,Forsch, Ronald A.,Queener, Sherry F.
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p. 1007 - 1017
(2007/10/03)
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- SUBSTITUTED TETRAHYDROBENZOPYRROLYL-FURANOIC ACID DERIVATIVES AS PHOSPHOLIPASE A2 INHIBITORS
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Compounds of the formula wherein R is hydrogen, alkyl1-8, geminal alkyl1-3, un-substituted or substituted aryl; X is alkylene, ?CR1=CR2? (E and/or Z), carbonyl, oxygen or sulfur, wherein one of Ri and R2 is alkyli.3 and the other is hydrogen; Y is unsubstituted alkyh-n or substituted by one or more alkyl1-3 groups, or unsubstituted or substituted phenylalkyl 1-3; or a salt thereof with a pharmaceutically acceptable base, are described. The compound of formula I are potent inhibitors of phospholipase A2 (PLA2) and are therefore useful in the treatment of inflammatory diseases, such as, psoriasis, inflammatory bowel disease, asthma, allergy, arthritis, dermatitis, gout, pulmonary, myocardial ischemia and trauma induced inflammation, such as, spinal cord injury
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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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- Imidazole derivatives
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Imidazole derivatives of general Formula I STR1 wherein R 1 means hydrogen, an optionally substituted C 1-10 hydrocarbon or hetaryl residue, or a cyclic ether residue,R 2 means hydrogen, halogen, an optionally substituted amino, nitro, azide, thiocyanate or cyano group, a linear or branched C 1-10 -alkyl residue optionally substituted with halogen, or -OR 1 wherein R 1 has the above-mentioned meanings, andR 1 and R 2 jointly with the oxygen atom form a saturated or unsaturated 5- to 7-membered ring which can contain still another hetero atom,R 3 means hydrogen, a linear or branched C 1-6 -alkyl group, or a C 1-6 -alkoxyalkyl group,R 4 means -COOR 5, -CONR 6 R 7, -CN, STR2 and their use as medicinal agents are disclosed.
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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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- 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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- Improved Synthesis of Fluoromethanesulfonyl Chloride
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Introduction of fluorine into 4-chlorobenzyl chloromethyl sulfide (7) by crown-ether-assisted nucleophilic substitution furnishes 4-chlorobenzyl fluoromethyl sulfide (5), a key intermediate for the preparation of fluoromethanesulfonyl chloride (1). Key Words: Fluoromethanesulfonyl chloride/ Potassium fluoride/ Crown ether
- Lange, Ulla,Senning, Alexander
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p. 1879 - 1880
(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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- MECHANISMS OF FREE-RADICAL REACTIONS. XX. REACTIVITY IN THE FREE-RADICAL HALOGENATION REACTIONS OF ARYLFLUOROALKANES
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The free-radical chlorination and bromination of meta- and para-substituted benzyl fluorides and 1,1-difluoro-2-phenylethane and also the chlorination of 1-fluoro-2-arylethanes by phenylchloroiodonium chloride and the bromination of meta- and para-substituted benzyl bromides were studied by the method of competing reactions.In all cases a good correlation is observed between log krel and the Brown ?+ constants.In cases where change in the reactivity in the transition from one reaction series to another is due mainly to the polar effect of the substituent whilethe selectivity is measured in relation to the polar effect direct relationships are observed between the reactivity and the selectivity.
- Dneprovskii, A. S.,Eliseenkov, E. V.
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p. 711 - 719
(2007/10/02)
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- Process for the preparation of substituted styrenes
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Substituted styrenes are prepared by treatment on N-acyl-B-phenethylamines with bases and removal by distillation of the styrene which is formed during the reaction.
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- Reduction of carbonyl compounds promoted by silicon hydrides under the influence of trimethylsilyl-based reagents
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The synthetic utility of hydrosilanes under the influence of trimethylsilyl-based reagents as new reducing systems is described. 1,1,3,3-Tetramethyldisiloxane (TMDS) reagent in combination with iodotrimethylsilane or bromotrimethylsilane produces alkyl halides from aldehydes in good to excellent yields.Polymethylhydrosiloxane (PMS) in the presence of iodotrimethylsilane also produces benzyl iodides in excellent yields.On the contrary, PMS reagent was found unsuitable for the synthesis of benzyl bromides.Similary, TMDS reagent in combination with trimethylsilyl triflate produces symmetrical ethers from aldehydes without concomitant formation of competitive products.Under similar conditions, PMS reagent failed to provide the expected symmetrical ethers and Friedel-Crafts products were formed.Reduction of quinones to hydroquinones is also described.
- Aizpurua, Jesus M.,Lecea, Begona,Palomo, Claudio
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p. 2342 - 2347
(2007/10/02)
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- Kinetics and Equilibria of Chloride Transfer Reactions. Stabilities of Carbocations Based on Chloride and Hydride Transfer Equilibria Measurements
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The kinetics of a number of gas-phase chloride transfer reactions R0(1+)+RCl=R0Cl+R(1+) were measured with a pulsed electron high pressure mass spectrometer.Most of the reactions were found to occur near the collision limit, i.e., with rate constants k ca. 10-9 molecules-1 cm3 s-1.However, several reactions were much slower and were exhibiting negative temperature dependence, i.e., decreasing rate with increasing temperature.Hydride and chloride transfer equilibria were determined for various carbocations R(1+) (R=isopropyl, cyclopentyl, tert-butyl, 1-methylcyclopentyl, substituted benzyls, norbornyl, 2-methyl-2-norbornyl, and adamantyl).Excellent agreement with earlier hydride transfer measurements of Solomon, Meot-Ner, and Field were observed.The chloride affinities generally support conclusions based on the hydride transfer data.Discussion of the data in connection with benzyl cation substituent effects, the norbornyl cation stability, and solvent effects on carbocation stability is presented.The data show that the 2-norbornyl cation is unusually stable.Significant differences between carbocation R(1+) stabilities in gas phase and solution are found which suggest that both differential nucleophilic solvent stabilization and differential nonspecific solvation occur in solution.
- Sharma, R. B.,Sharma, D. K. Sen,Hiraoka, K.,Kebarle, P.
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p. 3747 - 3757
(2007/10/02)
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- Chlorination of Toluene and Substituted Toluenes by Trichloroisocyanuric Acid: A Kinetic Investigation
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The kinetics of chlorination of toluene, o-, m- and p-xylenes, m- and p-chlorotoluenes and m-nitrotoluene by trichloroisocyanuric acid (TCCA) in aqueous acetic acid in the presence of perchloric acid (HClO4) have been studied.The reaction is first order each in and .The reaction is insensitive towards change in .Increase in the percentage of acetic acid in the reaction medium retards the reaction rate.Various thermodynamic parameters have been evaluated.A suitable mechanism is postulated taking the observed kinetic data into consideration.
- Pati, Subas C.,Sarangi, Chintamani
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p. 745 - 747
(2007/10/02)
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- DESULFONYLATION OF ARYLMETHANESULFONYL CHLORIDES CATALYZED BY DICLHOROTRIS(TRIPHENYLPHOSPHINE)RUTHENIUM(II)
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Reactions of arylmethanesulfonyl chlorides catalyzed by dichlorotris(triphenylphosphine)ruthenium(II) (1) have been studied.Desulfonylation occurred when arylmethanesulfonyl chlorides were treated with catalytic amounts of the ruthenium(II) catalyst to give chloromethylarene in high yields.No addition of the sulfonyl chloride to olefin was observed when the reaction was carried out in the presence of an equimolar amount of an olefin such as styrene.However, the rate of disappearance of the sulfonyl chloride was accelerated by addition of an olefin.The desulfonylation is assumed to proceed by a redox transfer promoted homolytic mechanism in the coordination sphere of the catalyst.In the presence of large excess of styrenes, arylmethanesulfonyl chlorides added to the olefins to give 1:1 adducts competitively with the desulfonylation yielding chloromethylarenes.
- Kamigata, Nobumasa,Suzuki, Norihiro,Kobayashi, Michio
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p. 139 - 144
(2007/10/02)
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- Structure-activity studies on antihyperlipidemic N-benzoylsulfamates, N-benzylsulfamates, and benzylsulfonamides
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A series of aryl substituted N-benzoyl- and N-benzylsulfamic acid sodium salts and benzylsulfonamide sodium salts have been prepared and examined for antihyperlipidemic activity in male CF1 mice at a dose level of 20 mg/kg/d ip for 16 d. These substances were also subjected to toxicological evaluation and chemical stability studies. In general, both series of sulfamates and sulfonamides significantly lowered serum cholesterol and triglyceride levels in mice. The compounds were nonmutagenic, showed no acute toxicity or impaired liver or kidney function in male mice, and were chemically stable both as the monohydrates and in aqueous solution over a pH range of 3.5-7.4. While both series of sulfamates and sulfonamides lowered serum cholesterol and triglyceride levels, the sulfamates were relatively more potent with regard to decreasing cholesterol levels, while the sulfonamides were more effective in lowering serum triglyceride levels in mice.
- Wyrick,Hall,Dubey
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p. 374 - 377
(2007/10/02)
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- Dioxalane containing imidazole compounds, compositions and use
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Compounds useful as antifungal, antibacterial and antiprotozoal agents are represented by the formula: STR1 wherein: Z is oxygen or sulfur; R1 is phenyl optionally substituted with one or more substituents selected from the group consisting of halo, lower alkyl of one to four carbon atoms, lower alkoxy of one to four carbon atoms and trifluoromethyl; R2 is phenyl or benzyl wherein the phenyl ring of R2 is optionally substituted by one or more substituents selected from the group consisting of halo, lower alkyl of one to four carbon atoms, lower alkoxy of one to four carbon atoms and trifluoromethyl; or by a phenyl optionally substituted by halo, lower alkyl of one to four carbon atoms, lower alkoxy of one to four carbon atoms or trifluoromethyl; and the antimicrobial acid addition salts thereof.
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- Preparation of Alkyl Chlorides, Acid Chlorides, and Amides Using Polymer-Supported Phosphines and Carbon Tetrachloride: Mechanism of These Reactions
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Alcohols and thiols were converted into alkyl chlorides, carboxylic acids were converted into acid chlorides, and mixtures of carboxylic acids and amines were converted into amides by reaction with carbon tetrachloride and 1percent cross-linked polystyrenes containing phosphine residues.Some of these conversions were also effected by using a linear polymer containing phosphine residues.The reactions proceed in high yield, and isolation of the products is facilitated by the ready removal of all the polymer-supported species.The mechanism of the reactions between triphenylphosphine, carbon tetrachloride, and alcohols is complex, but the polymer-supported reactions appear to follow analogous pathways to the low molecular weight reactions as judged by the yields of chloroform and the number of equivalents of phosphine consumed per mole of alkyl chloride produced.The mechanism requires polymer-supported groups reacting together.The slow step in the reactions appears to be the generation of the chlorinating species.The polymer-supported reactions are faster than those using triphenylphosphine or 4-(diphenylphosphinyl)isopropylbenzene.It is suggested that this is due to a microenvironmental effect.
- Harrison, Charles R.,Hodge, Philip,Hunt, Barry J.,Khoshdel, Ezzatollah,Richardson, Graham
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p. 3721 - 3728
(2007/10/02)
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- In Search of New Sulfur Transfer Agents
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The chemistry of various sulfur-transfer agents is studied.The reaction of aromatic sulfenyl chloride 5 in the presence of imidazole and/or triethylamine gives the aryl disulfides 7 in 14-85 percent yield, whereas in the case of the corresponding benzylsulfenyl chlorides 9 in the presence of triethylamine and/or caprolactam, both disulfide 10 and benzyl chlorides 11 are formed in 0-81 precent and 10-72 precent yield, respectively. - The transfer reactions of 3-sulfenylated hydantoins 18 with amines are useful for the preparation of the unsymmetric sulfenamides 20 in 31 -61 percent yield.Analogous transfer reactions of compounds 23 and 24 with piperidine give N,N'-thiodipiperidine (3, X = CH2) in 71-80 percent.
- Sosnovsky, George,Krogh, James A.
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p. 121 - 136
(2007/10/02)
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