- Improved efficiency and product selectivity in the photo-Claisen-type rearrangement of an aryl naphthylmethyl ether using a microreactor/flow system
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Ultraviolet (UV) irradiation of 2-[(2,4,6-trimethylphenoxy)methyl]-1- (methoxycarbonyl)naphthalene promotes a photochemical reaction that gives a cyclohexa-2,4-dienone product arising from a photo-Claisen-type ortho-rearrangement and a phenol derivative arising from a meta-rearrangement, along with 1-methoxycarbonyl-2-methylnaphthalene and 1,2-bis[1-(methoxycarbonyl) naphthalen-2-yl]ethane. When this process is carried out in a microreactor/flow system, its efficiency is dramatically enhanced and selectivity of products is improved. The effects on efficiency and product selectivity caused by the microreactor/flow system are attributed to more efficient light absorption and the suppression of secondary reactions.
- Maeda, Hajime,Nashihara, Satoshi,Mukae, Hirofumi,Yoshimi, Yasuharu,Mizuno, Kazuhiko
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Read Online
- Selective benzylic bromination of 2-methylnaphthalene
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A practical synthesis of 2-(bromomethyl)naphthalene (1) by selective benzylic bromination of 2-methylnaphthalene (2) with bromine in heptane in the presence of lanthanum acetate hydrate is described.
- Waykole, Liladhar,Prashad, Mahavir,Palermo, Stephen,Repic, Oljan,Blacklock, Thomas J.
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Read Online
- Catalytic Asymmetric Dearomatizing Redox Cross Coupling of Ketones with Aryl Hydrazines Giving 1,4-Diketones
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An asymmetric Bronsted acid catalyzed dearomatizing redox cross coupling reaction has been realized, in which aryl hydrazines react with ketones to deliver 1,4-diketones, bearing an all-carbon quarternary stereocenter in high enantiopurity.
- Huang, Shenlin,K?tzner, Lisa,Kanta De, Chandra,List, Benjamin
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Read Online
- Convenient ring-bromination of alkylnaphthalenes using N-bromosuccinimide in acetonitrile
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1-Alkyl- and 2-alkylnaphthalenes are conveniently brominated in the 4- and 1-positions respectively using N-bromosuccinimide (NBS) in acetonitrile. The reactions are easy to perform and give higher chemical yields and better regioselectivity compared to brominations employing bromine/dichloromethane.
- Cammidge, Andrew N.,Crepy, Karen V.,Fugier, Matthieu
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Read Online
- Intramolecular photocycloaddition reactions of 2- and 4-(5-arylpent-4-enyl)-1-cyanonaphthalenes
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Photoreactions of 1-cyanonaphthalene derivatives containing 5-arylpent-4-enyl groups at C-2 or C-4 of the naphthalene ring were investigated. Photoreactions of C-2 derivatives in benzene or CH3CN generated intramolecular [2 + 2] and [3 + 2] photocycloadducts. Substances bearing electron-rich and electron-poor phenyl groups produced respective [2 + 2] and [3 + 2] photocycloadducts preferentially. In contrast, photoreactions of C-4 linked 1-cyanonaphthalenes produced intramolecular [4 + 2] photocycloadducts as main products along with stereoisomers of tricyclic compounds as minor products. The formation of [4 + 2] photocycloadducts was promoted by using benzophenone or Michler's ketone triplet photosensitization, and quenched by O2 or ferrocene. Intramolecular singlet exciplexes, which serve as important intermediates in the mechanistic pathways for these reactions, governed the site-selectivities in photoreactions of both of the 2- and 4-(5-arylpent-4-enyl)-1-cyanonaphthalenes. In addition, [4 + 2] photocycloadducts were observed to undergo di-π-methane rearrangement under irradiation conditions to produce angular triquinane derivatives.
- Maeda, Hajime,Enya, Kouhei,Negoro, Naoki,Mizuno, Kazuhiko
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p. 173 - 184
(2019/02/15)
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- Synthesis of N-Substituted Condensed Tetrahydropyridine-Based Enaminones via Palladium-Catalyzed Intramolecular C–N Cross-coupling
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A number of β-enaminones with secondary amino group (alkyl, cyclopropyl, and aryl) were prepared from corresponding β-diketones. Two general protocols for their palladium-catalyzed intramolecular C–N cross-coupling were established to give corresponding N-substituted condensed tetrahydropyridines in good yields. The methodology is applicable for a wide variety of structural motifs. The work also extends the applicability of novel, recently established, palladium precatalysts to new substrates.
- Dou?ová, Hana,R??i?ková, Zdeňka,?im?nek, Petr
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supporting information
p. 670 - 684
(2018/01/22)
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- Applications of Selenonium Cations as Lewis Acids in Organocatalytic Reactions
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The use of trisubstituted selenonium salts as organic Lewis acids in electrophilic halogenation and aldol-type reactions has been developed. The substrate scope is broad. The reaction conditions are mild and compatible with various functionalities. This study opens a new avenue for the development of nonmetallic Lewis acid catalysis.
- He, Xinxin,Wang, Xinyan,Tse, Ying-Lung (Steve),Ke, Zhihai,Yeung, Ying-Yeung
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supporting information
p. 12869 - 12873
(2018/09/14)
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- Carbocation Catalyzed Bromination of Alkyl Arenes, a Chemoselective sp3 vs. sp2 C?H functionalization.
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The versatility of the trityl cation (TrBF4) as a highly efficient Lewis acid organocatalyst is demonstrated in a light induced benzylic brominaion of alkyl-arenes under mild conditions. The reaction was conducted at ambient temperature under common hood light (55 W fluorescent light) with catalyst loadings down to 2.0 mol% using N-bromosuccinimide (NBS) as the brominating agent. The protocol is applicable to an extensive number of substrates to give benzyl bromides in good to excellent yields. In contrast to most previously reported strategies, this protocol does not require any radical initiator or extensive heating. For electron-rich alkyl-arenes, the trityl ion catalyzed bromination could be easily switched between benzylic sp3 C?H functionalization and arene sp2 C?H functionalization by simply alternating the solvent. This chemoselective switch allows for high substrate control and easy preparation of benzyl bromides and bromoarenes, respectively. The chemoselective switch was also applied in a one-pot reaction of 1-methylnaphthalene for direct introduction of both sp3 C?Br and sp2 C?Br functionality. (Figure presented.).
- Ni, Shengjun,El Remaily, Mahmoud Abd El Aleem Ali Ali,Franzén, Johan
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supporting information
p. 4197 - 4204
(2018/09/25)
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- Transition-metal-free decarboxylative bromination of aromatic carboxylic acids
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Methods for the conversion of aliphatic acids to alkyl halides have progressed significantly over the past century, however, the analogous decarboxylative bromination of aromatic acids has remained a longstanding challenge. The development of efficient methods for the synthesis of aryl bromides is of great importance as they are versatile reagents in synthesis and are present in many functional molecules. Herein we report a transition metal-free decarboxylative bromination of aromatic acids. The reaction is applicable to many electron-rich aromatic and heteroaromatic acids which have previously proved poor substrates for Hunsdiecker-type reactions. In addition, our preliminary mechanistic study suggests that radical intermediates are not involved in this reaction, which is in contrast to classical Hunsdiecker-type reactivity. Overall, the process demonstrates a useful method for producing valuable reagents from inexpensive and abundant starting materials.
- Quibell, Jacob M.,Perry, Gregory J. P.,Cannas, Diego M.,Larrosa, Igor
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p. 3860 - 3865
(2018/04/26)
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- Synthesis of pentacyclic compounds via intramolecular [3 + 2] photocycloaddition of cycloalkene linked naphthalenes
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Intramolecular photocycloaddition reactions of cycloalkene linked naphthalenes lead to formation of pentacyclic compounds in a high yielding and stereoselective manner. Intramolecular [2 + 2] cycloadducts are formed initially in photoreactions of cycloalkene linked 1-cyanonaphthalenes. The initially formed intramolecular [2 + 2] cycloadducts absorb light at wavelengths used to promote the photochemical reactions and, as a result, they undergo efficient photocycloreversion to regenerate the starting substrates. In a less efficient competing process, the cycloalkene linked 1-cyanonaphthalenes react to form [3 + 2] intramolecular photoadducts, which do not absorb incident light under the conditions used. Consequently, these photoadducts become the major products in these processes. The relative configuration of the major diastereomers of the pentacyclic products formed from photoreactions of cyclopentene linked naphthalenes (cis-cis) differ from those (cis-trans) arising from the cyclooctene linked substrates. The results of theoretical calculations, which show that steric factors govern the preferred facial mode of intramolecular addition, are in good agreement with the stereochemical course of these photoreactions.
- Maeda, Hajime,Uesugi, Tomoya,Fujimoto, Yasufumi,Mukae, Hirofumi,Mizuno, Kazuhiko
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p. 198 - 206
(2017/02/10)
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- Method for synthesizing bromo-polycyclic aromatic hydrocarbon compound
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The invention discloses a method for synthesizing bromo-polycyclic aromatic hydrocarbon compounds. The method is characterized by comprising the following steps: utilizing a polycyclic aromatic hydrocarbon compound as a substrate, adding base metal bromide into a mixed solution of water and an organic solvent, then slowly adding ZnAl-BrO3--LDHs, reacting for 4 to 8h under 20 to 35 DEG C, TCL tracing a reaction process, washing a reaction mixture by a sodium sulfite solution after reaction is finished, extracting methylene dichloride, combining organic phases, reducing pressure and concentrating to obtain a coarse product, finally utilizing petroleum ether to ethyl acetate equal to (10 to 15) to 1 as an eluent and performing column chromatography isolation to obtain a mono bromo-polycyclic aromatic hydrocarbon compound or a dual brominated polycyclic aromatic hydrocarbon compound respectively. A brominating reagent utilized in the method disclosed by the invention is solid matter and is low in cost, easy to obtain and environmentally friendly. The method has the advantages of moderate reaction condition, convenience in aftertreatment, simpleness in reaction operation, high atom utilization rate, high selectivity, high target product yield and small side reaction.
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Paragraph 0044-0046; 0050; 0054
(2017/12/29)
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- Synthesis method of axially chiral dinaphthalene ligand precursor (s)-2,2'-dinaphthyl-1,1'-dicarboxylic acid
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The invention relates to the technical field of bromination, hydrolysis, oxidation and coupling reaction in organic synthesis, particularly a synthesis method of an axially chiral dinaphthalene ligand precursor (s)-2,2'-dinaphthyl-1,1'-dicarboxylic acid. The method comprises the following steps: synthesizing a compound 1-bromo-2-methylnaphthalene from an initial raw material 2-bromomethylnaphthalene, carrying out bromination, hydrolysis and oxidation on the 1-bromo-2-methylnaphthalene to obtain 1-bromo-2-naphthoic acid, generating an ester under the actions of methanol and thionyl chloride, protecting the carboxyl group, carrying out Ullmann reaction under the action of copper powder to perform coupling, carrying out hydrolysis to obtain 2,2'-dinaphthyl-1,1'-dicarboxylic acid, and finally, resolving to obtain the (s)-2,2'-dinaphthyl-1,1'-dicarboxylic acid. The method is simple to operate, and has the advantages of higher yield and favorable economical efficiency.
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Paragraph 0014; 0023
(2016/10/10)
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- Intramolecular Photocycloaddition Reactions of Arylcyclopropane Tethered 1-Cyanonaphthalenes
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Intramolecular photocycloaddition reactions of 1-cyanonaphthalenes bearing an arylcyclopropane containing side chain were investigated. Photoreactions of members of this family in which the arylcyclopropane moiety is bonded at the 2-position of the 1-cyanonaphthalene ring produce head-to-head and head-to-tail 1,2-[3+2] photocycloadducts. On the other hand, substances in this family containing an arylcyclopropane side chain linked to the 4-position of the cyanoarene ring undergo photoreactions to form [4+3] photocycloadducts along with novel nine-membered ring products, which are produced by photochemically induced 10 conrotatory ring opening of the initially formed intramolecular [3+2] cycloadducts. The results of solvent effects and fluorescence investigations along with those focusing on corresponding intermolecular photoreactions demonstrate that the photocycloadducts are formed predominantly through an intramolecular exciplex mechanism and that a photoinduced intramolecular electron transfer pathway via zwitterionic biradicals might be partly responsible for the process when CH3CN is the solvent.
- Maeda, Hajime,Matsuda, Shoji,Mizuno, Kazuhiko
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p. 8544 - 8551
(2016/09/28)
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- Synthesis of novel dihydronaphthothiazine S,S-dioxides by intramolecular sulfonylamidomethylation of 2-naphthylmethanesulfonamides using Amberlyst XN-1010
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We describe herein an efficient synthetic method for novel dihydronaphthothiazines S,S-dioxides by aromatic intramolecular sulfonylamidomethylation of 2-naphthylmethanesulfonamides with s-trioxane using Amberlyst XN-1010 as acid heterogeneous catalyst. Cyclization of the formed sulfonyliminium ion occurred with high regioselectivity and in excellent yields.
- Sasiambarrena, Leandro D.,Cánepa, Alicia S.,Bravo, Rodolfo D.
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supporting information
p. 7184 - 7189
(2015/12/12)
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- The oxidative halogenations of arenes in water using hydrogen peroxide and halide salts over an ionic catalyst containing sulfo group and hexafluorotitanate
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An ionic compound, bis[1-methyl-3-(3′-sulfopropyl)imidazolium] hexafluorotitanate (1), was proved to be the efficient and recyclable catalyst for the oxidative halogenations of arenes in water using H2O 2 as the oxidant and halide salts as the halogenation sources. The mono-halogenated products were obtained selectively by this method. The synergetic catalytic effect coming from the two incorporated functionalities of SO3H and [TiF6]2- was manifested in 1. The halogenation rate catalyzed by 1 was in the ranking of NaBr NaCl > KI. The UV-vis and FT-IR analyses indicated that the successful formation and regeneration of the active peroxo-Ti species (1A) with the aid of proton acid guaranteed the recycling uses of 1.
- Wang, Ling,Wang, Sa-Sa,Vo-Thanh, Giang,Liu, Ye
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- Fast and efficient bromination of aromatic compounds with ammonium bromide and Oxone
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A highly efficient, rapid and regioselective protocol was developed for the ring bromination of aromatic compounds under mild conditions with ammonium bromide as a source of bromine source and Oxone (potassium peroxysulfate) as an oxidant. No metal catalyst or acidic additive is required. A variety of aromatic compounds, including methoxy, hydroxy, amino, and alkyl arenes, reacted smoothly to give the corresponding monobrominated products in good to excellent yields in very short reaction times. Moreover, dibromination of deactivated anilines to give the corresponding dibromides proceeded in high yields. Interestingly, 1-(2-naphthyl)ethanone provided a ring-brominated product. Georg Thieme Verlag Stuttgart . New York.
- Naresh, Mameda,Arun Kumar, Macharla,Mahender Reddy, Marri,Swamy, Peraka,Nanubolu, Jagadeesh Babu,Narender, Nama
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p. 1497 - 1504
(2013/06/27)
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- Bromination of aromatic compounds using ammonium bromide and oxone
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A simple, efficient and mild method for the selective bromination of activated aromatic compounds using ammonium bromide as the source of bromine and Oxone as the oxidant in methanol or water as solvent is reported. The reaction proceeds at ambient temperature in yields ranging from moderate to excellent without a catalyst. Georg Thieme Verlag Stuttgart.
- Arunkumar, MacHarla,Rohitha, Chozhiyath Nappunni,Kulkarni, Shivanand Janardhan,Narender, Nama
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experimental part
p. 1629 - 1632
(2010/06/20)
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- Environmentally benign electrophilic and radical bromination 'on water': H2O2-HBr system versus N-bromosuccinimide
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A H2O2-HBr system and N-bromosuccinimide in an aqueous medium were used as a 'green' approach to electrophilic and radical bromination. Several activated and less activated aromatic molecules, phenylsubstituted ketones and styrene were efficiently brominated 'on water' using both systems at ambient temperature and without an added metal or acid catalyst, whereas various non-activated toluenes were functionalized at the benzyl position in the presence of visible light as a radical activator. A comparison of reactivity and selectivity of both brominating systems reveals the H2O2-HBr system to be more reactive than NBS for benzyl bromination and for the bromination of ketones, while for electrophilic aromatic substitution of methoxy-substituted tetralone it was higher for NBS. Also, higher yields of brominated aromatics were observed when using H2O2-HBr 'on water'. Bromination of styrene reveals that not just the structure of the brominating reagent but the reaction conditions: amount of water, organic solvent, stirring rate and interface structure, play a key role in defining the outcome of bromination (dibromination vs bromohydroxylation). In addition, mild reaction conditions, a straightforward isolation procedure, inexpensive reagents and a lower environment impact make aqueous brominating methods a possible alternative to other reported brominating protocols.
- Podgor?ek, Ajda,Stavber, Stojan,Zupan, Marko,Iskra, Jernej
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experimental part
p. 4429 - 4439
(2009/10/09)
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- Contrasting chemoselectivities in the ultrasound and microwave assisted bromination reactions of substituted alkylaromatics with N-bromosuccinimide
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Ultrasound and microwave assisted bromination reactions of various alkylaryls with N-bromosuccinimide, either neat or in water, shows diverse chemoselectivity. Thus, ring substitution occurs in water with ultrasound, whereas with microwaves both side-chain α-bromination and ring substitution occur. With neat reactants, side-chain α-bromination predominates for microwave assisted reactions. In the presence of water the chemoselectivity with microwave-promoted bromination is similar to that observed using classical methods.
- Heropoulos, Georgios A.,Cravotto, Giancarlo,Screttas, Constantinos G.,Steele, Barry R.
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p. 3247 - 3250
(2008/02/02)
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- A concise synthesis of novel naphtho[a]carbazoles and benzo[c]carbazoles
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Starting from simple indole precursors the synthesis of naphtho[a]carbazoles and benzo[c]carbazoles is described. Key steps include the use of the Suzuki-Miyaura reaction to afford 2- or 3-aryl substituted indoles, as well as a potassium t-butoxide and light assisted aromatic ring-forming reaction.
- Pathak, Rakhi,Nhlapo, Johanna M.,Govender, Sameshnee,Michael, Joseph P.,Van Otterlo, Willem A. L.,De Koning, Charles B.
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p. 2820 - 2830
(2007/10/03)
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- Site directed nuclear bromination of aromatic compounds by an electrochemical method
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Direct bromination of a wide range of aromatic compounds possessing electron-donating groups, such as methoxy, hydroxy or amino groups, have been carried out by two-phase electrolysis. This electrochemical method results in high yields (70-98%) of monobromo compounds and usually with high regioselectivity (>95%) for the para position.
- Raju,Kulangiappar,Anbu Kulandainathan,Uma,Malini,Muthukumaran
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p. 4581 - 4584
(2007/10/03)
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- A simple and regioselective α-bromination of alkyl aromatic compounds by two-phase electrolysis
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Electrochemical bromination of toluene and substituted toluenes by two-phase electrolysis yields the corresponding α-brominated products. The reaction has been carried out in a single compartment cell with platinum electrodes at 0°C in chloroform using an aqueous sodium bromide solution (60%) containing a catalytic amount of HBr. Two-phase electrolysis results in high yields (60-95%) of monobromo compounds with very high regioselectivity (>95%).
- Raju,Kulangiappar,Anbu Kulandainathan,Muthukumaran
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p. 7047 - 7050
(2007/10/03)
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- Novel bromination method for anilines and anisoles using NH 4Br/H2O2 in CH3COOH
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A simple, efficient, regioselective, environmentally safe, and economical method for the oxybromination of anilines and anisoles without catalyst is reported. The electrophilic substitution of bromine generated in situ from ammonium bromide as a bromine source and hydrogen peroxide as an oxidant for the first time.
- Krishna Mohan,Narender,Srinivasu,Kulkarni,Raghavan
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p. 2143 - 2152
(2007/10/03)
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- Efficient halogenation of aromatic systems using N-halosuccinimides in ionic liquids
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A simple, rapid and highly regioselective green protocol has been developed for the halogenation of aromatic systems with N-halosuccinimides using room temperature ionic liquids (ILs) as novel and recyclable reaction media to produce the corresponding halogenated aromatic compounds in high to quantitative yields. N-Halosuccinimides show enhanced reactivity in ionic liquids thereby reducing the reaction times dramatically and improving the yields substantially.
- Yadav,Reddy,Reddy,Basak,Narsaiah
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- Environmentally-friendly Wohl-Ziegler bromination: Ionic-liquid reaction and solvent-free reaction
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Environmentally-friendly Wohl-Ziegler bromination of benzylic methyl groups was successfully camed out in ionic-liquid and solvent-free systems, to produce the corresponding benzylic bromides in good to moderate yields.
- Togo, Hideo,Hirai, Takeshi
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p. 702 - 704
(2007/10/03)
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- Excited state carbon acid dissociation and competing photoarrangements of 5H-dibenzo[a,c]cycloheptene derivatives
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Structure reactivity studies of excited singlet state carbon acid dissociation and competing formal di-π-methane rearrangement have been carried out to gain more insights on the photochemistry displayed by these compounds. Photolysis in the presence of ethanolamine resulted in stereoselective deprotonation of the pseudo-axial proton. The results show that excited state carbon acid dissociation is a general reaction of dibenzo and dinaphtho cycloheptenes only if photochemical pathways are not competing.
- Budac,Wan
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p. 1447 - 1464
(2007/10/03)
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- Convenient synthesis of 1,1'-binaphthyl-2,2'-dicarboxylic acid
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Two syntheses of 1,1'-binaphthyl-2,2'-dicarboxylic acid (4) in good yields are presented via the oxidation of the 2'-methyl substituent of isopropyl 2'-methyl-1,1'-binaphthyl-2-carboxylate (8), which is readily obtainable by the reaction of 2-methyl-1-naphthyl Grignard reagent 7 with isopropyl 1-isopropoxy-2-naphthoate (6).
- Oi,Matsunaga,Hattori,Miyano
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p. 895 - 899
(2007/10/02)
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- Preparation of biaryl compounds
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A method for the preparation of biaryl compounds is disclosed which comprises contacting an aromatic halide in the presence of a catalyst comprising zerovalent nickel, a bidentate phosphorus-containing coordinating ligand and a reducing metal in a polar, aprotic solvent system for a time and under conditions suitable for the formation of biaryl compound.
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- Benzindene
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A convenient route to benzindene (1) has been developed in which 2-methylnaphthalene is brominated sequentially in the α-position and the methyl group followed by application of a standard malonic ester route to propionic acid 10.Cyclization of 10 via the acid chloride gave 11 (76percent).Simultaneous reduction of the carbonyl group and hydrogenolysis of the aryl bromide linkage of 11 gave secondary alcohol 12 in 55.4percent yield.Sulfuric acid dehydration of 12 gave 1 (85percent).Less successful routes to 1 involved dithionite reduction of unsaturated sulfones 6.Dihydro derivative 7 could be synthesized in 72percent yield by magnesium/methanol reduction of 5b.
- Carpino, Louis A.,Lin, Yao-Zhong
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p. 247 - 250
(2007/10/02)
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- Halogenation Using Quaternary Ammonium Polyhalides. XIV. Aromatic Bromination and Iodination of Arenes by Use of Benzyltrimethylammonium Polyhalides-Zinc Chloride System
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The reaction of arenes with benzyltrimethylammonium tribromide or benzyltrimethylammonium dichloroiodate in acetic acid in the presence of ZnCl2 at room temperature or at 70 deg C gave brome- or iodo-substituted arenes in good yield, respectively.
- Kajigaeshi, Shoji,Kakinami, Takaaki,Moriwaki, Masayuki,Tanaka, Toshio,Fujisaki, Shizuo,Okamoto, Tsuyoshi
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p. 439 - 443
(2007/10/02)
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- CHIRALITY TRANSFER FROM SILICON TO CARBON: USE OF OPTICALLY PURE CYCLIC SILANES WITH A BINAPHTHALENE CHIRAL UNIT
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The optically pure binaphthylic cyclic silanes R-6 and S-6 have been prepared and used in reductions and aldol condensations to achieve some of the highest ee's yet reported for chirality transfer with organosilanes.
- Jung, Michael E.,Hogan, Keith T.
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p. 6199 - 6202
(2007/10/02)
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- Asymmetric Synthesis Catalyzed by Chiral Ferrocenylphosphine-Transition-Metal Complexes. 6. Practical Asymmetric Synthesis of 1,1'-Binaphthyls via Asymmetric Cross-Coupling with a Chiral monophosphine/Nickel Catalyst.
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Cross-coupling of (2-methyl-1-naphthyl)magnesium bromide (1a) with 2-methyl-1-naphthyl bromide (2a) at -15 or 0 deg C in the presence of nickel catalyst prepared in situ from nickel bromide and (S)-1-ethyl methyl ether (3a) gave high yield of (R)-(-)-2,2'-dimethyl-1,1'-binaphthyl (4a) in up to 95percent ee.Ferrocenylphosphine 3a was also effective for the reaction of 1a with 1-naphthyl bromide (2b) and that of (2-ethyl-1-naphthyl)magnesium bromide (1c) with 2b to give corresponding cross-coupling products in 83 and 77percent ee, respectively.
- Hayashi, Tamio,Hayashizaki, Keiichi,Kiyoi, Takao,Ito, Yoshihiko
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p. 8153 - 8156
(2007/10/02)
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- A Novel Clathrate Design: Selective Inclusion of Uncharged Molecules via the Binaphthyl Hinge and Appended Coordinating Groups. X-ray Crystal Structures and Binding Modes of 1,1'-Binaphthyl-2,2'-dicarboxylic Acid Host/Hydroxylic Guest Inclusions
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1,1'-Binaphthyl-2,2'-dicarboxylic acid (1) is demonstrated as a novel type of clathrate host whose main mode of action is derived from a combination of the steric barrier and the coordinative interaction principle which constitutes the new "coordinatoclathrate" strategy.Inclusion properties of the crystal lattice of 1 are revealed for a variety of uncharged organic guest molecules (30 examples), ranging from OH-, to NH-, to CH-acidic compounds such as alcohols, carboxylic acids, amides, and nitriles to rather unpolar compounds like bromobenzene and toluene.Marked discrimination selectivities in the clathrate formation from solvent mixtures are found in regard to the group functionality, the substitution pattern, and the molecular size of the guest species, making accessible a simple process for chemical compound separation.The stoichiometries and the increased-temperature as well as the reduced-pressure stabilities of the various clathrates are discussed.The principles of stucture of five different alcohol clathrates of 1 are determined with the aid of X-ray structure analysis at 273 K: 1*2MeOH (10) 1/n, a = 15.642 Angstroem, b = 14.532 Angstroem, c = 9.292 Angstroem, β = 95.14 deg, Z = 4>; 1*2EtOH (11) ; 1*2(2-PrOH) (13) ; 1*2-BuOH (15) 1/n, a = 12.009 Angstroem, b = 12.747 Angstroem, c = 14.982 Angstroem, β = 105.52 deg, Z = 4>; 1*ethylene glycol (24) 1/n, a = 14.276 Angstroem, b = 9.533 Angstroem, c = 15.556 Angstroem, β = 109.19 deg, Z = 4>.In all these cases, however, hydroxyl groups of the host molecules were found to be intercalated via large pseudo-ring formation between the carboxyl functions of at least two host units of opposite chirality with a different mode of hydrogen bridging.Depending on the host:guest stoichiometry (1:1 or 1:2) and on the nature of the guest molecules, these entities consist of three, four, or eight moieties (COOH, OH).The direction of the strong and cooperative bonds is always homodromic.The shape and the size of the cleft formed in the matrix of cooperating host moieties are shown to vary, matching the specific needs of coordinating interactions (hydrogen bonding) and topological requirements (branching, e.g.) of the guest species.
- Weber, Edwin,Csoregh, Ingeborg,Stensland, Brigitta,Czugler, Matyas
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p. 3297 - 3306
(2007/10/02)
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- The easy preparation of many benzylic bromides using molecular bromine as a halogenating in the presence of catalytic amounts of lanthanum tri-acetate
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Many benzylic brominations were easily achieved by molecular bromine in CCl4 in presence of 1 percent of La (OAc)3 and a standard room lighting lamp.The selectivity is excellent except for certain electron-rich systems (p-methylaniline, p-cresol).
- Ouertani, Mohsen,Girard, Pierre,Kagan, Henry B.
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p. 327 - 328
(2007/10/02)
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