- Metal-free thermal organocatalytic pinacol coupling of arylaldehydes using an isonicotinate catalyst with bis(pinacolato)diboron
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The metal-free thermal organocatalytic pinacol coupling of arylaldehydes has been developed. The intermolecular coupling of arylaldehydes catalyzed byt-butyl isonicotinate with bis(pinacolato)diboron as the co-reducing agent afforded 1,2-diphenylethane-1,2-diols. This reaction was also applicable to the intramolecular coupling of 1,1′-biphenyl-2,2′-dicarbaldehydes to afford 9,10-dihydrophenanthrene-9,10-diols. Various functional groups were tolerated under this coupling condition.
- Hanaya, Kengo,Higashibayashi, Shuhei,Sugai, Takeshi,Yasui, Masamichi
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p. 24652 - 24655
(2021/07/29)
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- Reductive Coupling of Aromatic Aldehydes and Ketones under Electrochemical Conditions
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Reductive coupling of o-substituted carbonyl compounds and m-substituted carbonyl compounds by the direct transfer of electron to carbonyl group respectively gave 1-(4-(1-hydroxy-1-phenylethyl/methyl)phenyl)ethanones/methanones and 2,3-bis(3-substitutedph
- Li, Qian-Yu,Swaroop, Toreshettahally R.,Wang, Heng Shan,Wang, Zi-Qiang
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- Crystal-to-Crystal Synthesis of Photocatalytic Metal–Organic Frameworks for Visible-Light Reductive Coupling and Mechanistic Investigations
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Postmodification of reticular materials with well-defined catalysts is an appealing approach to produce new catalytic functional materials with improved stability and recyclability, but also to study catalysis in confined spaces. A promising strategy to this end is the postfunctionalization of crystalline and robust metal–organic frameworks (MOFs) to exploit the potential of crystal-to-crystal transformations for further characterization of the catalysts. In this regard, two new photocatalytic materials, MOF-520-PC1 and MOF-520-PC2, are straightforwardly obtained by the postfunctionalization of MOF-520 with perylene-3-carboxylic acid (PC1) and perylene-3-butyric acid (PC2). The single crystal-to-crystal transformation yielded the X-ray diffraction structure of catalytic MOF-520-PC2. The well-defined disposition of the perylenes inside the MOF served as suitable model systems to gain insights into the photophysical properties and mechanism by combining steady-state, time-resolved, and transient absorption spectroscopy. The resulting materials are active organophotoredox catalysts in the reductive dimerization of aromatic aldehydes, benzophenones, and imines under mild reaction conditions. Moreover, MOF-520-PC2 can be applied for synthesizing gram-scale quantities of products in continuous-flow conditions under steady-state light irradiation. This work provides an alternative approach for the construction of well-defined, metal-free, MOF-based catalysts.
- Bucci, Alberto,Escudero-Adán, Eduardo C.,Gutiérrez, Luis,Kandoth, Noufal,Lloret-Fillol, Julio,Mondal, Suvendu Sekhar,Shafir, Alexandr
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- Ring Closing Metathesis Approach for the Synthesis of o-Terphenyl Derivatives
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A linear synthesis of o-terphenyl derivatives has been delineated using ring closing metathesis (RCM) as the key step. In this approach, benzil derivatives upon allyl Grignard addition provides diphenyl-1,2-diallyl dihydroxy derivatives which undergo ring closing metathesis to afford tetrahydro terphenyl derivatives. Aromatization-driven dehydration then leads to a diverse set of electron rich and electron deficient o-terphenyls. Furthermore, oxidative coupling of electron rich o-terphenyls provides the corresponding triphenylene derivatives.
- Karmakar, Shilpi,Mandal, Tirtha,Dash, Jyotirmayee
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p. 5916 - 5924
(2019/08/21)
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- Stereoselective Barbier-Type Allylations and Propargylations Mediated by CpTiCl3
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CpTiCl2, prepared in situ by manganese reduction of CpTiCl3, is an excellent new system for the Barbier-type allylation and propargylation of carbonyl compounds. It can be used in catalytic amounts when combined with Et3N·HBr/TMSBr, which acts as a regenerating system. The high regio- and stereoselectivity shown by this system makes it useful for prenylation and crotylation processes in the synthesis of natural products.
- López-Martínez, Josefa L.,Torres-García, Irene,Rodríguez-García, Ignacio,Mu?oz-Dorado, Manuel,álvarez-Corral, Miriam
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p. 806 - 816
(2019/01/24)
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- Selective Pinacol Coupling on Regeneratable Supported Acids in Sole Water
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Efficient pinacol coupling was developed in sole water, using a reusable heterogeneous supported acid source and zinc as cheap available metal source. This medium can be easily regenerated up to 10-fold without loss of activity. Moreover, supported acids enhance the selectivity of the pinacol coupling reaction compared with homogeneous acids.
- Sotto, Nicolas,Billamboz, Muriel,Chevrin-Villette, Carole,Len, Christophe
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p. 6375 - 6380
(2015/06/30)
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- First pinacol coupling in emulsified water: Key role of surfactant and impact of alternative activation technologies
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For the first time, the influence of surfactants on the radical pinacol coupling reaction is investigated. The rate and selectivity of this reductive C-C coupling are compared under three different activation technologies: thermal activation, microwave irradiation, and sonication. The use of IgepalCO520, a neutral surfactant, led to the successful conversion of aromatic or α,β-unsaturated aliphatic carbonyl compounds in moderate to excellent yield (55-90 %). An insight on the potential mechanism involved in the reaction is also proposed, based on microscopic observations and particle size measurement.
- Billamboz, Muriel,Len, Christophe
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p. 1664 - 1675
(2015/06/02)
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- Biocatalyzed asymmetric reduction of benzils to either benzoins or hydrobenzoins: pH dependent switch
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Enantiopure benzoins and hydrobenzoins are precursors of various pharmaceuticals and biologically active compounds. In addition, hydrobenzoins are precursors of chiral ligands and auxiliaries in stereoselective organic synthesis. Biocatalytic reduction of benzils is a straightforward approach to prepare these molecules. However, known methods are not selective and lead to formation of a mixture of benzoin and hydrobenzoin, requiring expensive separation procedures. Here, we describe an enzyme system Talaromyces flavus, which exhibited excellent pH dependent selectivity for the conversion of benzil to either benzoin or hydrobenzion in high ee. Thus, (S)-benzoin was the exclusive product at pH 5.0 (ee >99%), whereas at pH 7.0, (S,S)-hydrobenzoin (ee >99%, dl/meso 97 : 3) was the exclusive product. The observed pH dependent selectivity was shown to be due to the presence of multiple enzymes in Talaromyces flavus, which specifically accepted either benzil or benzoin as a substrate and exhibited different pH profiles of their activity. The biocatalyst efficiently reduced a variety of symmetrical and unsymmetrical benzils. Moreover, a 36.4 kDa benzoin reductase was purified, the N-terminal sequence of which did not show a significant similarity to any of the known reductase/dehydrogenase in the database. The protein therefore appears to be a novel reductase.
- Pal, Mohan,Srivastava, Gautam,Sharma, Amar Nath,Kaur, Suneet,Jolly, Ravinder S.
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p. 4017 - 4028
(2015/08/03)
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- The scalable pinacol coupling reaction utilizing the inorganic electride [Ca2N]+·e- as an electron donor
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The scalable pinacol coupling reaction is realized utilizing the inorganic electride [Ca2N]+·e- as an electron donor in organic solvents. The bond cleavages of the [Ca2N] + layers by methanol play a vital role in transferring anionic electrons to electrophilic aldehydes, accompanying the formation of Ca(OMe) 2 and ammonia. The Royal Society of Chemistry 2014.
- Kim, Ye Ji,Kim, Sun Min,Hosono, Hideo,Yang, Jung Woon,Kim, Sung Wng
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supporting information
p. 4791 - 4794
(2014/05/06)
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- Synthesis of ferrocene derivatives with planar chirality via palladium-catalyzed enantioselective C-H bond activation
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The first catalytic and enantioselective C-H direct acylation of ferrocene derivatives has been developed. A series of 2-acyl-1-dimethylaminomethylferrocenes with planar chirality were provided under highly efficient and concise one-pot conditions with up to 85% yield and 98% ee. The products obtained could be easily converted to various chiral ligands via diverse transformations.
- Pi, Chao,Cui, Xiuling,Liu, Xiuyan,Guo, Mengxing,Zhang, Hanyu,Wu, Yangjie
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supporting information
p. 5164 - 5167
(2014/12/11)
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- Use of electrochemistry to provide efficient SmI2 catalytic system for coupling reactions.
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Samarium metal has been used for the first time as electrode material to perform as an efficient and versatile SmI2 catalytic system assisted by electrochemistry. The established electrocatalytic procedure that excludes any metal additives was successfully applied in various transformations mediated by this useful reagent.
- Sun, Linhao,Sahloul, Kamar,Mellah, Mohamed
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p. 2568 - 2573
(2013/11/19)
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- Catalytic enantioselective alkylation and arylation of aldehydes by using grignard reagents
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We have developed an efficient and practical method for the catalytic enantioselective alkylation and arylation of aldehydes by using Grignard reagents in combination with titanium tetraisopropoxide. Grignard reagents and titanium tetraisopropoxide are mixed in a molar ratio of ca. 1:2. In the presence of catalyst (24mol%), which is formed in situ from a BINOL ligand 4a and 4b and titanium tetraisopropoxide, the resulting mixed titanium reagents undergo addition to aldehydes with high enantioselectivities (typically >90% ee) and high yields. The method is applicable to various combination of aldehydes (R1CHO; R1 = aryl, heteroaryl, 1-alkenyl, and alkyl) and Grignard reagents (R2MgX; R2 = primary alkyl and aryl). Thus, a variety of enantiomerically enriched secondary alcohols (R1CH*(OH)R2) can be prepared. It has also been demonstrated that functionalized aryl Grignard reagents can be employed to generate highly functionalized diarylmethanols. The preparative utility of the method has been shown by the fact that the reaction is operationally simple, can be carried out on a 10-mmol scale without any difficulty, and the ligands can be readily recovered.
- Muramatsu, Yusuke,Kanehira, Shinichi,Tanigawa, Masato,Miyawaki, Yuta,Harada, Toshiro
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experimental part
p. 19 - 32
(2010/03/25)
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- A convenient synthesis of unsymmetrical pinacols by coupling of structurally similar aromatic aldehydes mediated by low-valent titanium
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The one-pot, selective cross pinacol-type couplings between two structurally similar aromatic aldehydes promoted by low-valent titanium generated unsymmetrical pinacols in moderate to good isolated yields in an erythrolthreo ratio of up to 91:9. This synt
- Duan, Xin-Fang,Feng, Jian-Xia,Zi, Guo-Fu,Zhang, Zhan-Bin
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experimental part
p. 277 - 282
(2009/06/24)
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- A convenient procedure for the synthesis of racemic syn-1,2-diarylethane-1, 2-diols by osmate catalyzed dihydroxylation of trans-stilbenes facilitated by Troeger base
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Racemic (dl) mixture of syn-1,2-diarylethane-1,2-diols are prepared from the corresponding substituted trans-stilbenes using osmate catalyzed dihydroxylation facilitated by racemic Troeger base under ambient conditions.
- Satishkumar, Sakilam,Periasamy, Mariappan
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p. 1080 - 1083
(2008/12/23)
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- Catalytic asymmetric alkylation of aldehydes with Grignard reagents
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(Chemical Equation Presented) Added benefits: Grignard reagents can be employed in the asymmetric alkylation of aldehydes by using a titanium(IV) catalyst derived from binol in the presence of excess titanium tetraisopropoxide (see scheme). The reaction proceeds with a low catalyst loading (2 mol%) and exhibits high enantioselectivity for both aromatic and unsaturated aldehydes and for both alkyl and aryl Grignard reagents.
- Muramatsu, Yusuke,Harada, Toshiro
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p. 1088 - 1090
(2008/09/21)
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- Reductive dehalogenation of arylhalides and alkylhalides with zinc in THF saturated aqueous ammonium chloride
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A low-cost and highly effective zinc/THF-saturated aqueous ammonium chloride has been developed for dehalogenation of arylhalides and alkylhalides in aqueous systems.
- Hekmatshoar, Rahim,Sajadi, Sodeh,Heravi, Majid M.
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experimental part
p. 616 - 618
(2009/05/07)
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- A highly diastereoselective pinacol coupling reaction of aldehydes and ketones using low-valence niobium generated from Nb(V)
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A simple method for the diastereoselective synthesis of racemic 1,2-diol mediated by low-valence niobium generated in situ is described. A 1,4-dioxane-toluene solvent system was found to be essential to achieve higher selectivities and to prevent other reactions of pinacols, such as deoxygenation and acetal formation. Aromatic aldehydes and ketones were converted to the corresponding pinacols with up to 97 and 85% de, respectively.
- Arai, Shigeru,Sudo, Yukinori,Nishida, Atsushi
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p. 287 - 288
(2007/10/03)
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- Novel and efficient Ni-mediated pinacol coupling of carbonyl compounds
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It was firstly found that the Rieke Ni generated in situ was able to promote the pinacol coupling of various carbonyls efficiently. Based on this information, another catalytically effective, cheaper and more convenient NiCl2(Cat.)/Mg/TMSCl system was designed and developed further successfully. The interesting single-electron transfer (SET) mechanisms for the coupling reactions were proposed. Additionally, the DL/meso diastereoselectivity and some additive effects were also explained in terms of the proposed mechanisms.
- Shi, Lei,Fan, Chun-An,Tu, Yong-Qiang,Wang, Min,Zhang, Fu-Min
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p. 2851 - 2855
(2007/10/03)
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- Synthesis, X-ray structures and chemistry of enantiomerically pure 10,11-dihydro-5-phenyl-5H-dibenzo[b,f]phosphepine 5-oxides
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Several phosphepine oxides were synthesised in optically pure form. Sharpless asymmetric dihydroxylation was used to introduce the chiral centres in all cases. Ring closure was achieved using either PhPCl2 or PrPCl2 together with a double nucleophile generated by either a double ortho-lithiation or double bromine-lithium exchange. The X-ray crystal structures of three phosphepine oxides illustrate their different conformations. The NMR spectra of several phosphepine oxides are described as is the chemistry which is shown to differ from that of acyclic phosphine oxides.
- Wyatt, Paul,Warren, Stuart,McPartlin, Mary,Woodroffe, Tom
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p. 279 - 297
(2007/10/03)
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- Reductive coupling of carbonyl compounds to pinacols with zinc in THF-saturated aqueous ammonium chloride
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In the presence of metallic zinc, aldehydes and ketones experience reductive coupling in tetrahydrofuran-saturated aqueous ammonium chloride (5:3) to afford the corresponding pinacols in moderate to high yields.
- Hekmatshoar,Yavari,Beheshtiha,Heravi
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p. 689 - 691
(2007/10/03)
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- Improved synthesis and crystal structure of TiCl3(tmeda)(thf): A highly stereoselective pinacol coupling reagent for aromatic aldehydes
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A monomeric titanium(III) complex, TiCl3(tmeda)(thf) (1), has been prepared by a reaction of TiCl4 with TMEDA, Zn, and a catalytic amount of PbCl2 in an almost quantitative yield. The solid state structure of 1 is revealed by X-ray crystallographic analysis. The complex 1 couples aromatic aldehydes under mild conditions to give 1,2-diols in good to excellent yields with high d/-selectivities.
- Oshiki, Toshiyuki,Kiriyama, Takayuki,Tsuchida, Kazuaki,Takai, Kazuhiko
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p. 334 - 335
(2007/10/03)
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- An efficient protocol for Sharpless-style racemic dihydroxylation
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Racemic dihydroxylation of alkenes is efficiently accomplished with catalytic osmium (added as OsCl3), stoichiometric K3Fe(CN)6 and quinuclidine under conditions similar to those of the Sharpless asymmetric hydroxylation.
- Eames, Jason,Mitchell, Helen J.,Nelson, Adam,O'Brien, Peter,Warren, Stuart,Wyatt, Paul
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p. 1095 - 1104
(2007/10/03)
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- Magnesium-mediated carbon-carbon bond formation in aqueous media: Barbier-Grignard allylation and pinacol coupling of aldehydes
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Magnesium-mediated Barbier-Grignard type alkylation of aldehydes with alkyl halides was studied in aqueous media. The reaction of aromatic aldehydes with allyl halides is highly effective with either THF or water as the reaction solvent but poor in a mixture of THF/water. It was found that the magnesium-mediated allylation of aldehydes with allyl bromide and iodide proceeds effectively in aqueous 0.1 N HCl or 0.1 N NH4Cl. Aromatic aldehydes reacted chemoselectively in the presence of aliphatic aldehydes. An exclusive selectivity was also observed when both aliphatic and aromatic aldehyde functionalities are present in the same molecule. In the absence of allyl halides, aldehydes and ketones reacted with magnesium in aqueous 0.1 N NH4Cl to form the corresponding pinacol coupling products in high yields. The effectiveness of the pinacol reaction was strongly influenced by the steric environment surrounding the carbonyl group. Aliphatic aldehydes and simple alkyl halides appear inert under the reaction conditions for either alkylation or the pinacol coupling reaction.
- Zhang, Wen-Chun,Li, Chao-Jun
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p. 3230 - 3236
(2007/10/03)
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- Magnesium in water: Simple and effective for pinacol-coupling
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A simple and effective pinacol-coupling has been carried out with magnesium. The reaction is highly effective in water in the presence of a catalytic amount of ammonium chloride. Under these conditions, various aromatic aldehydes and ketones undergo carbonyl coupling, generating 1,2-diols in good yields. The effectiveness of the reaction is strongly influenced by the steric environment surrounding the carbonyl group. Aliphatic aldehydes appear inert under the reaction conditions.
- Zhang, Wen-Chun,Li, Chao-Jun
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p. 3131 - 3132
(2007/10/03)
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- Manganese-mediated carbon-carbon bond formation in aqueous media: Chemoselective allylation and pinacol coupling of aryl aldehydes
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The use of manganese as a mediator for allylations and pinacol couplings in aqueous media was investigated. The combination of manganese and copper is found to be a highly effective mediator for the allylation of aryl aldehydes in water. Such a combination is found to be more reactive than other previously reported metals in aqueous media. No reaction was observed with either manganese or copper alone as the mediator. Only a catalytic amount of copper is required for the proceeding of the reaction. The uses of Cu(0), Cu(I), and Cu(II) as the copper source are all effective. The use of a catalytic amount of manganese combined with a stoichoimetric amount of copper led to the failure of the reaction. Allyl chloride is found to be more effective than allyl bromide for the corresponding reaction. The use of substituted allyl halides gave a mixture of regio- and diastereoisomers. Aromatic aldehydes reacted chemoselectively in the presence of aliphatic aldehydes. An exclusive selectivity was also observed when both an aliphatic and an aromatic aldehyde functionalities are present in the same molecule. In the presence of acetic acid or ammonium chloride, manganese was found to effect the pinacol-coupling reaction in water. The reaction proceeds selectively with aryl aldehydes.
- Li, Chao-Jun,Meng, Yue,Yi, Xiang-Hui,Ma, Jihai,Chan, Tak-Hang
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p. 7498 - 7504
(2007/10/03)
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- Pinacolic coupling of aromatic carbonyl compounds using Zn powder in aqueous basic media without organic solvents
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Treatment of aromatic carbonyl compounds with Zn powder in 10% aq NaOH solution without using any organic solvents under the mild conditions afforded the corresponding 1,2-diols in good yields.
- Tsukinoki, Takehito,Kawaji, Takatoshi,Hashimoto, Iwao,Mataka, Shuntaro,Tashiro, Masashi
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p. 235 - 236
(2007/10/03)
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- An Efficient Protocol for a Sharpless Style Racemic Dihydroxylation
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Dihydroxylation with solid OsCl3 to provide the catalytic oxidant, K3Fe(CN)6 as stoichiometric oxidant, quinuclidine as the accelerating ligand with added K2CO3 and methanesulfonamide in a two-phase system (water and t-butanol) gives excellent yields of r
- Eames, Jason,Mitchell, Helen J.,Nelson, Adam,O'Brien, Peter,Warren, Stuart,Wyatt, Paul
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p. 1719 - 1722
(2007/10/02)
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- Ytterbium Metal Mediated Synthesis of Symmetrical and Unsymmetrical Pinacols from Carbonyl Compounds
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Reaction of aromatic aldehydes and ketones with ytterbium metal gives the corresponding pinacols in high yields.Cross-coupling reaction of benzophenone with other carbonyl compounds to produce unsymmetrical pinacols is also described.
- Hou, Zhaomin,Takamine, Kan,Fujiwara, Yuzo,Taniguchi, Hiroshi
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p. 2061 - 2064
(2007/10/02)
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