- Double-Stranded Helical Oligomers Covalently Bridged by Rotary Cyclic Boronate Esters
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Novel double helices covalently bridged by cyclic boronate esters were synthesized from complementary dimers with an m-terphenyl backbone joined by a chiral or achiral phenylene linker bearing diethyl boronates and diols, respectively. The X-ray crystallographic analysis and variable-temperature NMR and circular dichroism measurements, along with theoretical calculations, revealed that the double helices function as a “molecular rotor” in which the cyclic boronate ester units rotate, yielding two stable rotamers at low temperatures. Moreover, our data indicates that the covalently bonded double helices can undergo a unique helix-inversion simultaneously with a rotational motion of the boronate esters.
- Iida, Hiroki,Ohmura, Kenji,Noda, Ryuta,Iwahana, Soichiro,Katagiri, Hiroshi,Ousaka, Naoki,Hayashi, Taku,Hijikata, Yuh,Irle, Stephan,Yashima, Eiji
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supporting information
p. 927 - 935
(2017/04/24)
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- Copper(i)-catalyzed amidation reaction of organoboronic esters and isocyanates
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A simple and efficient methodology for the preparation of amides from easily available organoboronic esters and isocyanates has been accomplished using a ligand-free copper(i) catalyst. The reaction system demonstrated a broad substrate scope and provided convenient access to a wide variety of secondary amides.
- Salim Lew, Tedrick Thomas,Wen Lim, Diane Shu,Zhang, Yugen
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supporting information
p. 5140 - 5143
(2015/12/05)
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- Generation of organolithium compounds bearing super silyl ester and their application to Matteson rearrangement
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It's super-silyl-fragilithyl-ester-aryl-docious: The super silyl group is a strong protecting group for carboxylic acids and provides a method for direct lithiation that is compatible with the ester moiety. Organolithium compounds bearing a super silyl ester react with a variety of electrophiles in high yields (see scheme). The reaction of lithiated super silyl chloroacetate with a boron compound gives α-functionalization of the ester moiety by Matteson rearrangement. Copyright
- Oda, Susumu,Yamamoto, Hisashi
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supporting information
p. 8165 - 8168
(2013/08/23)
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- NOVEL BORATE DERIVATIVES AND THEIR APPLICATIONS
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Borates, compositions comprising chiral (cyclic and acyclic) and achiral (cyclic and acyclic) borates; chiral (cyclic and acyclic) and achiral (cyclic and acyclic) biborates; and methods for their synthesis. Additionally, a significantly improved synthetic protocol for the synthesis of wide range of boronates starting from borates or biborates and Grignard or organolithium reagents that can be used for kilo lab and commercial scale production.
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Page/Page column 5
(2012/12/13)
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- Ruthenium(0)-catalyzed sp3 C-H bond arylation of benzylic amines using arylboronates
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A Ru-catalyzed direct arylation of benzylic sp3 carbons of acyclic amines with arylboronates is reported. This highly regioselective and efficient transformation can be performed with various combinations of N-(2-pyridyl) substituted benzylamines and arylboronates. Substitution of the pyridine directing group in the 3-position proved to be crucial in order to achieve high arylation yields. Furthermore, the pyridine directing group can be removed in high yields via a two-step protocol.
- Dastbaravardeh, Navid,Schnuerch, Michael,Mihovilovic, Marko D.
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supporting information; experimental part
p. 1930 - 1933
(2012/05/31)
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- Seven-membered ring boronates at trans-diol moieties of carbohydrates
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MS and 1H, 13C and 11B NMR results are presented revealing the formation of cyclic seven-membered boronate structures at trans-1,2-diol moieties of carbohydrates providing new opportunities for the activation, protection and analysis of glucopyranose-based oligomers and polymers such as cellulose or starch. 'Coordination-induced shifts' in 13C NMR spectra were identified for the esterification by boronic acids of carbohydrates, which can be applied for further studies.
- Meiland, Marcel,Heinze, Thomas,Guenther, Wolfgang,Liebert, Tim
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supporting information; experimental part
p. 469 - 472
(2009/05/11)
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- A comparative study of the relative stability of representative chiral and achiral boronic esters employing transesterification
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A comparative study of the transesterification of five representative chiral and achiral boronic esters with various structurally modified diols was undertaken to qualitatively understand the factors influencing the relative stability of these boronic esters. Several factors such as chelation, conformation, steric bulk of the substituents, size of the heterocycle, and entropy influence the relative rate of transesterification as well as the stability of the boronic esters. Amongst these boronic esters, pinanediol phenylboronic ester was found to be the most stable boronic ester whereas DIPT boronic ester appeared to be thermodynamically the least stable one. The transesterification with sterically hindered diols was observed to be relatively slow, but afforded thermodynamically more stable boronic esters. Boronic esters derived from cis-cyclopentanediols and the bicyclo[2.2.1]heptane-exo,exo-2,3- diols are relatively more stable. This study not only presents the qualitative picture of relative stability of various boronic esters, but also provides helpful hints regarding the possible recovery of chiral auxiliaries. Many C 2-symmetric chiral auxiliaries, such as 2,3-butanediol, 2,4-pentanediol, DIPT, and cis-cyclohexane-1,2-diol, can be retrieved by simple transesterification of the corresponding boronic esters with commercial inexpensive diols, such as pinacol, 1,3-propanediol, and neopentyl glycol.
- Roy, Chandra D.,Brown, Herbert C.
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p. 879 - 887
(2008/02/11)
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- Stability of boronic esters - Structural effects on the relative rates of transesterification of 2-(phenyl)-1,3,2-dioxaborolane
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Relative rates of reaction of the achiral cyclic phenylboronic ester 2-(phenyl)-1,3,2-dioxaborolane with a wide variety of structurally modified diols, have been studied to understand the factors influencing the relative stabilities of boronic esters. It is found that the alkyl substituents on the α-carbons of diols slow down the transesterification, but produce thermodynamically more stable boronic ester. Six-membered boronic esters are thermodynamically more stable than their corresponding five-membered analogs. Amongst cyclic 1,2-diols, cis-1,2-cyclopentanediol displaces ethylene glycol instantaneously whereas trans-1,2-cyclopentanediol is totally unreactive, which suggests that the cis-stereochemistry of the 1,2-diol is a prerequisite for transesterification. Among the 1,5-diols, diethanolamine displaces ethylene glycol quite rapidly forming a more stable bicyclic chelate in which nitrogen is attached to boron by a coordinating bond (as evident by 11B NMR spectroscopy). The oxygen atom of di(ethylene glycol) and the sulfur atom of 2,2′-thiodiethanol do not assist in displacing the ethylene glycol from their boronic esters.
- Roy, Chandra D.,Brown, Herbert C.
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p. 784 - 790
(2007/10/03)
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- Reaction of Arylboronic Acids and their Derivatives with Lead Tetra-acetate. The Generation of Aryl-lead Triacetates, and meta- and para-Phenylenebis(lead triacetate), in situ for Electrophilic Arylation
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Arylboronic acids and some of their derivatives have been found to undergo a rapid boron-lead exchange with lead tetra-acetate.In the presence of a catalytic amount of mercury(II) acetate, the reaction produces mainly the aryl-lead triacetate, and it has been developed as a convenient method for in situ generation of these useful electrophilic C-arylating reagents.The reaction allows the generation for the first time of meta- and para-phenylenebis(lead triacetate), compounds which behave as meta- and para-phenylene dication equivalents.
- Morgan, Jacqueline,Pinhey, John T.
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p. 715 - 720
(2007/10/02)
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- Derivatization and Mass Spectrometric Investigation of Substituted Benzeneboronic Acids. The Use of Linked Scanning During Gas Chromatography Mass Spectrometry
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Substituted benzeneboronic acids are important intermediates in the synthesis of support matrices for affinity chromatography but their analysis by mass spectrometry is hindered by thermal reactions in the ion source.A simple derivatization with 1,2- or 1
- Longstaff, Colin,Rose, Malcolm Edward
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p. 508 - 518
(2007/10/02)
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- Diol lipids - Communication 27. Identification of C2-C4-diols in the form of cyclic esters of phenylboric acid by the method of combined gas chromatography and mass spectrometry
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1. A new method was proposed for the analysis of small quantities of C2-C4-diols, formed in the cleavage of lipids, based on combined gas-chromatography and mass spectrography of their phenylborate esters. 2. Phenylborate esters of d
- Batrakov,Panosyan,Ushakov,Rozynov,Bergel'son
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p. 1662 - 1668
(2007/10/10)
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- The structure of the benzeneboronate of pentane-1,3,5-triol
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The relative ease of formation of five-, six-, seven-, and eight-membered cyclic benzeneboronates is discussed. Pentane-1,3,5-triol forms, by interaction with benzene-boronic anhydride, exclusively DL-4-(2-hydroxyethyl)-2-phenyl-1,3,2-dioxaborinane. It is suggested that, in this compound, the oxygen atom of the hydroxyl group is intramolecularly co-ordinated with the boron atom.
- Bourne, Edward J.,Mckinley, Ian R.,Weigel, Helmut
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p. 141 - 149
(2007/10/16)
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