- Asymmetric polymerization of triphenylmethyl methacrylate leading to a one-handed helical polymer: Mechanism of polymerization
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Asymmetric oligomerization of triphenylmethyl methacrylate (TrMA) was carried out with complexes of 9-fluorenyllithium and chiral ligands in toluene at -78°C, and the oligomers obtained were converted into methyl esters. The resulting oligo(methyl methacrylate)s were first fractionated by gel permeation chromatography in terms of degree of polymerization and further separated into diastereomers and optical isomers by high-performance liquid chromatography. The distribution of oligomers and the ratio of isomers in each oligomer gave important information on the mechanism of the asymmetric (helix sense selective) polymerization of TrMA. The reactivity of each oligomer anion depended greatly on its degree of polymerization and stereostructure. The oligomer anions whose asymmetric centers have R configuration in the system with the complex of 9-fluorenyllithium and (-)-sparteine and those of S configuration in the systems with (+)-(2S,3S)-2,3-dimethoxy-l,4-bis(dimethylamino)butane and (+)-(S)-1-(2-pyrrolidinylmethyl)pyrrolidine as chiral ligands predominantly propagated to a one-handed helical polymer. A stable helix starts at degree of polymerization 9 in the former system and at degree of polymerization 7 in the latter two systems. One helix turn seems to consist of three or four monomeric units. The main chain of the resulting polymer in the former system possessed RRR - absolute configuration and that in the latter systems SSS -, though both polymers are considered to be of the same helicity, P or M. These results indicate that the helicity of the polymer is not governed by the configuration of the main chain but by the chirality of the ligands.
- Nakano, Tamaki,Okamoto, Yoshio,Hatada, Koichi
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- Synthesis of 9-fluorenemethyl boranophosphonodiphosphate via an H-phosphonate approach
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9-Fluorenemethyl boranophosphonate 6 and its boranophosphonodiphosphate 7 were synthesized via an H-phosphonate approach. The method is efficient for the synthesis of acyclic compounds 6 & 7, and can be explored for the synthesis of nucleoside 5′-deoxy boranophosphonodiphosphate. Copyright Taylor & Francis Group, LLC.
- Liu, Hongyan,Hashmi, Syed N.,Shaw, Barbara Ramsay
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- One-pot preparation of alkyl iodides from esters by indium-catalyzed reductive cleavage of a carbon-oxygen bond
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We describe the indium-catalyzed reductive iodination of aliphatic and aromatic esters with iodine and 1,1,3,3- tetramethyldisiloxane (TMDS). This reducing procedure accommodates a variety of esters, including esters containing alkyl groups, halogens, a hydroxy group, a thioether, and an alkene moiety. Also, this procedure was applied to the cleavage of carbon-oxygen bonds in acrylate polymers.
- Sakai, Norio,Matsushita, Yohei,Konakahara, Takeo,Ogiwara, Yohei,Hirano, Keisuke
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supporting information
p. 1591 - 1595
(2015/03/04)
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- Indium(III)-catalyzed reductive bromination and iodination of carboxylic acids to alkyl bromides and iodides: Scope, mechanism, and one-pot transformation to alkyl halides and amine derivatives
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Highly effective indium(III)-catalyzed reductive bromination or iodination of a variety of carboxylic acids with 1,1,3,3-tetramethyldisiloxane (TMDS) and a source of bromine or iodine is described. This functional group interconversion has high tolerance for several functional groups, such as halogens, a hydroxy group, a nitro group, an olefin part, and a sulfide moiety. This indium catalytic system is also applicable to the reductive iodination of aldehyded, acyl chlorides, and esters. Furthermore, this reducing system can be applied to the one-pot synthesis of alkyl halides and amine derivatives via the addition of nucleophiles. Insight into the reaction mechanism was gained via the time course of 1H and 13C NMR monitoring experiments and the corresponding stepwise reactions.
- Moriya, Toshimitsu,Yoneda, Shinichiro,Kawana, Keita,Ikeda, Reiko,Konakahara, Takeo,Sakai, Norio
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p. 10642 - 10650
(2013/11/19)
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- Indium(III)-catalyzed one-pot synthesis of alkyl cyanides from carboxylic Acids
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The one-pot preparation of alkyl cyanides from carboxylic acids via alkyl iodides or alkyl bromides, which were in situ generated either by indium(III)-catalyzed reductive iodination or bromination of carboxylic acids, is described. Georg Thieme Verlag Stuttgart New York.
- Moriya, Toshimitsu,Shoji, Kohei,Yoneda, Shinichiro,Ikeda, Reiko,Konakahara, Takeo,Sakai, Norio
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p. 3233 - 3238
(2013/12/04)
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- Stepwise and concerted solvolytic elimination and substitution reactions: E1 reaction via a primary carbocation
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Solvolysis of 9-(X-methyl)fluorene (1-X, X = I, Br, OBs) in 25 vol % acetonitrile in water gives the elimination product 9- methylidenefluorene and the substitution products 9- (hydroxymethyl)fluorene (1-OH) and 9-(acetamidomethyl)fluorene (1- NHCOMe). Kinetic studies of the corresponding ring-substituted compounds 2-X and 3-X show that the rate of elimination increases with increasing acidity of the substrate, Bronsted α > 0. The small kinetic deuterium isotope effects measured for the elimination reactions of the brosylates 1-OBs and 3-OBs, k(H)/k(D) = 2.0 ± 0.1 and 2.8 ± 0.1, respectively, suggest significant amounts of E1 reaction. The bimolecular reactions of the brosylates with added bases may be of irreversible E1cB type in contrast to the reactions of the halides which exhibit E2 reaction with added bases as well as with solvent water.
- Meng, Qingshui,Thibblin, Alf
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p. 4834 - 4840
(2007/10/03)
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- Synthesis an CuCN-Promoted Cyanation of Iodoformic Esters
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A number of iodoformic esters have been prepared, isolated, and identified for the first time.Phenyl iodoformate has been converted into phenyl cyanoformate under mild conditions.Decarboxylative iodination of iodoformates ROCOIto give RI and CO2 can be slowed down by the choice of the group R.
- Hoffmann, H.M.R.,Iranshahi, Lotfollah
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p. 1174 - 1176
(2007/10/02)
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