- Diastereoselective photochromism of a bisbenzothienylethene governed by steric as well as electronic interactions
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Introduction of an asymmetric center to C-2 of one of the benzothiophene rings of bisbenzothienylperfluorocyclopentene results in a highly diastereoselective photochromic system. The stereogenic center bears a hydrogen atom, a methyl group, and a methoxymethoxy group. The steric as well as the electronic repulsions gave an 87-88% diastereomer excess in various solvents at room temperature with 80-85% conversion to the colored form. The enantioselective synthesis was also carried out. Upon photoirradiation in hexane, a change in optical rotation at 820 nm, where neither the open form nor the colored form absorbs light, was observed repeatedly. Copyright
- Yokoyama, Yasushi,Shiraishi, Hidenori,Tani, Yutaka,Yokoyama, Yayoi,Yamaguchi, Yoshitaka
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Read Online
- Oxidative β-Halogenation of Alcohols: A Concise and Diastereoselective Approach to Halohydrins
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β-Halohydrins bearing transformable halo- and hydroxyl groups, are easily converted into various valuable blocks in organic and pharmaceutical synthesis. A diastereoselective β-halogenation of benzylic alcohols was achieved under simple and low-cost conditions, which provided a direct synthesis of β-halohydrins. The simple reaction conditions, easily available reagents, high diastereoselectivities, and additional oxidant-free make this reaction very attractive and practical.
- Ai, Lingsheng,Wang, Weijin,Wei, Jialiang,Li, Qing,Song, Song,Jiao, Ning
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supporting information
p. 437 - 441
(2019/02/26)
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- FLP-Catalyzed Transfer Hydrogenation of Silyl Enol Ethers
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Herein we report the first catalytic transfer hydrogenation of silyl enol ethers. This metal free approach employs tris(pentafluorophenyl)borane and 2,2,6,6-tetramethylpiperidine (TMP) as a commercially available FLP catalyst system and naturally occurring γ-terpinene as a dihydrogen surrogate. A variety of silyl enol ethers undergo efficient hydrogenation, with the reduced products isolated in excellent yields (29 examples, 82 % average yield).
- Khan, Imtiaz,Reed-Berendt, Benjamin G.,Melen, Rebecca L.,Morrill, Louis C.
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p. 12356 - 12359
(2018/09/18)
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- Copper(I)-Catalyzed Chemoselective Reduction of Benzofuran-2-yl Ketones to Alcohols with B2pin2 via a Domino-Borylation-Protodeboronation Strategy
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A novel copper(I)-catalyzed chemoselective reduction of the carbonyls of benzofuran-2-yl ketones over furan rings with B2pin2 has been developed. This reaction proceeded under mild conditions. High valuable secondary alcohol derivatives of benzofurans were obtained in good to excellent yields with a broad substrate scope. The mechanistic studies suggested that a domino-borylation-protodeboronation pathway was involved in this reaction.
- Xuan, Qingqing,Kong, Weiguang,Song, Qiuling
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p. 7602 - 7607
(2017/07/26)
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- Tailored sol-gel immobilized lipase preparates for the enzymatic kinetic resolution of heteroaromatic alcohols in batch and continuous flow systems
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Tailored immobilized lipases from Candida antarctica B and Pseudomonas fluorescens, with improved thermal and operational stability, were prepared through fine tuning of the structure of the sol-gel matrix, using various binary or ternary precursor mixtures for the EKR of various chiral heteroaromatic secondary alcohols with benzofuran, benzo[b]thiophen, phenothiazine and 2-phenylthiazol moieties. The operational stability in batch process was studied for five selected systems by performing reuse experiments, using the conversion, enantiomeric excesses and enantiomeric ratio as parameters, demonstrating the dependence of the sol-gel lipase preparate performance on the structure of both biocatalyst and substrate. The resolution of the benzofuranic substrates with the best performing biocatalysts was studied in continuous-flow mode, using the productivity as a criterion. The specific reaction rates under continuous-flow operation (rflow) were higher than those obtained in batch mode (rbatch) in both cases, sustaining its usefulness for further process development.
- Moisǎ, Mǎdǎlina Elena,Spelmezan, Cristina Georgiana,Paul, Cristina,Bartha-Vári, Judith Hajnal,Bencze, László Csaba,Irimie, Florin Dan,Paizs, Csaba,Péter, Fráncisc,To?a, Monica Ioana
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p. 52977 - 52987
(2017/11/24)
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- Process for the Preparation of Zileuton
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The invention discloses a process for the preparation of Zileuton of formula I by employing acetic acid-1-benzo[b]thiophen-2-yl-ethyl-ester of formula-III as an intermediate.
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Paragraph 0110
(2017/01/19)
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- Chiral-at-metal iridium complex for efficient enantioselective transfer hydrogenation of ketones
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A bis-cyclometalated iridium(iii) complex with metal-centered chirality catalyzes the enantioselective transfer hydrogenation of ketones with high enantioselectivities at low catalyst loadings down to 0.002 mol%. Importantly, the rate of catalysis and enantioselectivity are markedly improved in the presence of a pyrazole co-ligand. The reaction is proposed to proceed via an iridium-hydride intermediate exploiting metal-ligand cooperativity (bifunctional catalysis).
- Tian, Cheng,Gong, Lei,Meggers, Eric
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supporting information
p. 4207 - 4210
(2016/03/19)
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- Ansa-Ruthenium(II) Complexes of R2NSO2DPEN-(CH2)n(η6-Aryl) Conjugate Ligands for Asymmetric Transfer Hydrogenation of Aryl Ketones
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New 3rd generation designer ansa-ruthenium(II) complexes featuring N,C-alkylene-tethered N,N-dialkylsulfamoyl-DPEN/η6-arene ligands, exhibited good catalytic performance in the asymmetric transfer hydrogenation (ATH) of various classes of (het)aryl ketones in formic acid/triethylamine mixture. In particular, benzo-fused cyclic ketones furnished 98 to >99.9% ee using a low catalyst loading.
- Ki?ic, Andrea,Stephan, Michel,Mohar, Barbara
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supporting information
p. 2540 - 2546
(2015/08/18)
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- IMPROVED PROCESS FOR THE PREPARATION OF (±)-1-(1-BENZO[B]THIEN-2-YLETHYL)-1-HYDROXYUREA
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The present invention relates to an improved process for the preparation of (±)-1-(I -Benzo[b]thien-2-ylethyl)-1-hydroxyurea compound of formula 1.
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Page/Page column 16
(2011/04/24)
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- Lipase-catalyzed kinetic resolution of racemic 1-heteroarylethanols-experimental and QM/MM study
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The kinetic resolution of racemic 1-(benzothiazol-2-yl)ethanol rac-2a, 1-(benzo[b]thiophen-2-yl)ethanol rac-2b, 1-(benzo[b]furan-3-yl)ethanol rac-2c and 1-(benzo[b]thiophen-3-yl)ethanol rac-2d was studied by enantiomer selective acylation catalyzed by a selection of commercially available and in house produced lipases. Alcoholysis of the corresponding racemic acetates rac-3a-d catalyzed by Candida antarctica lipase B (CaLB) was also investigated. Two racemic 1-heteroarylethanols rac-2a,b were prepared by addition of the corresponding lithiated heteroarylic compounds 1a,b to acetaldehyde, whereas two others, rac-2c,d were synthesized by the addition of MeMgI onto the corresponding heteroaryl-carbaldehydes 1c,d. The high enantiomer selectivities of CaLB in the acylation of racemic 1-heteroarylethanols rac-2a-d allowed the determination of the enantiomeric preference of these enzymatic acetylation reactions by QM/MM [pm3/uff or hf(3-21+g**)/uff] calculations. For acetylation of each of the racemic alcohols rac-2a-d, four possible tetrahedral intermediate states were compared and analyzed.
- Tosa, Monica,Pilbak, Sarolta,Moldovan, Paula,Paizs, Csaba,Szatzker, Gabor,Szakacs, Gyoergy,Novak, Lajos,Irimie, Florin-Dan,Poppe, Laszlo
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p. 1844 - 1852
(2008/12/22)
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- Chemoenzymatic synthesis of (R)- and (S)-1-heteroarylethanols
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A chemoenzymatic methodology for the synthesis of highly enantiomerically enriched (S)- and (R)-1-heteroarylethanols by enantioselective bioreduction with baker's yeast of the corresponding 1-heteroarylethanones followed by three racemization free chemical steps including a Mitsunobu reaction was developed.
- Tosa, Monica Ioana,Podea, Paula Veronica,Paizs, Csaba,Irimie, Florin Dan
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p. 2068 - 2071
(2008/12/22)
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- Chiral helicenoid diarylethene with large change in specific optical rotation by photochromism
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A diarylethene possessing one [4]thiaheterohelicene and one benzothiophene, the latter with a chiral methoxymethoxyethyl group on its C-3 position, was proved to work as a switch of specific optical rotation at a wavelength at which both colored and colorless forms have no absorption in solution. The difference of the specific optical rotation was 1300° between the open form and the photostationary state. The specific optical rotation of one of the isolated optically active major colored forms was -4680°. The conversion to the colored form was 64%, and the diastereomeric excess of photocyclization was 47%.
- Okuyama, Tomoyuki,Tani, Yutaka,Miyake, Kentaro,Yokoyama, Yasushi
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p. 1634 - 1638
(2007/10/03)
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- High pressure and thermal Diels-Alder reaction of 2-vinyl-benzo[b]furan and 2-vinyl-benzo[b]thiophene. Synthesis of new condensed heterocycles
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A new preparation of 2-vinyl-benzo[b]furan and 2-vinyl-benzo[b]thiophene is described. Diels-Alder reactions of these dienes with 3-nitro-2-cyclohexen-1-one and 2-inden-1-one was examined under thermal and high pressure conditions. The reaction products have been converted to multi-ring heteroaromatic compounds.
- Marrocchi, Assunta,Minuti, Lucio,Taticchi, Aldo,Scheeren, Hans W
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p. 4959 - 4965
(2007/10/03)
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- Synthesis of a 5-substituted benzo[b]thiophene
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The synthesis of a 5-substituted dimerie benzo[b]thiophene (3), utilizing a Friedel-Crafts alkylation and subsequent Newman-Kwart rearrangement, is described.
- Wayne, Gregory S.,Lannoye, Gregory S.,Haight, Anthony R.,Parekh, Shyamal I.,Zhang, Weijiang,Copp, Richard R.
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p. 1175 - 1182
(2007/10/03)
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- Synthesis and isolation of N-(aryl or heteroaryl)-alkyl-N-hydroxyurea
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The present invention provides a simple, 1-step process for preparing a N-(aryl or heteroaryl)-hydroxyurea comprising reacting the corresponding alcohol, ester or ether with hydroxyurea and acid. This reaction is particularly useful for preparing a benzo[b]thienyl substituted N-hydroxyurea of formula: from compound 1: by reacting compound 1 with hydroxyurea and acid. R1 is selected from the group consisting of hydrogen, 1-6 carbon alkyl, 1-6 carbon alkoxy, and halogen; R2 is an 1-4 carbon alkyl; and R3 is selected from the group consisting of hydrogen, acyl, methyl, ethyl and mixtures thereof. Additional steps to isolate the pure bulk product follow.
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- Characterization and Synthesis of a 6-Substituted Benzo[b]thiophene
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An impurity observed during the synthesis of zileuton (Zyflo) has been isolated and characterized as a benzo[o]thiophene derivative that has undergone electrophilic substitution in the 6 position (4). A nine-step synthesis confirms the structural assignment. Key steps in the synthesis include a regioselective Friedel-Crafts coupling between 2-hydroxythioanisole, 8, and 1-(benzo[6]thien-2-yl)ethanol, 1, and formation of a benzo[b]thiophene from an o-methylthiobenzaldehyde, 14, and chloroacetone. The synthesis provides a potentially general route to substituted benzo[6]thiophenes.
- Haight, Anthony R.,Wayne, Gregory S.,Lannoye, Gregory S.,Parekh, Shyamal I.,Zhang, Weijiang,Copp, Richard R.,Hollis, L. Steven
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p. 5903 - 5907
(2007/10/03)
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