- A Metal-Free Domino Process for Regioselective Synthesis of 1,2,4-Trisubstituted Pyrroles: Application toward the Formal Synthesis of Ningalin B
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A new one-pot, transition-metal, acid/base-free domino process is developed for the regioselective synthesis of 1,2,4-trisubstituted pyrroles. The process involves 1,3-dipolar cycloaddition of unsymmetrical azomethine ylide resulting from the thermal C-C bond cleavage of unactivated aziridines with β-bromo-β-nitrostyrene, followed by a cascade of elimination and aromatization reaction sequence to preferentially furnish 1,2,4-trisubstituted pyrroles instead of the expected 1,2,3-trisubstituted pyrroles, in good to excellent yields. Further, the application of the methodology for the formal synthesis of ningalin B is delineated.
- Kumar, Virendra,Awasthi, Annapurna,Metya, Abhisek,Khan, Tabrez
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p. 11581 - 11595
(2019/10/02)
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- How Reaction Conditions May Influence the Regioselectivity in the Synthesis of 2,3-Dihydro-1,4-benzoxathiine Derivatives
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The exploration of different reaction conditions aiming to obtain both 2,3-dihydro-1,4-benzoxathiine-2-yl derivatives and 2,3-dihydro-1,4-benzoxathiine-3-yl ones is reported. The treatment of 1,2-mercaptophenol with an organic base and a specific 2-bromo acrylate results in a solvent- and substrate-dependent exclusive solvation of O- and S-anions, thus managing the regioselectivity.
- Casiraghi, Andrea,Valoti, Ermanno,Suigo, Lorenzo,Artasensi, Angelica,Sorvillo, Erica,Straniero, Valentina
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p. 13217 - 13227
(2018/10/24)
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- Diaziridyl Ether of Bisphenol A
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Increased complexities in applications involving curable materials virtually need new materials that can overcome the limitations of existing ones. Resins, the structure of which is based on bisphenol A backbone terminated with three membered N-heterocycles - aziridines - have been synthesized, and their thermal-curing performance in solution and solid state was evaluated by NMR and FT-IR spectroscopies, differential scanning calorimetry, and single lap shear strength test and compared with that of analogous epoxy resin (diglycidyl ether of bisphenol A; DGEBA). Results reveal that the chemical reactivity of the aziridine-based resins is fine-tunable by controlling the N-substituent of aziridine. These resins can undergo ring-opening polymerization in the presence of various curing agents under unprecedentedly mild conditions and show remarkably rapid curing rate, wide substrate scope, and excellent chemoselectivity as compared to the analogous epoxy resin. Our results demonstrate superb curing ability of aziridine, making it promising for applications in materials and polymer sciences.
- Kang, Seohyun,Moon, Hyun Kyung,Yoon, Hyo Jae
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p. 4068 - 4076
(2018/06/19)
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- Halogen bonding enhances activity in a series of dual 5-HT6/D2 ligands designed in a hybrid bioisostere generation/virtual screening protocol
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A novel hybrid bioisostere generation/virtual screening method combined with narrowing of chemical space through similarity to compounds that are active at the second target was successfully applied for the development of structurally new dual 5-HT6/D2 receptor ligands. Consequently, a series of derivatives of the found hit 1d (N-[2-(dimethylamino)ethyl]-N-(2-phenylethyl)aniline) was synthesized. The most active 5-HT6/D2 ligands also showed affinity for 5-HT7R and 5-HT2AR. The para-chloroaniline derivative was identified as a potent dual 5-HT6/5-HT7 receptor antagonist (Ki = 24 nM and Kb = 30 nM, Ki = 4 nM and Kb = 1.4 nM, respectively). In the case of halogen-containing compounds, interesting structure-activity relationships were observed at 5-HT6, D2 and 5-HT7 receptors, and the ligand-receptor complexes were subsequently examined using a molecular modelling approach that combined quantum-polarized ligand docking (QPLD) and Molecular-Mechanics-Generalized-Born/Surface Area (MM/GBSA) free-energy calculation, which permitted the identification of putative halogen binding pockets.
- Staroń, Jakub,Warszycki, Dawid,Kurczab, Rafa?,Sata?a, Grzegorz,Bugno, Ryszard,Hogendorf, Adam,Bojarski, Andrzej J.
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p. 54918 - 54925
(2016/07/06)
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- Mesoporous silica-supported copper-catalysts for homocoupling reaction of terminal alkynes at room-temperature
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Amine-functionalized mesoporous silica-supported copper catalysts SBA-15@amine-Cu and SBA-15@Oamine-Cu were prepared and proved to be efficient and reusable for homocoupling of terminal alkynes at room temperature with air as the oxidant. SBA-15@amine-Cu exhibited better recyclability than SBA-15@Oamine-Cu. The differences in the catalytic performances of the catalysts could be ascribed to catalyst structure and the interaction between copper and the supports. The as-prepared catalysts were systematically characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), high resolution-transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and nitrogen physical adsorption. The analysis indicated that the mesoporous structure of the materials was retained during the immobilization process. XPS results suggested that the as-prepared catalysts were not obtained by a simple physical adsorption of CuCl on the supports. It is noted that, for aliphatic alkynes, the catalytic activity of SBA-15@amine-Cu is even higher than that of the homogeneous copper catalytic system and that of some previously reported heterogeneous systems.
- Li, Hongling,Yang, Min,Zhang, Xia,Yan, Liang,Li, Jing,Qi, Yanxing
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p. 1343 - 1349
(2013/05/21)
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- Nucleophilic trifluoromethylation of aziridinyl ketones: A convenient access to fluorinated aziridinyl alcohols
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A convenient synthesis of α-(aziridin-2-yl)-α-(trifluoromethyl) alcohols starting with ethyl aziridine-2-carboxylates is reported. Grignard reaction with the corresponding Weinreb amides led to aziridin-2-yl ketones, and subsequent treatment with Ruppert-Prakash reagent gave the trimethylsilylated target compounds as mixtures of diastereoisomers, which were desilylated with TBAF. In the case of ethyl 1-((S)-1-phenylethyl)aziridine-2-carboxylate, (S,S)- and (S,R)-aziridin-2-yl ketones were obtained, separated chromatographically and transformed into the desired enantiomerically pure α-trifluoromethylated alcohols.
- Mlostoń, Grzegorz,Obijalska, Emilia,Zi?bacz, Paulina,Matyszewski, Krzysztof,Urbaniak, Katarzyna,Linden, Anthony,Heimgartner, Heinz
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p. 192 - 197
(2013/11/19)
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- Direct sustainable bromination of alkenes in aqueous media and basic ionic liquids
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Electron-rich and electron-poor alkenes have been dibrominated using a rapid and sustainable procedure. The reactions were conducted in aqueous medium and basic ionic liquids which catalyzed the direct addition of bromine. The protocol leads to remarkable results, high yields under mild conditions, complete chemo- and stereo-selectivity and allows the recycling of ionic liquids, reducing costs, and environmental impact.
- Primerano, Patrizia,Cordaro, Massimiliano,Scala, Angela
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p. 4061 - 4063
(2013/07/25)
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- Chemoenzymatic synthesis of piperoxan, prosympal, dibozane, and doxazosin
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The synthesis of both enantiomers of 1,4-benzodioxan-2-carboxylic acid 1, a key synthetic intermediate for the therapeutic agents piperoxan, prosympal, dibozane, and doxazosin was achieved with good yields and high enantioselectivities via the Arthrobacter sp. lipase catalyzed kinetic resolution of ester (±)-17a. The influence of the co-solvents and the immobilization of the lipase upon kinetic resolution demonstrated that immobilized whole cells, in the presence of n-butanol as a co-solvent, resulted in the optimal resolution of the substrate (ee ~99%, E = 535) at 258 mmol (50 g/L) substrate concentration.
- Rouf, Abdul,Gupta, Pankaj,Aga, Mushtaq A.,Kumar, Brijesh,Chaubey, Asha,Parshad, Rajinder,Taneja, Subhash C.
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p. 1615 - 1623
(2013/02/22)
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- Anionic [4+3] heteroannulation of 2-azidoacrylates: A modular synthesis of 2-benzazepin-1-ones
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2-Azidoacrylates undergo [4+3] annulation with phthalides under anionic conditions at low temperatures to furnish 5-hydroxy-2-benzazepinones, the formation of which represents a new concept for the construction of azepines as well as a new reactivity of 2-azidoacrylates.
- Dinda, Bidyut Kumar,Jana, Amit Kumar,Mal, Dipakranjan
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supporting information; experimental part
p. 3999 - 4001
(2012/06/01)
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- Robust eco-friendly protocol for the preparation of γ-hydroxy- α,β-acetylenic esters by sequential one-pot elimination-addition of 2-bromoacrylates to aldehydes promoted by LTMP in 2-MeTHF
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An efficient and widely applicable preparation of γ-hydroxy-α, β-acetylenic esters is described by means of a one-pot dehydrobromination of a 2-bromoacrylate ester with LTMP followed by the electrophilic addition of the transient propiolate to different aldehydes in the eco-friendly solvent 2-MeTHF. The Royal Society of Chemistry 2012.
- Pace, Vittorio,Castoldi, Laura,Alcantara, Andres R.,Holzer, Wolfgang
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supporting information; experimental part
p. 1859 - 1863
(2012/08/14)
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- Efficient bromination of alkenes and alkynes using potassium bromide and diacetoxy iodobenzene
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Bromination of alkenes and alkynes has efficiently been carried out at room temperature in short reaction times using KBr and diacetoxy iodobenzene in CH2Cl2-H2O (1:1) to prepare the corresponding trans-dibromo compounds in excellent yields. Copyright Taylor & Francis Group, LLC.
- Das, Biswanath,Srinivas, Yallamalla,Sudhakar, Chittaluri,Damodar, Kongara,Narender, Ravirala
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experimental part
p. 220 - 227
(2009/04/07)
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- An economical and convenient synthesis of vinyl sulfones
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A general process for the efficient synthesis of vinyl sulfones has been developed using commercially available sulfinic acid sodium salts and dibromides. A variety of phenyl and methyl vinyl sulfones have been formed in good yields, in the absence of any catalyst. Georg Thieme Verlag Stuttgart.
- Guan, Zheng-Hui,Zuo, Wei,Zhao, Lian-Biao,Ren, Zhi-Hui,Liang, Yong-Min
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p. 1465 - 1470
(2008/02/05)
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- Aziridines as templates: A general strategy for the stereospecific synthesis of 2-azetidinones
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Various routes to a variety of azridine-2-carboxylates have been described and the stereochemistry of these compounds has been determined by spectroscopic methods. Further, greater diversity of β-lactams via ring expansion of these azridines-2-carboxylates were obtained by a general, efficient and direct stereospecific approach.
- Sharma,Kanwar, Seema,Rajpoot, Shivani
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- Poly(vinylpyrrolidone)-bromine complex; a mild and efficient reagent for selective bromination of alkenes and oxidation of alcohols
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Poly(vinylpyrrolidone)-bromine complex (PVP-Br2) is easily prepared and used as a mild and convenient reagent for selective bromination of alkenes and at the position α-hydrogen of active carbonyl compounds. Selective oxidation of benzylic alcohols in the presence of aliphatic alcohols were also achieved at room temperature.
- Lakouraj, Moslem Mansour,Tajbakhsh, Mahmood,Mokhtary, Masoud
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p. 481 - 483
(2007/10/03)
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- Activation of alkyl halides via a silver-catalyzed carbene insertion process
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The silver complex [HB(3,5-(CF3)2Pz)3]Ag(THF) featuring a highly fluorinated tris(pyrazolyl)borate ligand catalyzes the formation of aliphatic carbon-halogen bond activation products under remarkably mild conditions. For example, the reaction between CHCl3 and ethyl diazoacetate (EDA) at room temperature in the presence of the silver catalyst afforded HClC(CO2Et)CCl2H in 60% yield. The presence of β-hydrogens on the alkyl halide leads to net hydrogen halide addition to the carbene and an alkene. Copyright
- Dias, H. V. Rasika,Browning, R. Greg,Polach, Sharon A.,Diyabalanage, Himashinie V. K.,Lovely, Carl J.
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p. 9270 - 9271
(2007/10/03)
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- Phase-vanishing reactions that use fluorous media as a phase screen. Facile, controlled bromination of alkenes by dibromine and dealkylation of aromatic ethers by boron tribromide
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In fluorous triphasic reactions, such as bromination of alkenes by dibromine and dealkylation of aromatic ethers by boron tribromide, the middle fluorous phase acts as a liquid membrane permitting passive transport of the reagents at the bottom to the top layer involving the substrates, thereby regulating the reactions. Copyright
- Ryu, Ilhyong,Matsubara, Hiroshi,Yasuda, Shinji,Nakamura, Hiroyuki,Curran, Dennis P.
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p. 12946 - 12947
(2007/10/03)
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- Novel syntheses of indolizines and pyrrolo[2,1-a]isoquinolines via benzotriazole methodology
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Indolizines and pyrrolo[2,1-a]isoquinolines are synthesized by 1,3- dipolar cycloadditions of pyridinium benzotriazolylmethylides or isoquinolinium benzotriazolylmethylides with ethylenes and acetylenes.
- Katritzky, Alan R.,Qiu, Guofang,Yang, Baozhen,He, Hai-Ying
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p. 7618 - 7621
(2007/10/03)
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- Studies in the cycloproparene series: 3,8-dioxa-1H-cyclopropa[b]anthracene
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The application of known methodology has provided 2,3-dimethylidene-2,3-dihydro-1,4-benzodioxin (12) as the essential precursor for preparation of the cyclopropa-fused dibenzodioxin 3,8-dioxa-1H-cyclopropa[b]anthracene (14). Cycloproparene (14) is both unstable and acid-sensitive, and readily dimerizes to a mixture of the dihydrotetraoxaheptacene (15) and its heptaphene analogue (16).
- Cooney, Mark J.,Halton, Brian
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p. 533 - 538
(2007/10/03)
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- Kinetics and Mechanism of Bromine Addition to Derivatives of Unsaturated Aliphatic Carboxylic Acids in Aqueous Solution
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This paper deals with the kinetics of bromine addition to unsaturated compounds in presence of added bromide ions at 22, 30, 38, 46, and 54 deg C.The substrates used were acrylamide (AAm), methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), t-butyl acrylate (tBA), methacrylamide (MAAm), methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl crotonate (MC), and ethyl crotonate (EC).The kinetics was followed potentiometrically.The activation parameters (ΔH*, ΔS*, and ΔG*) were calculated and compared.Estimation of product ratio of bromohydrin to dibromide showed the absence of any correlation of the product formation with reactivity of the substrates.The observed parameters are discussed in relation to the proposed reaction mechanisms.
- Mohamed Farook, Syed Ahamed,Viswanathan, Seshaiyer,Ganesan, Ramachandran
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p. 1394 - 1400
(2007/10/02)
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- NEW DATA ON DERIVATIVES OF 1-ALKOXYAZIRIDINE-2-CARBOXYLIC ACIDS
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Esters of β-alkoxyamino-α-bromopropionic acids were obtained by reaction of α,β-dibromopropionic acid esters with alkoxyamines in the presence of triethylamine at 20 deg C for 1 month.When the products are refluxed in acetonitrile in the presence of triethylamine, they are converted to aziridines.Selective amidation of the alkoxyaziridines with excess dimethylamine in absolute methanol in the presence of sodium methoxide leads to enrichment with the cis isomer.The parameters of inversion of the nitrogen atom in the alkoxyaziridines were determined.
- Prosyanik, A.V.,Bondarenko, S.V.,Markov, V.I.,Chervin, I.I.,Isobaev, M.D.,et al.
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p. 154 - 158
(2007/10/02)
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