- A new fluorescent probe based on quinoline for detection of Al3+ and Fe3+ with "off-on-off" response in aqueous solution
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A new quinoline-based fluorescent probe 1 has been designed and synthesized. Fluorescence emission spectra of the probe showed red-shift and obvious enhancement of fluorescent intensity upon the addition of Al3+ (turn-on). 1-Al3+ showed high selectivity for Fe3+ over other metal ions, and eliminated the interference of Al3+ during Fe3+ detection (turn-off). It showed highly selective relay recognition of Al3+ and Fe3+via a fluorescence "off-on-off" mechanism. Fluorescence spectra indicated that the response of 1-Al3+ to Fe3+ was caused by central metal displacement. The detection limits for the analysis of Al3+ and 1-Al3+-Fe3+ ions were calculated to be 2.20 × 10-6 M and 1.96 × 10-5 M, respectively. Living HeLa cell imaging studies revealed that the probe was cell-permeable and it could be used to detect intracellular Al3+ and Fe3+ ions.
- Dai, Yanpeng,Liu, Xiaoyan,Wang, Peng,Fu, Jiaxin,Yao, Kun,Xu, Kuoxi
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Read Online
- Exploiting Peptidomimetics to Synthesize Compounds That Activate Ryanodine Receptor Calcium Release Channels
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Ryanodine receptor (RyR) Ca2+-release channels are essential for contraction in skeletal and cardiac muscle and are prime targets for modification of contraction in disorders that affect either the skeletal or heart musculature. We designed and synthesized a number of compounds with structures based on a naturally occurring peptide (A peptides) that modifies the activity of RyRs. In total, 34 compounds belonging to eight different classes were prepared. The compounds were screened for their ability to enhance Ca2+ release from isolated cardiac sarcoplasmic reticulum (SR) vesicles, with 25 displaying enhanced Ca2+ release. Competition studies with the parent peptides indicated that the synthetic compounds act at a competing site. The activity of the most effective of the compounds, BIT 180, was further explored using Ca2+ release from skeletal SR vesicles and contraction in intact skeletal muscle fibers. The compounds did not alter tension in intact fibers, indicating that (as expected) they are not membrane permeable, but importantly, that they are not toxic to the intact cells. Proof in principal that the compounds would be effective in intact muscle fibers if rendered membrane permeable was obtained with a structurally related membrane-permeable scorpion toxin (imperatoxin A), which was found to enhance contraction.
- Robinson, Ken,Easton, Christopher J.,Dulhunty, Angela F.,Casarotto, Marco G.
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p. 1957 - 1971
(2018/09/11)
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- Study on the synthesis of novel fluorescent macrocyclic sensors and their sensitive properties for Cu2+ and Fe3+ in aqueous solution
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In this work, we synthesised and characterised three novel fluorescence macrocyclic sensors containing optically active dansyl groups. The studies for the interaction of the synthesised compounds with various mental ions (Li+, Na+, K+, Ag+, Mg2+, Ca2+, Ba2+, Pb2+, Zn2+, Co2+, Cd2+, Hg2+, Ni2+, Cu2+, Mn2+, Cr3+, Al3+, Fe3+) were performed by fluorescence titration, Job’s plot, ESI-MS and DFT calculations. The results showed that the sensors 1a–1c displayed selective recognition for Cu2+ and Fe3+ ions and formed stoichiometry 1:1 complex through PET mechanism in DMSO/H2O solution (1:1, v/v, pH 7.4 of HEPES). The binding constant (K) and detection limit were calculated.
- Dai, Yanpeng,Xu, Kuoxi,Wang, Chaoyu,Liu, Xiaoyan,Wang, Peng
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p. 315 - 322
(2017/02/15)
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- Pinpoint-fluorinated polycyclic aromatic hydrocarbons (F-PAHs): Syntheses of difluorinated subfamily and their properties
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Difluorinated polycyclic aromatic hydrocarbons (PAHs) containing three to five benzene rings were systematically synthesized by the Pd(II)-catalyzed Friedel–Crafts-type cyclization of 1,1,2-trifluoro- and 1,1-difluoro-1-alkenes and the In(III)-catalyzed tandem cyclization of bis(1,1-difluoroallene)s. Using an array of the difluorinated PAHs that were obtained and previously reported monofluorinated PAHs, the physical properties of the pinpoint-fluorinated PAHs were investigated. (i) The 19F NMR signals of the bay-region fluorine atoms were shifted downfield by ca. 8–14 ppm for vic-difluorinated PAHs and ca. 11–19 ppm for non-vic-difluorinated and monofluorinated PAHs. (ii) The introduction of fluorine into PAH molecules increased their solubilities in organic solvents, which was best exemplified by the high solubilities of 6,7-difluoropicene (5.4 wt%) and 6-fluoropicene (5.3 wt%) in THF. (iii) The HOMO–LUMO energy gaps of the pinpoint-fluorinated PAHs were smaller than that of the corresponding fluorine-free PAH (i.e., picene) by 0.02–0.26 eV, and the HOMO and LUMO energy levels were lowered by 0.10–0.22 eV and 0.12–0.41 eV, respectively.
- Fuchibe, Kohei,Shigeno, Kento,Zhao, Nan,Aihara, Hiromichi,Akisaka, Rikuo,Morikawa, Toshiyuki,Fujita, Takeshi,Yamakawa, Kie,Shimada, Toshihiro,Ichikawa, Junji
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p. 173 - 184
(2017/10/23)
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- Improved Halogenation of Methyl Aromatics and Methyl Heteroaromatics: Unexpected Reactivity of Tetrahalogeno-diphenylglycolurils
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1,3,4,6-Tetrachloro (TCDGU) and 1,3,4,6-tetrabromo-3α,6α-diphenylglycolurils smooth halogen oxidizers have been exploited in a new direction as reagents for free radical substitution toward some N-halosuccinimide nonreactive bis-heterocycles. An unexpected selectivity and reactivity were observed with methyl benzenes, methyl heterocycles, and methyl-bis-heterocycles of interest. A chemometric study has been performed to optimize five independent factors of the chlorination reaction with TCDGU. The predictive model was established either for the halogenation conversion and the ratio of monochlorination.
- Moretti, Florian,Poisson, Guillaume,Marsura, Alain
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p. 173 - 183
(2016/05/19)
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- Synthesis and thermal stability of new polynitrostilbenes
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New polynitrostilbenes were directly synthesised by the Knoevenagel condensation of aromatic aldehydes with nitrotoluenes. The differential scanning calorimetry results demonstrated that the introduction of an amino group and C≤C double bonds could improve the thermal stability.
- Wei, Jianping,Li, Fangmei,Xu, Junhui,Peng, Xinhua
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p. 919 - 925
(2015/06/25)
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- Distinct structures of inorganic-organic supramolecular assemblies based on discrete metallocyclic complexes incorporating flexible imidazole ligands: Syntheses, crystal structures and properties
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Three new interesting discrete dinuclear metallocyclic complexes, namely, {[Pd2(1)4](NO3)4· 2DMSO· 2H2O}n (4), [Pd2(2) 2Br4]n (5), and {[Pd2(3) 2Cl4]·4DMSO}n (6) have been successfully synthesized by the reaction of flexible exo-bidentate imidazole-containing ligands 1, 3-bis(imidazol-1-ylmethyl)benzene (1), 1, 3-bis(imidazol-1-ylmethyl)- 5-methylbenzene (2), and 2, 6-bis(imidazol-1-ylmethyl)-4-tert-butyl-phenol (3) with corresponding palladium salts. All these complexes were characterized by NMR spectroscopy in combination with elemental analysis, powder X-ray diffraction (PXRD), single-crystal X-ray diffraction, and thermal gravimetric analysis (TGA), respectively. Though all three complexes involve the similar supramolecular building blocks [2+2] metallocyclic units, under the inducement effect of the organic ligands, compounds 4-6 exhibit delicate geometric diversification of the resulting high-dimensional inorganic-organic supramolecular assemblies (e.g., [4+2] lantern-like cage structure, 1D channel, and 2D undulating framework, respectively). Furthermore, these results demonstrate that the secondary interactions such as intermolecular π ··· π stacking interactions and hydrogen bonds could play important roles in the aspect of linking low-dimensional entities into high-dimensional supramolecular frameworks.
- Yang, Li,Chang, Guanjun,Luo, Liang,Ding, Feng,You, Jingsong
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p. 307 - 314
(2013/10/22)
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- Synthesis and intramolecular hydrogen bonding of syn -9-hydroxy-18- substituted [3.3]metacyclophanes
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Various anti-9-methoxy[3.3]metacyclophane-2,11-diones are exclusively obtained by the coupling reaction of the corresponding 1,3-bis(bromomethyl) benzenes and 2,6-bis[2-isocyano-2-(tolylsulfonyl)ethyl]-4-tert-butylanisole in dimethylformamide (DMF) with an excess of sodium hydride, from which the corresponding syn-[3.3]metacyclophanes (MCPs) are synthesized via anti/syn-isomerization during the Wolff-Kishner reduction. Demethylation of syn-9-methoxy[3.3]MCPs with BBr3 afforded the corresponding syn-9-hydroxy[3.3]MCPs in good yields. The existence of the strong intramolecular hydrogen bonding between the 9-hydroxy group and the 18-substituents, such as F, OH, and OMe groups at the opposing aromatic rings, are observed in solution and in the solid state. A distinct low-field shift of the phenolic OH proton was observed in the 1H NMR spectrum compared with that of the 18-unsubstituted analog. Furthermore, O-H...F through-space coupling was observed.
- Tazoe, Kazuya,Feng, Xing,Sharma, Bigyan,Miyamoto, Shinpei,Yamato, Takehiko
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body text
p. 222 - 229
(2012/03/07)
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- Generation of (nonafluoro-tert-butoxy)methyl ponytails for enhanced fluorous partition of aromatics and heterocycles
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The reaction of sodium perfluoro-tert-butoxide with benzylic carbon-bromide bond(s) leads to the formation of (nonafluoro-tert-butoxy)methyl ponytail(s), which can enhance the fluorous solubility and partition of aromatics and heterocycles.
- Zhao, Xi,Ng, Wing Yan,Lau, Kai-Chung,Collis, Alana E. C.,Horvath, Istvan T.
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experimental part
p. 3909 - 3914
(2012/06/30)
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- Homodimeric bis-quaternary heterocyclic ammonium salts as potent acetyl- and butyrylcholinesterase inhibitors: A systematic investigation of the influence of linker and cationic heads over affinity and selectivity
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A molecular library of quaternary ammonium salts (QASs), mainly composed of symmetrical bis-quaternary heterocyclic bromides exhibiting choline kinase (ChoK) inhibitory activity, were evaluated for their ability to inhibit acetyl- and butyrylcholinesterase (AChE and BChE, respectively). The molecular framework of QASs consisted of two positively charged heteroaromatic (pyridinium or quinolinium) or sterically hindered aliphatic (quinuclidinium) nitrogen rings kept at an appropriate distance by lipophilic rigid or semirigid linkers. Many homodimeric QASs showed AChE and BChE inhibitory potency in the nanomolar range along with a low enzymatic selectivity. Computational studies on AChE, BChE, and ChoK allowed identification of the key molecular determinants for high affinity and selectivity over either one of the three enzymes and guided the design of a hybrid bis-QAS (56) exhibiting the highest AChE affinity (IC50 = 15 nM) and selectivity over BChE and ChoK (SI = 50 and 562, respectively) and a promising pharmacological potential in myasthenia gravis and neuromuscular blockade.
- Conejo-García, Ana,Pisani, Leonardo,Del Carmen Nú?ez, Maria,Catto, Marco,Nicolotti, Orazio,Leonetti, Francesco,Campos, Joaquín M.,Gallo, Miguel A.,Espinosa, Antonio,Carotti, Angelo
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body text
p. 2627 - 2645
(2011/06/21)
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- Self-assembly from metal-organic vesicles to globular networks: Metallogel-mediated phenylation of indole with phenyl boronic acid
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Self-assembly of the conformationally flexible bismethylimidazolyl ligands with Pd(OAc)2 is described. Depending on whether the ligands provide the hydrogen bonding donor, a switching of metal-organic vesicles to globular networks gelating solvents is achieved. The metallogels exhibit catalytic activity for the cross-coupling of indole with phenyl boronic acid.
- Yang, Li,Luo, Liang,Zhang, Shuai,Su, Xiaoyu,Lan, Jingbo,Chen, Chi-Tien,You, Jingsong
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supporting information; scheme or table
p. 3938 - 3940
(2010/07/14)
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- Visible-light-promoted Wohl-Ziegler functionalization of organic molecules with N-bromosuccinimide under solvent-free reaction conditions
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The visible-light-induced transformation of toluenes with N-bromosuccinimide (NBS) under solvent-free reaction conditions (SFRC) was studied. The reaction took place in spite of the very restricted molecular motion; toluenes could be regioselectively converted to benzyl bromides. Selective radical-chain reactions with NBS were carried out in liquid/liquid and in solid/solid systems; furthermore, reactions could be performed in the presence of air. The radical scavenger TEMPO (=2,2,6,6-tetramethylpiperidin-1- yloxy) completely suppressed the side-chain bromination of toluenes with NBS under SFRC. Electron-withdrawing groups decreased the reactivity of the toluenes, and the Hammett reaction constant ρ+ = -1.7 indicated involvement of polar radical intermediates with electrophilic character.
- Jereb, Marjan,Zupan, Marko,Stavber, Stojan
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experimental part
p. 555 - 566
(2009/09/06)
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- Poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide), N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide and novel poly(N,N′-dibromo-N-phenylbenzene-1,3-disulfonamide) as powerful reagents for benzylic bromination
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N,N,N′,N′-Tetrabromobenzene-1,3-disulfonamide [TBBDA], poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide) [PBBS], and novel poly(N,N′-dibromo-N-phenylbenzene-1,3-disulfonamide) [PBPS] can be used for bromination of benzylic positions in solvent.
- Ghorbani-Vaghei, Ramin,Chegini, Mohammad,Veisi, Hojat,Karimi-Tabar, Mehdi
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scheme or table
p. 1861 - 1865
(2009/07/19)
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- Synthesis of 8-methyl[2.2]metacyclophanes and their charge-transfer complexes with tetracyanoethylene
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The regioselective 1:1 charge-transfer band of 13-substituted 8-methyl[2.2]metacyclophanes with tetracyanoethylene in CH2Cl 2, attributable to the 8-methyl substituted benzene-site complex, are observed in the field of 556-605 nm, which is strongly affected by π-electron density of the opposite aromatic ring.
- Shimizu, Tomoe,Hita, Katsuhiro,Rahman, Shofiur,Yamato, Takehiko
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experimental part
p. 293 - 297
(2009/12/07)
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- Secondary interactions in bromomethyl-substituted benzenes: Crystal structures of three α,α′-bis-bromoxylenes, 1,2,3,5-tetrakis(bromomethyl)benzene, and 1,2,4,5-tetrakis(bromomethyl)benzene
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X-Ray structure determinations of all three isomers of bis(bromomethyl) benzene and of two isomeric tetrakis(bromomethyl)benzenes show that the packing of the molecules is determined principally by interactions of the bromomethyl groups (C-H ? Br and Br ? Br), except for ortho-bis (bromomethyl)benzene, in which C-H ? π interactions play a major role.
- Jones, Peter G.,Ku?, Piotr
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p. 725 - 731
(2008/10/09)
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- Free radical bromination by the H2O2-HBr system on water
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An aqueous solution of hydrogen peroxide and hydrogen bromide illuminated by a 40 W incandescent light bulb serves as a source of bromine radicals. Various substituted toluenes (H, Me, tBu, Br, COOEt, COPh, NO2) were brominated at the benzyl position. This haloperoxidase-like system for benzylic bromination does not require the presence of metal ions or an organic solvent for efficient conversion of methyl-arenes to benzyl bromides.
- Podgor?ek, Ajda,Stavber, Stojan,Zupan, Marko,Iskra, Jernej
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p. 7245 - 7247
(2007/10/03)
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- An efficient and fast method for the preparation of benzylic bromides
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A mixture of triphenylphosphine and N-bromosuccinimide system is found to promote efficient conversion of benzylic alcohols into benzylic bromides under microwave irradiation conditions.
- Lee, Jong Chan,Hwang, Eui Yong
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p. 2959 - 2963
(2007/10/03)
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- Side chain bromination of mono and dimethyl heteroaromatic and aromatic compounds by solid phase N-bromosuccinimide reaction without radical initiator under microwave
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A series of side chain mono and dibromo derivatives of mono and dimethyl heteroaromatic and aromatic compounds (1-17) were synthesized by one step solid phase N-bromosuccinimide (NBS) reaction without radical initiator by microwave irradiation. The benzylic mono and dibromo products were exclusively preferred except in the case of 6-methylpyridine amides (8 and 9) where nuclear and also side chain bromination resulted. Naphthyridine systems resulted improved yields. By this method, we also report the synthesis of 2-pivaloylaminopterin-6- carbaldehyde.
- Goswami, Shyamaprosad,Dey, Swapan,Jana, Subrata,Adak, Avijit Kumar
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p. 916 - 917
(2007/10/03)
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- Rational Design and Synthesis of Novel Dimeric Diketoacid-Containing Inhibitors of HIV-1 Integrase: Implication for Binding to Two Metal Ions on the Active Site of Integrase
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Discovery of diketoacid-containing compounds as HIV-1 integrase (IN) inhibitors played a major role in validating this enzyme as an important target for the development of therapeutics against HIV infection. In fact, S-1360, the first clinically used IN inhibitor containing a triazole ring as a bioisostere of a carboxylic acid moiety belongs to this class of compounds. To understand the role of divalent metal-chelating in the inhibition of IN (J. Med. Chem. 2002, 45, 5661-5670), we designed and synthesized a series of novel dimeric diketo-containing compounds with the notion that such dimeric compounds may simultaneously bind to two divalent metal ions on the active site of IN. We rationalized that the two diketo subunits separated by uniquely designed linkers can potentially chelate two metal ions that are either provided from one IN active site or two active sites juxtaposed together in a higher order tetramer. Herein, we show that all the new compounds are highly potent against purified IN with varied selectivity for strand transfer, and that some of the analogues exert potent inhibition of the cytopathic effect of HIV-1 in infected CEM cells. This study represents the first attempt to rationally target two divalent metal ions on the active site of IN and may have potential implications for the design of second generation diketoacid-containing class of inhibitors.
- Long, Ya-Qiu,Jiang, Xiao-Hua,Dayam, Raveendra,Sanchez, Tino,Shoemaker, Robert,Sei, Shizuko,Neamati, Nouri
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p. 2561 - 2573
(2007/10/03)
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- Structure and conformational analysis of a macrocyclic ligand: [24, 26-DIOXO-3,6,14,17-tetraazapentacyclo (21.0.11,19.1 3,6.18,12.114,17)Hexacosan-1(23),8(25),9,11,19, 21-hexaene]
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24,26-Dioxo-3,6,14,17-tetraazapentacyclo((21.0.11,19.1 3,6.18,12.114,17)hexacosan-1(23),8(25),9,11,19, 21-hexaene, C22H24N4O2 FW=376.45, monoclinic, P21/n,a = 11.144(2) A, b = 6.395(1) A, c = 13.562(3) A, β = 95.81(1)°, V= 961.5(3) A3, Z =2, Dcol = 1.300 Mg/m3, μ = 0.685 mm-1, F(000)=400, λ (CuKα) = 1.5418 A final R1 and wR2 are 0.0409 and 0.1547, respectively. The macro ligand consists of two phenyl rings and two five-membered rings forming the walls of the central cavity which has roughly a square cross-section. The orientation of the phenyl ring is antiperiplanar and approximately perpendicular to the diazacyclopentanone ring which adopts envelope conformation. The molecules are stabilized by C-H ... O and C-H ... π types of intermolecular interactions in addition to van der Waals forces.
- Sony, S.M. Malathy,Kuppayee,Ponnuswamy,Murali,Rajakumar
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- An efficient method for the preparation of benzylic bromides
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Substituted benzylic compounds are brominated with an excess of N-bromosuccinimide (NBS) in CCl4 to the corresponding polybrominated mixtures which are then debrominated with diethyl phosphite and N,N-diisopropylethylamine to afford the desired monobromides in satisfactory yields and high purity.
- Liu,Chen,Deng,Tu
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p. 2078 - 2080
(2007/10/03)
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- A new synthesis and application of N, N'-dibromo-N, N'-1,2-ethylene bis(2,5-dimethyl benzene sulfonamide); as a novel selective bromination agent for aromatic compounds
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Reaction Between Novel Compound; N, N' dibromo-N, N'-1,2- ethylene bis(2,5- dimethyl benzene sulfonamide) and aromatic compounds in the carbontetrachloride produces bromo aromatic compounds. In the case of benzene rings that contain mono activated substituted, only para - bromo isomer was formed. At the presence of benzoyl peroxide in the reaction mixture α - Hydrogen from alkyl side chain was substituted with bromine.
- Ardeshir, Khazaei,Abbas, Shirdarreh
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p. 4079 - 4085
(2007/10/03)
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- Regioselective bromination of activated aromatic substrates with N-bromosuccinimide over HZSM-5
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The nuclear as well as side-chain bromination of activated aromatic substrates has been achieved in high yields and substantial regioselectivity wiht N-Bromosuccinimide (NBS) over HZSM-5.
- Paul, Vincent,Sudalai,Daniel, Thomas,Srinivasan
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p. 7055 - 7056
(2007/10/02)
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- Synthesis and characterization of 'picnic-basket' porphyrins with a substituent in the interior of the pocket
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'Picnic-basket' porphyrins of a new type, that have a substituent in the interior of the pocket, were synthesized to study stabilization of the bound oxygen in hemoprotein models. Though these Co(II) porphyrins have enormous equilibrium constants for the formation of base adducts, hydrogen-bonding interaction with coordinated dioxygen is not as effective for stabilization of the metal-dioxygen bond as we had expected. The results suggest that doming of the porphyrin plane plays an important role in the binding of dioxygen.
- Michida,Kyuhara,Nishiyama,Yoshimi,Fitzgerald,Sayo
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p. 3157 - 3162
(2007/10/02)
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- Reaction of Tosylamide Monosodium Salt with Bis(halomethyl) Compounds: An Easy Entry to Symmetrical N-Tosyl Aza Macrocycles
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A one-step, general procedure for a variety of N-tosyl aza macrocycles (including aza-crown ethers, pyridino- and bipyridino-aza-crown analogues, and azacyclophanes), by reaction of appropriate bis(halomethyl) precursors with tosylamide monosodium salt (TsNHNa) in N,N-dimethylformamide, is described.In polymethyl-substituted 2,11-diazacyclophane systems, the methyl substituents play an important role in inducing stereospecific ring closures.Thus, coupling of 1,4-bis(chloromethyl)-2,5-dimethylbenzene (15b) with TsNHNa produced only one of the two possible diastereomeric dimers, to which chiral structure 16db was assigned by means of the chiral Eu(dcm)3 shift reagent.This stereochemical assignment was confirmed by a single-crystal X-ray study on 16d.Detosylation of N-tosyl aza macrocycles to the free polyamino macrocycles by reductive (Na-NH3) or hydrolytic (90percent H2SO4) methods, followed by N-methylation (CH2O-HCO2H), was also accomplished in excellent yield.The 1H NMR spectra of 2,11-diazacyclophanes and 2,11-diaza(2,6)pyridinophanes are discussed in terms of conformation and conformational mobility.
- Bottino, Francesco,Grazia, Michele Di,Finocchiaro, Paolo,Fronczek, Frank R.,Mamo, Antonino,Pappalardo, Sebastiano
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p. 3521 - 3529
(2007/10/02)
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- Synthesis and Physical Properties of Novel 2,2'-Bridged Bis(1,3-dithiolylium-4-olates)
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The synthesis and physical properties of the novel title compounds of type 4, 8, and 11 which contain two identical mesoionic systems linked together at the 2-positions, as well as the oligomerization behaviour of 4b are described.
- Gotthardt, Hans,Pflaumbaum, Wolfgang
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- Intraanular phenyl-substituierte Phane - Synthese und dynamische Stereochemie
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The synthesis and properties of phanes of different ring size, substituted intraanularly by phenyl groups, and of new biphenylophanes 3, 38 - 43 with "pseudo-syn/anti"-structure are described.Barriers for the hindered rotation of intraanular phenyl substituents have been determined by D-NMR spectroscopy. syn/anti conformers of -, -, - and metacyclophanes are found.A better method for the preparation of mediocyclic bisdisulfides is reported.The pyrolysis of (2-biphenylyl)methyl sulfones leads to fluorenes; pyrolysis of the thiosulfonic S-ester 44 yields bibenzyl and dibenzyl sulfide.
- Boeckmann, Klaus,Voegtle, Fritz
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p. 1048 - 1064
(2007/10/02)
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- para-Terphenylophanes - Synthesis and Dynamic Stereochemistry
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Phane skeletons containing para-terphenyl units have been synthesized.Substituent effects on conformative movements can be investigated by DNMR spectroscopy.
- Boeckmann, Klaus,Voegtle, Fritz
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p. 467 - 475
(2007/10/02)
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- The Hantzsch 1,4-Dihydropyridine Synthesis as a Route to Bridged Pyridine and Dihydropyridine Crown Ethers
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Mono-, di-, tri-, and tetraethylene glycols were transesterified with ethyl acetoacetate to give the bis(acetoacetate esters) 1a-d.On treatment of 1c,d with formaldehyde and excess (NH4)2CO3 in H2O a crude mixture of 1,4-dihydropyridines was obtained from which, after dehydrogenation to the pyridine form, the 3,5-bridged 2,6-dimethylpyridines 2c,d were isolated along with dimers 7c,d.Similar reaction of 1a gave only dimer 7a.The bridged pyridine 2d was methylated to give pyridinium salt 3d, which was reduced with Na2S2O4 to give 1,4-dihydropyridine 4d.Stable sodium salts of 4d and 6d were isolated.Bridged pyridines 10a-c substituted with, respectively, methyl, phenyl, and 2-furyl at the γ position of the pyridine ring have also been prepared, using 1d, (NH4)2CO3, and acetaldehyde, benzaldehyde, and 2-furfuraldehyde and Hantzsch condensation followed by dehydrogenation and chromatographic separation.Protection of the 1,3-dicarbonyl system of ethyl 4-bromo-3-oxobutanoate as its Na chelate followed by nucleophilic substitution with the bisalkoxides from tetra-, penta-, and hexaethylene glycols gave 4-substituted bis(acetoacetate esters) 16a-c.These on Hantzsch condensation yielded in low yield 2,6-bridged Hantzsch 1,4-dihydropyridines (17a-c).Treatment of 17a,b with alkali metal hydrides gave insoluble materials thought to be the internally solvated alkali metal salts of the (vinylogous) amide nitrogen of the 1,4-dihydropyridine.
- Kellogg, Richard M.,Bergen, T. J. van,Doren, Henk van,Hedstrand, David,Kooi, J.,et al.
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p. 2854 - 2862
(2007/10/02)
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