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1.
Abhisek Midya Laxman Devidas Khalse Prof. Prasanta Ghorai 《European journal of organic chemistry》2023,26(14):e202201409
Disclosed here an amine-catalyzed reductive aldol-condensation followed by an intramolecular reductive Michael-addition cascade employing Hantzsch ester as hydride source to a keto-bis-enone to provide enantio- and diastereoselective benzannulated diquinanes having three consecutive stereocenters, one of which is an all-carbon quaternary formyl stereocenter. Interestingly, on changing a tether connecting the ketone and an enone moiety from an aliphatic to an aromatic, a change in reactivity is observed. In this case, instead of the above-mentioned reductive aldol condensation, an asymmetric aldol reaction occurs, followed by an iminium/enamine isomerization and, finally diastereoselective Michael addition reaction occurs. As a result, a bis-benzannulated diquinane is obtained with vicinal congested quaternary chiral centers. 相似文献
2.
We demonstrated how a reduction step with a reducing system comprised of In(OTf)3 and Et3SiH and a subsequent oxidation that occurred under an ambient (oxygen) atmosphere allowed the highly selective and catalytic conversion of aromatic nitro compounds into symmetrical or unsymmetrical azobenzene derivatives. This catalytic system displayed a tolerance for the functional groups on a benzene ring: an alkyl group, a halogen, an acetyl group, an ester, a nitrile group, an acetyl group, an ester moiety, and a sulfonamide group. 相似文献
3.
Raúl Montiel Roberto Alexander‐Katz 《Journal of Polymer Science.Polymer Physics》2003,41(12):1362-1374
The response of an elastic particle to an extensional field close to an advancing liquid–gas interface in a capillary was examined both from an experimental and theoretical viewpoint. Experimental evidence is given on both the protrusion and deformation of an elastic particle at an advancing front interface. To interpret our experimental results, we followed and extended Hoffman's approach to the case of deformable particles. A hybrid approach was followed where the height of the bump was calculated theoretically as an equilibrium between capillary and drag forces for a given deformation of the particle, whereas the latter was supplied by an independent experimental measurement. For an elastic particle, the height of the bump goes through a maximum and further on decay almost linearly when plotted against the dimensionless parameter introduced by Hoffman. The difference between the theoretical prediction and the experimental data is discussed in relation to the asymmetry of the bump profiles observed in the experiment that could be responsible for a larger contribution of capillary forces from those calculated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1362–1374, 2003 相似文献
4.
Olfactory assist systems that allow the user to sense smells with amplified sensitivities are reported. We have developed two types of systems. The first system, an olfaction augmenter, detects the presence of a volatile organic compound in the air using a gas sensor, and presents an odor with an amplified intensity to the user using an odor generator. The second system, an olfactory concentrator, collects odor molecules in the air using an adsorbent, and presents the concentrated odor to the user. Results of our initial experiments on a prototype concentrator are reported. 相似文献
5.
Pd‐Catalyzed Csp2H Functionalization of Heteroarenes via Isocyanide Insertion: Concise Synthesis of Di‐(Hetero)Aryl Ketones and Di‐(Hetero)Aryl Alkylamines
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Dr. Upendra K. Sharma Dr. Nandini Sharma Jun Xu Prof. Dr. Gonghua Song Prof. Dr. Erik V. Van der Eycken 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):4908-4912
We report herein an efficient Pd‐catalyzed direct C?H bond functionalization of heteroarenes via an isocyanide insertion strategy for the synthesis of di‐(hetero)aryl ketones and di‐(hetero)aryl alkylamines. The methodology involves a three component reaction between an azole, a haloarene and an isocyanide resulting in the formation of an imine, which in turn is either hydrolyzed or reduced to get the desired product. 相似文献
6.
1,2,3-Triazolyl-alkylphosphonates are synthesised according to a Huisgen 1,3-dipolar cycloaddition catalysed by copper salts. The cycloaddition of either an alkynylphosphonate with an azidoalkane or an azido-phosphonate with an alkyne is achieved in high yield and regiospecifically. As an illustration of the functionalisation of aromatic ligands by using the catalytic version of the Huisgen reaction, the coupling of 3-ethynyl-1,10-phenanthroline with azidoalkylphosphonate is reported. 相似文献
7.
Dr. Naohiko Yoshikai Sobi Asako Takeshi Yamakawa Dr. Laurean Ilies Prof. Dr. Eiichi Nakamura 《化学:亚洲杂志》2011,6(11):3059-3065
Direct arylation of the ortho‐C? H bond of an aryl pyridine or an aryl imine with an aryl Grignard reagent has been achieved by using an iron‐diamine catalyst and a dichloroalkane as an oxidant in a short reaction time (e.g., 5 min) under mild conditions (0 °C). The use of an aromatic co‐solvent, such as chlorobenzene and benzene, and slow addition of the Grignard reagent are essential for the high efficiency of the reaction. The present arylation reaction has distinct merits over the previously developed reaction that used an arylzinc reagent, such as its reaction rate and atom economy. Selective C? H bond activation occurs in the presence of a leaving group, such as a tosyloxy, chloro, and bromo group. Studies on a stoichiometric reaction and kinetic isotope effects shed light on the reaction intermediate and the C? H bond‐activation step. 相似文献
8.
A N(1)-C(5) bridged chiral bicyclic imidazole with a morpholine framework was synthesized from an enantiopure 2-amino alcohol. The resultant imidazole reacted with various electrophiles, including primary and secondary alkyl halides, benzyne, and an electron-deficient aryl halide, to give the corresponding imidazolium salts. Some of the imidazolium salts were found to have potential as the precursor of a chiral N-heterocyclic carbene catalyst; by the direct annulation of an enal and a ketone through the intermediacy of a homoenolate and an activated carboxylate, the target lactone was obtained in an enantiomerically enriched form (up to 66% ee). 相似文献
9.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(42):13028-13031
Crocagin A ( 1 ) combines an attractive molecular structure with an unusual biosynthesis and bioactivity. An efficient synthesis of crocagin A is presented that hinges on an early formation of the heterotricyclic core, an electrophilic amination, and the stereoselective hydrogenation of a tetrasubstituted double bond. This synthesis confirms the absolute configuration of crocagin A and provides access to the natural product and derivatives thereof for further biological testing. 相似文献
10.
In this work, a new series of 1,2,4,5-tetrahydro-2,4-dioxobenzo[b][1,4]diazepine and malonamide derivatives have been synthesized using an aromatic 1,2-diamine, Meldrum's acid, an isocyanide, and an arylidene malononitrile (or an aldehyde and malononitrile instead of an arylidene malononitrile) in CH2Cl2 at ambient temperature. Synthesis of 1,2,4,5-tetrahydro-2,4-dioxobenzo[b][1,4]diazepine proceeded via four- and five-component reactions; while the synthesis of malonamide derivatives was performed using five- and six-component reactions. In addition, a new series of the malonamide derivatives have been prepared using an aldehyde, malononitrile, Meldrum's acid, an isocyanide, and two molecules of 1,4-diamine via a six-component reaction. These procedures provide alternative methods to the synthesis of a new series of 1,2,4,5-tetrahydro-2,4-dioxobenzo[b][1,4]diazepine and malonamide derivatives. 相似文献
11.
Three‐Component Asymmetric Catalytic Ugi Reaction—Concinnity from Diversity by Substrate‐Mediated Catalyst Assembly
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Wenjun Zhao Dr. Li Huang Dr. Yong Guan Prof. William D. Wulff 《Angewandte Chemie (International ed. in English)》2014,53(13):3436-3441
The first chiral catalyst for the three‐component Ugi reaction was identified as a result of a screen of a large set of different BOROX catalysts. The BOROX catalysts were assembled in situ from a chiral biaryl ligand, an amine, water, BH3?SMe2 , and an alcohol or phenol. The catalyst screen included 13 different ligands, 12 amines, and 47 alcohols or phenols. The optimal catalyst system (LAP 8‐5‐47) provided α‐amino amides from an aldehyde, a secondary amine, and an isonitrile with excellent asymmetric induction. The catalytically active species is proposed to be an ion pair that consists of the chiral boroxinate anion and an iminium cation. 相似文献
12.
Ke-Jin Jiao Dong Liu Dr. Hong-Xing Ma Hui Qiu Ping Fang Prof. Dr. Tian-Sheng Mei 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(16):6582-6586
A highly regioselective Ni-catalyzed electrochemical reductive relay cross-coupling between an aryl halide and an alkyl halide has been developed in an undivided cell. Various functional groups are tolerated under these mild reaction conditions, which provides an alternative approach for the synthesis of 1,1-diarylalkanes. 相似文献
13.
Highly Stereoselective Synthesis of Natural‐Product‐Like Hybrids by an Organocatalytic/Multicomponent Reaction Sequence
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M. Sc. Radell Echemendía M. Sc. Alexander F. de La Torre M. Sc. Julia L. Monteiro M. Sc. Michel Pila Prof. Dr. Arlene G. Corrêa Prof. Dr. Bernhard Westermann Prof. Dr. Daniel G. Rivera Prof. Dr. Márcio W. Paixão 《Angewandte Chemie (International ed. in English)》2015,54(26):7621-7625
In an endeavor to provide an efficient route to natural product hybrids, described herein is an efficient, highly stereoselective, one‐pot process comprising an organocatalytic conjugate addition of 1,3‐dicarbonyls to α,β‐unsaturated aldehydes followed by an intramolecular isocyanide‐based multicomponent reaction. This approach enables the rapid assembly of complex natural product hybrids including up to four different molecular fragments, such as hydroquinolinone, chromene, piperidine, peptide, lipid, and glycoside moieties. The strategy combines the stereocontrol of organocatalysis with the diversity‐generating character of multicomponent reactions, thus leading to structurally unique peptidomimetics integrating heterocyclic, lipidic, and sugar moieties. 相似文献
14.
Hidetaka Noritomi Shogo Tamai Hiroaki Saito Satoru Kato 《Colloid and polymer science》2009,287(4):455-459
The extraction of methyl orange or methylene blue from an aqueous phase to an organic phase of reverse micelles of alkyl glucosides
was investigated. Dodecyl glucoside, a biodegradable and biocompatible surfactant, was employed as a kind of alkyl glucosides,
since a stable Winsor II system consisting of the water-in-oil type microemulsion and aqueous phases was formed when an organic
solution containing dodecyl glucoside was contacted with an aqueous solution. The water content in the reverse micellar organic
phase increased with an increase in the concentration of dodecyl glucoside. The extraction ratio of dyes also increased with
increasing the concentration of dodecyl glucoside. Furthermore, the extraction ratio of dyes was dramatically dependent upon
the pH of an aqueous phase and temperature. 相似文献
15.
Kameta N Nagawa Y Karikomi M Hiratani K 《Chemical communications (Cambridge, England)》2006,(35):3714-3716
A racemic [2]rotaxane, composed of an asymmetric rotor and an asymmetric axle, formed a diastereomer with an amino acid derivative, and showed an optical response for the chiral recognition. 相似文献
16.
Dr. Hiromichi Egami Prof. Dr. Yoshitaka Hamashima 《Chemical record (New York, N.Y.)》2023,23(7):e202200285
Fluorine is an attractive element in the field of pharmaceutical and agrochemical chemistry due to its unique properties. Considering the chiral environment in nature, where enantiomers often show different biological activities, the introduction of fluorine atom(s) into organic molecules to make chiral fluorinated compounds is an important subject. Herein, we describe the story of the development of our chiral carboxylate-based phase-transfer catalysts and their applications for asymmetric fluorocyclizations of alkenes bearing a carboxylic acid, an amide, and an oxime as an internal nucleophile with a dicationic fluorinating reagent, Selectfluor. We also describe dearomative fluorinations of indole derivatives, 2-naphthols, and resorcinols. 相似文献
17.
The novel generation and cycloaddition of azomethine ylides from an α-(trimethylsilyl)imine using (polyfluoro)silanes is described. The method was successfully applied to an efficient one-pot process. Namely, an azaallyl anion, generated by abstraction of the hydrogen α to an imino nitrogen, was treated with a di- or trifluorosilane to give an azomethine ylide intermediate below room temperature. The generated 1,3-dipole was smoothly trapped with dipolarophiles to afford nitrogen-containing five-membered heterocycles in good yields. 相似文献
18.
《International journal of quantum chemistry》2018,118(11)
The effect of an octagonal lattice configuration on a boron nitride nanotube is explored using first principle calculations. Calculations show that the formational energy of an octagonal boron nitride nanotube (o‐BNNT) is an exothermic reaction. Boron and nitrogen atoms within an o‐BNNT have an average of 2.88 electrons and 9.09 electrons, respectively, indicating ionic‐like bonding. In addition, the electronic structure of the octagonal boron nitride nanotube shows semiconductive properties, while h‐BNNT is reported to be an insulator. Additional o‐BNNTs with varying diameters are calculated where the results suggest that the diameter has an effect on the binding energy and bandgap of the o‐BNNT. The defect sites of the o‐BNNT are reactive against hydrogen where a boron defect is particularly reactive. Thus, this work suggests that physical and chemical properties of a boron nitride nanotube can be tailored and tuned by controlling the lattice configuration of the nanotube. 相似文献
19.
Ke‐Jin Jiao Dong Liu Hong‐Xing Ma Hui Qiu Ping Fang Tian‐Sheng Mei 《Angewandte Chemie (International ed. in English)》2020,59(16):6520-6524
A highly regioselective Ni‐catalyzed electrochemical reductive relay cross‐coupling between an aryl halide and an alkyl halide has been developed in an undivided cell. Various functional groups are tolerated under these mild reaction conditions, which provides an alternative approach for the synthesis of 1,1‐diarylalkanes. 相似文献
20.
An experimental study on the synthesis, tautomerism, and acid promoted structural changes of spiro-pyrazolines is described. The target was achieved through a [3+2]-dipolar cycloaddition of an alkene with nitrile imines generated in situ and was isolated in high yield. The synthesized cycloadduct displayed a tendency to exhibit an imine–enamine type of tautomerism as evidenced by X-ray crystal and NMR studies. Furthermore, addition of an acid resulted in the transformation of an imine tautomer to an enamine. The current report constitutes a first formal observation of this kind of tautomerism observed in spiro-indoline pyrazolines. 相似文献