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1.
Origin of the Regioselectivity in the Gas‐Phase Aniline+CH3+ Electrophilic Aromatic Substitution 下载免费PDF全文
Dr. Daniel Kinzel Prof. Shmuel Zilberg Prof. Dr. Leticia González 《Chemphyschem》2015,16(11):2366-2374
Nonadiabatic ab initio molecular dynamics simulations are carried out to monitor the attack of CH3+ on aniline in the gas phase to form the corresponding σ complexes. The reaction is ultrafast and is governed by a single electron transfer within 30 fs, which involves two sequential conical intersections and finally produces a radical pair. Positive‐charge allocation in the aromatic compound is found to govern the substitution pattern in ortho, meta, or para position. Although the major products in the first step of the electrophilic aromatic substitution are the ortho and para σ complexes, initially 26 % of the simulated trajectories also form meta complexes, which then undergo H shifts, mainly to the para position. 相似文献
2.
Ryuichi Yamaguchi Satoru Ito Byung Sun Lee Dr. Satoru Hiroto Prof. Dr. Dongho Kim Prof. Dr. Hiroshi Shinokubo 《化学:亚洲杂志》2013,8(1):178-190
We have demonstrated that the iridium‐catalyzed direct borylation of hexa‐peri‐hexabenzocoronene (HBC) enables regioselective introduction of boryl groups to the para‐, ortho‐, and meta‐substituted HBCs in high yields. The boryl groups have been transformed into various functionalities such as hydroxy, cyano, ethynyl, and amino groups. We have elucidated that the substituents significantly influence the photophysical properties of HBCs to enhance fluorescence quantum yields. DFT calculations revealed that the origin of the substituent effect is the lift in degeneracy in the frontier orbitals by an interaction with electron‐donating and electron‐withdrawing substituents at the para‐ and ortho‐positions. The change in molecular orbitals results in an increase of the transition probability from the S0→S1 states. In addition, the two‐photon absorption cross‐section values of para‐substituted HBCs are significantly larger than those of ortho‐ and meta‐substituted HBCs. 相似文献
3.
Direct CH Amidation of Benzoic Acids to Introduce meta‐ and para‐Amino Groups by Tandem Decarboxylation 下载免费PDF全文
Donggun Lee Prof. Sukbok Chang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5364-5368
The Ir‐catalyzed mild C?H amidation of benzoic acids with sulfonyl azides was developed to give reactions with high efficiency and functional‐group compatibility. Subsequent protodecarboxylation of ortho‐amidated benzoic acid products afforded meta‐ or para‐substituted (N‐sulfonyl)aniline derivatives, the latter being inaccessible by other C?H functionalization approaches. The decarboxylation step was compatible with the amidation conditions, enabling a convenient one‐pot, two‐step process. 相似文献
4.
Band‐Gap Manipulations of Monolayer Graphene by Phenyl Radical Adsorptions: A Density Functional Theory Study 下载免费PDF全文
Phenyl radical (Ph.) adsorption on monolayer graphene sheets is used to investigate the band‐gap manipulation of graphene through density functional theory. Adsorption of a single Ph. on graphene breaks the aromatic π‐bond and generates an unpaired electron, which is delocalized to the ortho or para position. Adsorption of a second radical at the ortho or para position saturates the radical by electron pairing and results in semiconducting graphene. Adsorption of a second radical at the ortho position (ortho–ortho pairing) is found to be more favorable than adsorption at the para position (ortho–para pairing), and the ortho–ortho pairing has stronger effects on band‐gap opening compared with ortho–para pairing. Adsorption of even numbers of Ph. on graphene by ortho–ortho and ortho–para pairings, in general, increases the band gap. Our study shows promise of band‐gap manipulation in monolayer graphene by Ph. adsorption, leading to potential wider applications of graphene. 相似文献
5.
High‐throughput salting‐out‐assisted liquid–liquid extraction for the simultaneous determination of atorvastatin,ortho‐hydroxyatorvastatin,and para‐hydroxyatorvastatin in human plasma using ultrafast liquid chromatography with tandem mass spectrometry 下载免费PDF全文
Yong Yang Qiufang Xu Lei Zhou Dafang Zhong Xiaoyan Chen 《Journal of separation science》2015,38(6):1026-1034
A high‐throughput, specific, and rapid liquid chromatography with tandem mass spectrometry method was established and validated for the simultaneous determination of atorvastatin and its two major metabolites, ortho‐hydroxyatorvastatin and para‐hydroxyatorvastatin, in human plasma. A simple salting‐out‐assisted liquid–liquid extraction using acetonitrile and a mass‐spectrometry‐friendly salt, ammonium acetate, was employed to extract the analytes from human plasma. A recovery of more than 81% for all analytes was achieved in 1 min extraction time. Chromatographic separation was performed on a Kinetex XB C18 column utilizing a gradient elution starting with a 60% of water solution (1% formic acid), followed by increasing percentages of acetonitrile. Analytes were detected on a tandem mass spectrometer equipped with an electrospray ionization source that was operated in the positive mode, using the transitions of m/z 559.3 → m/z 440.2 for atorvastatin, and m/z 575.3 → m/z 440.2 for both ortho‐ and para‐hydroxyatorvastatin. Deuterium‐labeled compounds were used as the internal standards. The method was validated over the concentration ranges of 0.0200–15.0 ng/mL for atorvastatin and ortho‐hydroxyatorvastatin, and 0.0100–2.00 ng/mL for para‐hydroxyatorvastatin with acceptable accuracy and precision. It was then successfully applied in a bioequivalence study of atorvastatin. 相似文献
6.
Reaction of ortho‐xylylbis(N‐2,4,6‐trimethylbenzylimidazolinium); xylylbis(N‐butylimidazolinium) and para‐xylylbis(N‐2,4,6‐trimethylbenzylimidazolinium); xylylbis(N‐butylimidazolinium) salts with KOBut and [RhCl(COD)]2 yields ortho‐ and para‐xylylbis{(N‐alkylimidazolidin‐2‐ylidene)chloro(η4‐1,5‐cyclooctadiene) rho dium(I)} complexes (2a–d). All compounds synthesized were characterized by elemental analysis and NMR spectroscopy, and the molecular structures of the 2a and 2d were determined by X‐ray crystallography. Triethylsilane reacts with acetophenone derivatives in the presence of catalytic amount of the new rhodium(I)–carbene complexes (2a–d), to give the corresponding silylethers in good yields (83–99%). Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
7.
Gerald G. Still 《Journal of mass spectrometry : JMS》1971,5(8):977-982
The mass spectra of isopropyl 2-hydroxychlorocarbanilate indicate a preferential ortho intramolecular rearrangement which yields a chloro 2-benzoxazolinone intermediate ion. A com-parison of the fragmentation of ortho, meta and para hydroxy analogs of isopropyl 3-chlorohydroxy-carbanilate indicates the existence of an ‘ortho effect’ during the fragmentation of isopropyl-chloro 2-hydroxycarbanilates. 相似文献
8.
M. Sc. Congjun Yu Prof. Dr. Frederic W. Patureau 《Angewandte Chemie (International ed. in English)》2018,57(36):11807-11811
A highly selective CuII‐catalyzed cross‐dehydrogenative ortho‐aminomethylation of phenols with aniline derivatives is described. The corresponding C(sp2)?C(sp3) coupling products were obtained in moderate to excellent yields under mild reaction conditions and with a broad substrate scope. A radical mechanism is proposed. 相似文献
9.
Meng Sun Chun Ma Si‐Jia Zhou Sai‐Fan Lou Jian Xiao Yinchun Jiao Feng Shi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(26):8795-8800
The first catalytic asymmetric (4+3) cyclization of in situ generated ortho‐quinone methides with 2‐indolylmethanols has been established, which constructed seven‐membered heterocycles in high yields (up to 95 %) and excellent enantioselectivity (up to 98 %). This approach not only represents the first catalytic asymmetric (4+3) cyclization of o‐hydroxybenzyl alcohols, but also enabled an unprecedented catalytic asymmetric (4+3) cyclization of 2‐indolylmethanols. In addition, a scarcely reported catalytic asymmetric (4+3) cyclization of para‐quinone methide derivatives was accomplished. 相似文献
10.
Polymers containing ortho‐ and para‐hydroquinone moieties 5a,b and 6a are prepared in good yields by ROMP from hydroquinone‐fused norbornadiene derivatives 1a,b and 2a . Oxidation of 5b yielded a quinone derivative 7 , which is evidenced by a strong absorption at 1656 cm?1 in infrared spectrum. 相似文献
11.
Bartosz Zarychta Anna Piecyk‐Mizgaa Zdzisaw Daszkiewicz Jacek Zaleski 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(8):o515-o517
The structures of the two title isomeric compounds (systematic names: N‐methyl‐N,2‐dinitroaniline and N‐methyl‐N,3‐dinitroaniline, both C7H7N3O4) are slightly different because they exhibit different steric hindrances and hydrogen‐bonding environments. The aromatic rings are planar. The –N(Me)NO2 and –NO2 groups are not coplanar with the rings. Comparison of the geometric parameters of the ortho, meta and para isomers together with those of N‐methyl‐N‐phenylnitramine suggests that the position of the nitro group has a strong influence on the aromatic ring distortion. The crystal packing is stabilized by weak C—H⋯O hydrogen bonds to the nitramine group. 相似文献
12.
Versatile and Sustainable Synthesis of Cyclic Imides from Dicarboxylic Acids and Amines by Nb2O5 as a Base‐Tolerant Heterogeneous Lewis Acid Catalyst 下载免费PDF全文
Md. Ayub Ali Dr. S. M. A. Hakim Siddiki Dr. Kenichi Kon Prof. Junya Hasegawa Dr. Ken‐ichi Shimizu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(44):14256-14260
Catalytic condensation of dicarboxylics acid and amines without excess amount of activating reagents is the most atom‐efficient but unprecedented synthetic method of cyclic imides. Here we present the first general catalytic method, proceeding selectively and efficiently in the presence of a commercial Nb2O5 as a reusable and base‐tolerant heterogeneous Lewis acid catalyst. The method is effective for the direct synthesis of pharmaceutically or industrially important cyclic imides, such as phensuximide, N‐hydroxyphthalimide (NHPI), and unsubstituted cyclic imides from dicarboxylic acid or anhydrides with amines, hydroxylamine, or ammonia. 相似文献
13.
《合成通讯》2013,43(5):933-940
Abstract Reactions of benzyl chloroformate with a series of substituted anilines produced N‐carbobenzyloxy “CBZ” products along with the unexpected N‐benzylated “Bn” compounds. Reaction of aniline, 1a, gave the CBZ, or 2a, and Bn, or 3a, products in 29% and 14% yield, respectively. For 2‐nitro‐, 2‐bromo‐, and 2‐bromo‐5‐nitroanilines, the N‐benzylated compounds were produced exclusively. However, 2‐methoxy‐, 4‐bromo, 4‐iodo, and 4‐ethylanilines gave mainly CBZ products. Other compounds reported in this study gave mixtures of the two products. For 4‐chloro‐3‐nitroaniline, in addition to the Bn and CBZ products (53% and 14% yield, respectively), a N,N‐dibenzylated product was isolated in 27% yield. Collectively, the results indicated that electron‐withdrawing groups, particularly at the ortho position, directed the formation of Bn compounds, whilst electron‐donating groups, especially at the ortho and para positions, favored the synthesis of CBZ products. 相似文献
14.
Dr. Daniel A. Horke Dr. Yuan‐Pin Chang Karol Długołęcki Prof. Dr. Jochen Küpper 《Angewandte Chemie (International ed. in English)》2014,53(44):11965-11968
Water exists as two nuclear‐spin isomers, para and ortho, determined by the overall spin of its two hydrogen nuclei. For isolated water molecules, the conversion between these isomers is forbidden and they act as different molecular species. Yet, these species are not readily separated, and no pure para sample has been produced. Accordingly, little is known about their specific physical and chemical properties, conversion mechanisms, or interactions. The production of isolated samples of both spin isomers is demonstrated in pure beams of para and ortho water in their respective absolute ground state. These single‐quantum‐state samples are ideal targets for unraveling spin‐conversion mechanisms, for precision spectroscopy and fundamental symmetry‐breaking studies, and for spin‐enhanced applications, for example laboratory astrophysics and astrochemistry or hypersensitized NMR experiments. 相似文献
15.
JrgA. Heerklotz Changchun Fu Anthony Linden Manfred Hesse 《Helvetica chimica acta》2000,83(8):1809-1824
Allylic N‐phenyl imides containing 12‐ and 14‐membered rings, such as compounds 3 and 12 , are easily synthesized by ring enlargement from cycloalkanones and phenyl isocyanates. Irradiation of 3 and 12 in EtOH and MeCN, with high‐ and low‐pressure Hg lamps, led, via the photo‐Fries rearrangement, to the same primary products: the orthocyclophane 8 and the paracyclophane 9 from 3 (Scheme 2), and the corresponding compounds 13 and 14 from 12 (Scheme 3). Besides the primary photorearrangement products, secondary products, the aminocyclophanes 10 and 11 , or 15 and 16 , respectively, were also formed. The total yields of the four products were very high when the N‐phenyl imides were irradiated in MeCN with a low‐pressure Hg lamp: 97 and 93%, respectively. If the para‐position in 3 or 12 is blocked by a Me group, the para‐photo‐Fries rearrangement is prevented. In this case, only one primary photoproduct is formed: the corresponding orthocyclophane ( 17 or 23 , resp.). The most remarkable result was observed on irradiation of the 12‐membered N‐(4‐tolyl) imide 5 in MeCN (low‐pressure lamp). It reacted nearly quantitatively to give only two products: 15‐methyl‐1‐aza[12]orthocyclophane‐2,12‐dione (=16‐methyl‐2‐azabicyclo[12.4.0]octadeca‐1(14),15,17‐triene‐3,13‐dione; 17 ) in 80% yield and 17‐amino‐14‐methyl[11]metacyclophane‐1,11‐dione (=17‐amino‐15‐methylbicyclo[11.3.1]heptadeca‐1(17),13,15‐triene‐2,12‐dione; 19 ) in 16% yield (Scheme 5). 相似文献
16.
Guy Bouchoux Michel Sablier Tetsuo Miyakoshi Takashi Honda 《Journal of mass spectrometry : JMS》2012,47(4):539-546
The competition between benzylic cleavage (simple bond fission [SBF]) and retro‐ene rearrangement (RER) from ionised ortho, meta and para RC6H4OH and RC6H4OCH3 (R = n‐C3H7, n‐C4H9, n‐C5H11, n‐C7H15, n‐C9H19, n‐C15H31) is examined. It is observed that the SBF/RER ratio is significantly influenced by the position of the substituent on the aromatic ring. As a rule, phenols and anisoles substituted by an alkyl group in meta position lead to more abundant methylene‐2,4‐cyclohexadiene cations (RER fragmentation) than their ortho and para homologues. This ‘meta effect’ is explained on the basis of energetic and kinetic of the two reaction channels. Quantum chemistry computations have been used to provide estimate of the thermochemistry associated with these two fragmentation routes. G3B3 calculation shows that a hydroxy or a methoxy group in the meta position destabilises the SBF and stabilises the RER product ions. Modelling of the SBF/RER intensities ratio has been performed assuming two single reaction rates for both fragmentation processes and computing them within the statistical RRKM formalism in the case of ortho, meta and para butyl phenols. It is clearly demonstrated that, combining thermochemistry and kinetics, the inequality (SBF/RER)meta < (SBF/RER)ortho < (SBF/RER)para holds for the butyl phenols series. It is expected that the ‘meta effect’ described in this study enables unequivocal identification of meta isomers from ortho and para isomers not only of alkyl phenols and alkyl anisoles but also in other alkyl benzene series. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
17.
Abdel‐Nasser Kawde Mohamed A. Morsy Nurudeen Odewunmi Wael Mahfouz 《Electroanalysis》2013,25(6):1547-1555
The present investigation of phenol and chlorophenols is conducted on the surface of glassy carbon by cyclic and square wave stripping voltammetry, and by Fourier‐transform infrared spectroscopy. The surface fouling is accompanied by the appearance of reversible peaks at lower potential range (+0.1 to+0.4 V), that grew up with CV‐cycling and attributed to the electro‐redox reactions of formed polymer film via electropolymerization. The electroanalytical monitoring of formed polymer oxidation peaks improved both sensitivity and detection limit by 35 and 10 times, respectively. The FT‐IR supported semiempirical prediction attributes the electropolymerization to the formation of ortho‐para and/or ortho‐meta C? C coupled‐system. 相似文献
18.
《Tetrahedron: Asymmetry》2006,17(1):92-98
A new case of the uncommon cis–trans enantiomerism is presented. The titled anhydride adducts were prepared in good yields by the known reaction of three 6-arylfulvenes with maleic anhydride (aryl = phenyl, p-tolyl and p-anisyl). The exo adducts were converted to the corresponding imides by reaction with (1S)-1-(naphth-1-yl)ethylamine in ∼80% yields, and the resulting diastereomeric imides separated by silica gel column chromatography. They were hydrolysed and recyclised to the chiral anhydrides, in ‘one-pot’ with 10% NaOH–EtOH, followed by treatment with 2 M HCl, in ∼40% yields. The titled anhydrides were thus obtained in homochiral form, in enantiomeric purities (generally) of ∼90% as indicated by chiral HPLC. The chiral anhydrides were also converted to the corresponding imides (presumably stereospecifically), by treatment with ammonia solution in excellent yields. The crystal structure of one of the above diastereomeric imides (derived from 6-phenylfulvene) was determined, and based on the known (S)-configuration of the naphthylethylamine moiety, the ‘configurations’ of the original anhydride adducts were assigned. 相似文献
19.
Caterina Canu Boido Vito Boido Federica Novelli Fabio Sparatore 《Journal of heterocyclic chemistry》1998,35(4):853-858
On the basis of previous occasional findings, the Fischer indole cyclization of ten ketone phenylhydrazones containing moieties of increasing bulkiness was investigated in order to isolate eventual side products. In the cases of the three 2-, 3- and 4-acetylpyridine phenylhydrazones the corresponding 2-pyridylindoles were the sole compounds so far isolated. In all the remaining cases, beside the indoles a mixture of basic compounds was obtained. In all cases aniline and a 2-substituted (2-methyl or 2-phenyl)benzimidazole were formed, the last resulting through an apparent ortho-semidinic rearrangements of phenylhydrazones. Starting from methyl isopropyl ketone phenylhydrazone a compound of formula C11H15NO was also isolated, to which the structure of 3-(4-aminophenyl)-3-methylbutanone was assigned on the basis of ir, nmr spectra and of the chemical reactivity. The formation of this compound seems related to a para-benzidine-like rearrangement of phenyl hydrazone. 相似文献
20.
Organocatalytic Domino Oxa‐Michael/1,6‐Addition Reactions: Asymmetric Synthesis of Chromans Bearing Oxindole Scaffolds 下载免费PDF全文
Kun Zhao Dr. Ying Zhi Tao Shu Dr. Arto Valkonen Prof. Dr. Kari Rissanen Prof. Dr. Dieter Enders 《Angewandte Chemie (International ed. in English)》2016,55(39):12104-12108
An asymmetric organocatalytic domino oxa‐Michael/1,6‐addition reaction of ortho‐hydroxyphenyl‐substituted para‐quinone methides and isatin‐derived enoates has been developed. In the presence of 5 mol % of a bifunctional thiourea organocatalyst, this scalable domino reaction affords 4‐phenyl‐substituted chromans bearing spiro‐connected oxindole scaffolds and three adjacent stereogenic centers in good to excellent yields (up to 98 %) and with very high stereoselectivities (up to >20:1 d.r., >99 % ee). 相似文献