共查询到20条相似文献,搜索用时 31 毫秒
1.
利用密度泛函和电子密度拓扑分析方法对CH3NO2 (NM)的异构化反应进行了研究。 找到了九种可能的异构体和八个反应通道。通过内禀反应坐标(IRC)分析确认了过渡态与异构体之间的连接关系。计算结果表明,在CH3NO2→CH3ONOt反应过程中,过渡态为紧密结构(在整个反应过程中CH3NO2没有分解为CH3 和NO2 ),与Arenass等人的结论一致。在CH3NOOc→CH2NOOH反应过程中,存在有一个含有四元环→五元环→四元环→五元环变化过程的结构过渡区,这也是在反应过程中首次发现五元环状过渡结构。 相似文献
2.
A collection of 33 hydrodipyrrins (9 targets, 21 intermediates, and 3 byproducts) has been prepared. The hydrodipyrrins (dihydrodipyrrins, tetrahydrodipyrrins, and hexahydrodipyrrins) contain a pyrrole ring and a geminal-dimethyl substituted 1-pyrroline (or pyrrolidine) ring. The α-substituents on the pyrrole ring (H, Br, CHO) and pyrroline ring (H, CH3, CH(OR)2, OMe, SMe) provide different reactivity combinations (Nu−, E+) and 0, 1, or 2 carbon atoms (which can give rise to the bridging meso-carbons in hydroporphyrins). Straightforward access to various hydrodipyrrins should facilitate development of syntheses of diverse hydroporphyrins. 相似文献
3.
Rebek Imide Platforms as Model Systems for the Investigation of Weak Intermolecular Interactions
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Michael Harder Marjorie A. Carnero Corrales Dr. Nils Trapp Dr. Bernd Kuhn Prof. Dr. François Diederich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8455-8463
A Rebek imide receptor with an acetylene‐linked phenyl ring complexes 2,6‐di(isobutyramido)pyridine in (CDCl2)2 via triple H‐bonding and π–π‐stacking interactions, and the influence of para‐substituents on both rings was investigated by 1H NMR binding titrations. When the phenyl ring was extended to biphenyl and the C(4)‐pyridine substituent varied, interaction energies increased in the order CH3CH2???phenyl<CH3S???phenyl<phenyl???phenyl?N‐methylcarboxamide???phenyl, highlighting the energetic gain from π stacking on amide fragments. The predicted preference of amide–π stacking for an antiparallel alignment of the local dipoles could not be confirmed with the studied system. Different substituents were introduced in the para position of the phenyl ring and their interaction with bound 2,6‐di(isobutyramido)pyridine was investigated. Theoretical predictions that the mere introduction of a substituent has a stabilizing effect on π–π stacking, regardless of its electronic nature, were experimentally confirmed. 相似文献
4.
The reaction of (η5-cyclopentadienyl)(η4-1,3-diphenylcyclobutadiene)cobalt ( I ) with excess Cr(CO)3py3 in BF3OEt2 yielded two identified heterometallic compounds. Compounds II and III with one and two phenyl rings complcxed with Cr(CO)3 fragment(s), respectively. These compounds were characterized by mass, infrared, 1H and 13C NMR spectra and elemental analysis. The crystal structure of II was determined. The Cr(CO)3 fragment bends inward toward the cyclobutadicne ring due to its electron-withdrawing ability, in accord with Hunter's postulate. A sharp line due to the non-complexed phenyl ring was observed in the 1HNMR spectrum, which implies that five protons are magnetically equivalent. The chemical shifts of two protons of the cyclobutadiene ring decreased from I to II then to III , possibly because of diminished deshielding effect from the phenyl ring in (arene)Cr(CO)3. 相似文献
5.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(7):531-535
3‐Aminocarbonyl‐1‐benzylpyridinium bromide (N‐benzylnicotinamide, BNA), C13H13N2O+·Br−, (I), and 1‐benzyl‐1,4‐dihydropyridine‐3‐carboxamide (N‐benzyl‐1,4‐dihydronicotinamide, rBNA), C13H14N2O, (II), are valuable model compounds used to study the enzymatic cofactors NAD(P)+ and NAD(P)H. BNA was crystallized successfully and its structure determined for the first time, while a low‐temperature high‐resolution structure of rBNA was obtained. Together, these structures provide the most detailed view of the reactive portions of NAD(P)+ and NAD(P)H. The amide group in BNA is rotated 8.4 (4)° out of the plane of the pyridine ring, while the two rings display a dihedral angle of 70.48 (17)°. In the rBNA structure, the dihydropyridine ring is essentially planar, indicating significant delocalization of the formal double bonds, and the amide group is coplanar with the ring [dihedral angle = 4.35 (9)°]. This rBNA conformation may lower the transition‐state energy of an ene reaction between a substrate double bond and the dihydropyridine ring. The transition state would involve one atom of the double bond binding to the carbon ortho to both the ring N atom and the amide substituent of the dihydropyridine ring, while the other end of the double bond accepts an H atom from the methylene group para to the N atom. 相似文献
6.
1.5-Bis(methylamino)hexamethyltrisildioxane reacts in the presence of triethylamine easily with germanium tetrachloride (equ. 1) and ethyldichlorophosphine (equ.2) to give the formerly unknown inorganic eightmembered ring systems Si3GeN2O2 and Si3PN2O2. Respectively. By analogous reacting of silicon tetrachloride only open chained Cl3Si? Nme? Sime2? O? Sime2? O? Sime? NHme (IV; equ. 3) is formed. With metallated 1.5-bis(alkylamino)trisildioxanes, dischlorodiorganylsilanes do not give the expected asymmetric-, but the symmetric cyclotetrasildioxdiazanes V–VII. Dichlorophenylborane, in an analogous reaction, leads to the novel eightmembered ring system BSi3N2O2, but the exact position of the N and O atoms in the ring could not be fixed beyond any doubt. The novel sixmembered ring system BSi2Ni2O was realized in compound IX via equ. (6). 相似文献
7.
Matsuo Nonoyama 《Transition Metal Chemistry》1990,15(5):366-370
Summary
N, N-Dimethyl-3-furancarbothioamide (Hbft) was cyclometallated with Li2PdCl4, K2PtCl4, RuCl2(CO)3, and RhCl (PBu3)2 (PBu3=tri-n-butylphosphine) to give, respectively, PdCl(bft), PtCl(bft), RuCl(bft)(CO)2, and RhCl2 (bft)(PBu3)2. These and some of their derivatives were characterized spectroscopically. Cyclometallation occurs regioselectively at position 2 of the furan ring to give a five-membered metallaheterocycle, along with Secoordination of the thioamide group. When the position 2 of the furan ring is blocked by a methyl group,N, N-dimethyl-2-methyl-3-furancarbothioamide (Hmft) is, in similar conditions, cyclopalladated at the N–Me substituout of the thioamide group, the furan ring being left intact. Position 4 of the furan ring of both Hbft and Hmft is unreactive toward cyclometallation. 相似文献
8.
Alan J. Chalk 《Journal of organometallic chemistry》1974,76(2):C38-C39
Reactions of MI(CH3)(PPh3)2 or MCl(CH2COR)(PPh3)2 (M = Pd, Pt) with sodium dicyanomethanide in methanol gave novel metal complexes. Spectroscopic data suggest that these complexes contain either an iminoether chelate ring or a carbon-carbon chelate ring which was derived from CH(CN)2-. 相似文献
9.
In order to evaluate more deeply the nature of the activation of oxirane ring opening reactions by HFIP, ring opening of both CF3-epoxy ethers 1a (R = Ph) and 1b (R = CH2CH2Ph) with HFIP alone, and with hard (MeOH) or soft (PhSH) nucleophiles in HFIP, were investigated and compared to reactions performed with Brönsted acids. Nucleophilic ring opening reactions in HFIP were facilitated with PhSH and only α-substituted trifluoromethyl ketone 5 was isolated (nucleophilic ring opening), while with MeOH, both processes, nucleophile and electrophile-assisted ring opening were in competition. In the Brönsted acid-catalysed ring opening of 1-CF3-epoxy ethers 1 in HFIP, only the acid-catalysed ring opening process occurred with an inversed regioselectivity. 相似文献
10.
1,1‐(Bicyclononyl‐9‐phosphino)hendecanoic acid and potassium 1,1‐(biscyclohexylphosphino)hendecylate were synthesized. A model nickel complex [η3−C8H13]Ni[(C8H14)P(CH2)10COO] containing a 14‐membered chelate ring was also synthesized. The catalytic activity of this large chelate ring nickel complex for the oligomerization of ethylene was studied and compared with that of six‐membered ring chelate nickel complexes. The influence of the chelate ring was rationalized in terms of intramolecular rotation. The 14‐membered ring P/O chelate nickel complex was shown to have efficient catalytic activity for the oligomerization of ethylene to α‐olefins. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
11.
Hongxia Zhou Fayan Zhu Hongyan Liu Wenqian Zhang Yongquan Zhou Chunhui Fang 《International journal of quantum chemistry》2020,120(5):e26118
[B4O5(OH)42−] is a representative borate anion with a double six-membered ring structure, but there is limited knowledge about the hydrolysis mechanisms of [B4O5(OH)42−]. Density functional theory-based calculations show that the tetraborate ion undergoes three-step hydrolysis to form [B(OH)4−] and an ring intermediate, [B3O2(OH)6−]. Other new structures, such as linear trimer, branched tetraborate, analogous linear tetraborate, are observed, but they are not stable in neutral systems and change to ring structures. [B3O2(OH)6−] hydrolyzes to [B(OH)4−] and [B(OH)3] in the last two steps. The structure of borate anion and the coordination environment of the bridge oxygen atom control the hydrolysis process. [B4O5(OH)42−] always participates in the hydrolysis reaction, even with a decrease in concentration. [B3O3(OH)4−], [B(OH)4−], and [B(OH)3] have different roles in “water-poor” and “water-rich” zones. Concentration and pH of solution are the key factors that affect the distribution of borate ions. 相似文献
12.
Leonard V. Interrante Gary Sigel Mary Garbauskas Carolyn Hejna 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):325-334
Abstract The crystal and molecular structures of the title compounds, [(CH3)2AlNH2]3 1 and [(t-C4H9)2AlNH2]3 2, have been determined in connection with their investigation as possible precursors to aluminum nitride. Both compounds have an (AlN)3 ring-structure with distorted tetrahedral geometries for the ring Al and N atoms. The distortion from tetrahedral geometry is most pronounced for the N atoms where the endocyclic Al-N-Al bond angles average 125.3 for 1 and 134.2 for 2. The (AlN)3 ring in 1 is in a skew-boat conformation with no unusual intra- or intermolecular contacts. Compound 2 on the other hand exhibits an unprecedented planar (AlN)3 ring as required by a crystallographic three-fold symmetry axis. The effects of the Al and N substituents on the (AlN)3 ring size and conformation, as well as on the endocyclic Al-N-Al bond angles, are discussed in the context of the structural results obtained for these and other (AlN)n ring compounds. 相似文献
13.
14.
Bahija Abouhamza Mustapha Ait Ali Smaïl Allaoud Olivier Blacque Bernard Frange Abdallah Karim 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(7):796-798
The structures of two atropisomers of the title compound, [Cr(C16H18B2Cl2N2)(CO)3], are reported. For both compounds, the Cr(CO)3 moiety is bound to the C6 aromatic ring of the molecule; the existence of atropisomers resulting from the non‐equivalence of both faces of the C6 aromatic ring is a consequence of the 3‐chloro‐2‐methylphenyl ring being nearly perpendicular to the mean plane of the 2,4‐dibora‐1,3‐diazanaphthalene ring. The orientation of the Cr(CO)3 tripod relative to the C6 aromatic ring is such that it is nearly eclipsed in one isomer (2.4° rotation from being eclipsed with C—N, C—Cl and C—H) and slightly twisted (16.2°) from an eclipsed conformation in the other. 相似文献
15.
Yu‐Pin Wang Hsien‐Li Leu Tso‐Shen Lin Yu Wang Gene‐Hsiang Lee 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(3):m131-m134
In the structures of each of the title compounds, [CrBr(C6H5O2)(NO)2], (I), and [CrBr(C12H9O)(NO)2], (II), one of the nitrosyl groups is located at a site away from the exocyclic carbonyl C atom of the cyclopentadienyl (Cp) ring, with twist angles of 174.5 (3) and 172.5 (1)°. The observed orientation is surprising, since the NO group is expected to be situated trans to an electron‐rich C atom in the ring. The organic carbonyl plane is turned away from the Cp ring plane by 5.6 (8) and 15.2 (3)°in (I) and (II), respectively. The exocyclic C—C bond in (I) is bent out of the Cp ring plane towards the Cr atom by 2.8 (3)°, but is coplanar with the Cp ring in (II); the angle is 0.1 (1)°. 相似文献
16.
Kazuto Takaishi Bikash Dev Nath Yuya Yamada Hiroyasu Kosugi Tadashi Ema 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(29):10089-10093
Unique self‐assembled macrocyclic multinuclear ZnII and NiII complexes with binaphthyl‐bipyridyl ligands (L) were synthesized. X‐ray analysis revealed that these complexes consisted of an outer ring (Zn3L3 or Ni3L3) and an inner core (Zn2 or Ni). In the ZnII complex, the inner Zn2 part rotated rapidly inside the outer ring in solution on an NMR timescale. These complexes exhibited dual catalytic activities for CO2 fixations: synthesis of cyclic carbonates from epoxides and CO2 and temperature‐switched N‐formylation/N‐methylation of amines with CO2 and hydrosilane. 相似文献
17.
The precise molecular structure of the title compound has been determined by single crystal X-ray diffractometry. It consists of a cyclohexadiene ring fused at the 5 and 6 positions to a cyclobutane ring which is in turn fused to a cyclohexane ring. The two six-membered rings are trans to each other with respect to the shared four-membered ring. The Fe(CO)3 moiety is bound in the usual way to the conjugated diene portion of the cyclohexadiene ring. The feature of greatest interest is the mutual influence of the conformations of the two fused cycloalkane rings, whose intrinsically preferred conformations are mutually incompatible. Under the influence of the fused cyclohexadiene ring the C4 ring would tend to be planar, while the cyclohexane ring would tend, of itself, to have a chair conformation. The actual result is a compromise, with the C4 ring being folded by 15° along its diagonal and the C6 ring having a conformation intermediate between planarity and a chair. Crystallographic data: space group, P21, Z = 2. Unit cell dimensions at 3°C are a = 6.176(1), b = 11.307(2), c = 9.781(2) Å and β = 92.89(2)°. A set of 1733 reflections having 2θ(Mo-Kα) < 63.7° and I > σ(I) was refined to convergence (R1 = 0.055; R2 = 0.034) with hydrogen atoms refined isotropically and all others anisotropically. 相似文献
18.
Anwar Usman Ibrahim Abdul Razak Hoong‐Kun Fun Suchada Chantrapromma Yan Zhang Jian‐Hua Xu 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(8):o477-o479
In the title compounds, C24H17NO3, (I), and C43H27NO5, (II), the dioxine ring is not planar and tends toward a boat conformation. The oxazoline ring adopts a twisted conformation in molecule (I) but is essentially planar in molecule (II). The configuration of the dioxine–oxazoline system is determined by the sp3 state of the two shared atoms. The phenanthrene moiety is nearly coplanar with the dioxine ring, while the phenyl ring is perpendicular to the attached oxazole ring. The triclinic unit cell of (II) contains two crystallographically independent molecules related by a pseudo‐inversion centre. 相似文献
19.
Alex Lovstedt Stephen H. Dempsey Steven R. Kass 《Acta Crystallographica. Section C, Structural Chemistry》2023,79(5):170-176
The tetramer of bis(4-di-n-butylaminophenyl)(pyridin-3-yl)borane [systematic name: 2λ4,4λ4,6λ4,8λ4-tetrabora-1,3,5,7(1,3)-tetrapyridinacyclooctaphane-11,31,51,71-tetrakis(ylium)], C132H192B4N12, was synthesized unexpectedly and crystallized. Its structure contains an unusual 16-membered ring core made up of four (pyridin-3-yl)borane groups. The ring adopts a conformation with pseudo-S4 symmetry that is very different from the two other reported examples of this ring system. Density functional theory (DFT) computations indicate that the stability of the three reported ring conformations is dependent on the substituents on the B atoms, and that the pseudo-S4 geometry observed in the bis(4-dibutylaminophenyl)(pyridin-3-yl)borane tetramer becomes significantly more stable when phenyl or 2,6-dimethylphenyl groups are attached to the boron centers. 相似文献
20.
《Magnetic resonance in chemistry : MRC》2003,41(7):517-525
Conformational states of the cyclohexanone ring were established for 3R‐methyl‐6‐(4‐phenylbenzylidene)cyclohexanone and several 2,6‐bis(4‐X‐benzylidene)‐3R‐methylcyclohexanones (X = Br, OCOCH3 and C6H5) by 1H NMR spectroscopy combined with molecular simulation using the semi‐empirical methods AM1 and PM3. The first compound studied contains only one arylidene group, and exists predominantly in a chair conformation of the cyclohexanone ring with an equatorial orientation of the methyl substituent in C6D6 and CDCl3 solutions at room temperature (22–23 °C). In contrast, the 2,6‐bis(arylidene) derivatives of 3R‐methylcyclohexanone preferentially adopt conformations with an axially oriented methyl group. The extent of twisting of enone fragments was also characterized for the compounds studied based on simulation results and comparison of chemical shifts for the arylidene protons of appropriate model compounds. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献