共查询到20条相似文献,搜索用时 15 毫秒
1.
Yukihiro Yoshikawa Masahiko Iyoda Masazurni Nakagawa Shinichi Nakatsuji Shuzo Akiyama 《Tetrahedron letters》1981,22(51):5209-5212
Trisdehydro[14]annuleno[16]annulene consisting of an aromatic bisdehydro[14]annulene and an antiaromatic bisdehydro[16]annulene has been synthesized. The strong paratropicity was observed in the [16]annulene moiety being comparable with that of extremely unstable parent bisdehydro[16]annulene. 相似文献
2.
Tetrakisdehydro[14]annuleno[20]annulene consisting of an aromatic bisdehydro[14]annulene and an antiaromatic trisdehydro[20]annulene has been synthesized. The 1H NHR spectra clearly indicate the induction of para- and diamagnetic ring currents in each of the [4n]- and [4n+2]-rings, respectively. 相似文献
3.
Koichi Sakano Tsutomu Nakagawa Masahiko Iyoda Masazumi Nakagawa 《Tetrahedron letters》1981,22(28):2655-2658
Tetrakisdehydro[16]annuleno consisting of trisdehydro[16]annulene and bisdehydro[18] annulene has been synthesized. Induction of para- and diamagnetic ring currents in 16- and 18-membered rings, respectively, was clearly recognized by the 1H NMR spectroscopy. A marked suppresion of the diatropicity in the 18π moiety was observed in the same trend as observed in tetrakisdehydro[14]annuleno[16]annulene. 相似文献
4.
Tetrakisdehydro[14]annuleno[16]annulene consisting of an aromatic bisdehydro[14]-annulene and an antiaromatic trisdehydro[16]annulene has been synthesized. The 1H NMR parameters clearly indicate the strong paratropicity and diatropicity of the 16-membered and 14-membered rings, respectively. 相似文献
5.
Hajime Ebe Tsutomu Nakagawa Masahiko Iyoda Masazumi Nakagawa 《Tetrahedron letters》1981,22(44):4441-4444
A bisdehydro[14]annuleno[c]furan, an isoannelated diatropic annulene, has been synthesized. Cyclic glycol, a precursor of the annuleno[c]furan, could be converted into bisdehydro[14]annulene derivatives under mild acidic conditions. 相似文献
6.
Synthesis of a naphtho-tri-t-butyltrisdehydro[16]annulene has been described. Suppression of paratropicity of the 16-membered ring was observed. Comparison of 1H NMR spectrum of the [16]annulene with that of naphtho-tri-t-butylbisdehydro[14]annulene suggests that the trans double bond adjacent to naphthalene in the [16]annulene is twisted out of the mean molecular plane. 相似文献
7.
Masahiko Iyoda Tsutomu Nakagawa Masazumi Nakagawa Masaji Oda 《Tetrahedron letters》1982,23(51):5423-5426
Tetrakisdehydro[14]annuleno[14]annulene consisting of ‘acetylene-cumulene’ bisdehydro[14]annulene and Sondheimer's bishydro[14]annulene has been synthesized. It was found that a strong diatropicity was observed in the ‘acetylene-cumulene’ bisdehydro[14]annulene moiety, whereas diatropicity of another bisdehydro[14]annulene moiety shows marked decrease comparable with that of napthobisdehydro[14]annulene synthesized by Sondheimer. 相似文献
8.
[reaction: see text] Trefoil-shaped tris(hexadehydrotribenzo[12]annulene) possessing a substructure of the ultimate two-dimensional C(sp)-C(sp(2)) network, graphyne, and the related tris(tetradehydrotribenzo[12]annulene) were synthesized, and their ground- and excited-state properties were investigated. 相似文献
9.
Shigeyasu Kuroda Rie KasaiRyo Nagaya Ryuta MiyatakeYoshikazu Horino Naoko MatsumotoMitsunori Oda 《Tetrahedron letters》2011,52(13):1426-1429
3,10-Dipyrrolidinyl-4,9-methanothia[11]annulene reacts with excess dimethyl acetylenedicarboxylate (DMAD) in refluxing toluene to give ring-enlarged 6,11-methanothia[15]annulene. X-ray crystallographic analysis of the product shows two different cis,trans-dienyl parts in the ring system. Product formation possibly involves π-facial selective addition of the enamine with DMAD and torque-selective ring opening of the intermediate cyclobutenes. 相似文献
10.
Kiesewetter MK Reiter RC Stevenson CD 《Journal of the American Chemical Society》2005,127(4):1118-1119
Reacting (at 0 degrees C) a mixture of CH2Cl2 and monobromo[8]annulene (C8H7Br) with potassium tert-butoxide in hexamethylphosphoramide (HMPA) and following with exposure to potassium metal led to the formation of the anion radical of an HMPA-[6.1.0]bicyclononatetraene condensation product, in which two HMPA fragments are geminal and attached to the number 9 carbon. When the reaction sequence is carried out in THF, the dianion of cycloprop[8]annulene is predominantly formed. Neutral cycloprop[8]annulene can be isolated via the I2 oxidation of the THF solution. The NMR analysis reveals that the eight-membered ring is nearly planar, and the three-membered ring is more like a dimethylenecyclopropane than it is like a cyclopropene. Further, the chemical shifts due to the protons on the eight-membered ring are nearly 2 ppm further upfield than are those for [8]annulene itself, suggesting a paratropic ring current. 相似文献
11.
12.
I. Agranat 《Tetrahedron》1973,29(10):1399-1400
The condensation of 2,2′-diaminobiphenyl and diphenylamine-2,2′-dicarboxaldehyde afforded Octabenzo[b,f,h,l,o,s,u,y][1,5,10,14,18,23]hexaaza[26]annulene in quantitative yield. 相似文献
13.
Tetrakisdehydro[18]annuleno[20]annulene has been synthesized. The 1H NMR spectra clearly indicate the induction of dia- and paramagnetic ring currents in 18- and 20-rings, respectively. A marked suppression of the diatropicity in the 18π moiety was observed being in the same trend in other tetrakisdehydro[4n]annuleno[4n′+2]annulenes. The 1H NMR spectroscopic behavior of the annulenoannulenes is consistent with theoretical conclusion. 相似文献
14.
[reaction: see text] High-level theoretical methods are applied to calculate the 13C NMR chemical shifts of three isomers of [10]annulene. Comparison with experiment clearly shows that the carrier of NMR signals of the so-called B form is the "twist" isomer. The results of this study strongly support predictions of relative energies of mono-trans [10]annulene isomers at the CCSD(T) level, which in turn are in qualitative disagreement with DFT and MP2 calculations. 相似文献
15.
Synthesis of naphtho-tri-t-butyltrisdehydro[16]annulene containing a hexapentaene and an acetylene units has been described. It was found that the [16]annulene is less stable and the paratropicity is much stronger as compared with previously reported isomeric naphtho[16]-annulene containing a diacetylene and a butatriene linkage. 相似文献
16.
Braten MN Castro C Herges R Köhler F Karney WL 《The Journal of organic chemistry》2008,73(4):1532-1535
A new global minimum for [12]annulene has been computationally located. This mono-trans minimum 5 (CCCCCT) is computed to be 1.5 kcal/mol more stable (CCSD(T)/cc-pVDZ//BHHLYP/6-311+G**) than the known tri-trans isomer 1 (CTCTCT) and 2.4 kcal/mol lower than the di-trans isomer 4 (CCTCCT), for which there is indirect evidence. The barriers for several rearrangements of 5 were all computed to be above 15 kcal/mol, indicating that direct experimental characterization of 5 should be possible. The computed barriers for the dynamic processes (including conformational automerization) coupled with computed 1H NMR shift values should aid in the future characterization of this [12]annulene isomer. 相似文献
17.
2-Chloromethyl and 3-chloromethyl-1,6-methano[10]annulene systems solvolyze in methanol to give simple substitution products. Solvent effect studies and the special salt effect support the involvement of cationic intermediates stabilized by the 1,6-methano[10]annulene group. Rate data indicate that the degree of cation stabilization greatly exceeds that of naphthyl groups. B3LYP/6-31G computational studies also suggest that the cationic intermediates are greatly stabilized by the 1,6-methano[10]annulene. By way of contrast to these findings, solvolytic and computational studies indicate that the 11-(1,6-methano[10]annulenyl) cation is a destabilized analogue of the cycloheptatrienyl cation. There are no favorable interactions with the annulene ring. Distortions from planarity prevent charge delocalization as in the analogous aromatic cycloheptatrienyl cation. 相似文献
18.
Dehydro[10]annulene had been prepared experimentally recently, which is considered to be a highly rigid structure with planar configuration. In this paper, the electronic structure and bonding character of dehydro[10]annulene had been studied by means of molecular orbital (MO), density of states (DOS), bond order (BO) and interaction region indicator (IRI) analyses. The delocalization characters of out-of-plane and in-plane π-electrons (πout- and πin-electrons) of the bond regions were studied by using localized orbital locator (LOL). The anisotropy of the induced current density (AICD), iso-chemical shielding surface (ICSS) and anisotropy of the gauge-including magnetically induced current (GIMIC) were used to investigate the molecular response to external magnetic field, including the induced ring current and the magnetic shielding characteristic. The results showed that the electron delocalization of dehydro[10]annulene is mainly contributed by πout system. The apparent clockwise current in the πout system proved that dehydro[10]annulene is πout aromatic. Finally, the photophysical properties and (hyper)polarizability of dehydro[10]annulene were studied by TD-DFT calculation. The results showed that dehydro[10]annulene has strong local excitation characters. Its (hyper)polarizability decreases with the increase of frequency and has the characteristics of nonlinear anisotropy. 相似文献
19.
《Tetrahedron letters》1986,27(8):975-976
Reductive coupling of 1, 6-bis(2-formylvinyl)cyclohepta-1, 3, 5-triene with a low-valent titanium reagent afforded a paratropic bismethano [24] annulene. 相似文献
20.
The synthesis of [2.2]paracyclophane/dehydro[14]annulene hybrids 1 and 2 is reported. Comparison of the proton NMR spectra of 1 and 2 with their open precursors and with related model compounds reveals the pronounced effect of macrocycle formation upon the cyclophane protons H15/H16, which lie above the shielding cone of the diatropic [14]annulene moiety. [structure: see text] 相似文献