Another aromaticity vs non-aromaticity dilemma: The structure of anti-1,6:8,13-biscarbonyl [14]annulene

The X-ray crystal structure determination of anti-1,6:8,13-bis-carbonyl [14] annulene (1) is described. The structure has been solved by direct methods and refined to an R of 0.046 for 1074 reflections with I > 2σ(I). The molecular structure of 1 appears to be aromatic, at least from geometrical parameters. This is in contrast with the great tendency of the compound to polymerize and also with the structure of the anti-bridged [14]annulenes previously studied, having polyenic character. It is possible that the geometry of the compound appears to be ‘aromatic’ due to disorder in the crystal.     

Zur konfigurativen stabilität syn/anti-isomerer überbrückter [14]annulene mit anthracen-perimeter

The existence of a thermal equilibrium between aromatic syn-1,6:8,13-bisoxido[14]annulene and its olefinic anti-isomer is deduced from stereochemical and theoretical studies.     

Tetrakisdehydro[14]annuleno[20]annulene

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.     

Tetrakisdehydro[14]annuleno[16]annulene

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.     

A naphtho-tri-t-butyltrisdehydro[16]annulene

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.     

An ortho-fused tetrakisdehydro[14]annuleno[14]annulene consisting of two different types of bisdehydro[14]annulenes

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.     

1,6:9,14-bismethano[16]annulene - a new bridged [4n]annulene

The molecular structure and dynamic behaviour of the bridged [4n] annulene 1,6:9,14-bismethano-[16]annulene is unravelled by NMR and X-ray investigations, combined with force field calculations.     

Trisdehydro[14]annuleno[16]annulene

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.     

7,10,14-Tri-t-butyl-3-amino-1,8-bisdehydro[14]annulene

Tri-t-butylcarboxybisdehydro[14]annulene was converted by the Curtius reaction into unstable aminoannulene, which could be characterized as N-acetyl derivative. The pK_a-value of the aminoannulene reflects aromatic nature of the annulene nucleus.     

Tetrakisdehydro[16]annuleno[18]annulene

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.     

Propellanes—XXXVI : Reactions of bridged [10]annulenes with 4-substituted-1,2,4-triazoline-3,5-diones

1,6-Methano-, 1,6-oxa-, 1,6-imino- and 1,6-methylimino[10]annulene as well as several derivatives of the first-named compound react with 4-substituted-1,2,4-triazoline 3,5 diones to give mono- and/or bis-adducts. Attack apparently occurs from the side anti- to the bridging atom. Mass spectral results are reported for certain mixed di-adducts.     

ESR.-Spektren des Radikal-Anions des syn-1, 6; 8, 13-Bis-oxido-[14]annulens

The ESR.-spectra of the radical anion of syn-1, 6; 8, 13-bis-oxido-[14]annulene have been recorded. The hyperfine structure of the electrolytically generated anion (solvent: N, N-dimethylformamide; gegenion: Et₄N^⊕) is that of an unassociated species; on the other hand, evidence of strong ion-pairing can be derived from the spectra of chemically prepared anions (solvent: 1,2-dimethoxyethane; gegenion: K⊕ or Na⊕). The distribution of the n-spin population confirms the conclusion previously drawn for the radical anion of 1,6-oxido-[70]annulene that the overall effect of the oxygen bridging is electron repelling.     

2.2]paracyclophane/dehydroannulene hybrids: probing the aromaticity of the dehydro[14]annulene framework

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]     

New dicationic derivatives of dibenzotetraaza[14]annulene: tuning DNA-binding properties

Four new water-soluble derivatives of dibenzotetraaza[14]annulene have been synthesized, bearing meso substituents with different structures and dimensions: 3-(N,N,N-trimethylammonium)propyl, 3-(N-pyridinium-1-yl)propyl, 2-[3-(N,N,N-trimethylammonium)propoxy]benzoyl, and 2-[3-(N-pyridinium-1-yl)propoxy]benzoyl. The crystal structures of 3-(trimethylammonium)propyl and (N,N,N-trimethylammonium)propoxy]benzoyl derivatives were determined by single crystal X-ray analysis. According to the UV-vis titrations, thermal denaturation experiments, and ethidium bromide displacement assays, all compounds presented here interact strongly with double stranded (ct)-DNA. The product equipped with 3-(trimethylammonium)propyl pendant groups and two positive charges interacts with DNA in one dominant binding mode, whereas the other three derivatives revealed more complex mixed-type interactions. The results have been discussed in terms of dimensions, geometry, and electronic properties of the evaluated compounds, on the basis of corresponding crystallographic data.     

The structures of the two isomers of monodehydro[14]annulene

Variable temperature ¹H nmr spectrometry has shown that the “unstable” isomer of monodehydro[14]annulene possesses the symmetrical di-$\text{trans}$ configuration $\text{1}$ or $\text{2}$, and the “stable” isomer (the precursor of [14]annulene) possesses the tri-$\text{trans}$ configuration $\text{4}$.     

Syntheses of an isoannelated annulene,a bisdehydro[14]annuleno[c]furan and bisdehydro[14]annulene derivatives

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.     

Disubstituted 1,6-methano[10]annulene derivatives for use in organic light-emitting diodes

Bis(carbazolylphenyl) and bis(diphenylaminophenyl) derivatives of 1,6-methano[10]annulene, which is luminescent material and contains seven-membered rings, are synthesized. The bis(phenylcarbazole) derivative 3 have high melting point and glass transition temperature. Electroluminescence characteristics of organic light-emitting diodes using these methano[10]annulenes were investigated.     

A naphtho-tri-t-butyltrisdehydro[16]annulene and related compounds

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.     

Stabilized and destabilized carbocations in the 1,6-methano[10]annulene series

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.     

简便合成3,3'-联-1,6-亚甲基桥[10]轮烯

以1,6-二甲酰基环庚三烯为原料通过10π电子环化反应等3步反应制备了3-溴代-1,6-亚甲基桥[10]轮烯, 通过3-溴代-1,6-亚甲基桥[10]轮烯的碱诱导的偶联反应, 简便地合成3,3'-联-1,6-亚甲基桥[10]轮烯, 并用NMR, MS等波谱进行了表征.