Circular dichroism spectra of 1,2,3,4,5,6-Hexahydro-2,6-methano-3-benzazocines

Circular dichroism curves of levorotatory 1,2,3,4,5,6-hexahydro-2,6-methano-3-benzazocin-8-ol derivatives have been determined and correlated with stereochemical features. Compounds with the rectus configuration at C-6 were found to exhibit negative extrema for the long wavelength phenolic π → π* transition. The remaining Cotton effects have been ascribed to specific aromatic π → π* transitions.     

Enantioselective chemo- and bio-catalysis in ionic liquids

Recent developments in the enantioselective chemo- and bio-catalysis in ionic liquids are reviewed. In many cases, the use of ionic liquids provides many advantages over reactions in conventional organic solvents in terms of activity, enantioselectivity, stability and the reusability of the solvent-catalyst systems.     

Synthesis of 4(5)-hydroxymethylimidazoles by hydroxymethylation and decarboxylation of imidazole-4(5)-carboxylic acids

4(5)-Hydroxymethylimidazoles were prepared by hydroxymethylation and decarboxylation of imidazole-4(5)-carboxylic acid esters. The reaction was simply carried out with aqueous formaldehyde solution in the presence of base.     

Thermal stability of some polyquinazolone polymers: Effect of acid catalysis

Thermal properties of polyquinazolones (PQ) polymers prepared from 4,4-diaminodiphenyl-3,3-dicarboxylic acid (BDC) and 4,6-diamino-isophthalic acid (DAIA) with diacetamido derivative of a number of diammines have been studied by thermogravimetry (TG) and differential scanning calorimetry (DSC). The effect of acid catalysis was also investigated. The results show that polyquinazolones prepared from DAIA have higher thermal stabilities and glass transition temperatures compared to those prepared from BDC. This can be attributed to the more stable and rigid fused quinazolone backbone unit in the PQ/DAIA system. Both polymer systems show improved thermal stability in the presence of catalyst which is a direct result of increased number of fully cyclised quinazolone rings in the polymer.

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Zusammenfassung Thermische Eigenschaften von aus 4,4-Diaminodiphenyl-3,3-dicarbonsäure (BDC) und 4,6-Diaminoisophtalsäure (DAIA) mit Diacetoimido-Derivaten einer Auswahl von Diaminen hergestellten Polymeren von Polyquinazolon (PQ) wurden mittels TG und DSC untersucht. Die mit DAIA erhaltenen Polyquinazolone sind thermisch stabiler und weisen höhere Glasübergangstemperaturen auf als die mit BDC hergestellten. Das kann der stabileren und fester ankondensierten Quinazolonhauptketteneinheit im PQ/DAIA-System zugeschrieben werden. Beide Polymersysteme weisen in Gegenwart eines Katalysators eine verbesserte thermische Stabilität auf, was auf eine größere Anzahl von voll zyklisierten Quinazolonringen im Polymer zurückzuführen ist.

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(), 4,4--3,3- () 4,6- () . . , , , , . /. , .

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Paper presented at the World Conference on Thermal Analysis, Madeira (Portugal), 1986.     

A novel synthesis of 2-aryl-2H-indazoles via a palladium-catalyzed intramolecular amination reaction

[reaction: see text] A variety of 2-aryl-2H-indazoles were synthesized by the palladium-catalyzed intramolecular amination of the corresponding N-aryl-N(o-bromobenzyl)hydrazines. Of several sets of reaction conditions surveyed, the combination of Pd(OAc)2/dppf/tBuONa gave the best results. This method applies to a wide scope of substrates containing electron-donating and electron-withdrawing substituents.     

Laser induced fluorescence and resonant two-photon ionization spectroscopy of jet-cooled 1-hydroxy-9,10-anthraquinone

We carried out laser induced fluorescence and resonance enhanced two-color two-photon ionization spectroscopy of jet-cooled 1-hydroxy-9,10-anthraquinone (1-HAQ). The 0-0 band transition to the lowest electronically excited state was found to be at 461.98 nm (21,646 cm(-1)). A well-resolved vibronic structure was observed up to 1100 cm(-1) above the 0-0 band, followed by a rather broad absorption band in the higher frequency region. Dispersed fluorescence spectra were also obtained. Single vibronic level emissions from the 0-0 band showed Stokes-shifted emission spectra. The peak at 2940 cm(-1) to the red of the origin in the emission spectra was assigned as the OH stretching vibration in the ground state, whose combination bands with the C=O bending and stretching vibrations were also seen in the emission spectra. In contrast to the excitation spectrum, no significant vibronic activity was found for low frequency fundamental vibrations of the ground state in the emission spectrum. The spectral features of the fluorescence excitation and emission spectra indicate that a significant change takes place in the intramolecular hydrogen bonding structure upon transition to the excited state, such as often seen in the excited state proton (or hydrogen) transfer. We suggest that the electronically excited state of interest has a double minimum potential of the 9,10-quinone and the 1,10-quinone forms, the latter of which, the proton-transferred form of 1-HAQ, is lower in energy. On the other hand, ab initio calculations at the B3LYP/6-31G(d,p) level predicted that the electronic ground state has a single minimum potential distorted along the reaction coordinate of tautomerization. The 9,10-quinone form of 1-HAQ is the lowest energy structure in the ground state, with the 1,10-quinone form lying approximately 5000 cm(-1) above it. The intramolecular hydrogen bond of the 9,10-quinone was found to be unusually strong, with an estimated bond energy of approximately 13 kcal/mol (approximately 4500 cm(-1)), probably due to the resonance-assisted nature of the hydrogen bonding involved.     

Optical properties of a polydiacetylene crystal: poly-[1,6-di(N-carbazolyl)-2,4-hexadiyne]

Normal incidence reflection spectra and Kramers-Kronig transforms are reported for a polydiacetylene crystal, DCHD (substituent group: N-carbazolymethyl). The lowest energy optical transition for the polymer backbone is found at 15 300 cm^?1, the lowest value obtained thus far for a polydiacetylene. The polymer chain and the carbazolyl substituent group may be treated as isolated chromophores - the former dominating the visible portion of the spectra and the latter dominating the UV portion. Polarization studies for the (001) and (10$\text{1}\text{?}$) faces of DCHD permit unambiguous assignment of the two lowest energy transitions in the carbazolyl group at 28 750 cm^?1 and 33 250 cm^?1 as short- and long-axis polarized, respectively.     

A comparison of protoporphyrin IX and protoporphyrin IX dimethyl ester as a photosensitizer in poorly differentiated human nasopharyngeal carcinoma cells

Protoporphyrin IX dimethyl ester (PME), a dimethyl esterification of protoporphyrin IX (PpIX), exhibits higher intracellular uptake into NPC/CNE2 cells, a poorly differentiated human nasopharyngeal carcinoma, than does PpIX. Phototoxicity studies reveal PME to be a more potent photosensitizer than is PpIX, at the early and late incubation time points. Correlating phototoxicity with subcellular localization indicates that PME is a more potent photosensitizer when its primary target of photodamage is mitochondria. Also, additional targeting of lysosome enhances phototoxicity.     

A novel one-step synthesis of 2-substituted 6-azaindoles from 3-amino-4-picoline and carboxylic esters

Dilithiation of 3-amino-4-picoline (1) was achieved with sec-BuLi at room temperature. Condensation of the resulting dianion (2) with carboxylic esters afforded a wide range of 2-substituted 6-azaindoles in good yields.