摘要:

AbstractOxidation of 1‐ethyl‐, 1‐propylazulenes, and their 5‐isopropyl derivatives with bromine gave 3‐bromo‐1,5‐ and 3‐bromo‐l,7‐azulenequinones (Type A) together with 3‐bromo‐l‐hydroxy‐5‐isopropyl‐l‐alkylazulen‐7‐one and its isomeric products (Type B), while the same reaction of 1‐methylazulenes afforded Type B products along with many unidentified products. On the other hand, 1‐phenylazulene gave 3‐phenyl‐1,5‐ and 3‐phenyl‐l,7‐azulenequinones (Type C) and Type B products in high yie]ds. 1,2‐Polymethyleneazulenes afforded a considerable amount of 3‐bromo‐2‐(ω‐formylalkyl)azulenequinones together with Type B products. Possible pathways

ISSN:0009-4536    

DOI:10.1002/jccs.199600044

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe mode of deactivation and coke formation in a H‐ZSM‐5 zeolite during ethylbenzene disproportionate has been investigated by TGA, adsorption, IR, and129Xe NMR techniques. The initial rate of deactivation and the total coke content are found to increase with increasing conversion level. Within the range of conversion (54‐63%) covered in the present study, the location and extent of coke deposition can be divided into three distinct regions. At low coke content, coke is found to deposit on the Brønsted acid sites and resulted in a notable decrease in catalytic activity. As the amount of coke increases (≤ 7 wt%), while the catalytic activity decreases slightly, most of coke still tends to deposit within the zeolite channels. The slight decrease in catalytic activity is ascribed to steric hindrance by coke residues. When the coke content exceeds 7 wt%, while the activity remains almost constant, the deposition of coke on the external surface of the zeolite crystallites is evident. It is found that neither the pore opening nor the acid site were completely blocked off by coke residues even at the highest coke

ISSN:0009-4536    

DOI:10.1002/jccs.199600045

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe determination of seven saponins in crude plant extracts by electrospray ionization mass spectrometry (ESI‐MS) and fast atom bombardment mass spectrometry (FAB‐MS) is described. Distinct protonated and natriated (Na‐adduct) molecular ions in ESI‐MS spectra readily provide molecular weight information, which can be further verified using clusters of molecular ions. Saponin mixtures can be analyzed by ESIMS on varying the potential difference between the capillary and skimmer in the ESI source to decompose impurities. ESI‐MS uses less amount of sample than that required by FAB‐MS. ESI‐MS does not produce structural information, however. The FAB‐MS spectra consist mainly of protonated and deprotonated molecular ions with limited structural information. (‐)‐FAB‐MS is more suitable for analyzing saponin sample

ISSN:0009-4536    

DOI:10.1002/jccs.199600046

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA superconducting (Bi, Pb)2(Sr, Ca)4Cu3O2material has been prepared by tbe oxalate coprecipitation method. The high‐Tc 110 K phase was effectively promoted by application of an intermediate grinding and pressing between the sintering heat treatments. The powder X‐ray diffraction shows the existence of single high‐Tc and high‐textured microstructures with strong (001) reflections within a short sintering time ( 18 h). The morphology of the sintered samples was examined by scanning electron microscopy (SEM). Also, the kinetics of the formation of the high‐Tc phase were investigated by the isothermal method. A possible mechanism of the formation of high‐Tc 2223 phase w

ISSN:0009-4536    

DOI:10.1002/jccs.199600047

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractMolecular structures of three emissive annular digold compounds [Au2(dmpm)(dtc)]Cl (dmpm = Me2PCH2PMe2,dtc = S2CNEt2),1, [Au2(dppm)(dtc)]PF6, (dppm = Ph2PCH2PPh2),2,and [Au2(dppe)(dtc)]‐(PF2) (dppe = Ph2P(CH2)2PPh2), 3, were determined. All three compounds are dimetallacycles having two gold atoms bridged by a dithiolate ligand and a diphosphine ligand, the geometry around each gold atom being almost linear. All the dimetal lacy die rings are slightly distorted from planarity with intramolecular Au‐Au distances shorter than 3.0 Å. Compound1forms a polymeric chain through intermolecular Au‐Au contacts (3.061 − 3.135 Å). Compound2forms a tetramer through intermolecular Au‐Au interactions (Au‐Au distances ranging from 3.086 to 3.222 ). Compound3is monomeric. All of the compounds luminesce at 77 K in the solid state. Emissions originating from3LMCT from dtc ligand to Au excited states are assigned. The emission maxima of1 − 3are at 541,535 and 520 nm respectively and are blue shifted as the number of Au‐Au interact

ISSN:0009-4536    

DOI:10.1002/jccs.199600048

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe preparation and mesogenic properties of a series of discotic β‐diketonate metal complexes are reported. The results show that the density of side chains, positions of side chains, and the geometries of the metal centers play important roles in determining the mesomorphic behaviors and thermodynamic stability of these complexes. In the series of copper complexes 3, all these disc‐like molecules with eight alkoxy side chains exhibit columnar hexagonal disordered (Dhd) mesophases. In the series of copper complexes 2 with six side chains, only compounds substituted with longer alkoxy chains (n = C14or C16) exhibit discotic columnar mesophase. However, in the series of complexes 1, only crystal‐to‐isotropic transitions were observed. The results showed that induction of liquid crystallinity not only depends on the numbers of side chains (i.e. side chain density), but also on the degree of distribution over the central core. Palladium complexes analogs exhibit similar discotic mesophases, and due to their greater core‐core organization, they also have higher clearing points and wider temperature range of mesophases than copper

ISSN:0009-4536    

DOI:10.1002/jccs.199600049

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

Abstract8‐Cedren‐14‐ol (4d) was oxidized with PCC, followed by autooxidation to yield 8,14‐cedranolide (2a) and 8‐cedren‐14‐carboxylic peracid (4e). 8β‐Hydroxycedran‐l3‐al (1d) was subjected to autooxidation in three different solvents to give eight products, from which the transformation from cedrane skeleton to noracorane and decahydroazulene skeletons were observed. A free radical

ISSN:0009-4536    

DOI:10.1002/jccs.199600050

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractHydride abstraction of tricarbonyl[η4phenylthio)‐l,3‐cyclohexadiene]iron(0) complex 2 with Ph3C+PF6−regiospecifically provided the title compound 3 in excellent yield. Cationic complex 3 could react with a variety of nucleophiles in good yield. Hard nucleophiles prefer to attack at the C‐l position, whereas soft and hindered nucleophiles favor attack at the C‐5 position. Some synthetic applications were al

ISSN:0009-4536    

DOI:10.1002/jccs.199600051

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

Abstract6‐Methoxy‐2‐methylazuleno[6,5‐d]thiazole5, 2‐benzamidoazuleno[6,5‐d]thiazole13and its 6‐methoxy derivative10were obtained by the decarbethoxylation of the diethyl 6‐methoxy‐2‐methylazuleno[6,5‐d]thiazole‐5,7‐dicarboxytate 4, diethyl 2‐benzamidoazuleno[6,5‐d]thiazole‐5,7‐dicarboxylate12and ite 6‐methoxy derivative9, respectively. The latter compounds were synthesized from diethyl 6‐amino‐2‐hydroxyazulene‐l,3‐dicarboxylate1, diethyl 5‐bromo‐6‐amino‐2‐acetylaminoazulene‐l,3‐dicarboxylate6band diethyl 5‐bromo‐6‐amino‐2‐

ISSN:0009-4536    

DOI:10.1002/jccs.199600052

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe homonuclear diatomic molecules are the simplest systems having both the σ framework and the lone pair orbitals naandbfor investigating their through space and through bond interaction. The striking orbital energy order ng∼ na+ nb>nn∼ na‐ nbhas been accounted for by the through bond interaction. However, when the p‐content in the lone pair orbitals naand nbdecreases, one may have the reverse orbital energy order: ng

ISSN:0009-4536    

DOI:10.1002/jccs.199600053

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY