摘要:

AbstractThe author's chemical studies dealing with the generation of carbonyl ylides via the rhodium(II) induced cyclization of α‐diazo alkanediones are summarized, Dipole formation occurs by reaction of a transient rhodium carbenoid intermediate with a neighboring carbonyl group. These cyclizations are performed under extremely mild conditions, typically at room temperature in a neutral organic solvent. Since these cycloadditions involve carbonyl ylides, the resulting products are oxabicycles of varying ring size. When the dipolarophile is intramolecularly tethered to the dipole, the subsequent cycloaddition affords complex oxapolycyclic systems with three (or more) component rin

ISSN:0009-4536    

DOI:10.1002/jccs.199300016

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractA program for neural networks was developed to evaluate many vibrational energies of harmonic oscillators, Morse oscillators and diatomic molecules. The tests of all the vibrational levels of SiH (A state) and HF (B state) withvmaxequal to 8 and 31, respectively, yielded results in excellent agreement with semi‐empirical Morse results. The program was also applied to the three vibrational modes of H2O accuratel

ISSN:0009-4536    

DOI:10.1002/jccs.199300017

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractPolycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorinated Pesticides (OCPs) on different absorbents were extracted and analyzed by a directly coupled supercritical fluid extraction and supercritical fluid chromatography system (on‐line SFE/SFC). The influence of various absorbents as sample matrixes on extraction efficiencies was evaluated. In general, the extraction efficiencies were decreased if a matrix had a larger surface area and a smaller pore size. The recoveries of PAHs and PCBs were decreased in inverse proportion to their molar mass. Recoveries of OCPs containing epoxy functional groups were greater than for OCPs lacking this functional group. In conclusion, online SFE/SFC is a rapid (1‐2 h) and high recovery (70%‐100%) analytical tech

ISSN:0009-4536    

DOI:10.1002/jccs.199300018

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractMethods are described for the determination of chlorinated hydrocarbons at levels of parts per billion in water and nonaqueous environmental samples by gas chromatography with electron‐capture detection. C18, Florisil, alumina N and silica Sep‐Pak cartridges were compared to evaluate their cleanup ability. The accuracy of the results of this analytical technique was proved by the analysis of a certified reference material (lake sediment EC

ISSN:0009-4536    

DOI:10.1002/jccs.199300019

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractSilicon phthalocyanines and silicon naphthalocyanines, which are two derivatives in the family of hematoporphyrin, have been synthesized to assess their potential as photosensitizers for photodynamic therapy. For these complexes the red shift of their Q‐band maximum absorption tends to depend on the nature of the axial substituent. The bimolecular rate coefficients for the interacting between photosensitizer, either SiNC or SiPC, and generated singlet molecular oxygen were determined from the time‐resolved emission spectrum of singlet oxygen at 1.27 μm. On the basis of these data the electron‐transfer quenching mechanism is discussed in relation to the Marcus

ISSN:0009-4536    

DOI:10.1002/jccs.199300020

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe benzene‐mediated iodine intercalation into the pseudo‐layered superconductor Bi2Sr1.8Ca1.2Cu2Ox(2212) is an efficient way to prepare an intercalate with nominal composition IBi2Sr1.8Ca1.2Cu2Ox. Expansion by 22 percent along the crystallographic c‐axis was observed but botha‐and b‐axes of the intercalates remained unchanged. The superconducting temperature (Tc) of 2212 phase decreased 10 K upon iodine intercalation. We report the First solvent‐mediated intercalation reaction and preliminary characterizations of a presumably stage‐1 phase IBi2Sr

ISSN:0009-4536    

DOI:10.1002/jccs.199300021

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe reactions of Fe(CN)5dpa3−and Ru(NH3)5dpa2+(dpa = 4,4′‐dipyridylamine) with Co(edta)−have been investigated kinetically. For Fe(CN)5dpa3−complex, a linear relationship was observed between the pseudo‐First‐order rate constants and the concentrations of Co(edta) which leads to a specific rate 0.876 ± 0.006 M−1S−1at T = 25°C., μ = 0.10 M and pH = 8.0. For the Ru(NH3)5dpa2+system, the plots kobsvs [Co(edta)−] become nonlinear at concentrations of Co(edta) greater than 0.01 M and the reaction is interpreted on the basis of a mechanism involving the formation of an ion pair between Ru(NH3)5dpa2+and Co(edta)−followed by electron transfer from Ru(II) to Co(III). The nonlinear least squares fit of the kinetic results shows that Qip= 10.6 ± 0.7 M−1and ket= 93.9 ± 0.7 s−1atpH

ISSN:0009-4536    

DOI:10.1002/jccs.199300022

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe title hydrocarbon 3, a C14H14tetracyclic tetraene of C2v‐symmetry, was synthesized by new routes starting from 1,8,9,10‐tetrachloro‐11,11‐dimethoxytricyclo[6.2.1.02,7]undeca‐3,5,9‐triene (1). The Diels‐Alder cycloaddition of 1 with 2‐chloroacrylyl chloride, a ketene equivalent, followed by subsequent reduction, dechlorination and deacctalization afforded the ketol 12 as a key intermediate. Elaboration of target compound 3 was carried out by either the method of ring enlargement of 12 or (better) the route of Diels‐Alder reaction of decarbonylated 12 withtrans‐1,2‐bis(phenylsulfonyl)ethcnc, an acetylene equivalent, to give trienol 17, followed by dehydration. Upon irradiation, 3 underwent intercyclic [2 + 2]‐addition to caged hexacyclic diene 4. At 120°C, 3 decomposed into barrelene an

ISSN:0009-4536    

DOI:10.1002/jccs.199300023

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractEnantioselective synthesis of optically active β‐lactam via ester enolate‐imine condensation using homochiral ester 16 and imine 17 provided β‐lactam 18a in 77% cc. Lactam 18a, carried C(3) functionality on β‐lactam nuclei, provided a potential precursor toward a synthesis of dipeptide

ISSN:0009-4536    

DOI:10.1002/jccs.199300024

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

Abstract4‐Arylpyridines 5 that contain electron‐withdrawing groups such as nitrile, methyl ester, fluoride, and trifluoromethyl on the benzene ring were synthesized in moderate yields (29‐63%) by reaction of mixed copper, zinc aryl organometallics 1 with various 1‐(ethoxycarbonyi)pyridinium chlorides 2 followed byo‐chloranil oxidization under reflux i

ISSN:0009-4536    

DOI:10.1002/jccs.199300025

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY