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121.
Natural products have been synthesized for billions of years in animals, plants, and microorganisms. As a rule they occur enantiomerically pure. Their chiral character corroborates their use in metabolism or as biologically active agents. Natural products may be insufficient in quality or quantity. They have recently begun to become accessible, either unchanged or modified, by biological synthesis; here, too, they are obtained enantiomerically pure. In the last twenty years chemical synthesis has become a major concern of organic chemists. Their target compounds are primarily enantiomerically pure natural products or biologically active variants thereof. 相似文献
122.
Schiefer M Reddy ND Ahn HJ Stasch A Roesky HW Schlicker AC Schmidt HG Noltemeyer M Vidovic D 《Inorganic chemistry》2003,42(16):4970-4976
The syntheses of the ionic compounds [Li(+).2 dioxane (2,6-iPr(2)C(6)H(3)N(SiMe(3))Al(C triplebond CSiMe(3))(3))(-)].0.75 dioxane (1), [(Li(+))(2).(dioxane)(7)](0.5) [2,6-iPr(2)C(6)H(3)N(SiMe(3))Ga(C triplebond CSiMe(3))(3)(-)].1.5 dioxane (2), and [(Li(+))(2).(dioxane)(7)](0.5) [2,6-iPr(2)C(6)H(3)N(SiMe(3))In(C triplebond CSiMe(3))(3)(-)].1.5 dioxane (3) by the reaction of the corresponding organo metal chloride with LiC triplebond CSiMe(3) are reported. The neutral ethynyl compounds Br-Al(C triplebond CtBu)(2).2 THF (4), Cl-Ga(C triplebond CtBu)(2).THF (5), Cl-In(C triplebond CtBu)(2).2 THF (6), Al(C triplebond CtBu)(3).C[N(Me)CMe](2) (7), Ga(C triplebond CtBu)(3).dioxane (8), and In(C triplebond CtBu)(3).NEt(3) (9) have been obtained in good yields from the reaction of AlBr(3), GaCl(3), and InCl(3) with LiC triplebond CtBu in the presence of a Lewis base. Compound 7 is the first heterocyclic carbene substituted ethynyl derivative. Aluminum and gallium compounds with three terminal ethynyl groups Al(C triplebond CPh)(3).NMe(3) (10) and Ga(C triplebond CPh)(3).NMe(3) (11) have been prepared by the reaction of AlH(3).NMe(3) or GaH(3).NMe(3) with three equivalents of phenylethyne. All the above-mentioned compounds have been structurally studied. In compound 1 the lithium ion is coordinated to the three terminal ethynyl groups, whereas in compounds 2 and 3 the lithium is coordinated to the solvent (dioxane). Compound 8 crystallizes as a coordination polymer with dioxane molecules bridging the individual gallium units. 相似文献
123.
The complex generated from 1/2[Ir(OMe)(cod)]2 and 4,4'-di-tert-butyl-2,2'-bipyridine catalyzes the regioselective borylation of ferrocenes, CpMn(CO)3 and CpMo(CO)3CH3 with a stoichiometric amount of B2pin2. 相似文献
124.
Ultrasound was found to increase the rate of hydrolysis of a series of esters by up to 15%. No effect of molecular structure upon this enhancement was observed. 相似文献
125.
Bicyclo[2.2.1]-2,5-heptadiene complexes of transition metal carbonyls have been treated with organometallic phosphines, to give the disubstituted compounds [(R3M′)3P]2M(CO)4 [R = CH3; M′ = Ge, Sn; M = Cr, Mo, W] by exchange of ligands. The chemical and spectroscopic properties of the new compounds are reported. 相似文献
126.
Zusammenfassung Die neben dem Monosubstitutionsprodukt bei der direkten Mercurierung von Cymantren entstehenden Di-(chlormercuri)-cymantrene lassen sich glatt zu den entsprechenden Dijodverbindungen umsetzen. Die Konstitutionszuordnung der Dijodcymantrene (- und -Isomeren) erfolgte nach Auftrennung mit Hilfe der an1, 2 und3 gemessenen Dipolmomente: Dem höher schmelzenden Isomeren kommt die -Konstitution zu. DieIR- undNMR-Daten der genannten Verbindungen werden mitgeteilt.
Unserem verehrten Lehrer, Herrn Prof. Dr.J. W. Breitenbach, zum 60. Geburtstag gewidmet.
Cymantren = Cyclopentadienyl-mangan-tricarbonyl.
4. Mitt.:H. Gowal undK. Schlögl, Mh. Chem.99, 972 (1968). 相似文献
Di-(chlormercuri)-cymantrenes obtained along with monosubstituted product were converted to the di-iodocymantrenes and the latter separated into the - and -isomers. Based on measurement of the dipol moments of1, 2, and3 the -structure was attributed to the higher melting isomer.IR- andNMR-data are presented.
Unserem verehrten Lehrer, Herrn Prof. Dr.J. W. Breitenbach, zum 60. Geburtstag gewidmet.
Cymantren = Cyclopentadienyl-mangan-tricarbonyl.
4. Mitt.:H. Gowal undK. Schlögl, Mh. Chem.99, 972 (1968). 相似文献
127.
We investigate the stationary nonequilibrium (heat transporting) states of the Lorentz gas. This is a gas of classical point particles moving in a region gL containing also fixed (hard sphere) scatterers of radiusR. The stationary state considered is obtained by imposing stochastic boundary conditions at the top and bottom of , i.e., a particle hitting one of these walls comes off with a velocity distribution corresponding to temperaturesT
1 andT
2 respectively,T
1 <T
2. Letting be the average density of the randomly distributed scatterers we show that in the Boltzmann-Grad limit,,R 0 with the mean free path fixed, the stationary distribution of the Lorentz gas converges in theL
1-norm to the stationary distribution of the corresponding linear Boltzmann equation with the same boundary conditions. In particular, the steady state heat flow in the Lorentz gas converges to that of the linear Boltzmann equation, which is known to behave as (T
2-T
1)/L for largeL, whereL is the distance from the bottom to the top wall: i.e., Fourier's law of heat conduction is valid in the limit. The heat flow converges even in probability. Generalizations of our result for scatterers with a smooth potential as well as the related diffusion problem are discussed.Research supported in part by NSF Grant no. Phy 77-22302.On leave of absence from the Fachbereich Physik der Universität, München. Work supported by a DFG fellowship. 相似文献
128.
Victoria V. Lipson Irina V. Ignatenko Sergey M. Desenko Svetlana V. Shishkina Oleg V. Shishkin Sergey A. Komykhov Natalya V. Logvinenko Valery D. Orlov Herbert Meier 《Journal of heterocyclic chemistry》2003,40(6):1081-1086
The reaction of 5,7‐diphenyl‐4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidine ( 1 ) with α,β‐unsaturated carbonyl compounds 2a‐f led to the formation of the alkylated heterocycles 3a‐f (Figure 1). However, the reaction of 5‐methyl‐7‐phenyl‐4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidine ( 5 ) with 2a‐c yielded under the same conditions the triazolo[5,1‐b]quinazolines 6a‐c (Figure 3). In this case, the alkylation is followed by a cyclocondensation. The structure elucidation of the products is based on ir, ms, 1H and 13C nmr measurements and on an X‐ray diffraction study. 相似文献
129.
Starting from activated benzoxazines 1 and 2 new synthetic pathways to the tricyclic compounds 4, 9, 12 and 16 are described. Reaction of the hydrazides 17a,b with thionylchloride leads to the novel thiatriazolo-benzoxazines 18a,b . 相似文献
130.
Kurt Egger 《Fresenius' Journal of Analytical Chemistry》1961,182(3):161-166
Zusammenfassung 14 Glykoside der Aglykone Kaempferol, Quercetin und Myricetin werden auf ihr Verhalten im Perlon-Dünnschichtchromatogramm geprüft. Es wird gezeigt, daß 3-Monoside, 3-Bioside und 3,7-Glykoside scharf voneinander getrennt werden und an den stark verschiedenen Rf-Werten erkannt werden können. Der Einfluß des Aglykons ist gering; der entscheidende Faktor für den Rf-Wert ist die Glykosidierung.
Herrn Prof. Dr. L. Hörhammer, Herrn Doz. Dr. H. Wagner und Herrn Dr. W. Leeb, München, danke ich sehr für die freundlicherweise erteilte praktische Einführung in die Polyamid-Dünnschichtchromatographie, sowie für die Überlassung einer Probe von Kaempferol-3-rhamnoglucosid. Die Durchführung der hier dargestellten Versuche hielt sich eng an die in den Münchner Laboratorien entwickelten Verfahren.
Die Untersuchungen wurden von der Görres-Gesellschaft zur Pflege der Wissenschaften und von der Deutschen Forschungsgemeinschaft gefördert, wofür an dieser Stelle gedankt sei. Der BASF Ludwigshafen danke ich für die großzügige Überlassung des Polyamids. 相似文献
Summary 14 glycosides of the aglycons quercetin, kaempferol and myricetin were examined for their behaviour in chromatography with polyamide. The results show that the 3-monosides can be easily differentiated from the 3-biosides, as well as from both the 3,7-glycosides, by their sharply different Rf-values. The influence of the aglycon is small; the decisive factor for the Rf-value is the glycosidation.
Herrn Prof. Dr. L. Hörhammer, Herrn Doz. Dr. H. Wagner und Herrn Dr. W. Leeb, München, danke ich sehr für die freundlicherweise erteilte praktische Einführung in die Polyamid-Dünnschichtchromatographie, sowie für die Überlassung einer Probe von Kaempferol-3-rhamnoglucosid. Die Durchführung der hier dargestellten Versuche hielt sich eng an die in den Münchner Laboratorien entwickelten Verfahren.
Die Untersuchungen wurden von der Görres-Gesellschaft zur Pflege der Wissenschaften und von der Deutschen Forschungsgemeinschaft gefördert, wofür an dieser Stelle gedankt sei. Der BASF Ludwigshafen danke ich für die großzügige Überlassung des Polyamids. 相似文献