Search results for "cyclic"
showing 10 items of 2439 documents
Coordinating properties of the Cephalexine antibiotic. A potentiometric study of the complexes formation between Cephalexine and Co(II), Ni(II) and C…
1989
Abstract The formation of complexes between Co(II), Ni(II) and Cu(II) with Cephalexine has been investigated using potentiometric techniques. The stability constants of the complexes formed were calculated using the non-linear least-squares computer program SUPERQUAD. The obtained values were: Co(II) logβ1=2.40, logβMLOH=8.89; Ni(II) logβ1=2.80, logβ2=5.10, logβML2OH=12.09; Cu(II) logβ1=4.094 (25 °C, 0.1 M KNO3). The compound [Ni(CEX)(OH2)4]BPh4 has been synthesized and characterized by electronic, IR and NMR spectroscopies as well as by magnetic measurements. From these studies it is proposed that the Cephalexinate anion acts as a bidentate ligand and is bound to the metal ion through the …
New Reactions of Amino-Functionalized 3-Vinyl-1H-indoles and Tetrahydropyridin-4-yl Analogues with Dienophiles
1991
Reactions of 3-[2-(morpholin-4-yl)vinyl]-1H-indole (1), the 1,2-dihydro-9H-carbazole 2, as well as the 3-(tetrahydropyridin-4-yl)-1H-indoles 3a and 3b with some carbo- and heterodienophiles are described. The scope and limitations of the synthetic utility of these amino- (or homoamino)-functionalized 3-vinyl-1H-indoles are reported and some MO calculations for the qualitative prediction of their reactivities are presented. The reactions gave rise to substitution products, redox products, Diels-Alder adducts, ene adducts, and Michael-type adducts (Schemes 2 and 3).
Reactions of 3-(tetrahydropyrid-4-yl)-indoles with dienophiles: new heterocyclic functionalized indoles and pyrido[]annellated carbazoles
1991
First reactions of 3-(1,2,3,6-tetrahydropyrid-4-yl)-indoles 1 with a variety of carbo- and heterodienophiles are described. These reactions provide a new access to heterocyclic functionalized indoles and pyrido[c]annellated carbazoles, compounds of interest as potential antidepressive and antitumor active agents.
Chemical and Spectroscopical Properties of Medium Sizedtrans- andcis-Bicyclo[n.1.0]alk-2-ynes
1997
Chemical and spectroscopical properties of cis- and trans-cyclopropano-anellated cycloalkynes of medium ring size are investigated and compared with results from force field calculations. IR and 13C-NMR data of the alkynes reflect the deformation of the triple bond due to ring strain. Parallel to bending the reactivity increases with decreasing ring size, the trans fused alkynes prove to be nearly as reactive as the cis fused with a two carbon smaller ring size. The bicycloalkynes are complexed with silver triflate. 13C NMR reveals that the triple bond as well as the cyclopropane serve as ligands.
Synthetically attractive indolization processes and newer methods for the preparation of selectively substituted indoles
1988
The synthetically interesting processes available for indolization reactions are discussed and illustrated in tabular form and particular emphasis is placed on the more recent methods.
Arynic species; effect of substituents on the reactivity of monosubstituted dehydrobenzenes
1986
Abstract Evidence is presented demonstrating the existence of free dehydrobenzenes in the thermal decomposition of diaryliodonium-2-carboxylates, and that o-benzyne itself and its 4-methyl-, 4-chloro-,4-bromo- and 4-nitro-derivatives are generated from insoluble polymer-bound precursors and trapped by a second solid phase in Diels-Alder reactions. Lifetimes for these elusive species are determined.
ChemInform Abstract: Stereoselective Synthesis of Polycyclic Thiopyrans.
2012
Reactions of benzothiete (I) with bicyclic alkenes exhibit very high π-side selectivity in the formation of polycyclic thiopyrans.
1H and 13C NMR investigation of the fluxional behavior of η6-(bicyclo[6.1.0]Nona-2,4,6-triene)hexacarbonyldiiron- (FeFe)
1977
Abstract The variable temperature 1 H and 13 C NMR spectra of (C 9 H 10 )Fe 2 (CO) 6 have been recorded. The molecule is fluxional. The high temperature spectra indicate an apparent plane of symmetry bisecting the bound organic ligand, whereas the low temperature limiting spectra are entirely consistent with the asymmetric skew-type structure found in the crystal. Thus the molecule is also properly described in solution as μ-(2-σ,6,7-η:35-η-bicyclo[6.1.0]nonatriene)hexacarbonyldiiron(FeFe). Based on the observed line shape changes of the carbonyl resonances between −140 and −110°C, it is shown that the twitching and not the gliding process is responsible for the relative movement of the F…
(8,9-Dihydro-7H-imidazo[1,2-c][1,3]diazepin-5-yl)-cyanamide und homologe imidazo-bizyklen
1984
Die Reaktion der 2-(ω-Aminoalkyl)-imidazole 4a-f mit N-Cyanodiphenyl-imidocarbonat (7) fuhrt zu den entsprechend hydrierten Imidazo[1,5-a]imidazolen, Imidazo[1,2-c][1,3]diazepinen und Imidazo[1,2-c][1,3]diazocinen (9a-f), die im Verhalten gegenuber Nucleophilen und in ihren spektroskopischen Eigenschaften den (7,8-Dihydro-imidazo[1,2-c]pyrimidin-5-yl)-cyanamiden (3) [1] vergleichbar sind. The reaction of the 2-(ω-aminoalkyl)imidazoles 4a-f with N-cyanodi-phenylimidocarbonate (7) leads to appropriately hydrogenated imidazo-[1,5-a]imidazoles, imidazo[1,2-c][1,3]diazepines and imidazo[1,2-c][1,3]diazocines (9a-f), which are similar to (7,8-dihydroimidazo)[1,2-c]pyrimidin-5-yl)cyanamides (3)[1]…
On the mechanism of catalytic isomerization of xylenes. Molecular orbital studies
1979
Abstract On the basis of CNDO/2 molecular orbital calculations, we postulate the following detailed mechanism for the catalytic isomerization of xylenes which explains the initial product distributions and also our previous finding that the reaction is intramolecular: (i) adsorption of xylene on a surface acid site to form a Wheland-type complex; (ii) disrotatory cyclization of the protonated species into a bicyclo[3, 1, 0]hexenyl complex; (iii) migration of the methylene bridge to a new side of the pentagonal ring; (iv) change of the new bicyclic species back into the corresponding Wheland-type complex; (v) desorption of the xylene isomer from the surface of the catalyst. The overall rate …