Search results for "stereo"
showing 10 items of 6147 documents
An exclusive approach to 3,4-disubstituted cyclopentenes and alkylidene cyclopentenes via the palladium catalyzed ring opening of azabicyclic olefins…
2013
A simple and efficient method for the stereoselective ring opening of bicyclic hydrazines with various aryl halides under palladium catalysis has been elaborated. The reactions afforded trans-3,4-disubstituted cyclopentenes or alkylidene cyclopentenes in good to excellent yields. By taking advantage of multiple points of functionalization in the synthesized trans-3-phenyl-4-hydrazino-cyclopentene, we have synthesized the antidepressant Cypenamine (trans-2-phenylcyclopentylamine).
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]…
Synthesis and Redox Behaviour of the Chalcogenocarbonyl Dianions, [(E)C(PPh2S)2]2−: Formation and Structures of Chalcogen−Chalcogen Bonded Dimers and…
2010
The lithium salts of the chalcogenocarbonyl dianions [(E)C(PPh(2)S)(2)](2-) (E=S (4 b), Se (4 c)) were produced through the reactions between Li(2)[C(PPh(2)S)(2)] and elemental chalcogens in the presence of tetramethylethylenediamine (TMEDA). The solid-state structure of {[Li(TMEDA)](2)[(Se)C(PPh(2)S)(2)]}-[{Li(TMEDA)}(2)4 c]-was shown to be bicyclic with the Li(+) cations bis-S,Se-chelated by the dianionic ligand. One-electron oxidation of the dianions 4 b and 4 c with iodine afforded the diamagnetic complexes {[Li(TMEDA)](2)[(SPh(2)P)(2)CEEC(PPh(2)S)(2)]} ([Li(TMEDA)](2)7 b (E=S), [Li(TMEDA)](2)7 c (E=Se)), which are formally dimers of the radical anions [(E)C(PPh(2)S)(2)](-) (.) (E=S (5 …
Formation of Pyrazol-1,3,4-Thiadiazoles through 1,3-Dipolar Cycloadditions of 3-Thioxo-[1,2,4]-Triazepin-5-one with Nitrilimines: An Experimental and…
2009
In this work the results of experimental and computational study of the title compounds and some ancillary compounds are reported. Two bicyclic pyrazol-1,3,4-thiadiazole derivatives were synthesized by reaction between 6-dimethylaminomethylene-3-thioxo-[1,2,4]- triazepin-5-one 1 and several nitrilimines 2a-f to give corresponding spirocycloadducts 3a-f, which undergo a rapid rearrangement leading to the new bicyclic compounds, 4a-f and 5a-f. These obtained bicyclic products were characterized by 1H and 13C NMR spectroscopy and finally by X-ray crystallography. Theoretical calculations have been carried out using DFT methods to rationalize the formation of the two new bicyclic compounds. Two…
Stereoselective Synthesis of Polycyclic Thiopyrans
2012
The reaction of benzothiete (1) and the bicyclic alkenes 5, 7, 9, or 12 shows a very high π side selectivity (de > 95%) in the formation of the polycyclic thiopyrans 6, 8, 10, 11, 13, and 14.
PHOSPHORORGANISCHE VERBINDUNGEN 1081DIE SYNTHESE FLUORESZIERENDER UND CHEMOSELEKTIVER REAGENTIEN ZUM GEZIELTEN NACHWEIS UND SCHUTZ BIOLOGISCH WICHTIG…
1984
Abstract Compounds of type A are fluorescent, if the donator groups, like NMe2, OMe, SMe and PR2, and the acceptor groups, like R′P(O)X, SO2R′ and CO2R′, are linked to different nuclei of the naphthalin ring system.
Stereocontrolled synthesis of azeto[2,1-b] quinazolines bearing three stereocenters via the intramolecular [2+2] cycloaddition between ketenimines an…
2004
Abstract A highly stereoselective synthesis of azeto[2,1- b ]quinazolines bearing three stereocenters (C1, C2, and C8) has been achieved via intramolecular [2+2] cycloaddition between ketenimine and imine functions supported on an ortho -benzylic scaffold. An asymmetric center adjacent to the iminic nitrogen atom, the future C8 carbon of the bicyclic product, efficiently controls the absolute configuration of the two new stereogenic carbon atoms of the azetidine ring, C1 and C2.
Ring transformation of furfural into an unusual bicyclic system: Characterisation and dynamic stereochemistry of 6,7-diethoxycarbonyl-6,7-diaza-8-oxa…
1997
Abstract 2-Formylthiophene and 3-formylindole react with diethyl azodicarboxylate to give simple products derived from reactions on the formyl group whereas 2-formylfuran reacts to give the unexpected bicyclic title compound. 1 H and 13 C NMR studies indicate that this compound undergoes a series of three dynamic conformational changes over the temperature range 50 to −90°C which are ascribed to slow rotation about the exocyclic carbamate bonds and hindered bridge inversion.