Search results for " molecule"

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- (FeFe)

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:35-η-bicyclo[6.1.0]nonatriene)hexacarbonyldiiron(FeFe). 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 …

ChemInform Abstract: An Easy Access to Fused Chromanones via Rhodium Catalyzed Oxidative Coupling of Salicylaldehydes with Heterobicyclic Olefins.

2016

Diazabicyclic and urea-derived bicyclic olefins react with salicylaldehydes to produce various types of fused chromanone systems of biological interest in a single step (mechanism).

How far the substituent effects in disubstituted cyclohexa-1,3-diene derivatives differ from those in bicyclo[2.2.2]octane and benzene?

2018

Substituents effects in cyclic diene derivatives are studied using quantum chemical modeling and compared to the corresponding effects in aromatic (benzene) and fully saturated (bicyclo[2.2.2]octane) compounds. In particular, electronic properties of the fixed group Y in a series of 3- and 4-X-substituted cyclohexa-1,3-diene-Y derivatives (where Y = NO2, COOH, COO− OH, O−, NH2, and X = NMe2, NH2, OH, OMe, Me, H, F, Cl, CF3, CN, CHO, COMe, CONH2, COOH, NO2, NO) are examined using the B3LYP/6-311++G(d,p) method. For this purpose, quantum chemistry models of the substituent effect: cSAR (charge of the substituent active region) and SESE (substituent effect stabilization energy) as well as trad…

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 …

Hybrid molecular materials formed by alternating layers of bimetallic oxalate complexes and tetrathiafulvalene molecules: Synthesis, structure, and m…

1996

Cycloaddition reactions of 3-vinylthiophen

1987

Abstract Cycloaddition reactions between 3-vinylthiophen and the dienophiles maleic anhydride, methyl acrylate, dimethyl acetylene - dicarboxylate, and methyl propiolate give products including methyl benzo[b]thiophen-7-carboxylate (11) and its dihydroderivative (10), the 6,7-dicarboxylic acid (3), its dimethyl ester (7) and dihydroester (6); the naphtho[a,b]dithiophen (14), and the novel ethano bridged benzo[b]thiophen (15).