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1.
Treitel N Eshdat L Sheradsky T Donovan PM Tykwinski RR Scott LT Hopf H Rabinovitz M 《Journal of the American Chemical Society》2006,128(14):4703-4709
Various cross-conjugated enediynes undergo "Bergman-type" cycloaromatizations upon reduction with potassium metal, generating anions of fulvenes and fulvalene derivatives. This new anionic cyclization is considerably more facile than the classic Bergman cyclization with linear enediynes, creating highly reactive diradicals at -78 degrees C. Not all cross-conjugated enediynes yield cyclized dianions upon reduction; some give uncyclized, Y-shaped, cross-conjugated dianions, while others apparently yield radical-anions that either dimerize or persist as monomers. One system yields both a cyclized and an uncyclized dianion. The substituents are thus shown to be a critical factor in determining the outcome of the reduction. Cyclization occurs within a specific "window of opportunity" that is governed by the substituents. 相似文献
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Dan Veierov Tuvia Bercovici Ernst Fischer Yehuda Mazur Amnon Yogev 《Helvetica chimica acta》1975,58(4):1240-1243
Enol-esters 1a-1e undergo clean Photo-Fries-rearrangements without side reactions. With anthroyl derivatives the reaction is observed only at 254 nm, not at 366 nm. 相似文献
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The computation of the imaginary Delbrück amplitudes with the formulae of Constantini et al. gave results whose accuracy is greater by a factor of 10 than that available in the literature. The real amplitudes were computed using the code of Papatzacos and Mork. This computation was extended to all angular and energy regions of interest, and hence may be very useful in the interpretation of scattering experiments. 相似文献
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Several aspects of the time-dependent-thermal-lensing (TDTL) technique were explored experimentally, including pressure effects, risetime behavior and falltime behavior. The experiments were performed using azulene vapor excited to high vibrational energies (≈ 17000 cm?1). It was found that the energy appears in translational degrees of freedom at very early times, but the intrinsic limitations of the technique permitted only an estimate of the V-T rate constant for excited azulene deactivation by krypton. The result is discussed in terms of other recent experiments, and it is tentatively concluded that deactivation of excited azulene by unexcited azulene molecules may proceed primarily by a V-V process. 相似文献
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The reactions of phenylglyoxal hydrate with (R)-phenylglycinol and with (1S,2R)-norephedrine were investigated. The expected 2-benzoyloxazolidines 3 and 2a , respectively are initially formed, and undergo a fast, spontaneous stereospecific rearrangement to the corresponding 2-hydroxy-3-phenyl-5,6-dihydro-1,4-oxazines 4 and 5 respectively. The mechanism of this new rearrangement is discussed. The structures and stereochemistry of 4 and 5 were established by X-ray diffraction analysis. 相似文献
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Sarah Shtelzer Tuvia Sheradsky Jochanan Blum 《Journal of heterocyclic chemistry》1987,24(6):1581-1585
The reactions of phenanthrene 9,10-imine ( 1 ) with aromatic aldehydes, benzoic acids and acetylenedi-carboxylic esters were investigated. The aldehydes were shown to give 1-[N-(arylmethylidene)-9-phenanthreneamine-10-yl]-1a,9b-dihydrophenanthro[9,10-b]azirine 2. The ‘dimeric’ structure of these products was established by X-ray diffraction analysis. The carboxylic acids proved to form in the presence of dicyclohexylcarbodiimide, N-aroylphenanthrene 9,10-imines 7 , that readily undergo rearrangement to N-aroyl-9-phenanthrenamines 8. Esters of acetylenedicarboxylic acid gave the corresponding esters of (Z)-2-(1a,9b-dihydrophenanthro[9,10-b]azirine-1-yl)-2-butendioic acid 10 . 相似文献
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Ivan Aprahamian HermannA. Wegner Tamar Sternfeld Karsten Rauch Armin deMeijere Tuvia Sheradsky LawrenceT. Scott Mordecai Rabinovitz 《化学:亚洲杂志》2006,1(5):678-685
A series of pyrene‐based polycyclic aromatic compounds, indeno[cd]pyrene, diindeno[cd,fg]pyrene, diindeno[cd,jk]pyrene, tris‐(tert‐butylindeno[cd,fg,jk])pyrene, and tetrakis‐(tert‐butylindeno[cd,fg,jk,mn])pyrene, were reduced with alkali metals in [D8]tetrahydrofuran, and the resulting anions were studied by NMR spectroscopy. It was found that the diatropic character of the dianions obtained depends on the number of annulated indeno groups. When one such group is present, a paratropic dianion is obtained, which is similar to the dianion of the parent pyrene; the effect, however, is weak. When more indeno groups are annulated, the dianions become diatropic owing to the greater number of five‐membered rings that can acquire aromatic character as a result of reduction. The 1H NMR chemical shifts of tetrakis‐(tert‐butylindeno[cd,fg,jk,mn])pyrene in the neutral state show an interesting dependence on concentration that reflects an association of the molecules in solution by π stacking. This phenomenon was not observed for the reduced species. The trianion radicals of tris‐(tert‐butylindeno[cd,fg,jk])pyrene and tetrakis‐(tert‐butylindeno[cd,fg,jk,mn])pyrene undergo reductive dimerization and form bilayered hexaanions. 相似文献
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The reaction of mesoionic 4-thiazolones with ethyl azidoformate (at 130°) gave 5-(ethoxy-carbonylthio)-1-imidazolin-4-ones, probably via a bicyclic nitrene-mesoion adduct. 相似文献