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1.
2.
The geminal regioselectivity observed in the ene reaction between singlet oxygen and alkenes with anion-stabilizing groups is rationalized on the basis of a perepoxide intermediate, in which in analogy to the nucleophilic attack on protonated epoxides, the perepoxide is opened preferentially at the C---O bond weakened by the substituent. 相似文献
3.
Substituted norbornenes and dibenzobarrelene react under forced conditions with -methyl-1,2,4-triazolin-3,5-diones to afford urazoles via (2+2)-cycloaddition. 相似文献
4.
The complexation of tetramethylresorc[4]arene with primary and secondary amines in acetonitrile was investigated spectrophotometrically. The stoichiometry of the complexes formed was shown to depend on the amine concentration. Based on the proposed complexation models, the formation constants of the complexes as well as their thermodynamical parameters were determined and discussed. Depending on the amine concentration, two types of solid complexes of tetramethylresorc[4]arene with amines were obtained. The composition of these complexes was confirmed by 1H NMR. 相似文献
5.
PHOTOCHEMISTRY and PHOTOBIOLOGY WITHOUT LIGHT 总被引:3,自引:0,他引:3
Abstract— This review covers the literature since 1980 on chemically and enzymatically generated electronically excited species. The emphasis lies on triplet states of carbonyl products that are derived from dioxetanes and dioxetanones as precursors or from suitable enzymatic oxygenations. Singlet oxygen, an important excited state species in biological processes, is not explicitly treated. The utilization of triplet excited carbonyl products to promote photochemical and photobiological transformations by energy transfer are of primordial interest and not the photomechanistic behavior, photophysical properties and inherent photochemical reactions of such excited state species. Thus, the coverage concentrates on photodamage of DNA and RNA, the photochemistry of flavins, vitamin D, tryptophan, arachidonic acid, chlorophyll, lipid peroxidation, urocanase activation, excitation of chlorophlasts, and the aerobic oxidation of Schiff bases derived from amino acids and proteins. The potential perspectives of employing authentic dioxetanes and enzymatically generated dioxetane intermediates as effective photon equivalents in photochemotherapy, phototoxicity, photoaffinity labeling and photogenotoxicity are pointed out, in the hope of stimulating more intensive activity in this emerging and novel bioorganic and photobiological field. 相似文献
6.
Tetraphenylporphyrin-sensitized photooxygenation of 2-methyl-5-trimethylsilylfuran () affords quantitatively trimethylsilyl 2-oxo-4-pentenoate (), presumably via intramolecular Baeyer-Villiger rearrangement of the intermediary dioxirane (). 相似文献
7.
Waldemar Adam 《Angewandte Chemie (International ed. in English)》1974,13(10):619-627
The photodecarboxylation of malonyl peroxides into α-lactones[1] and the thermal conversion of the 1,4-endo-peroxide 4,5-epoxy-3,6-epidioxy-1-cyclohexene into the novel benzene trioxide[2] are two recent examples of the potential of cyclic peroxides in the synthesis of unusual organic molecules. The former transformation entails a fragmentation, the latter a rearrangement process. Most reported examples fall into one of these two gross reaction types. Of the numerous examples that have been reported in the literature during the last two decades, only those shall be focused on that lead to unusual compounds or constitute efficient syntheses of known compounds, in order to stress the convenience of cyclic peroxides in the synthesis of organic compounds. 相似文献
8.
A micro determination for free uronic acids based on Tollens' reaction is proposed. Sources of error in earlier methods are avoided by the use of phosphoric acid, a reagent solution in glacial acetic acid, and extraction of the dye with toluene. Free glucuronic acid can be determined in presence of glucuronosides of the phenol-ether type up to molar ratios of ca. 1 : 5. Reliable results can also be obtained in the presence of other carbohydrates. 相似文献
9.
Kazimierz?DarowickiEmail author Waldemar?Felisiak Artur?Zieliński 《Journal of mathematical chemistry》2005,38(4):701-711
Oscillations of species concentration are phenomena accompanying several types of electrochemical and purely chemical processes.
Importance of analyzing of such processes results from both scientific and practical reasons. In the paper the authors deal
with investigation of time dependent spectra of various stages of Belousov-Zhabotinsky type chemical oscillations. As the
analytical tool the discrete wavelet transform is proposed. 相似文献
10.
Photo-extrusion of nitrogen from the azoalkane 1 in the presence of molecular oxygen gave besides the hydrocarbons 3 and 5, the endoperoxide 10 and hydroperoxide 11, the former via trapping of the 1,4-diradical 4 by triplet oxygen, the latter by ene-reaction-6f hydrocarbon 5 with singlet oxygen. 相似文献