Search results for "cyclic"
showing 10 items of 2439 documents
ChemInform Abstract: Dienediolates of Unsaturated Carboxylic Acids in Synthesis. Synthesis of Cyclohexenones and Polycyclic Ketones by Tandem Michael…
2010
Abstract Substituted 2-cyclohexenones 4 to 7 and hexaxydronaphthalenones and hexahydroindenones 13 to 18 are prepared by tandem Michael-Dieckmann addition of lithium dienediolates of acyclic and alicyclic unsaturated carboxylic acids to the lithium salts of the same or other unsaturated carboxylic acids.
Dienediolates of unsaturated carboxylic acids in synthesis. Synthesis of cyclohexenones and polycyclic ketones by tandem Michael-Dieckmann decarboxyl…
1994
Abstract Substituted 2-cyclohexenones 4 to 7 and hexaxydronaphthalenones and hexahydroindenones 13 to 18 are prepared by tandem Michael-Dieckmann addition of lithium dienediolates of acyclic and alicyclic unsaturated carboxylic acids to the lithium salts of the same or other unsaturated carboxylic acids.
Asymmetric Synthesis of Spirobenzazepinones with Atroposelectivity and Spiro-1,2-Diazepinones by NHC-Catalyzed [3+4] Annulation Reactions
2016
A strategy for the NHC-catalyzed asymmetric synthesis of spirobenzazepinones, spiro-1,2-diazepinones, and spiro-1,2-oxazepinones has been developed via [3+4]-cycloaddition reactions of isatin-derived enals (3C component) with in-situ-generated aza-o-quinone methides, azoalkenes, and nitrosoalkenes (4atom components). The [3+4] annulation strategy leads to the seven-membered target spiro heterocycles bearing an oxindole moiety in high yields and excellent enantioselectivities with a wide variety of substrates. Notably, the benzazepinone synthesis is atroposelective and an all-carbon spiro stereocenter is generated.
Reductive transformations - 11. stereoselective cycloannelation and bridging of the cyclooctatetraene dianionMakromol. Chem., Rapid. Commun. 1988, 9,…
1988
Abstract Bifunctional electrophiles with C4-, C6-, and C8-chains are reacted with the cyclooctatetraene dianion to selectively give novel cycloannelation and bridging products which possess a surprising stereochemistry and are useful starting compounds for further syntheses.
Synthesis of bi- and tricyclic β-lactam libraries in aqueous medium
2007
Water as a solvent is not only inexpensive and environmentally benign, but may allow good reactivity. The present work focuses on the application of a modified Ugi reaction, i.e. the Ugi four-centre three-component reaction (U-4C-3CR), in aqueous medium to construct β-lactam libraries. All the attempted reactions could be successfully performed in water. The reaction conditions under which the precipitation process was effective were investigated; no further work-up or purification was necessary. In several cases when less water-soluble β-amino acids were used, the precipitated products were isolated easily by simple filtration. In other cases, evaporation of the solvent was appropriate for…
Synthesis of various natural 8,12-elemanolides from artemisin
1989
Abstract This paper describes the chemical transformations of artemisin into various natural 8,12-elemanolides.
Mandelamide-zinc-catalyzed enantioselective alkyne addition to heteroaromatic aldehydes.
2006
The (S,S)-mandelamide III catalyzes the additions of both aryl- and alkylalkynylzinc reagents to heteroaromatic aldehydes with good yields and enantioselectivities up to 92%. This catalyst is easily prepared in a one-step procedure, and both enantiomers are available. Unlike most other described methods, using this catalyst does not require the addition of Ti(O(i)Pr)4.
UHPLC-Orbitrap mass spectrometric characterization of organic aerosol from a central European city (Mainz, Germany) and a Chinese megacity (Beijing)
2018
Abstract Fine urban aerosol particles with aerodynamic equivalent dimeter ≤2.5 μm (PM2.5) were collected in Mainz (a city within the Rhine-Main area, the third largest metropolitan region in Germany) and Beijing (Chinese megacity). A solvent mixture of acetonitrile-water was used to extract the organic aerosol fraction (OA) from the particle samples. The extracts were analyzed by an ultrahigh resolution mass spectrometer (UHRMS) Orbitrap coupled with ultra-high-performance liquid chromatography (UHPLC) both in the negative and positive ion mode. The number of compounds observed in Beijing is a factor of 2–10 higher compared to Mainz. The clear differences on chemical composition of OA in th…
Struktur-Wirkungsbeziehungen bei Histaminanaloga, 14. Mitt. 4-Aminomethyl-benzimidazole und 9-Amino-naphth[1,2-d]imidazole
1977
Es wird die Darstellung der bicyclischen Histaminanaloga 4-Aminomethyl-benzimidazol (3a) und 4-Aminomethyl-4,5,6,7-tetrahydro-benzimidazol (3b) sowie der tricyclischen Analoga 9-Amino-6,7,8,9-tetrahydro-naphth[1,2-d]imidazol (6b) und 9-Amino-4,5,5a,6,7,8,9,9a-octahydro-naphth[1,2-d]imidazol (6c) beschrieben. 4-(Aminomethyl)benzimidazoles and 9-Aminonaphth[1,2-d]imidazoles Syntheses of the bicyclic histamine analogues 4-(aminomethyl)benzimidazole (3a) and 4-aminomethyl-4,5,6,7-tetrahydrobenzimidazole (3b) and of the tricyclic analogues 9-amino-6,7,8,9-tetrahydronaphth[1,2-d]imidazole (6b) and 9-amino-4,5,5a,6,7,8,9,9a-octahydronaphth[1,2-d]-imidazole (6c) are described.