Results 141 to 150 of about 132,796 (171)

Clean-up of polynuclear aromatic hydrocarbons and 3-ring azaarenes and their GC-analysis on whisker-walled open tubular columns

, 1984
A modified clean-up of polynuclear aromatic (PNA) hydrocarbons on XAD-2 is described. n-Alkanes (C16C28) are separated quantitatively from the PNA hydrocarbons and are eluted in one fraction.
T. Spitzer, W. Dannecker
semanticscholar   +1 more source

Methodologies for synthesis of heterocyclic compounds

, 1992
Among many naturally occurring biotoxins, tetrodotoxin (1) and its analogues have particularly provided quite interesting problems to us for developing synthetic methodologies suitable to these specific targets as well as to others for general solution ...
M. Isobe, T. Nishikawa, N. Yamamoto, T. Tsukiyama, A. Ino, T. Okita   +5 more
semanticscholar   +1 more source

Chromenes - A Novel Class of Heterocyclic Compounds: Recent Advancements and Future Directions.

Mini-Reviews in Medical Chemistry, 2022
Chromenes are an important class of oxygen-containing heterocyclic compounds with intriguing biological activity, a simple structure with mild adverse effects.
A. Chaudhary, Kalpana Singh, Nishant Verma, Sachin Kumar, Deepak Kumar, Prince Prashant Sharma   +5 more
semanticscholar   +1 more source

Novel Ruthenium(II) N‐Heterocyclic Carbene Complexes as Catalyst Precursors for the Ring‐Opening Metathesis Polymerization (ROMP) of Enantiomerically Pure Monomers: X‐ray Structures, Reactivity, and Quantum Chemical Considerations

, 2007
Four chiral, enantiomerically pure monomers, exo,exo-N,N-(norborn-5-ene-2,3-dicarbimido)-L-valine ethyl ester (exo-1),endo,endo-N,N-(norborn-5-ene-2,3-dicarbimido)-L-valineethyl ester (endo-1), exo,exo-N,N-(norborn-5-ene-2,3-dicarbimido)-L-valine-tert ...
M. Buchmeiser, Dongren Wang, Yan Zhang, S. Naumov, K. Wurst   +4 more
semanticscholar   +1 more source

Self-Assembly of Nitrogen-Rich Heterocyclic Compounds with Oxidants for the Development of High-Energy Materials.

ACS Applied Materials and Interfaces, 2021
The development of energetic materials with high energy and low sensitivity has attracted immense interests due to their widespread applications in aerospace technology and national defense.
Yue Zheng, Xiu-juan Qi, Si-tong Chen, Siwei Song, Yaping Zhang, Kangcai Wang, Qinghua Zhang   +6 more
semanticscholar   +1 more source

Synthesis and Anticancer Activity of Some Fused Heterocyclic Compounds Containing Pyrazole Ring

Polycyclic aromatic compounds (Print), 2020
5-Amino-1-phenyl-1H-pyrazole-4-carbohydraizde(1) was used as a key to synthesize new imidazopyrazol-5(1H)-one 5, pyrazolopyrimidines 7 and 9. Furthermore, imidazopyrazoles 13, 15, pyrazolopyridine 16 and pyrazolopyrazolopyridopyrimidine 17 were prepared ...
Aisha Y. Hassan, M. A. Mohamed, A. Abdel‐Aziem, A. O. Hussain   +3 more
semanticscholar   +1 more source

Computational investigation of the suitability of heterocyclic aromatic compounds with two heteroatoms in the 1 and 3 ring positions as dienes for the diels alder reaction

Journal of Heterocyclic Chemistry, 1998
AbstractSemiempirical and density functional theory computational studies were carried out with the target determining the reactivity of five membered heterocycles with heteroatoms in the 1 and 3 positions as dienes for Diels‐Alder reactions. The relative reactivity was evaluated in their reaction with acetylene, ethylene, and cyclopropene as ...
openaire   +3 more sources

N,N-Dialkyl-N´-Chlorosulfonylchloroformamidines in Heterocyclic Synthesis. II. Thiazolo-, Thiadiazolo-, and Oxadiazolo-Fused [1,2,4,6]Thiatriazine Dioxides

, 2005
N,N-dialkyl-N′-chlorosulfonylchloroformamidines 1 were treated with 2-aminothiazoline, 2-aminothiazoles, 2-aminobenzothiazoles, 2-amino-1,3,4-thiadiazoles, and 2-amino-1,3,4-oxadiazoles to give a 6,7-dihydrothiazolo[3,2-b][1,2,4,6]thiatriazine dioxide 3,
G. Fallon, C. Francis, K. Johansson, A. Liepa, Ruth C. J. Woodgate   +4 more
semanticscholar   +1 more source

N,N-Dialkyl-N′-Chlorosulfonyl Chloroformamidines in Heterocyclic Synthesis. IV. 3-Dialkylamino-1,1,8-trioxo-1H-1λ6-pyrano[3,4-e][1,4,3]oxathiazines

, 2007
N,N-dialkyl-N′-chlorosulfonylchloroformamidines 1 reacted regioselectively with 4-hydroxy-2-pyrone derivatives 2 to give 3-dialkylamino-1,1,8-trioxo-1H-1λ6-pyrano[3,4-e][1,4,3]oxathiazines 3.
Teresa Cablewski, C. Francis, A. Liepa
semanticscholar   +1 more source

Synthesis of fused heterocycles: 1,2,3,4-tetrahydroisoquinolines and ring homologues via sulphonamidomethylation

, 1986
The title heterocycles (3) have been obtained by a two-step synthesis; namely an initial intramolecular sulphonamidomethylation of N-aralkylsulphonamides (1) in acid media followed by desulphonylation of compounds (2) under moderate conditions, either by
O. Orazi, R. Corral, H. Giaccio
semanticscholar   +1 more source