Ring-transformations of pyrimidines by intramolecular diels-alder reactions. Synthesis of annelated fyridines
作者:A.E. Frissen、A.T.M. Marcelis、H.C. Van Der Plas
DOI:10.1016/0040-4020(89)80111-5
日期:1989.1
Pyrimidines carrying an ω-alkyne side-chain -XCH2CH2CCH (X=O,N,S,SO,SO2) at the 2 or 5 position undergo intramolecularinverseelectrondemandDiels-Alderreactions across the C-2 and C-5 positions; elimination of hydrogen (or alkyl) cyanide from the intermediate adducts leads to condensed pyridines. The influence of the hetero atom (X) in the dienophilic side-chain and that of substituents in the
Crown ethers derived from bicyclocalix[4]arenes as chromoionophores
作者:Wojciech Wąsikiewicz、Michał Ślaski、Gabriel Rokicki、Volker Böhmer、Christian Schmidt、Erich F. Paulus
DOI:10.1039/b009260f
日期:——
The synthesis of calix[4]arenes in which opposite phenolic units are connected by a poly(oxyethylene) bridge at the narrow rim and a 2,6-dimethylene-4-nitrophenol bridge at the wide rim is reported. For two derivatives with tetra- (4) and penta(oxyethylene) (5) bridges UV-Vis spectrophotometric studies were carried out in buffered solution in the presence of alkali metal ions. Their complexation was