Intramolecular inverse electron demand Diels-Alder reactions of pyrazines
作者:Marek Biedrzycki、Dick A de Bie、Henk C van der Plas
DOI:10.1016/s0040-4020(01)85132-2
日期:1989.1
Thermally induced intramolecularDiels-Alder cyclisations of (alkynyloxyalkyl)pyrazines to dihydropyranopyridines have been studied in the solvent undecane. The introduction of a phenyl group in the α-position of the 3-butynyloxymethyl sidechain leads to a 3–4 fold increase of the reaction rate, while the influence of a γ-phenyl group on the rate is negligible. The (3-butynyloxymethyl)pyrazine reacts about
Intramolecular Diels-Alder reactions of quaternary pyrazinium salts and protonated pyrazinium cations. Synthesis of annelated pyridinium salts and annelated pyridines.
作者:Bart Geurtsen、Dick A. de Bie、Henk C. van der Plas
DOI:10.1016/s0040-4020(01)89528-4
日期:1989.1
quaternary pyrazinium salts as well as the protonated pyrazines undergo an intramolecular Diels-Alder reaction under considerably milder conditions than the corresponding neutral pyrazines. The products of the reactions were []-annelated quaternary pyridinium salts and []-annelated protonated pyridiniumcations, respectively.
如13 C NMR数据所示,炔基取代的吡嗪在二氯甲烷中用四氟硼酸三乙基氧鎓进行季铵化仅在N-4处产生3-炔基-1-乙基吡嗪鎓盐。同样的吡嗪与三氟乙酸的质子化也发生在N-4处。季吡嗪鎓盐以及质子化的吡嗪在比相应的中性吡嗪温和得多的条件下进行分子内Diels-Alder反应。反应产物分别为[ ]-退火的季吡啶鎓盐和[ ]-退火的质子化吡啶鎓阳离子。