作者:Fabian Fischer、Daniel Berger、Markus Neuenschwander
DOI:10.1002/(sici)1521-3773(19980817)37:15<2138::aid-anie2138>3.0.co;2-5
日期:1998.8.17
Strong nucleophiles are needed for inducing ring opening 3→4 since the pyrylium salt intermediates 3, formed from 5-X-substituted 5-aminopenta-2,4-dienals 2 upon treatment with acid, are quite unreactive due to "aromatic" stabilization. However, this allows an easy access to a variety of 2-aminopyrylium salts 3 from "push-pull" enynes 1. X=OAc, F, Cl, Br, I, OPh.
诱导开环3→4需要强亲核试剂,因为由5-X-取代的5-氨基戊-2,4-二烯2经酸处理形成的吡喃鎓盐中间体3由于“芳族”稳定作用而几乎没有反应性。然而,这允许容易地从“推挽”烯炔1获得各种2-氨基吡啶鎓盐3。X = OAc,F,Cl,Br,I,OPh。