The reactivity of Mannich bases derived from 6- and 7-hydroxycoumarins was studied in inverse electron demand Diels–Alder reactions with enamines. The reactions were shown to proceed by a cycloaddition mechanism followed by transformation of hemiaminals and resulted in the formation of heterocyclic pyrano[2,3-a]xanthene, pyrano[2,3-b]xanthene, and pyrano[3,2-b]xanthene.
                                    在逆电子需量Diels-Alder与烯胺的反应中,研究了由6和7-羟基
香豆素衍生的Mannich碱的反应性。反应显示是通过环加成机理进行的,随后是半胱
氨酸的转化,导致杂环
吡喃并[2,3- a ]
蒽,
吡喃并[2,3- b ]并
蒽和
吡喃并[3,2- b]的形成。 x吨。