A Pd-catalyzed oxa-(4+4)-cycloaddition between 1-azadienes and (2-hydroxymethyl)allyl carbonates is described. Aurone-derived azadienes furnished polycyclic 1,5-oxazocines in good yields. Interestingly, linear azadienes have also been involved and yielded monocyclic heterocycles with complete regioselectivity. DFT calculations were carried out to gain insight on this observation.
描述了钯催化的1-氮代烯与(2-羟甲基)烯丙基碳酸酯之间的氧杂-(4+4)-环加成反应。以花槿素衍生的氮代烯以较高的产率提供多环的1,5-氧杂环己烷。有趣的是,线性的氮代烯也参与其中,并产生具有完全区域选择性的单环杂环化合物。进行了密度泛函理论计算以深入了解这一观察结果。