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。
A base-promoted formal (2+1) cycloaddition of benzofuran-derived oxadienes with bromomalonates was established that afforded benzofuranone-based spirocyclopropanes in generally good yields (up to 98%) and high diastereoselectivities (up to 91:9 dr). This reaction is the first highly diastereoselective formal (2+1) cycloaddition of benzofuran-derived oxadienes, and will contribute to the chemistry of these compounds. In addition, this approach provides an atom-economic and useful protocol for constructing benzofuranone-based spiro skeletons.