Synthesis of Indenes and Benzofulvenes via a Palladium-Catalyzed Three-Component Reaction

A palladium-catalyzed three-component domino reaction to access indene derivatives is reported. This reaction proceeds via the sequential formation of three bonds: the first two resulting from inter- and intramolecular carbopalladation and the final bond arising from an attack by a terminating nucleophilic reagent. Modifying the starting tether on the iodoarene led to either indenes or benzofulvenes. Three termination variations were compatible with this sequence, which furnished products in moderate to good yields. The oxabicycle used in this work acts as an acetylene surrogate, which is revealed in a postcatalytic retro-Diels–Alder step. A diastereomerically enriched mixture of oxabicyclic derivatives allowed for preliminary results for the enantioselective synthesis of indenes.本研究报道了一种钯催化的三组分多米诺反应，可用于合成茚衍生物。该反应通过依次构建三个化学键完成：前两个化学键分别源自分子间与分子内碳钯化过程，最终一个化学键则由终止性亲核试剂的进攻形成。对碘代芳烃底物上的起始连接臂进行修饰，可分别得到茚类或苯并富烯类产物。该反应序列可兼容三种终止方式，所得产物的收率处于中等至良好水平。本研究中使用的氧杂双环化合物可作为乙炔替代物，其反应机制可通过催化后逆狄尔斯-阿尔德步骤得以阐明。采用非对映异构体富集的氧杂双环衍生物混合物作为底物，我们实现了茚类化合物对映选择性合成的初步探索。