Nickel/Zinc Chloride-Promoted Domino Reaction of polyenynes

Ni(0)/ZnCl2体系能有效地促进烯酮类化合物与烯烃类化合物的偶联反应。在与1，6-烯炔的反应中，烯酮上的Ni(0)物种发生氧化环化反应，然后在氯化锌的作用下发生裂解，生成烯基镍中间体。随后以5-外环化的方式进行链烯的迁移性插入。当生成的烷基镍中间体具有β-氢原子时，反应通过β-氢消除来终止，以提供环戊烷衍生物。另一方面，没有β-氢原子的烷基镍中间体通过插入第二个烯烃单元，通过三重C-C键的形成过程产生多米诺效应。

A Ni(0)/ZnCl_2 system effectively promotes the coupling of enones and alkene-tethered alkynes. In the reaction with 1,6-enynes, the oxidative cyclization of Ni(0) species on enones across the alkyne part followed by ZnCl_2-promoted cleavage generates alkenylnickel intermediates. Subsequent migratory insertion of the tethered alkene occurs with 5-exo-cyclization. When the resulting alkylnickel intermediates have β-hydrogen atoms, the reaction terminates by β-hydrogen elimination to provide cyclopentane derivatives. On the other hand, an alkylnickel intermediate that does not have β-hydrogen atoms undergoes the insertion of a second alkene unit to cause a domino effect via a three-fold C-C bond formation process.