A palladium-catalyzed cascade reaction of ortho-vinyl bromobenzenes with N-tosylhydrazones has been developed, which provides a facile approach to 2,2-disubstituted 2H-chromenes. The migration of palladium from the aryl to vinyl position is crucial, as the in situ produced vinyl palladium intermediate could further react with diazo compounds to generate the reactive species for the sequential annulation.

中文翻译：

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通过邻乙烯基溴苯与N-甲苯磺酰hydr的钯催化级联反应，可轻松获得2,2-二芳基2H-色烯。

已经开发了钯催化的邻乙烯基溴苯与N-甲苯磺酰hydr的级联反应，这为2，2-二取代的2 H-苯甲基提供了一种简便的方法。钯从芳基到乙烯基位置的迁移是至关重要的，因为原位生产的乙烯基钯中间体可能进一步与重氮化合物反应生成反应性物质，以进行顺序环化。