Efficient Assembly of Molecular Complexity Enabled by Palladium‐Catalyzed Heck Coupling/C(sp2)−H Activation/ C(sp3)−H Activation Cascade

Abstract A palladium‐catalyzed [2+2+1] annulation among 3‐iodochromones, benzyl bromides, and norbornene has been developed. This annulation consists of a domino sequence involving Heck coupling/C( sp 2 )−H activation/C( sp 3 )−H activation, affording a variety of complex chromone derivatives bearing five contiguous tertiary carbon centers in up to 94% yield and 99:1 dr. Interestingly, the diastereoselectivity could be switched by fine‐tuning the solvent, in which endo isomer and exo isomer were obtained using mesitylene/CH 3 CN and mesitylene, respectively. magnified image