[2.2]Benzoindenophane‐Based Chiral Indenyl Ligands: Design, Synthesis, and Applications in Asymmetric C−H Activation

Abstract

Development of chiral indenyl ligands for asymmetric C–H activation is a longstanding challenge, and extremely few successes have been achieved. In this paper, we describe a class of readily accessible, facilely tunable and user‐friendly chiral indenyl ligands featuring a [2.2]benzoindenophane skeleton via a divergent synthesis strategy. The corresponding chiral indenyl rhodium catalysts were successfully applied in the asymmetric C–H activation reaction of O‐Boc hydroxybenzamide with alkenes to give various chiral dihydroisoquinolone products (up to 97% yield, up to 98% ee). Moreover, the asymmetric C–H activation reaction of carboxylic acids with alkynes was also successfully accomplished, providing a range of axially chiral isocoumarins (up to 99% yield, up to 94% ee). Notably, this represents the first example of enantioselective transition metal catalyzed C(sp2)‐H activation/oxidative coupling of benzoic acids with internal alkynes to construct isocoumarins. Given many attractive features of this class of indenyl ligands, such as convenient synthesis, high tunability and exclusive face‐selectivity of coordination, its applications in more catalytic asymmetric C–H activation and in other asymmetric catalysis are foreseen.