Rationally designed Fe-cyclopentadienone with unique orientations for efficient asymmetric hydrogenation of acylsilanes

Fe-cyclopentadienone complexes have been widely utilized in various hydrogenation and dehydrogenation catalytic processes, yet their applications have largely been restricted to non-asymmetric versions. This limitation is primarily due to the considerable challenge of constructing an efficient chiral environment around the active iron center. In this study, we present a structurally distinctive chiral Fe-cyclopentadienone complex with excellent enantiocontrol capabilities. This new iron complex features bulky side arms oriented downward toward the cyclopentadienone plane, which create an ideal chiral environment in front of the catalytically active iron center. It demonstrates excellent performance in the catalytic asymmetric hydrogenation of acylsilanes, exhibiting both high reactivity and selectivity. The broad substrate scope, encompassing aryl-, alkenyl-, and alkyl-acylsilanes, along with successful gram-scale synthesis, underscores its potential applications in pharmaceutical synthesis. Experimental and DFT studies reveal the structural stability and rigidity of the catalyst during catalytic intervals. Additionally, weak interactions between the catalyst and the silyl group in the substrate play a critical role in achieving efficient enantioselectivity. More importantly, this type of chiral iron complex also shows excellent catalytic reactivity and selectivity for asymmetric transfer hydrogenation, utilizing i-PrOH as the hydrogen source.