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

TL;DR

Scientists designed a chiral iron complex that enables efficient asymmetric hydrogenation of acylsilanes, a process previously limited to non-asymmetric versions.

Contribution

A structurally unique chiral Fe-cyclopentadienone complex was developed for efficient asymmetric hydrogenation of acylsilanes.

Findings

The complex shows high reactivity and selectivity in asymmetric hydrogenation of acylsilanes.

It works with a broad range of substrates, including aryl-, alkenyl-, and alkyl-acylsilanes.

The catalyst is stable and rigid during catalysis, with weak interactions aiding enantioselectivity.

Abstract

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.

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. Herein, the authors report the synthesis of a chiral Fe- cyclopentadienone complex and its application in the catalytic asymmetric hydrogenation of acylsilanes.

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