Exciting Iron Catalysis: A route towards sustainable cross-couplings Enabled by Light

Introduction

The manufacture of many high-value chemicals that sustain our daily lives depends on the ability of palladium catalysts to link together (cross-coupling) complex structural motifs. Yet, in view of the rapid increase of the price of palladium and its progressive depletion, it is crucial to invent alternative and more sustainable systems based on Earth-abundant metals to ensure the viability in the long term of these strategic processes that provide us with materials, agrochemicals, or medicines.

Iron as an Alternative

Iron is considered the most benign of transition metals because it is endless, inexpensive, and biocompatible. However, despite its early discovery, iron-catalyzed cross-couplings have been underutilized owing to their narrower scope and the need for strong organometallic reductants or harsh conditions, which hampers their applicability in complex targets and densely-functionalized substrates.

Proposed Approach

This proposal introduces a fundamentally new approach to overcome the issues that restrain the development of iron-catalyzed cross-couplings, exploiting the innate ability of iron complexes to harvest light and repurposing it to “activate” catalysis.

Novel Modes of Reactivity

Capitalizing on novel modes of reactivity accessed upon visible-light irradiation, this research programme offers a strategy to access key catalytically active iron species under mild conditions without the use of strong organometallic reductants, enabling unprecedented transformations with extended scope.

Charge-Transfer Excited States

ExCEL recruits charge-transfer excited states of iron complexes, providing access to:

1. Fe(I)/Fe(III)
2. Fe(0)/Fe(II)

This allows for the achievement of C–C and C–heteroatom bond formation as well as multicomponent reactions that are currently out of the reach of state-of-the-art iron catalysis.

Conclusion

Overall, this proposal aims to introduce a new paradigm to upgrade and unleash the full potential of iron catalysis in organic synthesis, and will pave the way for the discovery of exciting new synthetic transformations.