A Molecular Iron-Based System for Divergent Bond Activation: Controlling the Reactivity of Aldehydes

Abstract

The direct synthesis of amides and nitriles from readily available aldehyde precursors provides access to functional groups of major synthetic utility. To date, most reliable catalytic methods have typically been optimized to supply one product exclusively. Herein, we describe an approach centered on an operationally simple iron-based system that, depending on the reaction conditions, selectively addresses either the CO or C–H bond of aldehydes. This way, two divergent reaction pathways can be opened to furnish both products in high yields and selectivities under mild reaction conditions. The catalyst system takes advantage of iron’s dual reactivity capable of acting as (1) a Lewis acid and (2) a nitrene transfer platform to govern the aldehyde building block. The present transformation offers a rare control over the selectivity on the basis of the iron system’s ionic nature. This approach expands the repertoire of protocols for amide and nitrile synthesis and shows that fine adjustments of the catalyst system’s molecular environment can supply control over bond activation processes, thus providing easy access to various products from primary building blocks.

Nitrogen Atom Transfer Catalysis by Metallonitrene C−H Insertion: Photocatalytic Amidation of Aldehydes

“…Werlé and co‐workers recently reported an iron‐catalyzed photocatalytic protocol for silylamidation of aromatic and aliphatic aldehydes with Me 3 SiN 3 . [14f] However, in that case more electron‐rich aldehydes gave higher yields, which led to the proposal of a nitrenoid {Fe−N−SiMe 3 } intermediate that undergoes electrophilic C−H activation. In order to probe direct trimethylsilylnitrene transfer for the current case, an isotopic cross‐labelling experiment was carried out.…”

Controlling Chemoselectivity of Catalytic Hydroboration with Light

“…[2] In the arena of catalysis, increased interest has arisen in chemodivergent methods which allow easy generation of new structurally diverse chemicals from common intermediates. [3] These methods typically rely on varying a parameter such as catalyst, [4] ligand [5] or reagent. [6] As a non-invasive stimulus which offers excellent spatialtemporal control, light would be particularly attractive to control selectivity.…”

Nitrogen Atom Transfer Catalysis by Metallonitrene C−H Insertion: Photocatalytic Amidation of Aldehydes

“…Werlé and co‐workers recently reported an iron‐catalyzed photocatalytic protocol for silylamidation of aromatic and aliphatic aldehydes with Me 3 SiN 3 [14f] . However, in that case more electron‐rich aldehydes gave higher yields, which led to the proposal of a nitrenoid {Fe−N−SiMe 3 } intermediate that undergoes electrophilic C−H activation.…”