Using Light to Modify the Selectivity of Transition Metal Catalysed Transformations

Abstract

Light has a remarkable and often unique ability to promote chemical reactions. In combination with transition metal catalysis, it offers exciting opportunities to modify catalyst function in a non‐invasive manner, most frequently being reported to switch on or accelerate reactions that do not occur in the dark. However, the ability to completely change reactivity or selectivity between two different reaction outcomes is considerably less common. In this Minireview we bring together examples of this concept and highlight their mechanistically distinct approaches. Our overview demonstrates how these non‐natural, photo‐switchable systems provide key fundamental mechanistic insights, enhancing our understanding and stimulating development of new catalytic activity, and how this might lead to tangible applications, impacting fields such as polymer chemistry.

Mild and Chemoselective Carboxylic Acid Reduction Promoted by Borane Catalysis

“…[17][18][19] In this context, we recently reported a unique cobalt catalysed platform whereby the chemoselectivity of ketoacid hydroboration could be controlled by visible light. [20,21] In line with our previous work, [22] we suggested that the reactivity observed with carboxylic acid hydroboration was consistent with a Co 0 /Co I catalytic cycle. [23] Upon further mechanistic probes of this carboxylic acid selective hydroboration with in situ NMR (see Supporting Information for more details), we noted key features in the 11 B NMR.…”

Controlling Chemoselectivity of Catalytic Hydroboration with Light

“…[8] Previous examples of modifying the selectivity of metal catalysed processes are limited in number but have taken a variety of different approaches. [9] For instance, light responsive motifs can be incorporated into the ligand structure [10] or direct excitation can lead to a change in redox properties [11] amongst other strategies. [12] Our group has recently exploited light induced modification of the coordination sphere of a cobalt hydride catalyst (Scheme 1a) to control ambidoselectivity in the hydroboration of α,β-unsaturated ketones (Scheme 1b), [13] and this idea has begun to attract more attention for opening up new mechanistic platforms.…”

Radical Brook Rearrangements: Concept and Recent Developments

“…Since 2008, photoredox chemistry has become an emerging area in synthetic chemistry [39][40][41][42][43][44][45][46][47][48] and triggered the renaissance of radical chemistry as a result of its mild conditions, selectivity, and efficiency. [49][50][51][52] Brook rearrangements have been widely explored in organic chemistry, [7] especially after Smith and co-workers extended this molecular rearrangement to remote migration, which they coined anion relay chemistry (ARC).…”