Spatiotemporal Control of Amide Radicals During Photocatalysis

Abstract

Despite the continuing popularity of radical reactions in organic synthesis, much remains to be explored in this area. Herein, we describe how spatiotemporal control can be exerted over the formation and reactivity of divergent exchangeable formamide radicals using nickel complexes with a semiconductor material (TiO<sub>2</sub>) under irradiation from near-UV–Vis light. Depending on the bipyridine ligand used and the quantity of the nickel complex that is hybridized on or nonhydridized over the TiO<sub>2</sub> surface, these radicals selectively undergo substitution reactions at the carbon center of carbon–bromine bonds that proceed via three different pathways. As the scalable production of formamides from CO<sub>2</sub> does not produce salt waste, these methods could add a new dimension to the search for carbon neutrality through the indirect incorporation of CO<sub>2</sub> into organic frameworks.

Switchable Divergent Synthesis Using Photocatalysis

“…In Type-II, the reaction gives each product (products 1 and 2) via different reaction pathways. Note that the reactions using heterogeneous photocatalysts have not been covered in this Perspective. Several diversity-oriented reactions, in which similar substrates provide structurally different types of products, are not highlighted in this Perspective …”