Triplet ketone sensitizers are of central importance within the realm of photochemical transformations. Although the radical-type character of triplet excited states of diaryl ketones suggests the viability for triggering hydrogen-atom transfer (HAT) and single-electron transfer (SET) processes, among others, their use as multifaceted catalysts in C-C bond-formation via sp C-H functionalization of alkane feedstocks still remains rather unexplored. Herein, we unlock a modular photochemical platform for forging C( sp)-C( sp) and C( sp)-C( sp) linkages from abundant alkane sp C-H bonds as functional handles using the synergy between nickel catalysts and simple, cheap and modular diaryl ketones. This method is distinguished by its wide scope that is obtained from cheap catalysts and starting precursors, thus complementing existing inner-sphere C-H functionalization protocols or recent photoredox scenarios based on iridium polypyridyl complexes. Additionally, such a platform provides a new strategy for streamlining the synthesis of complex molecules with high levels of predictable site-selectivity and preparative utility. Mechanistic experiments suggest that sp C-H abstraction occurs via HAT from the ketone triplet excited state. We believe this study will contribute to a more systematic utilization of triplet excited ketones as catalysts in metallaphotoredox scenarios.

A redox-neutral intermolecular dicarbofunctionalization of styrenes with CO at atmospheric pressure and carbon-centered radicals is described. This mild protocol results in multiple C-C bond-forming reactions from simple precursors in the absence of stoichiometric reductants, thus exploiting a previously unrecognized opportunity that complements existing catalytic carboxylation events.

Give it a tweak: A novel oxidizing directing group was developed for a rhodium(III)-catalyzed CH functionalization of N-phenoxyacetamides with alkynes. A small change in the reaction conditions leads to either ortho-hydroxyphenyl-substituted enamides or cyclization to deliver benzofurans with high selectivity (see scheme; Cp*=C5 Me5 ).

A visible light-mediated atom transfer radical cyclization of unactivated alkyl iodides is described. This protocol operates under mild conditions and exhibits high chemoselectivity profile while avoiding parasitic hydrogen atom transfer pathways. Preliminary mechanistic studies challenge the perception that a canonical photoredox catalytic cycle is being operative.