Photoinduced Electron Transfer from Xanthates to Acyl Azoliums: Divergent Ketone Synthesis via N‐Heterocyclic Carbene Catalysis

Abstract

Considering the prevalence of alcohols and carboxylic acids, their fragment cross-coupling reactions could hold significant implications in organic synthesis. Herein, we report a versatile method for synthesizing a diverse range of ketones from alcohols and carboxylic acid derivatives via N-heterocyclic carbene (NHC) catalysis. Mechanistic investigations revealed that photoexcited xanthates and acyl azoliums undergo single electron transfer (SET) under photocatalyst-free conditions, generating NHC-derived ketyl radicals and alkyl radicals. These open-shell intermediates subsequently undergo the radical-radical cross-coupling reaction, yielding valuable ketones. Furthermore, this approach can be employed in three-component reactions involving alkenes and enynes, resulting in structurally diverse cross-coupled ketones. The unified strategy offers a unique opportunity for the fragment coupling of a diverse range of alcohols and carboxylic acid derivatives, accommodating diverse functional groups even in complex settings.

Manganese Complexes with Consecutive Mn(IV) → Mn(III) Excitation for Versatile Photoredox Catalysis

“…Our group dedicated to developing cost-effective photochemical synthetic methods, propelled by the use of transition metal catalysts. − Drawing from our research experiences and inspired by relevant literature, − we postulated that manganese complexes with promising visible light response and elongated excited-state lifetimes could be attained through careful selection of complex frameworks and tailored modification of binding ligands. Central to this approach is the integration of robust σ-donor ligands to amplify ligand field strength, as evidence by increased ligand field parameters (10 Dq). − Fundamentally, the nature of excited-state electronic configurations is governed by the intricate balance between the 10 Dq parameter and the Racah B factor, reflecting the degree of covalency in metal–ligand bonds and playing a pivotal role in modulating nephelauxetic effects. − By meticulous adjustment of metal–ligand covalency to diminish the Racah B value, enhanced delocalization of d-electrons around the manganese nucleus becomes attainable, a strategy that reduces electron–electron repulsion and is instrumental in achieving the desired prolongation of excited-state lifetimes (Figure B).…”