Light-assisted functionalization of aryl radicals towards metal-free cross-coupling.

The many synthetic possibilities that arise when using radical intermediates, in place of their polar counterparts, make contemporary radical chemistry research an exhilarating field. The introduction of photocatalysis has helped tame aryl radicals, leading to a resurgence of interest in their chemistry, and an expansion of viable coupling partners and attainable transformations. These methods are more selective and safer than classical approaches, and they utilize new radical precursors.

Alkyl Cyclopropyl Ketones in Catalytic Formal [3 + 2] Cycloadditions: The Role of SmI Catalyst Stabilization.

Alkyl cyclopropyl ketones are introduced as versatile substrates for catalytic formal [3 + 2] cycloadditions with alkenes and alkynes and previously unexplored enyne partners, efficiently delivering complex, sp-rich products. The key to effectively engaging this relatively unreactive new substrate class is the use of SmI as a catalyst in combination with substoichiometric amounts of Sm; the latter likely acting to prevent catalyst deactivation by returning Sm to the catalytic cycle. In the absence of Sm, background degradation of the SmI catalyst can outrun product formation.

Flavin-Mediated Photocatalysis Provides a General Platform for Sulfide C-H Functionalization.

Functionalized sulfides are important in many areas of science, ranging from chemical biology through drug discovery to organic materials chemistry. Sulfides bearing pendant reactive groups in the α-position are particularly useful; however, methods for the selective valorization of simple sulfides or the late-stage functionalization of complex sulfides by the convenient addition of valuable functionality are underexplored. Here we exemplify a general reaction platform for sulfide functionalization by showcasing three modes of α-sulfur C-H functionalization; cyanation, alkenylation, and alkynylation.