Photoinduced PhI(OAc)2-Mediated Cross-Dehydrogenative Heteroarylation of Aldehydes

Direct acylation of heteroarenes with aldehydes has been established through a photoinduced hypervalent iodine-mediated cross-dehydrogenative coupling reaction. The reaction proceeds through the in situ generation of nucleophilic acyl radicals from aldehydes via acyl C-H hydrogen atom transfer (HAT), followed by a Minisci-type reaction with heteroarenes. The developed reaction system proved to be suitable for cross-coupling a diverse range of heterocycles and aldehydes.

Visible-Light-Induced C(sp3)-H Activation for Minisci Alkylation of Pyrimidines Using CHCl3 as Radical Source and Oxidant

A highly efficient Minisci reaction of pyrimidines with alkyl radical generated from visible-light-induced activation of simple C(sp3)-H feedstocks such as (cyclo)alkanes, ethers, alcohols, esters, and amides is reported. A mechanistic study revealed that alkyl radical was generated via hydrogen atom transfer (HAT) of C(sp3)-H with dichloromethyl radical (·CHCl2), which was generated by photoreduction of chloroform.

A visible-light-induced photosensitizer-free decarbonylative Minisci-type reaction

This study presents a green and practical visible-light-induced photosensitizer-free decarbonylative Minisci-type reaction using aldehydes as alkyl radical precursors. The photocatalytic system exhibits a broad substrate scope and synthetically useful yields. Mechanistic experiments revealed that alkyl radicals could be generated through auto-oxidation of aldehydes under irradiation, which is a mild and effective method for achieving late-stage functionalization of N-heteroarenes. Some biologically active N-heteroarenes could be alkylated using this photocatalytic system smoothly.

Photocatalytic Cyclization Cascades by Radical Relay toward Pyrrolo[1,2-a]indoles: Synthesis, Mechanism, and Application

A photocatalytic annulation cascade of unactivated N-alkene-linked indoles with Langlois' reagent by a radical relay is developed at room temperature under blue LED irradiation. The reaction afforded a series of tri/difluoromethylated pyrrolo[1,2-a]indoles in moderate to good yields. The DFT study suggests that the reaction is ascribed to a rhodamine 6G-induced cyclization cascade involving vinyl addition-radical relay and hydrogen-atom-abstraction (HAA) processes, and interestingly, pyrrolo[1,2-a]indoles are applied as fluorescent dyes into the fluorescence spectrum and live-cell imaging. This paper represents an initial example on photocatalytic cyclization cascades by radical relay and the HAA process.

Cathodically Coupled Electrolysis to Access Biheteroaryls

An electrochemical approach to biheteroaryls through the coupling of diverse N-heteroarenes with heteroaryl phosphonium salts is reported. The reaction features pH and redox-neutral conditions and excellent regioselectivity, as well as exogenous air or moisture tolerance. Additionally, a one-pot, two-step protocol can be established to realize formal C-H/C-H coupling of heteroarenes, thereby greatly expanding the substrate availability. The utility of this method is demonstrated through late-stage functionalization, the total synthesis of nitraridine, and antifungal activity studies.

Photoinduced Metal- and Photosensitizer-Free Decarbonylative C-H Alkylation of Cyclic Sulfamidate Imines

Photoinduced decarbonylative C-C bond formation with readily accessible aldehydes as alkyl sources is described. This protocol provides a sustainable alternative for the effective construction of diverse valuable 4-alkylated sulfonyl ketimines under metal- and photosensitizer-free conditions. Significantly, in this reaction, air serves as the green oxidant, and cyclic sulfamidate imines play a dual role of substrate and photocatalyst, thus affording a concise reaction system for C-H alkylation of cyclic sulfamidate imines.