Organophotoredox-Catalyzed Direct C-H Amination of 2H-Indazoles with Amines.

A general and practical method for the direct C-H amination of 2H-indazoles with a series of amines including aliphatic primary amines, secondary amines, azoles, and sulfoximines via organophotoredox-catalyzed oxidative coupling has been disclosed at room temperature under ambient air conditions. Additionally, this protocol is used for free aminated 2H-indazole synthesis. A mechanistic study revealed that a single electron transfer (SET) pathway might be involved in this reaction.

Visible-Light-Mediated Synthesis of Unsymmetrical Diaryl Sulfides via Oxidative Coupling of Arylhydrazine with Thiol.

A metal-free visible-light-promoted oxidative coupling between thiols and arylhydrazines has been developed to afford diaryl sulfides using a catalytic amount of rose bengal as photocatalyst under aerobic conditions. A library of unsymmetrical diaryl sulfides with broad functionalities was synthesized in good yields at room temperature. The present methodology is also applicable to benzo[ d]thiazole-2-thiols, benzo[ d]oxazole-2-thiol, 1 H-benzo[ d]imidazole-2-thiols, and 1 H-imidazole-2-thiol.

Visible-Light-Promoted C(sp3)-C(sp2) Cross-Dehydrogenative Coupling of Tertiary Amine with Imidazopyridine.

A metal-free visible-light-promoted C(sp3)-C(sp2) cross-dehydrogenative coupling between tetrahydroisoquinoline and imidazo[1,2- a]pyridine has been developed to afford 3-substituted imidazopyridines using a catalytic amount of rose bengal as photosensitizer under aerobic conditions. The present methodology is also applicable to imidazo[1,2- a]pyrimidine, indolizine, indole, and pyrrole as well as N, N-dimethyl aniline. Wide substrates scope, use of organo photocatalyst, metal-free, and mild reaction conditions are the attractive features of this methodology.

Visible light induced tetramethylethylenediamine assisted formylation of imidazopyridines.

A metal-free visible light induced C-3 formylation of imidazo[1,2-a]pyridine has been developed using tetramethylethylenediamine (TMEDA) as a one carbon source. An array of 3-formyl imidazo[1,2-a]pyridines with wide functionality are synthesized using rose bengal as a photosensitizer under ambient air.

Visible Light Organic Photoredox-Catalyzed C-H Alkoxylation of Imidazopyridine with Alcohol.

The visible light-mediated C-3 alkoxylation of imidazopyridines with alcohols has been achieved using rose bengal as an organic photoredox catalyst at room temperature. Widely abundant air acts as the terminal oxidant that avoids the use of a stoichiometric amount of peroxo compounds. A wide range of functional groups could be tolerated under the reaction conditions to produce C(sp2)-H alkoxylated products in high yields.

FeCl3-Catalyzed Cross-Dehydrogenative Coupling between Imidazoheterocycles and Oxoaldehydes.

An Fe(III)-catalyzed efficient dicarbonylation of imidazoheterocycles has been developed through cross-dehydrogenative coupling between imidazoheterocycles and oxoaldehydes under ambient air in high yields. The present protocol is also applicable to indolizines. Imidazopyridine produced bisimidazopyridine with arylaldehyde. Experimental results suggest that the reactions proceed through the nonradical pathway.