Mn-Mediated Direct Regioselective C-H Trifluoromethylation of Imidazopyridines and Quinoxalines

Synthesis of imidazopyridines via NaIO4/TBHP-promoted (3 + 2) cycloaddition and biological evaluation as anticancer agents

A novel and simple NaIO4/TBHP-promoted (3 + 2) cycloaddition reaction of propargyl alcohols and 2-aminopyridines was discovered for the synthesis of imidazo[1,2-a]pyridines. This protocol exhibits a broad substrate scope for both propargyl alcohols and 2-aminopyridines, with high functional group tolerance, leading to the formation of various C3-carbonylated imidazopyridines in moderate yields. More importantly, these synthesized compounds were evaluated for their antiproliferation activity against MOLM-13 and MV4-11 cells, indicating that 3n, 5a and 5d possessed good bioactivity. Molecular docking analysis showed the strong interaction between 5a, 5d and FLT3 kinase, which have practical values in the development of kinase inhibitors.

Iodine-mediated regioselective C-3 sulfenylation using elemental sulfur and arylhydrazine hydrochloride to access 3-sulfenylated imidazo[1,2-a]pyridines

A transition metal-free protocol for the regioselective C-3 sulfenylation of imidazo[1,2-a]pyridines has been explored using arylhydrazine hydrochloride and elemental sulfur, in the presence of molecular iodine and DABCO via C(sp2)-H functionalization to achieve structurally diverse 3-sulfenylated imidazo[1,2-a]pyridines in reasonably high yields.

Tosylhydrazide-Induced 1,6-Enyne Radical Cyclization under Copper Catalysis: Access to 3,4-Dihydronaphthalen-1(2H)-one Derivatives

We describe an approach to access 4-aroyl-3-aryl-3,4-dihydronaphthalen-1(2H)-one derivatives in 41-79% yields through the Cu-catalyzed radical cyclization/desulfonylation of 1,6-enynes with tosylhydrazide under air conditions. This alternative desulfonylation strategy combines mild conditions, external oxidant-free processes, and sustainability, contributing to more environmentally friendly organic synthesis. The mechanistic studies showed that the CuCl/O2 combination serves as the source of the oxygen atom needed to form the C═O bond. The existence of tosylhydrazide is crucial for this conversion.

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.

Synthesis of Fluoromethylated Chromones and Their Heteroatom Analogues via Sodium Fluoromethanesulfinate-Enabled Direct Fluoromethylation

An array of biologically interesting tri/difluoromethylated chromones and their heteroatom analogues were conveniently synthesized from the reaction of chromones and their heteroatom analogues with CF3SO2Na or HCF2SO2Na in the presence of tert-butyl hydroperoxide under mild conditions. A mechanistic pathway involving the generation of the electrophilic tri/difluoromethyl radical, followed with the radical substitution of chromones and their heteroatom analogues, was postulated.