Methylene-Tethered Arylsulfonation and Benzotriazolation of Aryl/Heteroaryl C-H Bonds with DMSO as a One-Carbon Surrogate

Ketosulfonylmethylenation and sulfonylethyleneation of imidazoheterocycles with dimethylformamide as a methylene source

A hitherto unreported ketosulfonylmethylenation occurring at the C-3 position of imidazoheterocycles, with dimethylformamide as the methylene source was described. Using CoCl2·6H2O or Fe(acac)3 as efficient and inexpensive catalysts, some important biologically active methylenated compounds were prepared, with high efficacy, favorable functional group compatibilities, and a broad substrate scope.

Synthesis and site selective C-H functionalization of imidazo-[1,2-a]pyridines

Imidazo[1,2-a]pyridine has attracted much interest in drug development because of its potent medicinal properties, therefore the discovery of novel methods for its synthesis and functionalization continues to be an exciting area of research. Although transition metal catalysis has fuelled the most significant developments, extremely beneficial metal-free approaches have also been identified. Even though pertinent reviews focused on imidazo[1,2-a]pyridine synthesis, properties (physicochemical and medicinal), and functionalization at the C3 position have been published, none of these reviews has focused on the outcomes obtained in the field of global ring functionalization. We wish here to describe a brief synthesis and an overview of all the functionalization reactions at each carbon atom, viz, C2, C3, C5, C6, C7 and C8 of this scaffold, divided into sections based on site-selectivity and the type of functionalization methods used.

Selectfluor-Promoted Reactions of Aryl Methyl Ketones with Dimethyl Sulfoxide to Give 2,5-Diacylthiophenes and β-Acyl Allylic Methylsulfones

In this paper, a convenient synthesis of 2,5-diacylthiophenes and β-acyl allylic methylsulfones from aryl methyl ketones with dimethyl sulfoxide (DMSO) through Selectfluor-promoted cascade cyclization and cross-coupling reactions by simple solvent modification is described. This method enables the formation of new C-C and C-S bonds via the selection of different solvent ratios, in which DMSO molecules as synthons can be selectively introduced into methyl ketones. The features of this transformation include readily available starting materials, excellent chemoselectivity, and good functional group tolerance.

Halogen Bond-Activated Visible-Light-Mediated Regioselective C-H Arylation of 2-Phenylimidazo-[1,2-a]pyridines

An efficient method for transition metal-free halogen bond-assisted regioselective C-H arylation of 2-phenylimidazo-[1,2-a]pyridines under visible-light condition has been developed. The halogen bond between an aryl halide and base KO^tBu initiates an electron transfer process and generates an aryl radical, which catalyzes its coupling with 2-phenylimidazo-[1,2-a]pyridines to give arylated products in good yield. Several control experiments, density functional theory calculations, and ultraviolet-visible analysis indicate the presence of a halogen bond between an aryl halide and KO^tBu. This methodology has been successfully utilized to synthesize antileishmanial agents.