A convenient and efficient approach for the formation of nitrogen heterocycle-fused imidazo[1,2-a]pyridine and benzo[b]selenophenes has been developed through copper-catalyzed direct selenylation of readily available 2-(2-bromophenyl)imidazo[1,2-a]pyridines via regioselective cleavage of C(sp2)–Br and C(sp2)–H bonds using readily available selenium powder as the selenylating reagents under ligand- and base-free conditions in air. Preliminary mechanistic investigations indicated that radical species were involved in the present transformation.

A facile and eco-friendly protocol for the construction of C-4 sulfenylated pyrazoles via a radical pathway was established for the first time. The reaction worked smoothly under catalyst- and solvent-free conditions to afford a wide range of sulfenylated pyrazole derivatives in good to excellent yields. The thiyl free radical generated in situ, here, also served as a single electron transfer medium for the present transformation. This reaction provides a new strategy for the formation of C–S bonds.

The visible light and Eosin B-catalyzed direct sulfenylation of sp2 C–H bonds with sulfinic acids through a photoredox process has been demonstrated at room temperature under transition metal-free conditions for the first time. Diverse heteroaryl sulfides were obtained in moderate to good yields. This is the first example of the sulfenylation of sp2 C–H bonds using arylsulfinic acids as odorless sulfur reagents under visible light-induced conditions. More interestingly, the reductive products could be obtained under visible light-induced oxidative conditions. This protocol demonstrates a new model for C–S bond formation, which serves as a novel approach toward the synthesis of heteroaryl sulfides.

We describe herein a green and efficient MCRs protocol to synthesize C-4 sulfenylated pyrazoles by iodine-catalyzed cyclocondensation and direct CH bond sulphenylation reactions. Through this protocol, two new CN bonds and one CS bond are constructed simultaneously in a single step. This method provides a straightforward and sustainable way to construct valuable sulfenylated pyrazoles under metal- and solvent-free conditions.A facile access to C-4 sulfenylated pyrazoles via a domino multicomponent reaction has been realized under metal-free conditions.Download high-res image (285KB)Download full-size image

An efficient copper-catalyzed decarboxylative coupling of cinnamic acids with N-fluorobenzenesulfonimide (NFSI) to give the corresponding substituted (E)-amination products stereospecifically is demonstrated. This new method is efficient and practical, and the corresponding products were obtained in moderate to good yields. The present protocol should broaden the scope of the decarboxylative cross-coupling reactions and provide a useful strategy for the construction of C–N bonds.

A novel, efficient, and catalyst-free strategy has been initially developed for the construction of thioesters via the direct radical oxidative decarboxylation of α-keto acids with thiols, and the corresponding target products were obtained in moderate to good yields. It offers an alternative approach for the synthesis of useful diverse thioesters.

Metal-free efficient iodine-mediated synthesis of vinyl sulfones utilizing aryl sulfinates and alkenes has been realized under mild conditions in water. Notably, sodium methanesulfinate was used in this transformation, affording the β-iodo sulfones in good yields. This simple, efficient and environmentally benign transformation provides an attractive approach to various vinyl sulfones or β-iodo sulfones.

A highly regioselective TBHP-mediated ring opening of imidazopyridines via cleavage of C–C and C–N bonds has been achieved for the first time to afford N-(pyridin-2-yl)benzamides. Preliminary mechanistic investigations revealed that the present metal-free transformation involved a radical pathway, and the oxygen atom incorporated in the end products might derive from TBHP.

A direct thiolation of methoxybenzenes with various thiols has been developed. The protocol uses inexpensive reagents: catalytic iodine in the presence of DTBP. Importantly, no base or ligand was necessary. This method opens a new avenue to a variety of valuable thioethers that would be more difficult to access with traditional methods.A direct Thiolation of methoxybenzenes with various thiols has been developed. The protocol uses inexpensive reagents: catalytic iodine in the presence of DTBP. Importantly, no base or ligand was necessary. This method opens a new avenue to a variety of disulfides that would be more difficult to access with traditional methods.

A novel and convenient silver-mediated radical cyclization method for the synthesis of coumarin derivatives via the direct difunctionalization of alkynoates with α-keto acids through double C–C bond formation under mild conditions has been developed. This new method is highly efficient and practical, and the starting materials are readily prepared. The present method should provide a useful strategy for the construction of coumarin motifs.

A silver-catalyzed double-decarboxylative protocol has been proposed for the construction of chalcone derivatives via cascade coupling of substituted α-keto acids with cinnamic acids under the mild aqueous conditions. The developed method for constructing C–C bonds via double-decarboxylative reactions is efficient, practical, and environmentally benign by using the readily available starting materials. It should provide a promising synthesis candidate for the formation of diverse and useful chalcone derivatives in the fields of synthetic and pharmaceutical chemistry.

A novel, effective and sustainable strategy for the synthesis of aldehydes has been developed using inexpensive, readily available, oxygen-stable and recyclable CuFe2O4 nanoparticles as the catalyst. The corresponding substituted aldehydes were obtained in moderate to good yields by aerobic oxidation of aromatic alcohols in water under dioxygen atmosphere. Importantly, a ligand or a base was not necessary. The catalyst was completely recoverable with an external magnet and could be reused six times without significant loss of catalytic activity.

A novel, efficient, and catalyst-free strategy has been initially developed for the construction of thioesters via the direct radical oxidative decarboxylation of α-keto acids with thiols, and the corresponding target products were obtained in moderate to good yields. It offers an alternative approach for the synthesis of useful diverse thioesters.

A facile and eco-friendly protocol for the construction of C-4 sulfenylated pyrazoles via a radical pathway was established for the first time. The reaction worked smoothly under catalyst- and solvent-free conditions to afford a wide range of sulfenylated pyrazole derivatives in good to excellent yields. The thiyl free radical generated in situ, here, also served as a single electron transfer medium for the present transformation. This reaction provides a new strategy for the formation of C–S bonds.