Kelu Yan

Silver-Mediated Radical Cyclization of Alkynoates and α-Keto Acids Leading to Coumarins via Cascade Double C–C Bond Formation

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.

Catalyst-Free Regioselective C-3 Thiocyanation of Imidazopyridines

A direct and straightforward approach for highly regioselective thiocyanation of imidazoheterocycles through sp(2) C-H functionalization has been realized at room temperature. Various C-3 thiocyanated imidazopyridines are formed in moderate to good yield. The present method exhibits a mild and selective access to a variety of imidazopyridine derivatives of pharmacological interest.

Metal-Free Iodine-Catalyzed Direct Arylthiation of Substituted Anilines with Thiols

Iodine-catalyzed direct arylthiation of substituted anilines for the synthesis of various diaryl sulfides has been developed under metal- and solvent-free conditions. The present method uses readily available thiols as the arylthiation reagents, and environmentally friendly and inexpensive I2 as the catalyst. Importantly, no base or ligand was necessary. Such a simple, efficient, and economical transformation provides an attractive approach to various diaryl sulfides in good to excellent yields.

Metal-free n-Et4NBr-catalyzed radical cyclization of disulfides and alkynes leading to benzothiophenes under mild conditions

A novel n-Et4NBr-catalyzed method for the synthesis of benzothiophene derivatives via cascade reactions of substituted disulfides with alkynes through S–S bond cleavage and alkenyl radical cyclization reactions has been developed. The reaction has a high functional-group tolerance. The new method is environmental and practical, and the starting materials are readily available. These advantages, relative to previous methods, provide an opportunity for the construction of diverse and useful benzothiophene motifs.

Copper-catalyzed domino synthesis of benzo[b]thiophene/imidazo[1,2-a]pyridines by sequential Ullmann-type coupling and intramolecular C(sp2)–H thiolation

The copper-catalyzed double C–S bond formation via Ullmann-type S-arylation and C–H thiolation using K2S as a sulfur source is described. This novel one-step sulfur-incorporation method provides a straightforward avenue to benzo[b]thiophene and imidazo[1,2-a]pyridine frameworks.

A copper-catalyzed cascade reaction of o-bromoarylisothiocyanates with isocyanides leading to benzo[d]imidazo[5,1-b]thiazoles under ligand-free conditions

A convenient and efficient copper-catalyzed domino method has been initially developed for the synthesis of benzo[d]imidazo[5,1-b]thiazole derivatives via the reactions of readily available substituted o-bromoarylisothiocyanates with isocyanides under ligand-free conditions. This chemistry involves intermolecular [3 + 2] cycloaddition and intramolecular Ullmann-type C–S bond formation.

Metal-free TBHP-mediated oxidative ring openings of 2-arylimidazopyridines via regioselective cleavage of C-C and C-N bonds†

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.