Achieving C3-selective pyridine functionalization is a longstanding challenge in organic chemistry. The existing methods, including electrophilic aromatic substitution and C–H activation, often require harsh reaction conditions and excess pyridine and generate multiple regioisomers. Herein, we report a method for borane-catalyzed tandem reactions that result in exclusively C3-selective alkylation of pyridines. These tandem reactions consist of pyridine hydroboration, nucleophilic addition of the resulting dihydropyridine to an imine, an aldehyde, or a ketone, and subsequent oxidative aromatization. Because the pyridine is the limiting reactant and the reaction conditions are mild, this method constitutes a practical tool for late-stage functionalization of structurally complex pharmaceuticals bearing a pyridine moiety.

Herein, we report a method for C3-selective C−H tri-and difluoromethylthiolation of pyridines. The method relies on borane-catalyzed pyridine hydroboration for generation of nucleophilic dihydropyridines; these intermediates react with trifluoromethylthio and difluoromethylthio electrophiles to form functionalized dihydropyridines, which then undergo oxidative aromatization. The method can be used for late-stage functionalization of pyridine drugs for the generation of new drug candidates.

A catalytic carbonylative ring-opening and functionalization reaction of poorly activated cyclopropanes has been developed. The key achievement of this work is the accomplishment of an unprecedented effective intermolecular trapping of the rhodacyclopentanone intermediate, which is derived from rhodiummediated carbonylative insertion of poorly activated cyclopropanes, by an external reactant. The success of this development hinges upon the use of a dual directing strategy.

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