Meta-Selective C─H Monofluoroalkylation of Pyridines With Difluoroalkyl Radicals
Ming Zhang1, Heng Luo1, Yi Chang1
1State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Haihe Laboratory of Sustainable Chemical Transformations, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin, China.
Abstract:
C─H monofluoroalkylation of pyridines is a highly desirable transformation in medicinal chemistry because the monofluoroalkyl group is known to impart favorable properties to drug candidates, and pyridine rings are prevalent in drug molecules. However, only a few methods have been reported, and they are limited to ortho-selective reactions. Herein, we report an unprecedented method for meta-selective C─H monofluoroalkylation of pyridines via reactions between difluoroalkyl radicals and dihydropyridines generated in situ. During the reactions, a defluorination/olefin isomerization cascade converts initially formed difluoroalkylated dihydropyridines to monofluoroalkylated pyridines. The method accommodates a broad range of pyridine substrates, as well as other N-heteroarenes and fluoroalkylating reagents, and shows promise for late-stage functionalization of pyridine-containing drugs.
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