P. Fier, J. Hartwig
Nov 22, 2013
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Science
Abstract
Fluorinating Pyridine Appending fluorine substituents to carbon centers is commonly used to tune small-molecule properties in pharmaceutical and agrochemical research. However, fluorinations often require the use of corrosive, hazardous reagents. Fier and Hartwig (p. 956) present an unusually mild and convenient protocol for fluorinating carbon sites adjacent to nitrogen in pyridines and related nitrogen-bearing arenes. The reaction entails treatment with silver difluoride and proceeds rapidly at room temperature. A mild fluorination method could help produce compounds of interest in medicinal research. Fluorinated heterocycles are prevalent in pharmaceuticals, agrochemicals, and materials. However, reactions that incorporate fluorine into heteroarenes are limited in scope and can be hazardous. We present a broadly applicable and safe method for the site-selective fluorination of a single carbon-hydrogen bond in pyridines and diazines using commercially available silver(II) fluoride. The reactions occur at ambient temperature within 1 hour with exclusive selectivity for fluorination adjacent to nitrogen. The mild conditions allow access to fluorinated derivatives of medicinally important compounds, as well as a range of 2-substituted pyridines prepared by subsequent nucleophilic displacement of fluoride. Mechanistic studies demonstrate that the pathway of a classic pyridine amination can be adapted for selective fluorination of a broad range of nitrogen heterocycles.