Theoretical Explanation of Reaction Site Selectivity in the Addition of a Phenoxy Group to Perfluoropyridine.

Pentafluoropyridine, a potentially useful precursor in organofluorine methodology, undergoes selective substitution of a fluorine with a phenoxide at the site para to the nitrogen. Subsequent aryloxide substitutions can be accomplished at the ortho-positions with aryloxide groups containing various functional groups para to the phenoxide oxygen. During this phase of the reaction, "reverse reactions" involving substitutions of the original para substituent with a free fluoride or with another aryloxide moiety are observed with a frequency that depends on the functional group para to the oxygen on the aryloxide. Herein, we provide a theoretical explanation of these observations through use of density functional theory.