Hetarenium salts from pentafluoropyridine. Syntheses, spectroscopic properties, and applications

Abstract magnified image Reaction of pentafluoropyridine with nucleophilic heteroaromatics such as 4‐(dimethylamino)pyridine, 4‐(pyrrolidin‐1‐yl)pyridine, 4‐(morpholin‐4‐yl)pyridine, 4‐aminopyridine, and 3,4‐diaminopyridine resulted in the formation of 4‐hetarenium substituted tetrafluoropyridines. The 4‐(dimethylamino)‐pyridinium derivative underwent substitution reactions with isopropanolate, isopropanethiolate, and benzylthiolate to F 2 ,F 3 ,O 4 ,F 5 ,F 6 ‐ and O 2 ,F 3 ,O 4 ,F 5 ,F 6 ‐pentasubstituted pyridines as well as their sulfur analogs. N ‐Propylamine, isopropylamine, and piperidine formed 4‐amino‐N 2 ,F 3 ,F 5 ,F 6 ‐pentasubstituted pyridines in the presence of sodium amide as base, whereas morpholine gave the 4‐amino‐2,6‐bis‐morpholino‐substituted 3,5‐difluoropyridine. 19 F, 15 N, 13 C, and 1 H nmr spectrocopy was performed to elucidate the structures of the substitution products.