Preparation and reactions of 2,3,4,6-tetrafluoropyridine and its derivatives

A reliable route to 2,3,4,6-tetrafluoropyridine has been established starti ng from the readily available 3,5-dichlorotrifluoropyridine by halogen exch ange under controlled conditions to give 3-chlorotetrafluoropyridine and it s subsequent hydrodechlorination using hydrogen over palladium on alumina a t 250-270 degrees C. The formation and reactions of the 3-lithio derivative have been studied with the aim of obtaining 3,4-disubstituted trifluoropyr idines. Routes to such materials have been developed and their conversion t o deazapurine derivatives as potential substrates for the generation of ant i-sense nucleosides are reported. (C) 2000 Elsevier Science S.A. All rights reserved.