Facile Pyridine S Ar Reactions via -Phosphonium-Pyridinium Intermediates.

Here we report that -phosphonium pyridinium intermediates are unusually reactive for pyridine S Ar reactions. Specifically, forming phosphonium salts from halopyridines typically requires elevated temperatures and Lewis acid additives. The alternative activation mode described in this paper permits C-P bond formation to occur at ambient temperatures in many cases, and functions across a broad range of substrates.