An unexpected and efficient synthesis of 3‐chloro‐4‐cyanopyridine

Abstract

Abstract Reaction of 4‐cyanopyridine N ‐oxide with phosphorus oxychloride/phosphorus pentachloride gave 3‐chloro‐4‐cyanopyridine in good yield in sharp contrast to the expected chlorination in the 2‐position. A mechanistic interpretation of the results is proposed involving a chloride attack at the 4‐position as the main feature.