THE REACTION OF CYANOGEN WITH 1,3-BUTADIENE

Cyanogen and butadiene have been found to react. The main product of the reaction was identified as 2-cyanopyridine. Some 2,2′-dipyridyl and a number of unidentified compounds were also found present in the product in small yields. No evidence for the presence of β-hydromucononitrile could be found. The reaction has been studied at atmospheric pressure in the vapour phase, and in ether solution, and at superatmospheric pressures in steel or glass bombs. In all cases the course of the reaction was essentially the same, 2-cyanopyridine being the main product. The formation of 2-cyanopyridine from butadiene and cyanogen is formulated as a Diels–Alder synthesis, in which the primary adduct undergoes a dehydrogenation to yield the final product. This is the first time to our knowledge that cyanogen has been reported as a dienophile in the diene synthesis.