A new route to functionalized 3‐aminopyridazines by ANRORC type ring transformation of 1,2,4‐triazines with carbon nucleophiles

The reaction of 3‐chloro‐6‐phenyl‐1,2,4‐triazine 1a with carbon nucleophiles 2a? d bearing a cyano substituent at a carbanionic center has been studied. In all reactions the formation of the corresponding 3‐aminopyridazines 3a? d takes place via ANRORC mechanism involving addition of the nucleophile at position 5 in compound 1a , ring opening with breaking of the N₄? C₅ bond and intramolecular ring closure of the resulting open‐chain intermediate. A ¹⁵N study with labeled phenylacetonitrile 2a* has shown that the nitrogen atom of the exocyclic amino group of 3‐amino‐4,6‐diphenylpyridazine 3a was originally present in phenylacetonitrile.