Synthesis and ring transformation of a new fused <i>as</i>‐triazinium salt

Abstract

Abstract The 1,2‐Diaminopyridinium salt 1 was treated with furandione 2 to give pyrido‐ as ‐triazinone 3 , which could be cyclized to the tricyclic furo[2,3‐ e ]pyrido[1,2,‐ b ]‐ as ‐triazinium salt 5 . Reaction of 5 with nucleophiles resulted in different types of products. Thus, aqueous base afforded bicyclic triazinone 4 , methoxide ion or secondary amine led to stable zwitterions 7a , b , whereas ammonia and hydrazines resulted in ring transformation of the furan moiety, and gave new fused tricyclic pyrroles ( 10, 11 ) and pyridazines ( 13 , 14 ), respectively.