Synthesis of Two Isomers of pyrido/benzo[b][1,4]selenazines: A Selective Catalyst‐Dependent Formation of C−N and C‐Se Bonds

Abstract This work describes the selective synthesis of a series of pyrido/benzo‐fused 1,4‐selenazines, through the reaction of bis(3‐amino‐2‐pyridyl) or bis(2‐aminophenyl) diselenides with different β‐ dicarbonyl compounds. When molecular I 2 was used as catalyst, a series of ( Z )‐1‐(1 H ‐pyrido[2,3‐ b ][1,4]selenazin‐2(3 H )‐ylidene)propan‐2‐ones were obtained. On the other hand, in the absence of catalyst, 1‐(2‐methyl‐1 H ‐pyrido[2,3‐ b ][1,4]selenazin‐3‐yl)ethan‐1‐ones could be prepared selectively. The structure of the prepared compounds was elucidated by NMR and HRMS analysis and confirmed by single crystal X‐ray diffraction. The versatility of the protocol was demonstrated not only by the access to a variety of 1,4‐selenazine derivatives, but also by the structural diversity in the 1,3‐dicarbonyl precursors, incorporating multifunctionalities in the synthesized heterocycles.