We reported an unprecedented chalcogen element (Se, S) insertion reaction with functionalized aminomaleimide to assemble medium-sized nitrogen-containing organic selenium/sulfur catalyzed by bases. During these [5/6 + 1] tandem annulations, a variety of low-valent inorganic chalcogenides exhibited excellent compatibility, providing a wide scope of structurally diverse 1,4-selenazepanes (17 examples, 60-71% yields), 1,4-benzothiazepines (20 examples, 74-86% yields), and 1,4-thiazines (6 examples, 31-68% yields). The characteristics of this transformation are high atomic economy, formation of two C-Se or C-S bonds in one step, and avoiding the use of unstable and toxic selenium/sulfur reagents under mild conditions.