Catalytic Annulation of Epoxides with Heterocumulenes by the Indium-Tin System

Abstract

In the synthesis of five-membered heterocycles by the annulation of epoxides with heterocumulenes such as carbon dioxide and isocyanates, we developed the indium-tin catalytic system and synthesized various cyclic adducts including novel types products under mild reaction conditions.

Electrochemical Selenylation‐Induced Annulation of Alkenyl Ureas to Access Cyclic Isoureas

“…On the basis of the above‐mentioned results and the previous reported, [4–8,13] a possible mechanism for this reactions is proposed, as depicted in Figure 3. Initially, a selenonium cation A is formed from the anodic oxidation of the diselenide 2 a .…”

“…In addition, several catalytic system had developed for cyclic isoureas by the employment of transition metal catalyst, such as Pd, [6a–c] Ag, [6c–e] Au, [6d–e] and Cu [6f–h] (Scheme 1c). Moreover, Shibata's group reported the Bu 2 SnI 2 −InCl 3 catalyzed annulation of epoxides and diphenyl carbodiimide to afford cyclic isoureas (Scheme 1d), [7] and Cariou's group reported an iodine(III)‐mediated for the synthesis of cyclic isoureas through cationic cyclizations of unsaturated N ‐alkoxyureas (Scheme 1e) [8] . Despite these efforts, developing alternative methods to access functionalized cyclic isoureas from readily available starting substrates is still highly desirable and also represented a continuing challenge.…”