Silver‐Catalyzed Acyl Nitrene Transfer Reactions Involving Dioxazolones: Direct Assembly of N‐Acylureas

Abstract

Dioxazolones and isocyanides are useful synthetic building blocks, and have attracted significant attention from researchers. However, the silver-catalyzed nitrene transfer reaction of dioxazolones has not been investigated to date. Herein, a silvercatalyzed acyl nitrene transfer reaction involving dioxazolones, isocyanides, and water was realized in the presence of Ag 2 O to afford a series of N-acylureas in moderate to good yields. The incorporation of an amide moiety into a molecule is of considerable importance because of the presence of this substructure in many biologically active molecules and natural products. [1] In the late 1960s, 1,4,2-dioxazol-5-ones (dioxazolones) 1 were identified by Sauer and Mayer as safe alternatives to acyl azides for N-acyl nitrene formation. [2] Owing to their low cost, ready availability, and environmental friendliness, 1,4,2dioxazol-5-ones have been extensively studied as amidating reagents in the past several years. In 2009, Dubé et al. published a pioneering method to prepare isocyanates by employing 1,4,2-dioxazol-5-ones. [3] Later, Bolm and co-workers reported the first light-induced ruthenium-catalyzed N-acyl nitrene transfer to sulfides and sulfoxides by the decarboxylation of 1,4,2dioxazol-5-ones (eq 1, Scheme 1). [4] Subsequently, dioxazolones were reported as amidating reagents for Rh-catalyzed CÀ H amidation by the Chang group. [5] Thereafter, a series of Rh-, [6] Co-, [7] and Ir-catalyzed [8] CÀ H amidation reactions were developed using this amidating reagent (eq 2, Scheme 1). Furthermore, Li, Zhu, Glorius, Ackermann, and other research groups described the cascade C À H amidation and cyclization reactions for the syntheses of various heterocycles. [9] Bruin and co-workers recently reported the fast N-acyl amidations via Cucatalyzed three-component reaction of aryl acetylenes, amines, and 1,4,2-dioxazol-5-ones (eq 3, Scheme 1). [10] However, to the best of our knowledge, the silver-catalyzed reaction of 1,4,2dioxazol-5-one via acyl nitrene has not been reported in the literature.

Silver‐Catalyzed and Silver‐Promoted Reactions of Isocyanides

“…In 2021, a silver-catalyzed one-pot acyl nitrene transfer reaction involving dioxazolones, isocyanides, and water in the presence of Ag 2 O was reported by Mao and Zhou's group (Scheme 31a). [44] A series of N-acylureas 244 were afforded in moderate to good yields. The reaction of 3substituted-1,4,2-dioxazol-5-ones 242 bearing various functional groups with various isocyanides 243 proceeded smoothly, whereas 2-isocyano-1-morpholinoethan-1-one, tosylmethylisocyanide and 1-isocyano naphthalene failed to yield the desired product.…”