NIS/PhI(OAc)₂‐Mediated Diamination/Oxidation of N‐Alkenyl Formamidines: Facile Synthesis of Fused Tricyclic Ureas

Abstract

Facile synthesis of bicyclic ureas by NIS/PhI(OAc)2-mediated diamination/oxidation of N-alkenyl formamidines is reported. Bulky aromatic groups such as 2,6-diisopropylphenyl and mesityl and alkyl groups were tolerated towards the process. Several control experiments have been performed, and the reaction outcomes indicate that the oxidation process is probably concerted with the diamination cyclization, and succinimide generated from NIS-mediated aminoamidiniumation step promoted the PhI(OAc)2-mediated oxidation step. The new methodology provides an efficient method for the synthesis of fused tricyclic ureas.

NHCs in Main Group Chemistry

“…Oxidation with N 2 O leads to the formation of stable NHC–N 2 O adducts, which eliminate N 2 and form ureas upon heating (60–100 °C). , While free NHCs are inert to oxidation with CuO, Cu 2 O, or HgO, their copper complexes (NHC)­CuCl are prone to form ureas in the presence of oxidation agents. , Analogously, reactions of NHC–AgCl complexes with elemental sulfur led to the formation of thiones . Oxidation of [SIMes-H]I with PhI­(OAc) 2 in the presence of succinimide and oxidation of bis­(benzimidazolidin-2-ylidenes) − under air yields the corresponding imidazolidin-2-ones.…”

Synthesis of Imidazolidinone, Imidazolone, and Benzimidazolone Derivatives through Oxidation Using Copper and Air

“…Among the previously described synthetic methods, the oxidation of imidazolium, imidazolinium, and benzimidazolium substrates into urea derivatives has been disclosed, using strong oxidants, such as PhI­(OAc) 2 , NaOCl, − di- tert -butyl peroxide, H 2 O 2 , , and m -chloroperoxybenzoic acid ( m -CPBA) (Scheme ). , A major disadvantage of using strong oxidants is their incompatibility with oxidant-sensitive functionalities, thus hindering the substrate scope.…”

Recent Advancements on Metal‐Free Vicinal Diamination of Alkenes: Synthetic Strategies and Mechanistic Insights

“…[40] An unprecedented metal-free and facile synthesis of several fused tricyclic ureas 11 a-j and their thiourea analogs by using the NIS/PhI(OAc) 2 mediated diamination/oxidation process in several N-alkenyl formamidines 10 a-j has been described by Jun Zhang and co-workers (Scheme 3). [41] The authors suggested that during the reaction byproduct succinimide pro-Scheme 1. PIDA/KI oxidative inter-/intermolecular diamination of terminal hydroxy styrenes with electron-rich amines.…”

“…An unprecedented metal‐free and facile synthesis of several fused tricyclic ureas 11 a – j and their thiourea analogs by using the NIS/PhI(OAc) 2 mediated diamination/oxidation process in several N ‐alkenyl formamidines 10 a ‐ j has been described by Jun Zhang and co‐workers (Scheme 3). [41] The authors suggested that during the reaction byproduct succinimide produced from the NIS‐ mediated aminoamidiniumation promoted the successive PhI(OAc) 2 ‐mediated key oxidation process. Fascinatingly, several sterically bulky aryl groups including 2,4,6‐trimethylphenyl (11 f , 11 i) , 2,6‐diethylphenyl (11 g) , and even the alkyl groups have been efficaciously tolerated towards the optimized reaction conditions.…”