Iodoaniline Dependent Formation of N‐Aroylguanidines Versus 2‐Aminoquinazolinones from Palladium(0) Catalysed Aminocarbonylation of N‐Arylguanidines

Abstract

A family of N,N´‐diaryl‐N″‐(pyridine‐2‐ylmethyl)guanidines (B) were prepared in 70%−92% yields and subjected to palladium(0) catalyzed aminocarbonylation reactions with aryl iodides using CsOH/CHCl3 mixture as CO surrogate to afford the corresponding N‐aroylguanidines (C) in 70%−93% yields. A gram scale synthesis was reported for a representative example. When the aforementioned reaction was carried out with 2‐iodoaniline as an electrophile, either a mixture of two distinct 2‐aminoquinazolinones (D and E) or one of these 2‐aminoquinazolinones are formed. The scope of guanidines and aryl iodides were explored for both of the above‐mentioned reactions. The role of directing group in the substrates upon the successful aminocarbonylation of guanidines, B is outlined. When the ‐C(O)Ar unit in N‐aroylguanidines contain 2‐aminophenyl unit, a spontaneous cyclisation occurs to afford D or E or a mixture of both. The reactions of a pair of N‐aroylguanidines, C with PhI(OAc)2 afforded 2‐aminobenzimidazoles, T with unanticipated core. Plausible mechanisms of formation of C, D, E and T are outlined.