Substituent effects in aminocarbonylation of para-substituted iodobenzenes

Iodobenzene derivatives possessing various substituents (amino, hydroxy, tert-butyl, methyl, isopropyl, phenyl, fluoro, chloro, methoxycarbonyl, acetyl, trifluoromethyl, nitro) in the para position were aminocarbonylated using tert-butylamine and n-butylamine as N-nucleophiles. A palladium(0) catalyst formed in situ from palladium(II) acetate and triphenylphosphine was used. Carboxamide and keto-carboxamide type compounds were formed via single and double carbon monoxide insertion, respectively. While 4-substituents with negative Hammett constants (sigma(p)) decrease reactivity of the substrates, the iodoaromatics possessing electron-withdrawing group (characterized by positive Hammett constants (sigma(p))) in the 4-position have shown high reactivity. Highly active catalysts were obtained in the presence of xantphos accompanied by the chemoselective formation of the corresponding carboxamides. The difference in reactivity of iodoarene and bromoarene functionalities enabled the synthesis of bromo-substituted compounds suitable for further functionalization. (C) 2016 Elsevier Ltd. All rights reserved.