Dendritic bis- and tetrakis-iminodiacetic acid-boronate complexes in one-pot cross-coupling reactions

Iminodiacetic acids are versatile metal chelating ligands. We herein undertook a study of dendritic bis- and tetrakis-iminodiacetic acids functionalized at the peripheries of branched core moieties. The dendritic iminodiacetic acids are synthesized by O- and N-alkylations of chosen alcohol and amine reactive sites emanating from a branched core. In order to identify the reactivities of such dendritic iminodiacetic acids, chelation with arylboronates is conducted. An assessment of the hydrolysis under aq. basic condition shows that dendritic boronates hydrolyze to boronic acid significantly slower than monomeric boronates. Slower hydrolysis of dendritic boronates is taken advantage, in order to conduct competitive C-C bond-forming Suzuki-Miyaura cross-coupling reactions. Teraryl synthesis is performed using monomeric and dendritic boronates. The iterative, multiple aryl-aryl bond formation is conducted subsequently, so as to prepare tetraaryls, through consecutive reactions of chosen boronic acid, monomeric boronate, dendritic boronate and aryl bromide, in one-pot. The study shows that slower hydrolysis of dendritic boronate is valuable in order to conduct multiple consecutive aryl-aryl bond formation. (C) 2016 Elsevier B.V. All rights reserved.