Elusive Metal-Free Primary Amination of Arylboronic Acids: Synthetic Studies and Mechanism by Density Functional Theory

Abstract

Herein, we disclose the first metal-free synthesis of primary aromatic amines from arylboronic acids, a reaction that has eluded synthetic chemists for decades. This remarkable transformation affords structurally diverse primary arylamines in good chemical yields, including a variety of halogenated primary anilines that often cannot be prepared via transition metal-catalyzed amination. The reaction is operationally simple, requires only a slight excess of aminating agent, proceeds under neutral or basic conditions and, importantly, it can be scaled up to provide multigram quantities of primary anilines. Density functional calculations reveal that the most likely mechanism involves a facile 1,2-aryl migration and that the presence of an ortho nitro group in the aminating agent plays a critical role in lowering the free energy barrier of the 1,2-aryl migration step.

Direct Stereospecific Synthesis of Unprotected N-H and N-Me Aziridines from Olefins

“…This pathway is akin to the mechanism proposed for amination of aryl boronic acids with 1a . (32) While this mechanism may account for amino-oxyarylated products (e.g., 4a & 4b ) observed under some experimental conditions, the calculated barrier for this mechanism, as well as alternative polar mechanisms, are higher in energy than the nitrene mechanism presented in Pathway A.…”

“…1) as the stoichiometric aminating agent. (32) The transformation proceeds under neutral or basic conditions and can be conducted on a multi-gram scale to provide structurally diverse primary arylamines. The versatility and robustness of 1a prompted us to explore other uses of this aminating agent, specifically for the direct functionalization of readily available and inexpensive olefins.…”

Synthesis, characterization and catalytic activity of gold complexes with pyridine-based selone ligands

“…Moreover, the catalytic activities using gold complexes with selone ligands are better than those of gold complexes with thione ligands [38] and HAuCl 4 . Then, the complex 3 was chosen as the optimal catalyst to screen the various solvents (Table 3, entries [8][9][10][11][12]. High yield of 95% of the desired products was achieved within 3 h in water solvent.…”

“…Therefore, a variety of protocols for synthesizing functionalized anilines have been developed [7][8][9][10][11][12][13][14][15][16][17][18][19]. The desirable method for the synthesis of functionalized anilines is the reduction of nitroarenes using transition metal catalysts in the presence of sodium tetrahydroborate (NaBH 4 ) [20].…”

Rh/Cu-cocatalyzed Ring-opening Diborylation of Dibenzothiophenes for Aromatic Metamorphosis via Diborylbiaryls

“…Kürti's group reported the oxidative amination of arylboronic acids or esters with an aryloxyamine reagent. 20 The electrophilic amination of 2a successfully took place, and the corresponding hydroxydibenzazaborin 7a was formed in 53% yield (Scheme 4b).…”