Arylamination of 1,3,7-Triazapyrene

The practical importance of aromatic and heteroaromatic amines is commonly known [1, 2]. Such compounds are traditionally obtained by nucleophilic substitution of halogens or other nucleophilic groups under the standard conditions [3] or in the presence of catalysts [4]. An alternative approach in the case of electron-deficient azines may be direct oxidative nucleophilic substitution of hydrogen [5, 6] for the corresponding amino group, because these reactions do not require a prior modification of the molecule with good leaving groups, or the use of costly catalysts or ligands. We have previously reported a successful oxidative amination [7] and alkylamination [8] of 1,3,7-triazapyrenes in aqueous medium, by using a single-electron oxidant – K3Fe(CN)6. For the next stage of our research we were interested in the possibility of preparing arylamino derivatives of this heterocycle, which became the goal of the present work. The mechanism of oxidative SNH-amination reactions includes a nucleophilic addition of the amine with the formation of σ-adduct and its subsequent rearomatization by the action of an oxidant. However, the conditions of these reactions were not suitable for conducting arylamination due to the low nucleophilicity of arylamine and their propensity to oxidation. For this reason, SNH-arylamination reactions are quite rare. The majority of known examples are intramolecular processes [9-11]. Intermolecular oxidative arylamination in the azine series is currently known only for the cases of 5-azacinnoline [12], 1,2,4-triazine [13], and 3-nitropyridine [14, 15]. The reactions in all cases were performed with arylamines and hetarylamines in the presence of strong bases (LiHMDS, LDA, BuLi), thus the reactive nucleophile was not arylamine, but rather its N-anion (arylamide anion). The hydride ion acceptor at the second stage of the process is usually air oxygen [12], but in its absence – a nitro group [15] or a C=N bond of the substrate [13]. We generated sodium arylamides from primary arylamines by the action of an excess of sodium hydride. However, the arylamination of 1,3,7-triazapyrene (1) in anhydrous tetrahydrofuran, dioxane, or acetonitrile at the temperature range from 20°С to the boiling points of the solvents could not be achieved. The