Ring Closure Reactions of 2,6-Diazaheptatrienyl Metal Compounds: Synthesis of 3-Aminoindole Derivatives and 14-Membered Macrocyclic Dimers

2,6-Diazaheptatrienyl metal compounds <b>6</b>^<b>–</b><b>K</b>^<b>+</b> are easily accessible from the corresponding diimines <b>6</b> by deprotonation using KO-<i>t</i>-Bu as base. According to quantum chemical calculations, they are, in comparison to other isomeric species with nitrogen atoms in other positions, highly reactive intermediates, which undergo in dilute solution at 50 °C ring closure reactions to form 3-aminoindole derivatives <b>8/10</b>. In contrast, in more concentrated solution at room temperature, the formation of 14-membered macrocyclces <b>13</b> as a result of formal dimerization is observed. The 3-aminoindole derivatives obtained in this work possess rare substitution patterns, and the macrocyclic compounds are essentially unknown. Two-fold vinylogous derivatives <b>7</b> give rise to tricyclic systems with δ-carboline backbone <b>12</b>. The experimental results are interpreted using high-level DFT calculations with regard to the possible reaction mechanism and the nature of the transition state of the five-membered ring formation. The molecular structures in the solid state of all types of compounds were elucidated by X-ray diffraction.