Eine vielseitige Aminobenzanellierungsmethode durch Deprotonierung von 2-(1-Alkinyl)benzaldiminen und ähnlichen 2-Aza-2,4-heptadienyl-6-inen: eine mehrstufige Umlagerungskaskade

Ring closure reactions of 2,6-diazaheptatrienyl metal compounds: synthesis of 3-aminoindole derivatives and 14-membered macrocyclic dimers

2,6-Diazaheptatrienyl metal compounds 6(-)K(+) are easily accessible from the corresponding diimines 6 by deprotonation using KO-t-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 8/10. In contrast, in more concentrated solution at room temperature, the formation of 14-membered macrocyclces 13 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 7 give rise to tricyclic systems with δ-carboline backbone 12. 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.

Mechanistic Study on Rearrangement Cascades Starting from Annulated 2-Aza-hepta-2,4-dienyl-6-ynyl Anions: Formation of Aniline and Azepine Derivatives

Deprotonation of benzothiophene-derived alkynyl imine 11 with lithium diisopropylamide (LDA) and subsequent transmetalation with ZnCl2 etherate furnished azepine 12 upon aqueous workup. Similarly, alkynyl benzaldimine 1a gave a mixture of benzazepine 13 and naphthylamine 14. Allylic benzonitriles 15 a,b reacted to produce naphthylamine 16 upon deprotonation with LDA at room temperature. In an analogous manner, imino benzonitrile 17 may be converted into 4-amino isoquinoline 18 by means of an intramolecular nucleophilic attack on the nitrile function upon treatment with LDA. The allylic benzonitriles 19 a,b were prepared by LDA treatment of alkynyl imine 11. They were further converted to amino dibenzothiophene 20 by LDA deprotonation and aqueous workup. These various transformations represent the key steps of a multistep reaction cascade, which was previously postulated on the basis of quantum chemical calculations. Thus, all features of this complex rearrangement mechanism could now be confirmed experimentally. DFT calculations support the lower reactivity of zinc species in the ring-opening step compared to the lithium intermediates. All new compounds were completely characterized by spectroscopic data, including X-ray diffraction studies for the key compounds 12, 19 a, and 20.

Novel Synthesis of Azepine Derivatives via Copper-Mediated Cyclization of 2-Aza-hepta-2,4-dien-6-ynyl Anions. Intramolecular Addition of Organocopper Centers to the C−C Triple Bond

Deprotonation of alkynyl imines 1 with LDA at low temperature and subsequent transmetalation with copper thiophenolate gives the annulated azepines 11a-i in 41-73% yield after aqueous workup. The key step of the reaction is a copper-mediated intramolecular nucleophilic attack at the triple bond. [reaction: see text]