Diffusion Control in Single-Site Zinc Reticular Amination Catalysts

Synthesis of Azuleno[2,1-b]quinolones and Quinolines via Brønsted Acid-Catalyzed Cyclization of 2-Arylaminoazulenes

Quinolone and quinoline derivatives are frequently found as substructures in pharmaceutically active compounds. In this paper, we describe a procedure for the synthesis of azuleno[2,1-b]quinolones and quinolines from 2-arylaminoazulene derivatives, which are readily prepared via the aromatic nucleophilic substitution reaction of a 2-chloroazulene derivative with several arylamines. The synthesis of azuleno[2,1-b]quinolones was established by the Brønsted acid-catalyzed intramolecular cyclization of 2-arylaminoazulene derivatives bearing two ester groups at the five-membered ring. The halogenative aromatization of azuleno[2,1-b]quinolones with POCl3 yielded azuleno[2,1-b]quinolines with a chlorine substituent at the pyridine moiety. The aromatic nucleophilic substitution reaction of azuleno[2,1-b]quinolines bearing chlorine substituent with secondary amines was also investigated to afford the aminoquinoline derivatives. These synthetic methodologies reported in this paper should be valuable in the development of new pharmaceuticals based on the azulene skeleton.

Hydroamination of Phenylacetylene with Aniline over Gold Nanoparticles Embedded in the Boron Imidazolate Framework BIF-66 and Zeolitic Imidazolate Framework ZIF-67

The hydroamination of alkynes is an atom-economy process in the organic synthesis for the C-N bond formation, thereby allowing the production of fine chemicals and intermediates. However, direct interaction between alkynes and amines is complicated due to the electron enrichment of both compounds. Therefore, efficient hydroamination catalysts, especially heterogeneous ones, are in great demand. This work aimed at the development of novel heterogeneous catalysts based on zeolite-like metal-organic frameworks for phenylacetylene hydroamination. The sodalite (SOD) type zeolitic imidazolate framework ZIF-67 (Co(meim)₂, meim = 2-methylimidazolate) and boron imidazolate framework BIF-66 ({Co[B(im)₄]₂}_n, im = imidazolate) were studied as the carriers for the gold nanoparticles (Au-NPs). Au-NPs were embedded in the ZIF-67 and BIF-66 matrices by incipient wetness impregnation. Au@ZIF-67 and Au@BIF-66 hybrids were studied for the first time in the liquid phase hydroamination of phenylacetylene with aniline in an air atmosphere and have shown high activity and selectivity in respect to imine in this process. The pronounced impact of the nature of the metal-organic carrier, Au source, and reducing agent on the catalytic performance of the synthesized nanomaterials was found. To the best of our knowledge, it is the first example of using the zeolitic imidazolate framework and boron-imidazolate framework as the components of the gold-containing catalytic systems for the alkyne hydroamination.