title: Intramolecular Gold-Catalyzed and NaH-Supported Cyclization Reactions of N-Propargyl Indole Derivatives with Pyrazole and Pyrrole Rings: Synthesis of Pyrazolodiazepinoindole, Pyrazolopyrazinoindole, and Pyrrolopyrazinoindole.
abstract: Gold-catalyzed and NaH-supported intramolecular cyclization of N-propargyl indole derivatives with pyrazole and pyrrole units attached to indole is described. An efficient route to the synthesis of pyrazolodiazepinoindole, pyrazolopyrazinoindole, and pyrrolopyrazinoindole has been established. First, N-propargyl 2-(1H-pyrazol-5-yl)-1H-indole and 2-(1H-pyrrol-2-yl)-1H-indole were synthesized. Introduction of various substituents into the alkyne functionality was accomplished by Sonogashira cross-coupling reaction. Gold-catalyzed cyclization of pyrazoles having a terminal alkyne afforded the 6-exo-dig cyclization product. However, exclusive formation of 7-endo-dig cyclization products was observed with internal alkynes. On the other hand, cyclization with NaH only resulted in the formation of 6-exo-dig cyclization products regardless of the substitution of the alkyne functionality. Allenic intermediates were postulated for this outcome.
authors.affiliation: Department of Chemistry, Middle East Technical University , 06800 Ankara, Turkey.|Department of Chemistry, Hitit University , 19030 Corum, Turkey.
authors.forename: Sinan
authors.initials: S
authors.lastname: Basceken
authors.affiliation: Department of Chemistry, Middle East Technical University , 06800 Ankara, Turkey.|Department of Chemistry, Giresun University , 28200 Giresun, Turkey.
authors.forename: Serdal
authors.initials: S
authors.lastname: Kaya
authors.affiliation: Department of Chemistry, Middle East Technical University , 06800 Ankara, Turkey.
authors.forename: Metin
authors.initials: M
authors.lastname: Balci