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.

DOI: 10.1021/acs.joc.5b02419

Cite this paper

@article{Basceken2015IntramolecularGA, 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.}, author={Sinan Basceken and Serdal Kaya and Metin Balci}, journal={The Journal of organic chemistry}, year={2015}, volume={80 24}, pages={12552-61} }