Intramolecular Gold-Catalyzed and NaH-Supported Cyclization Reactions of N-Propargyl Indole Derivatives with Pyrazole and Pyrrole Rings: Synthesis of Pyrazolodiazepinoindole, Pyrazolopyrazinoindole, and Pyrrolopyrazinoindole

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...

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Bibliographic Details
Published in:Journal of organic chemistry 2015-12, Vol.80 (24), p.12552-12561
Main Authors: Basceken, Sinan, Kaya, Serdal, Balci, Metin
Format: Article
Language:English
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Summary: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.
ISSN:0022-3263
1520-6904
DOI:10.1021/acs.joc.5b02419