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

Basceken S., Kaya S., BALCI M.

JOURNAL OF ORGANIC CHEMISTRY, vol.80, no.24, pp.12552-12561, 2015 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 80 Issue: 24
  • Publication Date: 2015
  • Doi Number: 10.1021/acs.joc.5b02419
  • Journal Name: JOURNAL OF ORGANIC CHEMISTRY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.12552-12561
  • Middle East Technical University Affiliated: Yes

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 pyratoles 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 hark; 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.