Rhodium-Catalyzed Oxidative Cycloaddition of N-tert-Butoxycarbonylhydrazones with Alkynes for the Synthesis of Functionalized Pyrroles via C(sp3)–H Bond Functionalization

Chun Ming Chan, Zhongyuan Zhou, Wing Yiu Yu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

11 Citations (Scopus)

Abstract

� 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim A rhodium(III)-catalyzed cycloaddition of N-tert-butoxycarbonylhydrazones with internal alkynes was developed. The reaction features a regioselective α-imino alkyl C(sp3)−H bond functionalization resulting in selective formation of highly functionalized NH-free pyrroles. Our studies showed that utilizing the N-tert-butoxycarbonyl (N-Boc) as the oxidizing directing group is critical for achieving the observed pyrrole formation versus the isoquinoline formation. To account for the pyrrole formation, we hypothesized that a prior tautomerization of the N-Boc-hydrazones to enamines should occur, followed by regioselective C(sp2)–H cleavage to form a putative five-membered rhodacycle. Subsequent coupling of the rhodacycle with the alkynes would afford the pyrrole products. (Figure presented.).
Original languageEnglish
Pages (from-to)4067-4074
Number of pages8
JournalAdvanced Synthesis and Catalysis
Volume358
Issue number24
DOIs
Publication statusPublished - 1 Jan 2016

Keywords

  • alkynes
  • cycloaddition
  • C–H activation
  • nitrogen heterocycles
  • rhodium

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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