Reaction of alkynes and azides: Not triazoles through copper-acetylides but oxazoles through copper-nitrene intermediates

Estela Haldón, Maria Besora, Israel Cano, Xacobe C. Cambeiro, Miquel A. Pericàs, Feliu Maseras, M. Carmen Nicasio, Pedro J. Pérez

Research output: Contribution to journalArticleResearchpeer-review

32 Citations (Scopus)

Abstract

Well-defined copper(I) complexes of composition [Tpm* ,BrCu(NCMe)]BF4 (Tpm*,Br=tris(3,5- dimethyl-4-bromo-pyrazolyl)methane) or [Tpa* Cu]PF6 (Tpa*=tris(3,5-dimethyl-pyrazolylmethyl)amine) catalyze the formation of 2,5-disubstituted oxazoles from carbonyl azides and terminal alkynes in a direct manner. This process represents a novel procedure for the synthesis of this valuable heterocycle from readily available starting materials, leading exclusively to the 2,5-isomer, attesting to a completely regioselective transformation. Experimental evidence and computational studies have allowed the proposal of a reaction mechanism based on the initial formation of a copper-acyl nitrene species, in contrast to the well-known mechanism for the copper-catalyzed alkyne and azide cycloaddition reactions (CuAAC) that is triggered by the formation of a copper-acetylide complex. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Original languageEnglish
Pages (from-to)3463-3474
JournalChemistry - A European Journal
Volume20
Issue number12
DOIs
Publication statusPublished - 17 Mar 2014

Keywords

  • alkynes
  • click chemistry
  • copper
  • nitrenes
  • oxazoles
  • reactive intermediates

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