Ruthenium-catalyzed cycloadditions of 1-haloalkynes with nitrile oxides and organic azides: Synthesis of 4-haloisoxazoles and 5-halotriazoles

James S. Oakdale, Rakesh K. Sit, Valery V. Fokin

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

(Cyclopentadienyl)(cyclooctadiene) ruthenium(II) chloride [CpRuCl(cod)] catalyzes the reaction between nitrile oxides and electronically deficient 1-choro-, 1-bromo-, and 1-iodoalkynes leading to 4-haloisoxazoles. Organic azides are also suitable 1,3-dipoles, resulting in 5-halo-1,2,3-triazoles. These air-tolerant reactions can be performed at room temperature with 1.25 equivalents of the respective 1,3-dipole relative to the alkyne component. Reactive 1-haloalkynes include propiolic amides, esters, ketones, and phosphonates. Post-functionalization of the halogenated azole products can be accomplished by using palladium-catalyzed cross-coupling reactions and by manipulation of reactive amide groups. The lack of catalysis observed with [Cp RuCl(cod)] (Cp=pentamethylcyclopentadienyl) is attributed to steric demands of the Cp* (η5-C5Me5) ligand in comparison to the parent Cp (η5-C5H5). This hypothesis is supported by the poor reactivity of [(η5-C 5Me4CF3)RuCl(cod)], which serves as a an isosteric mimic of Cp* and as an isoelectronic analogue of Cp.

Original languageEnglish
Pages (from-to)11101-11110
Number of pages10
JournalChemistry - A European Journal
Volume20
Issue number35
DOIs
Publication statusPublished - 25 Aug 2014
Externally publishedYes

Keywords

  • alkynes
  • cycloadditions
  • halides
  • regioselectivity
  • ruthenium

ASJC Scopus subject areas

  • Chemistry(all)

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