Selective formation of 1,4-disubstituted triazoles from ruthenium-catalyzed cycloaddition of terminal alkynes and organic azides: Scope and reaction mechanism

Pei Nian Liu, Juan Li, Fu Hai Su, Kun Dong Ju, Li Zhang, Chuan Shi, Herman H Y Sung, Ian D. Williams, Valery V. Fokin, Zhenyang Lin, Guochen Jia

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Abstract

The catalytic activity of a series of ruthenium complexes lacking cyclopentadienyl ligands has been evaluated for the cycloaddition of terminal alkynes and azides to give selectively 1,4-disubstituted 1,2,3-triazoles. The complex RuH(η 2-BH 4)(CO)(PCy 3) 2 was found to be an effective catalyst for the cycloaddition reactions. In the presence of RuH(η 2-BH 4)(CO)(PCy 3) 2, primary and secondary azides reacted with a range of terminal alkynes containing various functionalities to selectively produce 1,4-disubstituted 1,2,3-triazoles. The ruthenium-catalyzed azide-alkyne cycloaddition appears to proceed via a Ru-acetylide species as the key intermediate, which undergoes formal cycloaddition with an azide to give a ruthenium triazolide complex. The 1,4-disubstituted 1,2,3-triazole product is generated by metathesis of the triazolide complex with a terminal alkyne. In support of the reaction mechanism, the acetylide complex Ru(C≡CCMe 3) 2(CO)(PPh 3) 3 reacts cleanly with benzyl azide to give a ruthenium triazolide complex, which reacts with excess tert-butylacetylene in the presence of PPh 3 to give 4-tert-butyl-1-benzyl-1,2,3-triazole and the diacetylide complex Ru(C≡CCMe 3) 2(CO)(PPh 3) 3. The mechanism is also supported by DFT calculations.

Original languageEnglish
Pages (from-to)4904-4915
Number of pages12
JournalOrganometallics
Volume31
Issue number13
DOIs
Publication statusPublished - 9 Jul 2012
Externally publishedYes

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ASJC Scopus subject areas

  • Organic Chemistry
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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