Abstract
Suitably substituted electron-deficient 1,2,3-triazoles exist in equilibrium with
their ring-opened α-diazoimine tautomers. This phenomenon was used to facilitate the
generation of synthetically useful metallo azavinyl carbene intermediates. In this
short review, we describe recent developments in the transition-metal-catalyzed decomposition
of electron-deficient (annulated) 1,2,3-triazoles to form metallo azavinyl carbenes,
and their application in the synthesis of highly functionalized nitrogen-based heterocycles
and building blocks through various synthetic transformations, such as transannulation,
cyclopropanations, insertion reactions, ylide formation/rearrangements, and ring expansions.
1 Introduction
2 Ring–Chain Isomerism
3 Synthesis of N-Sulfonyl-1,2,3-triazoles
4 Denitrogenative Transformations of 1,2,3-Triazoles
4.1 Transannulations with Nitriles and Alkynes
4.2 Transannulations with Alkenes or Carbonyl Compounds
4.3 Transannulations with (Hetero)cumulenes or 1,3-Dienes
4.4 Insertions into X–H or C–X bonds
4.5 Rearrangement/Ring Expansion
4.6 Miscellaneous Transformations
5 Summary and Outlook
Key words
triazoles - carbenes - imines - diazo compounds - catalysis - rhodium
