Development of Catalytic Reactions Using N-Sulfonyl-1,2,3-triazoles as Precursors of Carbene Complexes

N-Sulfonyl-1,2,3-triazoles are readily prepared by a copper (I)-catalyzed 1,3-dipolar cycloaddition reaction of terminal alkynes with sulfonyl azides. Their ring-chain tautomerization generates alpha-imino diazo compounds, although the equilibrium lies far to the triazole form in general. Transition metal catalysts, especially rhodium (II) carboxylate dimers, can efficiently trap the transient alpha-imino diazo compounds to give alpha-imino metal carbene complexes with the extrusion of molecular nitrogen. These metal carbene complexes share many features with the well-known alpha-oxo metal carbene complexes derived from alpha-dizao carbonyl compounds. However, in some cases, the presence of the nucleophilic imino nitrogen endows their unique reactivity depending on the reactants as well as the catalysts. In this article, we describe nickel (0) and rhodium (II)-catalyzed inter- and intramolecular reactions of N-sulfonyl-1,2,3-triazoles with various types of reactants such as carbon, oxygen, and sulfur nucleophiles, which provide a facile method for the synthesis of nitrogen-containing compounds. These reactions are successfully applied to all-in one-pot reactions starting from terminal alkynes.