Synthesis of Indenyl Triazenes by Rhodium-Catalyzed Annulation Reactions

The synthesis of vinyl triazenes by metal-catalyzed processes is attractive, but only few examples have been described so far. Here, we describe Rh-catalyzed [3+2] annulation reactions of arylboronic acid derivatives and alkynyl triazenes. These reactions provide access to functionalized indenyl triazenes. The regioselectivity of the annulations is mostly high, but strongly dependent on the substituents on the alkyne. The triazene group in the products can be cleaved under acidic condition. In contrast to what has been reported for other vinyl triazenes, rearrangements are observed instead of direct substitution reactions.