Interrupting the [Au]-Catalyzed Nitroalkyne Cycloisomerization: Trapping the Putative α-Oxo Gold Carbene with Benzo[c]isoxazole

The [Au]-catalyzed nitroalkyne cycloisomerization of 2-alkynylnitrobenzenes leading to anthranils has been interrupted by possible trapping of the postulated intermediate alpha-oxo gold carbene with an external nucleophile such as benzo[c]isoxazole (anthranil). At the outset, this provides a simple synthesis of highly functionalized 3-acyl-(2-formylphenyl)-2H-indazoles with the sequential C-O, C-N, and N-N bond formations. This provides indirect support for the existence of alpha-oxo gold carbenes in the [Au]-catalyzed internal redox processes of nitroalkynes.

Automated summary

The [Au]-catalyzed nitroalkyne cycloisomerization process leading to anthranils may be affected by the trapping of the postulated intermediate alpha-oxo gold carbene with external nucleophiles. This study also provides evidence for the synthesis of highly functionalized indazoles through sequential bond formations.