Cycloisomerization of 2-alkynylanilines to indoles catalyzed by carbon-supported gold nanoparticles and subsequent homocoupling to 3,3'-biindoles.

However, the reductive nature of those conditions limited thereaction scope and precluded the possibility of furthercascade functionalization. Soon after, Somorjai, Toste, andco-workers reported that Pt nanoparticles supported onmesoporous silica are able to efficiently promote the intra-molecular heterocyclization of N-carbamate protected 2-alkynylanilinestoaffordthecorrespondingindoleproductsinexcellent yields.