AgNO3·SiO2: Convenient AgNPs source for the sustainable hydrofunctionalization of allenyl-indoles using heterogeneous catalysis.

The great catalytic performance of supported silver nitrate in silica gel for indole-tethered allene hydrofunctionalization together with a selectivity reversal in comparison with homogeneous gold catalysis have been shown. • Convenient silver-catalyzed heterogeneous method for the intramolecular allene hydroarylation of indoles. • Divergent and controlled preparation of three different final products: 9 H -carbazoles, 4,9-dihydro-1 H -carbazoles, and spiroindolenines. • The AgNPs-catalyzed allene reactions contrast with the reaction pattern previously reported in homogeneous gold-catalyzed reactions. Supported silver nitrate in silica gel has been demonstrated as an excellent heterogeneous catalytic system for the selective hydroarylation of indole-tethered allenes, with a selectivity reversal in comparison with homogeneous gold catalysis. In this way, the controlled preparation of 1,2-disubstituted-9 H -carbazoles, 1,2-disubstituted-4,9-dihydro-1 H -carbazoles, and 2,4-disubstituted-spiro[cyclopentane-1,3′-indol]-3-enes has been accomplished. Control experiments supported by Density Functional Theory calculations strongly suggest that indole-tethered allenes react through a 5- endo - dig -carbometallation/rearrangement sequence, which contrasts to the previously reported 6- endo - dig -carbometallation pathway promoted by [Au(I)]-catalysts in related systems. [ABSTRACT FROM AUTHOR]