Ruthenium-Catalyzed 1,6-Aromatic Enamide-Silylalkyne Cycloisomerization: Approach to 2,3-Disubstituted Indoles

Cycloisomerization is an atom economic procedure that converts dienes and enynes into cyclic molecules. To date, cycloisomerization between enamides and silylalkynes has not been explored. We found that N-acyl-N-vinyl-2-silylalkynylaniline derivatives undergo a cycloisomerization in the presence of a well-defined ruthenium hydride to give a 2,3-disubstitued indole. The vinyl and silylmethyl substituents on the 2- and 3-positions of the indole can be easily converted to other functional groups.