Synthesis of 1,2,3,4-tetrahydrocarbazoles and related tricyclic indoles

Reduction of 2-(2-nitrophenyl)-2-cyclohexene-1-ones using palladium on carbon under 1 atm of hydrogen gas at ambient temperature affords 1,2,3,4-tetrahydrocarbazoles in excellent isolated yields. The starting materials were prepared by intermolecular Stille coupling of 2-iodo-2-cyclohexen-1-ones with 2-(tributylstannyl)-1-nitrobenzenes.