Computational analysis of the formation mechanisms of carbazoles.

Gold-, platinum-, and silver-catalyzed formation mechanisms of carbazole alkaloids were investigated computationally. The structural properties of the reactants were studied in various solvents and with different functionals. The hybrid functionals B3LYP and M06-2X in density functional theory were used to determine and discuss the energetics of the compounds. The electronic properties of groups attached to the terminal alkyne played an essential role in the formation of carbazoles. The stereo- and chemoselectivity of the mechanism were investigated and the natural bond orbitals of the reactants were determined. Furthermore, this theoretical study has suggested a gold-catalyzed alternative mechanism for the synthesis of 1,4-dihydrocyclopenta[b]indole derivative.