Gold(I)-Catalyzed enantioselective synthesis of tetrahydrocarbazoles through dearomative [4+2] cycloadditions of 3/2-substituted 2/3-vinylindoles

The gold-catalyzed synthesis of tetrahydrocarbazoles through dearomative [4+2] cycloaddition reactions of 3/2-substituted 2/3-vinylindoles with allenamides is reported. In particular, we optimized the enantioselective variant of these cycloadditions. Using allenamides as dienophiles 3-substituted 2-vinylindoles gave the corresponding carbazoles with high chemo-, regio- and enantioselectivity. Good results were obtained also with 2-methyl 3-vinylindoles even if mixtures of (Z) and (E) isomers were isolated in high er and in excellent overall yields.