A new procedure for the preparation of 2-vinylindoles and their [4+2] cycloaddition reaction

A new approach for the synthesis of 2-vinylindole derivatives by 5-exo mode cyclization of 2-(3-silyloxymethylallenyl)anilines was developed. The starting allenylanilines were easily prepared by the Stille coupling of o-iodoaniline and allenylstannanes. The formed 2-vinylindole derivatives were transformed into several carbazole derivatives via the [4+2] cycloaddition reaction with suitable dienophiles.