Synthesis of a new series of 2-vinylindoles and their cycloaddition reactivity

The regioselective synthesis of 2-vinylindoles was achieved through the use of 4,7-dihydroindole 19. Reactions of these 2-vinylindoles as 4π-component gave 2,3-disubstitue indoles as well as the expected Diels–Alder products.