New 3-vinylation products of indole and investigation of its Diels–Alder reactivity: synthesis of unusual Morita–Baylis–Hillman-type products

3-Vinylindoles as precursors of carbazole and bis-indole derivatives were synthesized. Then, to form new carbazoles, Diels–Alder reactivity of these vinylindoles was studied with various dienophiles. During the cycloaddition reaction, unusual Morita–Baylis–Hillman-type products were observed. The structure and the formation mechanism of the products is discussed.