Synthesis of carbazoles from ynamides by intramolecular dehydro Diels-Alder reactions.

[reaction: see text]. A new approach to carbazoles and benzannulated carbazoles by means of intramolecular dehydro Diels-Alder reactions of ynamides is reported. By using this approach, carbazoles and benzo[b]-, tetrahydrobenzo[b]-, naphtho[1,2-b]-, naphtho[2,1-b]-, and dibenzo[a,c]carbazoles have been prepared in moderate-to-good yields.