Heat Versus Basic Conditions: Intramolecular Dehydro-Diels-Alder Reaction of 1-Indolyl-1,6-heptadiynes for the Selective Synthesis of Substituted Carbazoles

The intramolecular dehydro-Diels-Alder reaction of 1-indolyl-1,6-heptadiynes proceeds smoothly under rather mild heating conditions to give substituted carbazoles in moderate to good yields. The reaction of 7-aryl-1-indolyl-1,6-heptadiynes under heating gives the corresponding carbazoles chemoselectively in high yields, whereas the reaction under basic conditions gives naphthalenes as major products.