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

Takayuki Kudoh, Syo Fujisawa, Megumi Kitamura, Akira Sakakura* 
Synlett2017, 28 (16), 2189–2193.  (Published  online: July 6, 2017) 
DOI: 10.1055/s-0036-1588461 

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.