Synthesis of Cyclohepta[]indoles and Furo[3,4-]carbazoles from Indoles, Tertiary Propargylic Alcohols, and Activated Alkynes.

A robust metal-free and environmentally friendly approach to cyclohepta[]indole and furo[3,4-]carbazole frameworks via a three-component reaction from indoles, tertiary propargylic alcohols, and activated alkynes is described. A probable mechanism was proposed on the basis of the isolation and characterization of a key intermediate of the reaction. A gram-scale reaction and product derivatizations were also performed to demonstrate the practicality of the developed methodology.