Sulfur-Assisted and 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU)-Catalyzed Cyclization of 2-Alkynylanilines for the Metal-Free Synthesis of Indole Derivatives.

A sulfur-assisted and 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU)-catalyzed cyclization of 2-alkynylanilines for the metal-free synthesis of indole derivatives is reported. As a result of the metal-free process, the ready availability of the starting materials and the simple and convenient operation, the type of reaction presented here has potential utility in organic synthesis. A 10-gram scale preparation may demonstrate the possibility of its application in the environmentally friendly synthesis of indole derivatives.