Regioselectivity of Larock heteroannulation: A contribution from electronic properties of diarylacetylenes

• Main Authors: Nared Phetrak, Thanya Rukkijakan, Jakkapan Sirijaraensre, Samran Prabpai, Palangpon Kongsaeree, Chayada Klinchan, Pitak Chuawong
• Other Authors: Faculty of Engineering
• Format: Article
• Published: 2018
• Subjects: Chemistry
• Online Access: https://repository.li.mahidol.ac.th/handle/123456789/31501
• Institution: Mahidol University

A series of 2,3-diarylindoles were synthesized from 2-iodoaniline and unsymmetrical diarylacetylenes using the Larock heteroannulation. Diarylacetylenes bearing electron-withdrawing substituents lead to 2,3-diarylindoles with substituted phenyl moieties at the 2-position as major products, while those with electron-donating groups preferably yield indole products with substituted phenyl moieties at the 3-position. The regioisomeric product ratios exhibit a clear correlation with Hammett σp values. DFT calculations reveal the origin of this effect, displaying smaller activation energy barriers for those pathways leading to the major regioisomer. © 2013 American Chemical Society.