1507357-32-5Relevant articles and documents
Dissecting the Electronic Contribution to the Regioselectivity of the Larock Heteroannulation Reaction in the Oxidative Addition and Carbopalladation Steps
Chuawong, Pitak,Gable, Kevin P.,Yiamsawat, Kanyapat
, p. 1218 - 1229 (2022/01/27)
Substituted 2-iodoaniline derivatives were prepared and utilized as reactants, along with asymmetric diarylacetylenes, to synthesize a series of 6-substituted-2,3-diarylindole derivatives via the Larock heteroannulation reaction. Electron-donating substituents on the 2-iodoaniline derivatives retarded the reaction, while electron-withdrawing substituents provided a complete conversion to the indole products. In addition, the electronic properties of the substituted 2-iodoaniline reactants displayed no influence toward regioselectivity. On the contrary, the electronic effect from unsymmetrical diarylacetylenes significantly influenced the regiochemical outcome of the reaction. Density functional theory calculations of the oxidative addition and carbopalladation steps revealed the electronic influences of the substituted 2-iodoaniline derivatives toward the overall rate of the reaction. In contrast, the electronic properties of the asymmetric diarylacetylene remained the critical product-determining factor of regioselectivity.
Regioselectivity of Larock heteroannulation: A contribution from electronic properties of diarylacetylenes
Phetrak, Nared,Rukkijakan, Thanya,Sirijaraensre, Jakkapan,Prabpai, Samran,Kongsaeree, Palangpon,Klinchan, Chayada,Chuawong, Pitak
, p. 12703 - 12709 (2014/01/17)
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.