Electronic effects of ruthenium-catalyzed [3+2]-cycloaddition of alkynes and azides
KAUST DepartmentBiological and Environmental Sciences and Engineering (BESE) Division
KAUST Catalysis Center (KCC)
Chemical Science Program
Physical Sciences and Engineering (PSE) Division
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AbstractA combined experimental and theoretical study of ruthenium-catalyzed azide-alkyne cycloaddition (RuAAC) reactions is presented and various electronic analyses were conducted to provide a basis in understanding the observed regioselectivity of the 1,2,3-triazole products. Computational studies using density functional theory (DFT) and atoms in molecules quantum theory (AIM) further yield fresh details on the electronic factors that determine the regioselectivity in the RuAAC. It is found that the formation of 1,2,3-triazole products is irreversible and from the Hammett study, the pathway involving a vinyl cationic intermediate is ruled out. The electronic effect favors the formation of 5-electron-donating-group substituted-1,2,3-trizoles. © 2010 Elsevier Ltd. All rights reserved.
SponsorsWe acknowledge the financial support from NSC (95-2113-M-008-007-MY3) to D.-R.H., from National University of Singapore (R-143-000-346-133 and R-143-000-376-112) and KAUST (400000 0076) to K.-W.H. R.L. is grateful for a Provost fellowship from KAUST. We are indebted to Dr. Dodi Heryadi of KAUST Super-computing Laboratory for advice on computational chemistry and to Prof. Jorg Eppinger for useful discussions.