Hypervalent-Iodine-Mediated Formation of Epoxides from Carbon(sp2)-Carbon(sp3) Single Bonds
Shan Jiang1, Tai-Shan Yan1, Yong-Chao Han1
1State Key Laboratory of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering, College of Chemistry, Nankai University , Tianjin 300071, China.
Abstract:
We have developed an efficient method for direct formation of epoxide groups from carbon(sp2)-carbon(sp3) single bonds of β-keto esters; the reaction is mediated by the water-soluble hypervalent iodine(V) reagent AIBX (5-trimethylammonio-1,3-dioxo-1,3-dihydro-1λ5-benzo[d][1,2]iodoxol-1-ol anion). On the basis of the results of density functional theory calculations and experimental studies, we propose that the reaction proceeds by a two-stage mechanism involving dehydrogenation of the β-keto ester substrates and epoxidation of the resulting enone intermediates. The rate-limiting step is abstraction of the β'-C-H (calculated free energy of activation, 24.5 kcal/mol).
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