Asymmetric Aza-Diels–Alder Reaction with Ion-Paired—Iron Lewis Acid—Brønsted Acid Catalyst |
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Authors: | Rei Tomifuji Prof Takuya Kurahashi Prof Seijiro Matsubara |
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Institution: | Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510 Japan |
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Abstract: | The development and use of a multiple-activation catalyst with ion-paired Lewis acid and Brønsted acid in an asymmetric aza-Diels–Alder reaction of simple dienes (non-Danishefsky-type electron-rich dienes) was achieved by utilizing the FeBr2]+FeBr4]− combination prepared in situ from FeBr3 and chiral phosphoric acid. Synergistic effects of the highly active ion-paired Lewis acid FeBr2]+FeBr4]− and a chiral Brønsted acid are important for promoting the reaction with high turnover frequency and high enantioselectivity. The multiple-activation catalyst system was confirmed using synchrotron-based X-ray absorption fine structure measurements, and theoretical studies. This study reveals that the developed catalyst promoted the reaction not only by the interaction offered by the ion-paired Lewis acid and the Brønsted acid but also noncovalent interactions. |
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Keywords: | asymmetric reactions density functional calculations Diels–Alder reaction in situ XAS iron |
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