Asymmetric Aza-Diels-Alder Reaction with Ion-Paired-Iron Lewis Acid-Brønsted Acid Catalyst

Rei Tomifuji; Takuya Kurahashi; Seijiro Matsubara

doi:10.1002/chem.201901563

Asymmetric Aza-Diels-Alder Reaction with Ion-Paired-Iron Lewis Acid-Brønsted Acid Catalyst

Chemistry. 2019 Jul 5;25(38):8987-8991. doi: 10.1002/chem.201901563. Epub 2019 Jun 11.

Authors

Rei Tomifuji¹, Takuya Kurahashi¹, Seijiro Matsubara¹

Affiliation

¹ Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan.

PMID: 31066945
DOI: 10.1002/chem.201901563

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.

Keywords: Diels-Alder reaction; asymmetric reactions; density functional calculations; in situ XAS; iron.