Optimized iminium-catalysed 1, 4-reductions inside the resorcinarene capsule: achieving >90% ee with proline as catalyst. Issue 40 (14th July 2021)

• Record Type: Journal Article
• Authors: Sokolova, Daria; Tiefenbacher, Konrad
• Is Part Of: RSC advances. Volume 11:Issue 40(2021)
• Page Start: 24607
• Page End: 24612
• Publication Date: 2021-07-14
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d1ra04333a
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : A supramolecular container enables highly enantioselective iminium chemistry using simple proline as the chiral source. Abstract : In previous work, we demonstrated that iminium-catalysed 1, 4-reductions inside the supramolecular resorcinarene capsule display increased enantioselectivities as compared to their regular solution counterparts. Utilizing proline as the chiral catalyst, enantioselectivities remained below 80% ee. In this study, the reaction conditions were optimized by determining the optimal capsule loading and HCl content. Additionally, it was found that alcohol additives increase the enantioselectivity of the capsule-catalysed reaction. As a result, we report enantioselectivities of up to 92% ee for iminium-catalysed 1, 4-reductions relying on proline as the sole chiral source. This is of high interest, as proline is unable to deliver high enantioselectivities for 1, 4-reductions in a regular solution setting. Investigations into the role of the alcohol additive revealed a dual role: it not only slowed down the background reaction but also increased the capsule-catalysed reaction rate.