Nanosheet-enhanced efficiency in amine-catalyzed asymmetric epoxidation of α, β-unsaturated aldehydes via host-guest synergy

- We proposed an efficient strategy for enhancing catalytic activity and enantioselectivity of amine-catalyzed asymmetric epoxidation of α, β-unsaturated aldehydes.
- The strategy simply used α-amino acid anion intercalated in the interlayer space of LDHs as chiral catalysts.
- The LDH nanosheet enhanced the catalytic activity by affording the desired basicity and the enantioselectivity by serving as the rigid substituent of amino acids.

Amine-catalyzed asymmetric epoxidation of α, β-unsaturated aldehydes has been promoted by attaching the nanosheets of layered double hydroxides (LDHs), a natural and/or synthetic anionic layered compound. 76% of epoxide yield and 93% ee of major diastereomer have been afforded in the asymmetric epoxidation of cinnamaldehyde. The amine sites employed here are the amino group in α-amino acid anion intercalated in the interlayer space of LDHs. The nanosheets of LDHs have been revealed to play key role in the enhancement of catalytic activity by affording the desired basicity and the boost of enantioselectivity by serving as the rigid substituent of amino acids. The hydrophobic interlayer microenvironment and ordered arrangement of intercalated amino acid anions additionally contribute to the catalytic efficacy. Stronger interlayer hydrophobicity favors the conversion and epoxide yield and better arrangement of interlayer anions favors the ee.

The attachment of nanosheets of layered double hydroxides (LDHs) impressively promoted amine-catalyzed asymmetric epoxidation of α, β-unsaturated aldehydes by affording the desired basicity and serving as the rigid substitution.