Role of Adamantane Amide Based on L-Proline Double-H Potential Organocatalyst in Aldol Reaction with Product Separated via Host-guest Interaction

Novel chiral proline-based organocatalysts with amide and thiourea–amine units for highly efficient asymmetric aldol reaction in saturated brine without additives

A series of novel proline-based organocatalysts with amide and thiourea-amine units (7a–7f) were developed and evaluated in the asymmetric aldol reaction of 4-nitrobenzaldehyde with cyclohexanone. The organocatalyst (7c or 7d, 5 mol%) exhibited efficient catalytic activity to afford aldol products in high diastereoselectivity (up to >99:1), enantioselectivity (up to >99%), and yield (up to >96%) at 0 °C in saturated brine without adding an acid. Aldol products of benzaldehyde derivatives almost universally provide high diastereoselectivity and enantioselectivity.

Preparation of prolinamide with adamantane for aldol reaction catalysis in brine and separation using a poly(AN-MA-β-CD) nanofibrous film via host-guest interaction

Prolinamides with double-H potential were prepared and employed as organocatalysts in asymmetric aldol reactions. The catalyst with adamantane showed improved catalytic activity, which was further enhanced by using brine as the solvent. A series of aldol reactions in brine at 0 °C provided good yields (up to 98%) with high diastereoselectivities (>99 : 1) and enantioselectivities (>99%). The prepared catalyst was adsorbed by a nanofibrous film of poly(AN-MA-β-CD) via host-guest interaction in the reaction system. The catalyst was separated from the film by applying ultrasound, with a total recovery of 96.2%. The catalyst was reused up to five times without a significant change in diastereoselectivity and enantioselectivity.