“Ship‐in‐a‐Bottle” Strategy for Immobilization of 9‐Amino(9‐deoxy)epi‐Cinchona Alkaloid into Molecularly Imprinted Solid Acid: Acetal Hydrolysis/Asymmetric Aldol Tandem Reaction

Abstract

AbstractDirect immobilization of versatile 9‐amino(9‐deoxy)epi‐cinchona alkaloids without molecule modification to achieve heterogeneous organocatalysis is of interest in the low‐cost production of optically active compounds. In this paper, an exquisite “ship‐in‐a‐bottle” strategy for direct and simple immobilization of 9‐amino‐(9‐deoxy)epi‐quinine (QNNH2) into hollow polystyrene nano‐bowl with imprinted free space around −SO3H was developed via acid‐base reaction and radical polymerization. The heterogeneous organocatalyst with 0.44 mmol g−1 of QNNH2 and 0.48 mmol g−1 of residual −SO3H possessed fast mass transfer due to the characteristic architectural features, such as thin shell thickness, free space around catalytic site, and hollow interior. In heterogeneous acetal hydrolysis/asymmetric aldol tandem reaction, good to excellent catalytic performances (90–95 % yields, anti/syn=88/12–96/4, and 97–99 % ee anti) for acetals bearing electron‐withdrawing substituents (R=o, m, p‐NO2, Cl) were achieved. The “ship‐in‐a‐bottle” QNNH2 displayed good stability and reusability with excellent catalytic performances in the reuses.