SummaryEnantioselective desymmetrization of meso-aziridines and meso-epoxides with various nucleophiles by organocatalysis has emerged as a cutting-edge approach in recent years. This review summarizes the origin and recent developments of enantioselective desymmetrization of meso-aziridines and meso-epoxides in the presence of organocatalysts.
A series of bifunctional phase-transfer catalysts with a quaternary onium center and a hydrogen-bonding donor group were prepared for the fixation of CO2 with epoxides under mild conditions by using a CO2 balloon (1 atm) to produce cyclic carbonates up to 95% yields.
Ferrocene (Fc) as a privileged framework for chiral organocatalysts (Orgcat) has been developed rapidly in recent years. Herein, five categories have been summarized, including Fc‐based nucleophilic, bifunctional, Brønsted acid, hydrogen‐bonding organocatalysts and Fc‐based frustrated Lewis pairs. Their applications in enantioselective transformations were also highlighted and discussed in this Minireview.
A novel series of dipeptide-like organocatalysts derived from proline, amino acids and primary amines have been prepared for direct asymmetric aldol reactions between various aromatic aldehydes and acetone to afford aldol products in good yields (up to 82%) and moderate enantioselectivities (up to 67% ee) with only 1 mol% of catalyst-loading in brine. Under the same conditions, the direct asymmetric aldol reactions of aromatic aldehydes and cyclohexanone give aldol products with high yields (up to 91%) and moderate to good enantioselectivities (up to 88% ee) and excellent diastereoselectivities (up to 99% dr).These organocatalysts are easily synthesized from commercially available materials in multi-gram scale with high modularity in their structural and stereogenic properties. Fig. 1 Typical small peptides catalysed direct aldol reactions.
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