Advances on Asymmetric Organocatalyzed Mannich Reactions in Aqueous and Non-aqueous Media

Considerable number of nitrogen containing active pharmaceutical ingredients and natural products are frequently synthesized from optically pure β-amino ketones, aldehydes, esters, and alcohols. Synthesis of 1,3-amino ketones, aldehydes, alcohols and esters engages Mannich-type reactions, the most important basic reaction-types in organic chemistry. The current trend in the development of asymmetric Mannich-type reaction is to employ unmodified ketones and aldehydes as starting materials in the presence of simple and easily accessible metal-free organocatalysts under mild and convenient reaction conditions. Although L-Proline and its derivatives are commonly and extensively studied organocatalysts in Mannich reactions, many other organocatalysts based on bifunctional thiourea, chiral Bronsted acids and some other organocatalytic systems are also equally effective. The present review comprehensively describes an overview of asymmetric Mannich reactions under different organocatalytic systems in both organic and aqueous media.