Advances in Mannich-type Reactions Based on the Classification of Compounds with Activated alpha-H

Mannich-type reaction utilizes active alpha-H compounds (aldehydes and ketones, carboxylic acids and their esters, nitroalkanes, nitriles, phenols, and alkynes), amines and aldehydes to synthesize beta-aminocarbonyl compounds, which are valuable intermediates for the synthesis of natural products and drugs. The reaction yield, enantioselectivity, diastereoselectivity, and regioselectivity of the Mannich reaction are mainly affected by the catalysts and structural characteristics of the reaction substrates. In particular, the structural features of the reaction substrates can be classified into the steric effect and electronic effects of the substituents. In this article, we summarize the developments of symmetric and asymmetric Mannich-type reactions according to the type of reaction substrates and analyze the factors affecting the reaction yield, enantioselectivity, diastereoselectivity, and regioselectivity.