Abstract An anti-selective Mannich reaction of aldehydes with N-sulfonyl imines has been developed by using a 4-hydroxypyrrolidine in combination with an external Brønsted acid. The catalyst design is based on three elements: the α-substituent of the pyrrolidine, the 4- hydroxy group, and the Brønsted acid, the combination of which is essential for high chemical and stereochemical efficiency. The reaction works with aromatic aldehyde- ...
![N-[(4-methoxyphenyl)methylidene]-4-nitrobenzenesulfonamide Structure](https://image.chemsrc.com/caspic/126/840529-62-6.png)