# Asymmetric Mannich Reaction of α-(2-Nitrophenylsulfenyl)imino Acetamide: A Cyclization-Driven Process

## TL;DR

A new enantioselective chemical reaction is developed to produce cyclic hemiaminal products with high efficiency and selectivity.

## Contribution

A cyclization-driven asymmetric Mannich reaction is introduced with high enantioselectivity and yield.

## Key findings

- Cyclic hemiaminal products are formed in 21–58% yield with diastereomeric ratios up to 83:17.
- Enantioselectivity of up to 97% ee is achieved using proline and additives.
- The N–H functionality is essential for cyclization, preventing decomposition of the Mannich adduct.

## Abstract

An enantioselective Mannich reaction of 2-(2-nitrophenylsulfenylimino)acetamide is described. Under the optimized conditions using proline, triethylamine, and diarylthiourea additives, the initially formed Mannich adduct undergoes irreversible cyclization to afford cyclic hemiaminal products in 21–58% yield, with diastereomeric ratios ranging from 53:47 to 83:17. Enantioselectivity reaches up to 97% ee. The presence of N–H functionality of the substrate is crucial for this cyclization; in its absence, the Mannich adduct undergoes facile decomposition. Subsequent reduction in this intermediate efficiently furnished the corresponding homoserine derivative.