已传文件：photo/1769491065.png
When the furan ring contains both carboxyl groups and acylamino groups (-NHCOCH₃), the recommended method for selectively hydrolyzing the acylamino group to the amine group (-NH₂) is as follows:
1. **Optimization of acidic conditions**:
- Use **dilute hydrochloric acid (2-4 M HCl)** at **60-80℃** for a reaction of 2-4 hours (avoiding concentrated acid that causes dehydrogenation of the carboxyl group or ring-opening of the furan ring);
- Or use **AcOH/H₂O (1:1)** for gentle hydrolysis, suitable for substrates sensitive to acid (such as the derivative of antibiotic **furantoin**).
2. **Control of alkaline conditions**:
- **5% NaOH/MeOH** solution, reacting at 50℃ for 1-2 hours, followed by neutralization with dilute hydrochloric acid (the carboxyl group can be converted to a salt for recovery);
- Add a **phase transfer catalyst** (such as TBAB) to enhance efficiency (*J. Org. Chem.* 2015, **80**, 4564). **Note**: Through TLC monitoring (indophenol color reaction), prioritizing the protection of carboxyl groups (such as methylation) can enhance selectivity.
