Henze modification

The first improvement of the Bucherer-Bergs reaction was the Bucherer-Lieb variation using the diluted alcoholic solution as described at the end of section 7.2.2. The Bucherer-Lieb variation is possibly the most popular process for synthesizing hydantoins. Another notable variation is the Henze modification using fusing acetamide as the solvent in place of water, benzene or 50% alcohol. Recently, ultrasound-promoted hydantoin synthesis has been reported to accelerate the reaction. 

The other most important synthetic utility of the Bucherer-Bergs reaction is the preparation of amino acids from the hydrolysis of hydantoins. When carbonyl 1 was symmetrical, the Henze modification gave hydantoin 2, which was then hydrolyzed to the... 

---