Fuming sulfuric acid → 9-Chloro-6-fluoro-4-hydroxybenzo[g]isoquinoline-5,10-dione

Participants

Reaction Steps

A mixture of 4-(5'-chloro-2'-fluorobenzyl) -5-hydroxynicotinic acid of Preparative Example 27 (0.15 g) and 20% oleum (2 mL) is stirred for 45 minutes at 125°-130° C. (external bath temperature). The reaction mixture is then allowed to cool at room temperature and poured over 20 g of crushed ice and the resultant mixture neutralized with solid sodium bicarbonate to pH=7. The dione is extracted with dichloromethane (4×20 mL) and the combined organic phases are dried over MgSO4 and concentrated to dryness. The product is obtained as a yellow-tan solid (0.12 g) which darkens on standing in air.

Provenance & Evidence