68701-52-0

150560-58-0

The general procedure for the synthesis of 5-isopropylindoline-2,3-dione using the compound (CAS: 68701-52-0) as starting material was as follows: 41.2 g of isonitrosoacetyl-p-isopropylaniline was slowly added to 294 g of 95% sulfuric acid at room temperature. Subsequently, the temperature of the reaction system was gradually increased to 30°C over a period of 10 minutes and the reaction mixture was continuously stirred at this temperature for 2 hours. Upon completion of the reaction, the reaction solution was slowly added dropwise to a separate vessel containing 419 g of water and the precipitate precipitated was subsequently collected by filtration. The precipitate was washed with 1,300 g of water and dried in a drying oven at 60 °C to yield 37.3 g of 5-isopropylisatin. The yield of this step was 98.7%, the purity of the product was 98.1% (wt%) and the melting point was 137-140 °C. In this embodiment, the molar ratio of isonitrosoacetyl-p-isopropylaniline to sulfuric acid was 1:14.3.