Isatins are synthetically versatile substrates, where they can be used for the synthesis of a large variety of heterocyclic compounds. In this, a convenient method has been developed for the conversion of Indoles into Isatins and some heterocyclic derivative were synthesised such as 5- nitro-1H-indole-2,3-dione, 2-methylquinoline-4-carboxylic acid which may be used as raw material for drug synthesis. The general process utilizes the effective method for synthesis of Isatin from Indole is bromination and oxidation with an N-bromosuccinimide-dimethyl sulfoxide reagent. The nitration of Isatin at C-5 takes place by using KNO3, conc. H2SO4, 2-methylquinoline-4-caboxylic acid are usually obtained from pfitzinger reaction.
International Letters of Chemistry, Physics and Astronomy (Volume 12)
R. P. Sonawane and R. R. Tripathi, "The Chemistry and Synthesis of 1H-indole-2,3-dione (Isatin) and its Derivatives", International Letters of Chemistry, Physics and Astronomy, Vol. 12, pp. 30-36, 2013