Department of Chemistry, Lucknow University, Lucknow-226 007 Manuscript received 25 March 1988, accepted 29 July 1988 INDOLIN-2, 3-dione and 5,7-substituted-indolin-2,3-dione have been conveniently prepared via Sandmeyer isonitroso synthesis1 . The 3-carbonyl group in indolin-2,3-diones behaves normally towards nucleophilic reagents and as such numerous addition-elimination reactions have been performed leading to the 3- substituted products2 ; many such products have shown interesting

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... l activity3. While nucleophilic 'reactions on indolin-2,3-diones and 5,7-substituted-indolin-2,3-diones have been reported, not much work has been done on 4-and/or 6-substituted-indolin-2,3-diones, the reason might be the difficulty in getting pure 4- and/or 6-substituted-indolin-2,3-diones via Sandmeyer method We have now obtained 4- and 6-chloroindolin-2,3-diones in a pure state by a pH-dependent separation procedure from their mixture4.