Patent ID: 6706890
Filing Date: 2004-03-16
Classification: C07D

Abstract:
A process for preparing 2-oxindoles of the formula (II) where R is H, CH3, phenyl or benzyl, R1 is H, C1-C4-alkyl, C1-C4-alkoxy, phenyl, phenoxy, halogen, amino, nitro or hydroxy, by reacting the corresponding isatins of the formula (I) in a polar solvent with hydrazine hydrate in the presence of a tertiary amine catalyst, characterized in that the isatin is converted to the corresponding isatin hydrazone at a temperature of from 15 to 185Â° C. which is directly reacted further by adding a diazabicyclooctane and/or diazabicycloundecane and/or ethyldiisopropylamine catalyst at temperatures of from 100 to 185Â° C. while distilling off the water of reaction formed to give the corresponding 2-oxindole of the formula which is then isolated by distilling off the solvent and crystallizing out of the reaction mixture.