Isatin derivatives and their chemoselective reductions with NaBH4

The Chemistry of isatin is well developed in Brazil mainly from the Pinto´s contributions1. Eleven derivatives have been prepared using classical reactions like acetylation, bromination, nitration and chlorination2,3 as shown in Scheme 1. Due to the synthetic versatility of isatin, it is possible, among many reactions, to reduce chemoselectively the ketone and amide carbonyl using sodium borohydride4. It is important to note that the control of the number of equivalents of the reducing agent (NaBH4: 0.6, 1.2 and 1.5) led to a desired reduced derivative. Using this strategy, fourteen substances were used as substrates, leading to many isatin derivatives.