usually achieved by cross-coupling reactions with aryl halides using copper al palladium catalysts. Ring expansion In the field of organic synthesis, ring expansions are considered valuable reactions since they allow the obtainment medium-size ring (7-9 atoms) which are difficult to synthesize through "classical" methods. To date, only few articles concerning the ring expansion of isatin derivatives has been reported. The first one is an acid-catalyzed one-pot multicomponent reaction involving isatins, aminouracils, and isooxazolones to form isoxazoquinolines, important scaffolds in medicinal chemistry. In another one-pot multicomponent reaction, a unique two-carbon expansion has been achieved by reacting isatin with indene-1,3-dione and N-substituted pyridinium bromide to form dibenzo[b,d]azepin-6-ones. C-2/C-3 nucleophilic addition Isatin suffers nucleophilic addition on carbonyls at C-2 and C-3 positions. The regioselectivity of the process strongly depends both on the substrate (properties of the substituents on the isatin core, especially those bonded to the nitrogen atom) and the reaction conditions (solvent, temperature etc.). In some cases the nucleophilic addition could be followed by secondary reactions (e.g. cyclization, ring expansion, ring opening etc.) Oxidation The oxidation of isatin using hydrogen peroxide or chromic anhydride yields isatoic anhydride, a compound widely used either in herbicide products and in medicinal chemistry. Dimerization Dimerization of isatin with KBH4 in methanol yield Indirubin. This represent the indigo pigment's red component and a highly effective cytotoxic compound. Reduction Reduction of the non-amide carbonyl group obviously occurs to give oxindole, respectively. See also Pfitzinger reaction References Reviews External links Lactams Indolines