Microwave-assisted solvent-free synthesis of the substituted spiroindolinonaphth[2,1-b][1,4]oxazines

The synthesis of the substituted spiroindolinonaphth[2,1-b][1,4]oxazines 3a-e is developed through the condensation of 2-methylene-1,3,3-trimethylindoline derivatives and 1-nitroso-2-naphthol under microwave irradiation. In the same conditions, in presence of morpholine the 6'-morpholinosubstituted compounds 4a, b, d, e are formed. The main advantages of the method are the short reaction time, solvent-free reaction condition, cleaner reaction products and the higher product yields in comparison with known methods of synthesis.