Magnetically recoverable copper ferrite catalyzed cascade synthesis of 1,3-dimethyl-6-nitro-5-arylpyrido[2,3-d]pyrimidine-2,4(1H,3H)-diones under microwave irradiation and solvent-less condition

In recent years, magnetically active CuFe2O4 nanoparticles have been gaining significant interest in the field of heterogeneous catalysis as those can be easily prepared and effortlessly recovered from a reaction system. Here, we are reporting our work on cascade syntheses of 1,3-dimethyl-6-nitro-5-arylpyrido[2,3-d]pyrimidine-2,4(1H,3H)-diones starting from 6-[(dimethylamino)methylene-amino]-1,3-dimethyluracil, aromatic aldehydes and nitromethane using magnetically active CuFe2O4 catalyst system under microwave irradiation and solvent-less condition. The current methodology is a valued addition to the existing procedures of 5-arylpyrido[2,3-d]pyrimidines syntheses making best use of the diene behavior of 6-[(dimethylamino)methylene-amino]-1,3-dimethyluracil. However, heterogeneous catalysis has been employed for the first time to do the syntheses by carrying out [4 + 2]cycloaddition reaction between 6-[(dimethylamino)methylene-amino]-1,3-dimethyluracil and in situ generated 2-(2-nitrovinyl)arenes/heteroarenes. The methodology is highly time-economic, and along with other features like easy recovery and good reusability of the catalyst, simple operating procedure, wide substrate scope, and good to excellent product yield, it offers the chemists a reaction protocol worth trying for the syntheses of 1,3-dimethyl-6-nitro-5-arylpyrido[2,3-d]pyrimidine-2,4(1H,3H)-diones. While laboratory prepared catalyst system was characterized using FT-IR, XRD, SEM-EDX, VSM, XPS and TEM analysis, all the synthesized compounds have been characterized using H-1 and C-13 NMR spectroscopy and HRMS.