Microwave-assisted one-pot synthesis of pyrimido [4, 5-b] quinolines derivatives

Two series of pyrimido [4, 5-b] quinolone derivatives were synthesized via the reaction of aldehydes with pyrimidiones and 1, 3-cyclohexanediones in ethylene glycol under microwave irradiation. The optimum reaction conditions were as follows: microwave power 480 W, reaction temperature 85°C and irradiation time 6-9 min. This method is applicable not only to aromatic aldehydes with electron donating group or electron withdrawing groups but also to heterocyclic aldehydes. The structures of the products were identified by infrared spectroscopy (IR), H-nuclear magnetic resonance spectroscopy (1HNMR) spectra and elemental analysis. The structure of 1d was further confirmed by X-ray single crystallography.