Aryl α, β-Unsaturated Ketones as Efficient Precursor for Synthesis of Unsaturated 1,3-oxazine-2-amines under Solvent-free Conditions

Abstract. Present study describes the efficient synthesis of some unsaturated 1,3-oxazine-2-amines including thirteen 4-(6-methoxy-2-naphthyl)-5,6-dihydro-6(substituted phenyl)-4H-1,3-oxazine-2-amines by KF/Al2O3 catalysed solvent-free cyclization of enones with urea under microwave irradiation. The yields of the synthesized oxazines are more than 85%. The catalytic activity of this catalyst was studied by increasing the catalyst quantity from 0.05 to 0.25g in the step-wise cyclization of chalcone and urea. The optimum quantity of the catalyst for this cyclization will be found to be 0.2 g. The effect of solvent on the cyclization reaction was studied with conventional heating method and microwave irradiation technique. Comparatively, the microwave assisted solvent-free method gave more yields of the product. In this study, the effect of substituents also studied. The electron donating substituted chalcones gave more yield than electron-withdrawing substituted chalcones. This synthetic methodoly offers easy work-up procedure, non-hazardousness, shorter reaction time, environmentally benign reaction and better yield. The physical constants, analytical and spectroscopic data are supported for establishment of their structure.