An efficient and novel protocol for the synthesis of spiro[1,3]oxazino[5,6-c]quinoline derivatives by one-pot, three-component reaction

One-pot, three-component reaction of various aryl glyoxal monohydrates, 5-methylisoxazol-3-amine and 4-hydroxyquinolin-2(1H)-one in the presence of a catalytic amount of DBU in H2O/EtOH (1:1) at 50 °C produced the 4-aroyl-5′-methyl-3,4-dihydro-2′H-spiro[[1,3]oxazino[5,6-c]quinoline-2,3′-isoxazol]-5(6H)-one derivatives containing spiro[1,3]oxazino[5,6-c]quinoline moiety in 82–89% yield. The high yields of products, easy work-up, and availability of starting materials are the main advantages of this synthetic strategy.