Abstract Partially hydrogenated pyrido [2, 1-b][1, 3] oxazine, cyclopenta [d] pyrido [2, 1-b][1, 3] oxazine and pyrido [1, 2-a]-[3, 1] benzoxazine ring systems were easily formed in the reaction of 3-hydroxy-2-(2-hydroxy-1, 3-dioxo-2-indanyl)-2-alken-1-one derivatives with tosyl chloride and pyridine bases. A facile interconversion between pyridooxazines and the corresponding pyridinium salts was also realized.
![spiro[4a,8,9,10-tetrahydropyrido[1,2-a][3,1]benzoxazine-6,2'-indene]-1',3',7-trione Structure](https://image.chemsrc.com/caspic/392/77708-58-8.png)
