Nitrogen bridgehead compounds. Part 85. Synthesis and reactivity of 3,4-dihydro-1H,6H[1,4]oxazino[3,4-b]quinazolin-6-ones

3,4-Dihydro-1H,6H-1,4]oxazino3,4-b]quinazolin-6-one 3 and its 1-methyl and 1-hydroxy derivatives 8 and 13 were prepared by different routes. The active methylene group of compound 3 was reacted with electro-hilic reagents (bromine, phenyldiazonium chloride, nitrous acid, a Vielsmeier-Haack reagent, aromatic aldehydes and diethyl oxalate) to yield 1-substituted-3,4-dihydro1H,6H)-1,4-oxazino3,4-b]quinazo-lin-6-ones. The reactivity of 1-hydroxy and 1-bromo derivatives 13 and 15 were also investigated in some reactions. The 3,4-dihydro-lH,6H-1,4]oxazino3,4-b]quinazolin-6-ones were characterized by means of uv, ¹H and ¹³C nmr spectroscopy.