Synthesis and antioxidant properties of some novel 1,3,4,2-oxadiazaphosphepino[6,7-c]quinolinones and pyrazolo[3,4:4′,3′]quinolino[5,1-c][1,4,2]oxazaphosphinine

A series of novel 1,3,4,2-oxadiazaphosphepino[6,7-c]quinolinones 3-5, 9, and 11 have been synthesized from treatment of 4-hydroxy-1-methyl-3-[1-(2-phenylhydrazinylidene)ethyl]quinolin-2(1H)-one (2) with some phosphorus sulfides, diethyl phosphite and phenyl phosphonic dichloride, respectively, in dry dioxane. Also, reaction of hydrazone 2 with tris(2-chloroethyl)phosphite under the same reaction conditions gave pyrazolo[3,4:4,3]quinolino[5,1-c][1,4,2]oxazaphosphinine 10. However, when hydrazone 2 was treated with phosphonic acid, phosphorus tribromide or phosphorus oxychloride, 3,5-dimethyl-1-phenyl-1,5-dihydro-4H-pyrazolo[4,3-c]quinolin-4-one (7) was isolated in all cases. The compounds were evaluated for their antioxidant activities. Among the synthesized compounds, 1,3,4,2-oxadiazaphosphepino[6,7-c]quinolinone-2-sulfide 5 and its analogue 2-oxide 11 exhibited higher antioxidant activities than the standard antioxidant. [GRAPHICS] .