Synthesis and reactions of 1,5-disubstituted-1,3-propanediones

The title compounds have been synthesized by the base catalyzed Baker-Venkataraman transformation of esters of substituted 2-hydroxyacetophenones. These propanediones (III) on acid catalyzed cyclization afforded substituted 2-(nitrosubstituted phenyl)-4H-1-benzopyran-4-ones (IV) while condensation with hydrazine hydrate and phenyl hydrazine afforded 3-(2'-hydroxyphenyl)-5-(nitrosubstituted phenyl) pyrazoles (V) and 3 (2'-hydroxyphenyl)-5-(nitrosubstituted phenyl)-1-phenyl-pyrazoles (VI) respectively. Condensation of these propanediones with NH2OH.HCl in pyridine gave 3-(2-hydroxyphenyl)-5-(nitrosubstituted phenyl) isoxazoles (VII) while in alcohol the isomeric 3-(nitrosubstituted phenyl)-5-(2-hydroxyphenyl)-isoxazoles (VIII) were obtained.