CONDENSATION OF 2-NITROBENZALDEHYDE WITH PYRAZOLIN-5-ONES - STRUCTURE OF 4-(2'-NITROBENZY-LIDENE)PYRAZOLIN-5-ONES AND THEIR REDUCTIVE CYCLIZATION

The condensation of 1-H-3-methyl-, 3-methyl-1-phenyl-, 1,3-diphenyl- and 1-methyl-3-phenyl-pyrazolin-5-ones with 2-nitrobenzaldehyde resulted in forming the corresponding 4-(2'-nitrobenzylidene)pyrazolin-5-ones. In some cases these products were assisted by side products formed by the condensation of two molecules of pyrazolin-5-ones with one molecule of the aldehyde. All the benzylidene compounds were cyclized on reduction of the nitro group to the amino group. The cyclization confirms that all the benzylidene compounds prepared were the cis-isomers. The UV absorption spectra confirm additionally their structures.