CONDENSATION OF 2-NITROBENZALDEHYDE WITH PYRAZOLIN-5-ONES - STRUCTUREOF 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- a nd 1-methyl-3-phenyl-pyrazolin-5-ones with 2-nitrobenzaldehyde resulte d in forming the corresponding 4-(2'-nitrobenzylidene)pyrazolin-5-ones . In some cases these products were assisted by side products formed b y the condensation of two molecules of pyrazolin-5-ones with one molec ule of tile aldchyde. All the benzylidene compounds were cyclized on r eduction of the nitro group to the amino group. The cyclization confir ms that all the benzylidene compounds prepared were the cis-isomers. T he UV absorption spectra confirm additionally their structures.