Abstract
When maleic anhydride derivatives (IV), containing alkyl group, was condensed with phenylhydrazine in acetic acid, (IVa) affoded N-anilino derivative (V) mainly, besides minor amount of pyridazine derivative (VI) as a by-product. However, (IVb) afforded (Vb) only, without producing (VIb).
In the case of 3, 4, 5, 6-tetrahydrophthalic anhydride (IVc) whose alkyl groups increased, the cyclization was so difficult that neither (V) nor (VIc) could be produced, but only (VIc) was obtained, when 20% sulfuric acid was employed instead of acetic acid.
(Va) and (Vb) rearranged to (VIa) and (VIb) when they were boiled in dilute sulfuric acid (or hydrochloric acid). Though the derivatives (Type E in Table V) of having VI-type structure provided the ketonic group at a fixed region, on IR-spectra its intensity was so weak that monoketo-monoenol structure have been presumed from both UV-spectra (EtOH) and IR-spectra. The resembling derivatives of Type B, C and D, having C=O group did not show any characteristic absorption of νc=o that was observed with Type E and gave an usual ketonic absorption.
