Synthesis of various 6-substituted 1,4,5,6-tetrahydropyridazines by substitution of a 1,4,5,6-tetrahydro-6-tosylhydrazinopyridazines

1,4,5,6-Tetrahydro-1-tosyl-6-tosylhydrazinopyridazines were prepared by reaction of a 1,4-ketoaldehyde with two equivalents of tosylhydrazine. Thus-obtained hydropyridazines were utilized as a substrate for synthesis of various 1,4,5,6-tetrahydropyridazine derivatives by activation with a Lewis acid, and various nucleophiles reacted to give the corresponding 6-substituted 1,4,5,6-tetrahydropyridazine derivatives. Self-reaction of a 1,4,5,6-tetrahydro-6-tosylhydrazinopyridazine in the presence of 0.5 equivalent of titanium tetrachloride gave a 1,4,5,6-tetrahydropyridazine bearing a pyrrole ring at the 6-position.