Studies on the syntheses of heterocyclic compounds. Part DII. Synthesis of 1-substituted 1,2,3,4-tetrahydrophthalazines by a pictet–spengler-type reaction of 3-hydroxybenzylhydrazine with carbonyl compounds

Condensations of 3-hydroxybenzylhydrazine with acetone, ethyl methyl ketone, diethyl ketone, cyclohexanone, and 1-methyl-4-piperidone in the presence of acid gave the 1,1-disubstituted 1,2,3,4-tetrahydrophthalazines (2)–(6). On the other hand, the reactions of 3-hydroxybenzoylhydrazine (7) with acetone, cyclohexanone, and benzalde-hyde gave the Schiff's bases (8)–(10).