Syntheses of Piperazine and N-Alkylpiperazines. I

Heating of diethanolamine hydrochloride at 200-230° results in the formation of morpholine alone, but the same at 230-240° gives morpholine and piperazine. The product from the heating at 250-260° is chiefly piperazine and only a small amount of morpholine is formed. N-Alkyldiethanolamine hydrochloride also forms N-alkylmorpholine and N-alkylpiperazine by heating. Both morpholine and N-alkylmorpholine undergo partial decomposition when heated at a high temperature to form piperazine and N-alkylpiperazine, respectively. By heating a mixture of diethanolamine hydrochloride and monoalkylamine hydrochloride at 250-260° for 3-4 hours, N-monoalkylpiperazine is obtained in 20-30% yield of the theoretical amount. Similar heating of the mixture of the hydrochloride of diethanolamine and dialkylamine also yields N-monoalkylpiperazine. Heating of a mixture of the hydrochloride of diethanolamine or N-alkyldiethanol-amine and ammonium chloride also results in the formation of the corresponding piperazine or N-monoalkylpiperazine in 20-25% yield of the theoretical amount. Morpholine, piperazine, and N-alkylmorpholine are formed as by-products in these reactions.