トリメチレンジアミンとアルデヒド類の環化脱水素による2-アルキルピリミジン類の合成とその動力学

抄録

Dehydrogenocyclization of trimethylenediamine and aldehyde to 2-alkylpyrimidine was studied on platinum group metal-Al₂O₃ catalysts in the streams of water vapor and hydrogen gas. In a flow system, the reaction was carried out between 290° and 410°, at atmospheric pressure. The optimum temperature range was 340-380° for 9 kinds of alkehydes used. On a Pt-Rh-Al₂O₃ catalyst and in a molar ratio aldehyde/trimethylenediamine of 1.2, 2-alkylpyrimidine was obtained in a good yield (30-50%) without the decay of catalyst activity. From kinetic studies, the reaction mechanism was considered as follows : Homogeneous rapid reaction of trimethylenediamine and aldehyde yielded 2-alkylhexahydropyrimidine, which, on a catalyst, was immediately dehydrogenated to 2-alkyl-1, 4, 5, 6-tetrahydropyrimidine. Dehydrogenation of 2-alkyl-1, 4, 5, 6-tetrahydropyrimidine to 2-alkylpyrimidine was the rate-determining step and followed the first-order kinetics. As the alkyl group became bulkier, the rate of formation and the final yield of 2-alkylpyrimidine decreased.