Yumiko Kakuno, Hideshi Hattori
1984
Citations
0
Influential Citations
16
Citations
Journal
Journal of Catalysis
Abstract
Addition of amines to conjugated dienes to yield unsaturated amines was carried out over solid base catalysts such as MgO, CaO, SrO, La2O3, ThO2, and ZrO2. Dimethylamine, ethylamine, piperidine, aniline, and triethylamine were used as amines, and 1,3-butadiene, and 2-methyl-1,3-butadiene were used as dienes. From all the reactions examined, CaO exhibited the highest activity, while ZrO2 was inactive. The activities of catalysts varied with the pretreatment temperature. For the addition of dimethylamine to 1,3-butadiene, the pretreatment temperatures which gave the maximum activities were 600 °C for CaO, 650 °C for La2O3, 700 °C for MgO(I) (prepared from Mg(OH)2), and 500°C for MgO(II) (prepared from commercial MgO). The reactivities of amines are in the order: dimethylamine > ethylamine > piperidine ⪢ aniline, triethylamine. In the addition of dimethylamine to 1,3-butadiene, primary products consisted mainly of N,N-dimethyl 2-butenyl-amine which resulted from 1,4-addition of a dimethylamino group and an H to the diene for all catalysts. As the reaction proceeded, the 1,4-addition product underwent double-bond migration to the enamine over CaO, MgO(II), and SrO. The double-bond migration was slow over MgO(I), La2O3, and ThO2. In particular, double-bond migration was not appreciable over La2O3. In the reaction of 2-methyl-1,3-butadiene with dimethylamine, N,N-dimethyl-3-methyl-2-butenylamine, which resulted from 4,1-addition of the amino group and an H, was produced as the main product for all catalysts except for MgO(I). Exchange of dimethylamine with D2 was studied over CaO. Only one D atom was incorporated into dimethylamine, suggesting that amines dissociate into an H+ and an amide ion on the catalyst surface. Based on these results, the reaction mechanisms were discussed, and it is proposed that addition of amines to conjugated dienes on basic catalysts proceeds via the amino allylic carbanion intermediates which result from addition of amide ions to the dienes.