NOVEL EFFICIENT PROCEDURE FOR THE CONJUGATE ADDITION OF AMINES
COOCH3
655
NH2
N
10 mmol
cat, R.T.
25 min
94%
+
COOCH3
12 mmol
NH2
NH2
10 mmol
Scheme 2. The chemoselectivity of the catalyst.
RESULTS AND DISCUSSION
The Reuse of the Catalyst
One property of the catalyst is the heterogeneous
catalytic process. Thus, recovery of the catalyst is very
convenient. After reactions, the reaction mixture was
Catalytic Procedure for the Conjugate Addition
The conjugate additions of various amines with
alkenes under solventꢀfree conditions were investiꢀ
gated first (table). The results showed that the reacꢀ
tions underwent smoothly at room temperature just
within several minutes. The methylamine showed
extremely high activity for all kinds of electron defiꢀ
cient alkenes with almost complete conversion within
extracted with ethyl acetate (2 × 20 ml) and the lower
phase, the ionic liquid, could be reused without any
disposal. The recovered activities were investigated
through the reaction of cyclohexamine and methyl
acrylate carefully (figure). The yield remained
unchanged even after the catalyst had been recycled
for six times.
5
min (entries 1, 6, 11). The yields slightly dropped
with the increasing carbon atomicity of the amines
because of the steric hindrance (entries 2, 3, 7, 8, 12,
The Chemoselectivity of the Catalyst
1
3). The primary amines underwent the single substiꢀ
It is noteworthy that aromatic amines could not be
tution reaction under the reaction condition. These transformed to the corresponding products under the
results indicated the usefulness of the novel catalyst for same reaction conditions (Scheme 2). This result indiꢀ
cated that the present protocol could be applicable to
the chemoselective addition of aliphatic amines in the
presence of aromatic amines.
In conclusion, a novel efficient procedure has been
developed for the conjugate addition of amines to
electron deficient alkenes. Operational simplicity,
without need of any solvent, low cost of the catalyst
used, high yields, excellent chemoselectivity, wide
applicability are the key features of this methodology.
the reactions and the reaction conditions are mild and
not sufficient enough to cause double substitution
reaction. The multusubstitution reactions could also
be activated when more alkenes and high temperature
applied, then the double substituted products were
obtained with high yields. As to the alkenes, the reacꢀ
tivity was affected by the electronic withdrawing
groups (EWG) and the steric hindrance also had the
certain effect on the reaction.
ACKNOWLEDGMENTS
Yield, %
This work was supported by the Shaoxing Key Disꢀ
cipline Foundation, China.
100
80
60
40
20
0
REFERENCES
1
2
3
4
. Zhang, D., Wang, G., and Zhu, R., Tetrahedron: Asymꢀ
metry, 2008, vol. 19, no. 5, p. 568.
. Singh, R. and Goswami, T., J. Phys. Org. Chem., 2008,
vol. 21, no. 3, p. 225.
. Wang, C., Zhang, Z., Dong, X., and Wu, X., Chem.
Commun., 2008, no. 12, p. 1431.
. Xu, L., Yang, M., Qiu, H., Lai, G., and Jiang, J., Synth.
Commun., 2008, vol. 38, no. 7, p. 1011.
1
2
3
4
5
6
Run
5. Miao, T. and Wang, L., Tetrahedron Lett., 2008, vol. 49,
no. 13, p. 2173.
6
. Wang, Y., Li, P., Liang, X., Zhang, T., and Ye, J., Chem.
Commun., 2008, no. 10, p. 1232.
The reuse of the catalyst.
KINETICS AND CATALYSIS Vol. 51
No. 5
2010