catalyzed aziridination was not affected by water in the reaction
system. When the reaction of imine 4aa with EDA was carried
out in the presence of a small amount of water, 3aa was obtained
in almost the same yield as the reaction in the absence of water
[(eqn. (2)].
Scheme 1 A possible reaction pathway for reaction of 4af with EDA.
Furthermore, the reaction of N-butylidene-tert-butylamine
4
af with EDA took place in high stereoselectivity, giving 3af in
8
5% yield (cis+trans = 95+5) [(eqn. (3)]. For the reaction of N-
aldehydes, aliphatic amines and EDA, catalyzed by [Ir-
benzylideneaniline 4dg with EDA, however, diethyl maleate 5
and diethyl fumarate 6 were formed in 46% yield, and 4dg was
recovered unchanged.
(
2
cod)Cl] . High stereoselectivity was attained by the reaction of
aldehyde, tertiary amine and EDA.
Notes and references
†
Typical reaction procedure: to a THF solution (1.0 mL) of di-
chlorobis(cycloocta-1,5-diene)diirdium {[Ir(cod)Cl] } (0.05 mmol) was
2
added aldehyde (1.0 mmol) and amine (1.0 mmol) at 210 °C under Ar.
After stirring for 10 min, EDA (2.0 mmol) was added, and then the reaction
mixture was stirred at 210 °C for 3 h. The reaction was quenched with wet
diethyl ether, and products were isolated by column chromatography
[(230–400 mesh silica gel, ethyl acetate–hexane (1+12) eluent].
Addtionally, the reaction of a ketimine such as N-(1-ethylpro-
pylidene)-n-butylamine with EDA led to 1-butyl-3,3-diethyl-
1
‡ Spectral data for 3aa: H NMR d 4.25–4.15 (m, 2H), 2.42–2.06 (m, 2H),
2
.09 (d, J 6.6 Hz, 1H), 1.72–1.69 (m, 1H), 1.60–1.30 (m, 6H), 1.31 (q, J 7.3
2-ethoxycarbonylaziridine in 54% yield.
Hz, 2H), 1.27 (t, J 7.3 Hz, 3H), 0.92 (t, J 7.3 Hz, 3H), 0.90 (t, J 7.3 Hz, 3H);
From the mechanistic point of view, it is of note that the
selectivity of aziridine is affected by the order of the addition of
substrates to the catalyst solution. When 1.0 mmol of imine 4aa
2
was added to a THF solution containing [Ir(cod)Cl] (0.05
mmol) at 210 °C, the solution changed immediately from
orange–red to light yellow, and EDA (2 mmol) was added to
this solution to form aziridine 3aa (73%). However, the addition
1
3
C NMR d 170.0, 60.8, 60.7, 46.6, 42.6, 31.4, 29.7, 20.6, 20.3, 14.3, 13.9,
21
+
1
3.7; IR (neat) 2959, 1747, 1183 cm ; MS, m/z = 213 (M ), 198, 140, 84;
Anal. Calc. for C12 23NO : C, 67.57; H, 10.87; N, 6.57. Found: C, 67.25,
H, 10.52; N, 6.62%.
The stereochemistry of 3af was determined by comparison of the coupling
constant obtained from H NMR spectral data for 3af with that of
2-ethoxylcarbonyl-1,3-diphenylaziridine reported in the literature.
¶ NMR observation showed the formation of the complex A from
Ir(cod)Cl] and imine; i.e. when [Ir(cod)Cl] was added to 1.0 equiv. of 4af
in a NMR tube, the C NMR signals at d 164.5 (–CHNN–) and 61.0
NNCH –) of 4af were shifted to d 171.6 and 63.6, respectively.
H
2
§
1
4a,f
2
of EDA (2.0 mmol) to a THF solution of [Ir(cod)Cl] resulted in
[
2
2
a change from orange–red to dark purple, and then 4aa (1.0
mmol) was added to produce 3aa in lower yield (59%) along
with a homocoupling product of EDA, 5 and 6 (13%), the
formation of which may be explained by in situ generation of
carbene from EDA by the action of an Ir complex. Hence, it is
probable that the present Ir-catalyzed aziridine synthesis
proceeds via the formation of an Ir–imine complex rather than
an Ir–carbene complex.
13
(
2
1
J. S. Brimacombe, R. Hanna and L. C. N. Tucker, J. Chem. Soc., Perkin
Trans. 1, 1983, 2277; J. Martens and M. Scheunemann, Tetrahedron
Lett., 1991, 32, 1417; D. Tanner, Angew. Chem., Int. Ed. Engl., 1994, 33,
5
99.
2 D. A. Evans, M. M. Faul and M. T. Bilodeau, J. Am. Chem. Soc., 1994,
116, 2742; Z. Li, K. R. Conser and E. N. Jacobsen, J. Am. Chem. Soc.,
1993, 115, 5326; P. Muller, C. Baud and Y. Lacueier, Tetrahedron, 1996,
In addition, when imine 4dg was added to a THF solution of
Ir(cod)Cl] , no color change was observed, and the aziridine
2
[
5
2, 1543.
expected was not obtained and instead, dimers of EDA, 5 and 6
as shown above. Therefore, it is reasonable to presume that the
reaction of 4dg with EDA is difficult to occur owing to the
difficulty of the complexation of 4dg with the Ir-complex.
The high stereoselectivity of the reaction of 1a, 2f and EDA
3
P. Baret, H. Buffet and J. L. Pierre, Bull. Soc. Chim. Fr., 1972, 2493; A. J.
Hubert, A. Feron, R. Warin and G. Mloston, Tetrahedron Lett., 1976,
1
317; R. Bartnik and G. Mloston, Synthesis, 1983, 924; V. K. Aggarwal,
A. Thompson, R. V. H. Jones and M. C. H. Standen, J. Org. Chem., 1996,
1, 8368.
6
(
Table 1, run 11) may be explained by assuming a similar
reaction path suggested in the Yb(OTf) -catalyzed reaction of
N-benzylidene-tert-butylamine with EDA (Scheme 1).4f It is
probable that the Ir complex [Ir(cod)Cl] coordinates to imine
af to lead to a complex A.¶ The nucleophilic attack of EDA to
4
(a) K. B. Hansen, N. S. Finney and E. N. Jacobsen, Angew. Chem., Int.
Ed. Engl., 1995, 34, 676; (b) Z. Zhu and J. H. Espenson, J. Org. Chem.,
1995, 60, 7090; (c) Z. Zhu and J. H. Espenson, J. Am. Chem. Soc., 1996,
118, 9901; (d) L. Casarrubios, J. A Pérez, M. Brookhart and J. L.
Templeton, J. Org. Chem., 1996, 61, 8358; (e) V. K. Aggarwal, A.
Thompson, R. V. H. Jones and M. C. H. Standen, J. Org. Chem., 1996,
3
2
4
the resulting complex A would take place from the direction to
reduce the steric repulsion between the ester moiety of the
incoming EDA and the tert-butyl group of the imine to form cis-
6
1, 8386; (f) K. G. Rasmuussen and K. A. Jørgensen, J. Chem. Soc.,
Perkin Trans. 1, 1997, 1287; (g) M. F. Mayer and M. M. Hossain, J. Org.
Chem., 1998, 63, 6839; (h) K. Juhl, R. G. Hazell and K. A. Jørgensen,
J. Chem. Soc., Perkin Trans. 1, 1999, 2293.
3
af.
In summary, various types of aziridine derivatives, which are
5
S. Nagayama and S. Kobayashi, Chem. Lett., 1998, 685.
difficult to prepare by the conventional methods, have been
prepared by the three-component coupling reaction of aliphatic
Communication b000518p
626
Chem. Commun., 2000, 625–626