Enantioselective aziridination and amination using p-toluenesulfonyl azide in the presence of Ru(salen)(CO) complex

Article abstract of DOI:10.1246/cl.2003.354

(R,R)-Ru(salen)(CO) complex (1) was found to catalyze enantioselective aziridination of conjugated terminal olefins and allylic C-H amination of conjugated olefins bearing geminal- and/or trans-substituent(s) in the presence of p-toluenesulfonyl azide.

Full text of DOI:10.1246/cl.2003.354

354
Chemistry Letters Vol.32, No.4 (2003)
Enantioselective Aziridination and Amination Using p-Toluenesulfonyl Azide
in the Presence of Ru(salen)(CO) Complex
Kazufumi Omura, Masakazu Murakami, Tatsuya Uchida, Ryo Irie, and Tsutomu Katsukiꢀ
Department of Chemistry, Faculty of Science, Graduate School, Kyushu University 33, CREST, Japan Science and Technology (JST),
Hakozaki, Higashi-ku, Fukuoka 812-8581
(Received January 16, 2003; CL-030047)
(R,R)-Ru(salen)(CO) complex (1) was found to catalyze
enantioselective aziridination of conjugated terminal olefins and
allylic C–H amination of conjugated olefins bearing geminal-
and/or trans-substituent(s) in the presence of p-toluenesulfonyl
azide.
We first examined aziridination of conjugated terminal
olefins (Table 1).12 The reactions of all the substrates examined
proceeded with high enantioselectivity, except that the reaction of
2-phenylbutadiene was very slow (entry 6). However, non-
conjugated terminal olefins such as 1-octene underwent neither
aziridination nor allylic C–H amination.
1 (2 mol %), MS 4A
R
R
+
CH3C6H4SO2N3
Nitrene transfer is a fundamental C–N bond formation
reaction. It is well known that many metal complexes catalyze the
nitrene transfer reaction via a metal nitrenoide intermediate,1 and
much effort has been directed to development of metal-mediated
asymmetric nitrene transfer reactions,2 aziridination and C–H
amination. Various chiral metal complexes such as
metalloporphyrin,3 metallosalen4 [hereafter referred to as
M(salen), M=Mn4a-c or Ru4d], Cu-bis(oxazoline),5 Cu-bis(Schiff
base),6 Cu-axially chiral Schiff base,7 and Cu-diamine complex-
es8 have been introduced as catalysts for the asymmetric nitrene
transfer reaction, and good to high enantioselectivity has been
achieved. Most of these reactions use N-arylsulfonyliminophe-
nyliodinanes as nitrene precursors, which are, however, not very
efficient reagents in terms of atom economy. On the other hand,
N-arylsulfonyl and N-carbamoyl azides are more atom-economic
nitrene precursors. Jacobsen et al. reported that N-arylsulfonyl
azide served as a nitrene precursor for asymmetric aziridination in
the presence of copper ion under photo-irradiation, albeit with
CH2Cl2, r.t., 24 h
*
NTs
Table 1. Asymmetric aziridination of terminal conjugated ole-
fins with complex 1 as catalyst
Entry
R
Yield/%a
% ee
Confign
Sc
1
2
3
4
5
6
C6H5
p-BrC6H4
p-O2NC6H4
C6H5CꢁC
2-C10H7
71
87
98
85
86
7.3
87b
90d
92e
95f
87g
90h
—
—
—
—
—
H2C=C(C6H5)
aIsolated yield. bDetermined by HPLC using DAICEL
CHIRALCEL OJ-H (hexane-i-PrOH=1:1). Determined by
comparison of the specific optical rotation with the reported
c
22
D
value: ½aŠ þ 84:0 (c 0.63, CHCl3); Lit.13 ½aŠD þ 27:4 (c 1,
CHCl3) for (S)-isomer (28% ee). dDetermined by HPLC using
DAICEL CHIRALPAK AS-H (hexane-i-PrOH=2:1).
eDetermined by HPLC using DAICEL CHIRALPAK AD-H
(hexane-i-PrOH=2:1). fDetermined by HPLC using DAICEL
moderate enantioselectivity.9 Back and Korber reported sulfimi-
¨
dation using N-tert-butoxycarbonyl azide as the precursor in the
presence of FeCl3.10 Recently, we found that Ru(salen)(CO) (1)
decomposed N-arylsulfonyl azides in the presence of various
alkyl aryl sulfides to give the corresponding alkyl aryl sulfimides
in a highly enantioselective manner, without photo-irradiation
(Scheme 1).11 We also expected that complex 1 would catalyze
nitrene transfer reaction to alkenes of high nucleophilicity. Thus,
we examined aziridination of conjugated olefins.
g
CHIRALPAK AS-H (hexane-i-PrOH=7:3). Determined by
HPLC using DAICEL CHIRALCEL OF (hexane-i-
PrOH=2:1). Determined by HPLC using DAICEL CHIR-
ALCEL OD-H (hexane-i-PrOH=1:1).
h
We next examined the reactions of di- and tri-substituted
conjugated olefins under the same conditions (Table 2). Con-
sumption rates of these olefins were slow but the reaction pathway
varied with the substrate used.14 When olefin possessed
substituent(s) trans and/or geminal to the aryl substituent, allylic
C–H amination occurred exclusively (entries 1-3). It is, however,
noteworthy that C–H amination occurred at the E-substituent in
preference to the geminal substituent (entry 2). On the other hand,
inden underwent aziridination exclusively with high enantio-
selectivity, though the chemical yield was only modest. No C–H
amination at C1 was observed. However, the reaction of
dihydronaphthalene gave a trace amount (< 5%) of an allylic
aminated product.
-
+
Ar
1 (2 mol %)
NTs
S
+
CH3C6H4SO2N3
(1 eq)
Ar
R
S
R
MS 4A, CH2Cl2, r.t.
(1.3 eq)
93-99% ee, >81%
CO
Ru
N
O
N
O
Ph Ph
As expected from the above discussion, aziridination
occurred at the mono-substituted double bond, when compound
2 bearing both mono- and tri-substituted double bonds was
submitted to the present nitrene transfer reaction (Scheme 2).
Neither aziridination of the trisubstituted olefin nor C–H amina-
tion was observed.
1
Scheme 1.
Copyright Ó 2003 The Chemical Society of Japan

Chemistry Letters Vol.32, No.4 (2003)
355
Table 2. Reactions of substituted conjugated olefins with tolue-
nesulfonyl azide in the presence of complex 1
pathway was strongly affected by the substitution pattern of the
olefin used.
References and Notes
1
a) J. T. Groves and T. Takahashi, J. Am. Chem. Soc., 105, 2073
(1983). b) D. Mansuy, J.-P. Mahy, A. Dcureault, G. Bedi, and P.
Battioni, J. Chem. Soc., Chem. Commun., 1984, 1161.
a) M. M. Faul and D. A. Evans, in ‘‘Asymmetric Oxidation
Reaction, Practical Approach in Chemistry,’’ ed. by T. Katsuki,
Oxford University Press, Oxford (2001), Chap. 2.7. b) E. N.
Jacobsen, in ‘‘Comprehensive Asymmetric Catalysis II,’’ ed. by
E. N. Jacobsen, A. Pfaltz, and H. Yamamoto, Springer, Berlin
(1999), Chap. 17.
2
3
4
a) T.-S. Lai, H.-L. Kwong, C.-M. Che, and S.-M. Peng, Chem.
Commun., 1997, 2373. b) X.-G. Zhou, X.-Q. Yu, J.-S. Huang, and
C.-M. Che, Chem. Commun., 1999, 2377.
a) K. Noda, N. Hosoya, R. Irie, Y. Ito, and T. Katsuki, Synlett,
1993, 469. b) H. Nishikori and T. Katsuki, Tetrahedron Lett., 37,
9245 (1996). c) S. Minakata, T. Ando, M. Nishimura, I. Ryu, and
K. Komatsu, Angew. Chem., Int. Ed. Engl., 37, 3392 (1998). d)
C.-M. Ho, T.-C. Lau, H.-L. Kwong, and W.-T. Wong, J. Chem.
Soc., Dalton Trans., 1999, 2411. e) Y. Kohmura and T. Katsuki,
Tetrahedron Lett., 42, 3339 (2001). f) J.-L. Liang, X.-Q. Yu, and
C.-M. Che, Chem. Commun., 2002, 124.
b
aIsolated yield. The number in the parentheses is the percent
conversion of olefin, which was calculated by 1H NMR analysis.
cDetermined by HPLC using DAICEL CHIRALCEL OD-H
d
(hexane-i-PrOH=2:1). Determined by HPLC using DAICEL
CHIRALCEL OD-H (hexane-i-PrOH=1:1). eDetermined by
HPLC using DAICEL CHIRALPAK AD (hexane-i-
PrOH=5:1). Absolute configuration was determined to be
22
D
1S,2R by comparison of the specific rotation: ½aŠ þ 27:7 (c
5
a) D. A. Evans, K. A. Woerpel, N. M. Hinman, and M. M. Faul, J.
Am. Chem. Soc., 113, 726 (1991). b) D. A. Evans, M. M. Faul, M.
T. Bilodeau, B. A. Anderson, and D. M. Barnes, J. Am. Chem.
0.13, CHCl3); Lit.13 ½aŠD þ 11:6 (c 1, CHCl3) for 1S,2R-isomer
(52% ee).
Soc., 115, 5328 (1993). c) M. J. Sodergren, D. A. Alonso, and P.
¨
Ts
N
G. Andersson, Tetrahedron: Asymmetry, 8, 3563 (1997). d) S.
Tayler, J. Gullick, P. Mcmorn, D. Bethell, P. C. B. Page, F. E.
Hanock, F. King, and G. J. Hutichings, J. Chem. Soc., Perkin.
Trans. 2, 2001, 1714.
6
7
8
9
Z. Li, K. R. Conser, and E. N. Jacobsen, J. Am. Chem. Soc., 115,
5326 (1993).
C. J. Sanders, K. M. Gillespie, D. Bell, and P. Scott, J. Am. Chem.
Soc., 122, 7132 (2000).
D.-J. Cho, S.-J. Jeon, H.-S. Kim, C.-S. Cho, S.-C. Shim, and T.-J.
Kim, Tetrahedron: Asymmetry, 10, 3833 (1999).
Z. Li, R. W. Quan, and E. N. Jacobsen, J. Am. Chem. Soc., 117,
5889 (1995).
49%, 90% ee
not detected
1 (2 mol%)
+
MS 4A, CH2Cl2, r.t.
TsNH
2
Scheme 2.
10a) T. Bach and C. Ko rber, Eur. J. Org. Chem., 1999, 1033. b) T.
¨
11 M. Murakami, T. Uchida, and T. Katsuki, Tetrahedron Lett., 42,
7071 (2001).
¨
Bach and C. Korber, J. Org. Chem., 65, 2358 (2000).
These results suggest that olefins approach the Ru-nitrenoid
species in a perpendicular or skewed-perpendicular manner
which impedes interaction of the Z-substituent (RZ) with the
nitrene atom and the Z-substituent is reluctant to C–H amination
(Figure 1).15 The coefficient of the b-carbon of HOMO of the
styrene derivative is larger than that of the a-carbon. Therefore,
the allylic C–H bond on the E-substituent (RE) is considered to be
more activated than the allylic C–H bond on the geminal
substituent (RG). This explains why the E-substituent was
aminated in preference to the geminal substituent (Table 2, entry
2).
12 Typical experimental procedure is exemplified by the aziridina-
tion of styrene: under nitrogen atmosphere, a toluene solution
(0.25 mL) of complex 1 (1.9 mg, 2 mmol) was concentrated twice
azeotropically in vacuo. MS 4A (20mg) and styrene (10.4 mg,
0.1 mmol) were added to the residue. To the mixture was added
dichloromethane (0.5 mL) and the resulting suspension was
stirred for 0.5 h at room temperature. To the suspension was
added p-toluenesulfonyl azide (15.5 mL, 0.1 mmol) and stirred
for 24 h. The reaction mixture was directly chromatographed on
silica gel using hexane and ethyl acetate (hexane:ethyl acetate =
1/0-19/1-8/2) to give the corresponding aziridine (19.4 mg) in
71% yield. The enantiomeric excess of the product was
determined by HPLC analysis using DAICEL CHIRALCEL
OJ-H (hexane:i-PrOH = 1:1).
In conclusion, we were able to demonstrate that Ru(salen)
(CO) complex 1 served as the catalyst for enantioselective nitrene
transfer reaction (aziridination or C–H amination) using N-
toluenesulfonyl azide as the nitrene source and that the reaction
13 M. Shi and C.-J. Wang, Chirality, 14, 412 (2002).
14 It has been reported that metal nitrenoid species undergoes
aziridination and allylic C–H amination competitively: D. Evans,
M. M. Faul, and M. T. Bilodeeau, J. Org. Chem., 56, 6744 (1991).
15 A similar approaching model has been proposed for Mn(salen)-
catalyzed epoxidation via the corresponding oxo manganese
species: B. D. Brandes and E. N. Jacobsen, J. Org. Chem., 59,
4378 (1994).
RZ
RE
Ar
Ar
Ar
SO2Ar
SO2Ar
SO2Ar
N
N
RG
N
Ru
Ru
Ru
perpendicular approach
skewed-perpendicular approach
Figure 1. Proposal for substrate approach.