Enantioselective aziridination reaction of α,β-unsaturated aldehydes using an organocatalyst and tert-butyl N-arenesulfonyloxycarbamates

Article abstract of DOI:10.1016/j.tetlet.2009.02.095

An organocatalytic enantioselective aziridination reaction of α,β-unsaturated aldehydes including aromatic substrates using N-arenesulfonyloxycarbamates in the presence of diphenylprolinol triethylsilyl ether and sodium carbonate or sodium acetate is desc

Full text of DOI:10.1016/j.tetlet.2009.02.095

Tetrahedron Letters 50 (2009) 3329–3332
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Enantioselective aziridination reaction of
a,b-unsaturated aldehydes
using an organocatalyst and tert-butyl N-arenesulfonyloxycarbamates
*
Hiromi Arai, Naomi Sugaya, Neri Sasaki, Kazuishi Makino, Sylvain Lectard, Yasumasa Hamada
Graduate School of Pharmaceutical Sciences, Chiba University, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
An organocatalytic enantioselective aziridination reaction of
matic substrates using N-arenesulfonyloxycarbamates in the presence of diphenylprolinol triethylsilyl
ether and sodium carbonate or sodium acetate is described.
a
,b-unsaturated aldehydes including aro-
Received 25 December 2008
Revised 6 February 2009
Accepted 12 February 2009
Available online 15 February 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Chiral aziridines are useful synthetic intermediates with one
stereogenic center or two stereogenic centers, which are effectively
used for the synthesis of amino acids, natural products, and phar-
maceuticals.1–3 In this context, the development of a method for
the simple preparation of chiral aziridines from commercially
available starting materials is of significant interest.4,5 Recently,
via nitrene addition reactions, base-catalyzed tandem Michael-
substitution reactions, and metal-catalyzed aziridination reac-
tions.10 However, there are no reports on the use of N-arenesulfo-
nyloxycarbamates in secondary amine-catalyzed enantioselective
aziridination reactions.
Our investigation commenced with the optimization of the azir-
idination reaction using 2-hexen-1-al (1a), benzyl N-toluenesulfo-
nyloxycarbamate (2a), and (S)-diphenylprolinol triethylsilyl
ether11 (3), and the results are summarized in Table 1. Since the
presence of a base was essential for this aziridination reaction (en-
try 2), we examined the background reaction without the organo-
catalyst. The reaction was sluggish, but gave the racemic aziridine
4a in low yield with a trans/cis ratio of 86/14 (entry 1). Fortunately,
the aziridination reaction using 20 mol % (S)-3 in the presence of
sodium carbonate (3 equiv) in methylene chloride at room temper-
ature proceeded in a stereoselective manner to afford the aziridine
4a in 38% yield and in an enantiomeric excess of 99% ee with a high
level of diastereoselectivity12 (entry 3). The enantiomeric excess
was determined after derivatization of 4a into the ester 5a in
two steps by its HPLC analysis. Since there was a poor reproducibil-
ity for the chemical yield, we carried out the optimization of the
reaction conditions. For the examination of the reaction solvents,
methylene chloride was the solvent of choice for this aziridination
reaction and toluene also gave the product with a comparable ste-
reoselectivity (entries 4–7). A slight excess of the substrate was
essential for a smooth reaction and good chemical yield. Other
bases, such as sodium acetate and potassium acetate, produced
comparable results (entries 8–9). Finally, the serious problem of
the reproducibility was solved using tert-butyl p-toluenesulfonyl-
oxycarbamate (2b) as the nucleophile (entry 10). Although the sec-
ond channel, the background sodium carbonate-catalyzed reaction,
exists and should cause a low enantioselectivity, it is very interest-
ing that the asymmetric aziridination reaction proceeds with a
high enantioselectivity and diastereoselectivity.
the organocatalytic asymmetric aziridination of
a,b-unsaturated
aldehydes using N-acetyloxycarbamate has been reported.6,7 This
method is an efficient procedure with a high enantioselectivity.
However, the yields and diastereoselectivities are insufficient and
need to be improved. In addition, the range of the substrates is re-
stricted to aliphatic
a,b-unsaturated aldehydes, and the reaction of
aromatic ,b-unsaturated aldehydes has never been reported.
a
We have been working on the synthesis of functionalized amino
acids and naturally occurring cyclodepsipeptides.8 As part of this
research, we now describe an organocatalytic enantioselective
aziridination reaction of a,b-unsaturated aldehydes including aro-
matic substrates using N-arenesulfonyloxycarbamates9 as a source
of nitrogen (Scheme 1). These carbamates are mostly stable crys-
talline solids and have been already used in aziridination reactions
Ph
Ph
N
H
PG
N
O
Ar
O
H
OTES
O
S
3
PG
O
O
N
H
R
H
+
R
H
base
H
2a: PG = Cbz, Ar = p-MePh
2b: PG = Boc, Ar = p-MePh
2c: PG = Boc, Ar = Mes
2d: PG = Boc, Ar = Mbs
4
Scheme
1. Enantioselective
aziridination
reaction
using
N-
arenesulfonyloxycarbamates.
Using the conditions of entry 10 in Table 1, other aliphatic
unsaturated aldehydes were examined, and the results are summa-
a,b-
* Corresponding author. Tel./fax: +81 43 290 2987.
E-mail address: hamada@p.chiba-u.ac.jp (Y. Hamada).
0040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2009.02.095

3330
H. Arai et al. / Tetrahedron Letters 50 (2009) 3329–3332
Table 1
Optimization of organocatalytic aziridination reactiona
1) NaBH4
Cbz
N
(S)-3 (20 mol%)
MeOH
Cbz
N
O
H
H
base (3 equiv.)
0 ºC, 1h
O
Ts
Cbz
O
n-Pr
H
N
H
n-Pr
OBz
n-Pr
H
+
2) Bz2O
CH2Cl2 (0.2 M)
rt, time
H
H
TEA
DMAP
CH2Cl2
5a
4a
1a (1.2-1.5 equiv.)
2a
Entry
Base
Solvent
Time (h)
Yield (%)
Trans/cis
% eeb
d
1c
2
3
4
5
6
7
8
Na2CO3
—
CH2CI2
CH2CI2
CH2CI2
DMSO
CH3CN
THF
PhCH3
CH2CI2
CH2CI2
CH2CI2
25
24
3.5
2
24
23
4
0.5
0.5
3.5
—
86/14
—
—
—
99
52.7
30.5
—
94.4
97.8
99.4
98
nre
38
26
36
8
54
69
48
60
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
NaOAc
KOAc
>99/1
91/9
88/12
83/17
95/5
94/6
96/4
97/3
9
10f
Na2CO3
a
The reaction was carried out using 2-hexen-1-al (excess) and the carbamate 2a (1 equiv) in the presence of (S)-3 (0.2 equiv) and base (3 mol equiv).
b
c
d
e
f
The enantiomeric excess was determined after conversion of 4a–5a.
The reaction was carried out without (S)-3.
A 1:6.2 mixture of 4a and 1a was obtained.
No reaction.
tert-Butyl p-toluenesulfonyloxycarbamate (2b) was used instead of 2a.
rized in Table 2. The crotonaldehyde (1b) afforded aziridine 4b in
good yield and 96.4% ee as an inseparable trans/cis mixture of
91/9 (entry 2). An excess amount of the substrate was again essen-
tial for a smooth reaction. Under the conditions using a large ex-
cess amount of crotonaldehyde, the reaction proceeded even at
the 5 mol % amount of (S)-3 to afford 4b in a similar yield and ste-
reoselectivity (entry 3). The obtained aziridine 4b was directly oxi-
dized with activated manganese dioxide in the presence of sodium
cyanide in methanol to give the methyl ester 6 in good yield
(Scheme 2). Although the preparation of esters by the oxidation
Boc
N
NaCN (2 equiv.)
MnO2
Boc
N
O
O
H
H
Me
H
Me
OMe
H
H
MeOH (0.2 M)
rt, 11 h
6
4b
76% yield
Scheme 2.
tion of an ester from an aziridine aldehyde, a saturated aldehyde,
using activated manganese dioxide. The fumaric acid methyl ester
half aldehyde (1c), a substrate with an electron-withdrawing
of
a,b-unsaturated aldehydes and benzylic aldehydes with acti-
vated manganese dioxide is a well-known procedure,13 to the best
of our knowledge, this is the first example of the directed forma-
Table 2
Enantioselective aziridination reaction of aliphatic substratesa
1) NaBH4
(S)-3
Boc
N
MeOH
Boc
N
O
H
base (3 equiv.)
H
0 ºC, 1h
O
Ts
Boc
O
R
H
N
H
R
OBz
R
H
+
2) Bz2O
CH2Cl2 (0.2 M)
rt, time
H
H
TEA
DMAP
CH2Cl2
4
1
2b
5
Entry
1 (equiv)
Cat. (S)-3 (mol %)
Base
Time (h)
Yieldb (%)
Trans/cis
% eec
1
2
3
4
5
6
7
8
1a: R = n-Pr (1.5)
1b: R = Me (2.5)
1b: R = Me (5)
1c:R = CO2Me (1)
1c: R = CO2Me (1)
1d: R = cyclohexyl (1)
1e: R = H (5.2)
1e: R = H (2.2)
20
20
5
10
30
30
20
20
20
20
Na2CO3
3.5
3
3
11
2.5
4
6
2
2
2.5
60d
62d
73d
61e
71e
51d
58
37
58
66
97/3
91/9
91/9
>99/1
>99/1
90/10
98
Na2CO3
NaOAc
Na2CO3
NaOAc
NaOAc
Na2CO3
K2CO3
96.4
97.8
98
92.3
92
91
48
72
94
9
1e: R = H (5.2)
1e: R = H (5.2)
NaOAc
Na2CO3
10f
a
The reaction was carried out using a,b-unsaturated aldehyde (excess) and p-toluenesulfonyloxycarbamate (1 equiv) in the presence of (S)-3 (0.05–0.3 equiv, see table)
and base (3 mol equiv) in methylene chloride at room temperature.
b
Yield based on 2b.
Enantiomeric excess after conversion to ester 5.
Yield of a trans/cis mixture.
Yield after reduction with sodium borohydride in two steps.
c
d
e
f
Compound 2c was used instead of 2b.

H. Arai et al. / Tetrahedron Letters 50 (2009) 3329–3332
3331
group, was reactive for the present aziridination reaction and pro-
duced the aziridine 4c, which was isolated after the conversion to
the corresponding alcohol in 61% yield and 98% ee with complete
diastereoselectivity (entry 4). 3-Cyclohexyl-2-propenal (1d) with
a secondary alkyl group had a low reactivity. In the case of a slow
reacting substrate, sodium acetate was the base of choice for
avoiding the decomposition of the carbamate. In the presence of
a 30 mol % catalyst and sodium acetate (3 equiv), the reaction of
1d afforded the aziridine 4d in 51% yield and 92% ee as an insepa-
rable trans/cis mixture of 90/10 (entry 6).
We next examined the asymmetric aziridination reaction of
acrolein (1e), the simplest substrate. The enantioselectivity was
dependent on the base and the nitrogen source. Sodium carbonate
was again the base of choice (entries 7–9), and the bulky tert-butyl
mesitylenesulfonyloxycarbamate (2c) maximized the enantiose-
lectivity to afford the product 4e in 66% yield and 94% ee (entry
10). The result of the enantioselective aziridination reaction of 1e
is noteworthy because the obtained 4e is a useful building block
for the preparation of unusual amino acids and natural products,
which has been conventionally prepared from serine in several
steps.14
of sodium cyanide and methanol, which was stable to silica gel
purification.
After some experiments, the use of sodium acetate and tert-bu-
tyl N-p-methoxybenzenesulfonyloxycarbamate (2d) instead of so-
dium carbonate and 2b affected the reaction to afford 9a in a
good yield with an excellent stereoselectivity (entry 2). The abso-
lute stereochemistry of 9a was unambiguously confirmed after
the hydrogenolysis of 9a to the N-tert-butoxycarbonyl-(S)-phenyl-
alanine methyl ester by its comparisons to the authentic sample.
The substrate with an electron-donating group at an aromatic
nucleus did not react under the above conditions (entry 3). The
reaction of p-methoxycinnamaldehyde (7b) with 2b in the pres-
ence of sodium acetate resulted in the recovery of the starting
aldehyde and in the complete decomposition of 2b. However, the
substituted cinnamaldehydes with an electron-withdrawing group
at an aromatic nucleus were excellent substrates, and they
smoothly reacted with 2b in the presence of sodium acetate to
yield the corresponding aziridines in good to excellent yields with
high levels of diastereoselectivity and enantioselectivity (entries
4–18), which could be isolated by silica gel chromatographic puri-
fication. In particular, the nitrocinnamaldehydes (7e–7g) reacted
with 1–1.2 equivalent of 2b to furnish the corresponding aziridines
8e–8g in high yields (entries 8–12).15 The aziridination reaction
Next, the enantioselective aziridination of aromatic a,b-unsatu-
rated aldehydes were examined as shown in Table 3. Although we
first examined the reaction of cinnamaldehyde (7a) and 2b using
the above optimized conditions, 7a was a difficult substrate due
to the low reactivity. In addition, the corresponding aziridine 8a
was sensitive to silica gel, which resulted in the decomposition
of 8a during the silica gel purification. To avoid this inherent prob-
lem, 8a was directly converted to the corresponding methyl ester
9a by oxidation using activated manganese dioxide in the presence
of the b-(3-pyridyl)-a,b-unsaturated aldehyde (7j) with 2b
(1.2 equiv) also proceeded to give the product 8j in a 77% yield
and 98.7% ee.
In conclusion, we have succeeded in the development of the
enantioselective aziridination reaction of
a,b-unsaturated alde-
hydes using N-arenesulfonyloxycarbamates in the presence of so-
dium carbonate or sodium acetate. The present reaction is an
Table 3
Enantioselective aziridination reaction of aromatic substratesa
NaCN
(S)-3 (10 mol%)
Boc
N
Boc
N
(2 equiv.)
MnO2
BocNHOSO2p-MePh (2b)
O
O
H
H
O
NaOAc (3 equiv.)
Ar
H
Ar
OMe
Ar
H
CH2Cl2 (0.2 M)
temp., time
MeOH (0.2 M)
rt, 0.5-1.5 h
H
H
7
8
9
trans/cis = >99/1
Entry
Ar
Equiv of 2b
Temp (°C)
Time (h)
Yield (%) of 8b
Yield (%) of 9
% eec
1
Ph (7a)
Ph (7a)
1.2
1.2e
1
1
1
1
1
1
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
rt
rt
rt
4
1.2
2
1.5
1
7.5
1
22.5
8
2.5
13
2.5
23.5
6.5
18.5
1.5
23
3
–
–
–
14d
41d
–
97.9
97
2
3f
p-MeOPh (7b)
p-TfOPh (7c)
p-TfOPh (7c)
p-TsOPh (7d)
p-TsOPh (7d)
p-NO2Ph (7e)
m-NO2Ph (7f)
m-NO2Ph (7f)
o-NO2Ph (7g)
o-NO2Ph (7g)
p-FPh (7h)
–
g
4h
5
68
75
48
57
82
99
97
77
90
61
32
84
72
94
77
38
57
49
52
55
49
46
43
40
37
30
63
58
66
62
93.6i
99
ꢀ20
6h
7
4
95.5i
94.7
98.1
95.8i
98.7
97.2i
96.7
84.4i
94.2
84.5i
97.2
90.4i
98.7
ꢀ20
ꢀ20
4
8
9h
10
11h
12
13h
14
15h
16
17h
18
ꢀ20
4
ꢀ20
4
p-FPh (7h)
ꢀ20
p-CF3Ph (7i)
p-CF3Ph (7i)
3-Pyridyl (7j)
3-Pyridyl (7j)
4
ꢀ20
4
ꢀ20
14
a
The reaction was carried out using the
(3 equiv) in methylene chloride.
a,b-unsaturated aldehyde (1 equiv) and the carbamate (1–1.2 equiv) in the presence of the catalyst (0.1 equiv) and sodium acetate
b
Yield based on 7.
Enantiomeric excess after the conversion to the methyl ester 9.
Yield in two steps.
The carbamate 2d was used instead of 2b.
The reaction was carried out using the substrate (1.8 equiv) and the catalyst (19 mol %) in CHCI3.
The substrate was recovered.
c
d
e
f
g
h
i
(R)-Catalyst 3 was used instead of the (S)-catalyst.
The (2R,3R)-isomer 8 was obtained.

3332
H. Arai et al. / Tetrahedron Letters 50 (2009) 3329–3332
23, 4549–4552; (e) Fioravanti, S.; Morreale, A.; Pellacani, L.; Tardella, P. A.
Synlett 2004, 1083–1085; (f) Fioravanti, S.; Colantoni, D.; Pellacani, L.; Tardella,
P. A. J. Org. Chem. 2005, 70, 3296–3298; (g) Mohr, F.; Binfield, S. A.; Fettinger, J.
C.; Vedernikov, A. N. J. Org. Chem. 2005, 70, 4833–4839; (h) Lebel, H.; Huard, K.;
Lectard, S. J. Am. Chem. Soc. 2005, 127, 14198–14199; (i) Lebel, H.; Lectard, S.;
Parmentier, M. Org. Lett. 2007, 9, 4797–4800; (j) Pesciaioli, F.; De Vincentiis, F.;
Galzerano, P.; Bencivenni, G.; Bartoli, G.; Mazzanti, A.; Melchiorre, P. Angew.
Chem., Int. Ed. 2008, 47, 8703–8706.
efficient method applicable to aliphatic aldehydes, acrolein, and
aromatic aldehydes, and it proceeds with a high diastereoselectiv-
ity and excellent enantioselectivity. Further investigations on the
applications to the synthesis of unusual amino acids and natural
products are now underway.
11. Hayashi, Y.; Gotoh, H.; Hayashi, T.; Shoji, M. Angew. Chem., Int. Ed. 2005, 44,
4212–4215.
References and notes
12. Although N-arenesulfonyloxycarbamates afforded aziridine aldehydes with a
high diastereoselectivity, the origin of the high diastereoselectivity is unclear.
13. Corey, E. J.; Gilman, N. W.; Ganem, B. E. J. Am. Chem. Soc. 1968, 90, 5616–5617.
14. For ester derivatives of 4e, see: Nakajima, K.; Takai, F.; Tanaka, T.; Okawa, K.
Bull. Chem. Soc. Jpn 1978, 51, 1577–1578. and; Sato, K.; Kozikowski, A. P.
Tetrahedron Lett. 1989, 4073–4076.
1. For a review of aziridines, see: Sweeney, J. B. Chem. Soc. Rev. 2002, 32, 247–248.
2. For reviews on the synthesis of aziridines, see: (a) Halfen, J. A. Curr. Org. Chem.
2005, 9, 657–669; (b) Muller, P.; Fruit, C. Chem. Rev. 2003, 103, 2905–2919; (c)
Osborn, H. M. I.; Sweeney, J. B. Tetrahedron: Asymmetry 1997, 8, 1693–1715.
3. For synthetic applications of aziridines, see: (a) Hu, X. E. Tetrahedron 2004, 60,
2701–2743; (b) McCoull, M.; Davis, F. A. Synthesis 2000, 10, 1347–1365; (c)
Zwanenburg, B.; ten Holte, P. Top. Curr. Chem. 2001, 216, 93–124.
15. Typical procedure: To
a stirred solution of (S)-3 (7.4 mg, 0.02 mmol), 3-
nitrocinnamaldehyde (7f, 35.4 mg, 0.20 mmol), and sodium acetate (49.3 mg,
0.60 mmol) in methylene chloride (1.0 mL) at ꢀ20 °C was added tert-butyl p-
toluenesulfonyloxycarbamate (2b, 69.0 mg, 0.24 mmol). After stirring the
mixture at ꢀ20 °C for 13 h, the reaction mixture was diluted with ethyl
acetate, washed with saturated aqueous sodium hydrogen carbonate and
brine, dried over sodium sulfate, filtered, and concentrated in vacuo. The
residue was purified by silica gel column chromatography (n-hexane/ethyl
4. For recent examples of enantioselective aziridination, see: (a) Yamawaki, M.;
Tanaka, M.; Abe, T.; Anada, M.; Hashimoto, S. Heterocycles 2007, 72, 709–721;
(b) Wang, X.; Ding, K. Chem. Eur. J. 2006, 12, 4568–4575; (c) Ma, L.; Jiao, P.;
Zhang, Q.; Xu, J. Tetrahedron: Asymmetry 2005, 16, 3718–3734; (d) Ma, L.; Du,
D.-M.; Xu, J. J. Org. Chem. 2005, 70, 10155–10158; (e) Xu, J.; Ma, L.; Jiao, P. Chem.
Commun. 2004, 1616–1617; (f) Omura, K.; Murakami, M.; Uchida, T.; Irie, R.;
Katsuki, T. Chem. Lett. 2003, 32, 354–355.
5. For recent examples of organocatalytic aziridinations, see: (a) Shen, Y.-M.;
Zhao, M.-X.; Xu, J.; Shi, Y. Angew. Chem., Int. Ed. 2006, 45, 8005–8008; (b)
Armstrong, A.; Baxter, C. A.; Lamon, S. G.; Pape, A. R.; Wincewics, R. Org. Lett.
2007, 9, 351–353; (c) Minakata, S.; Murakami, Y.; Tsuruoka, R.; Kitanaka, S.;
Komatsu, M. Chem. Commun. 2008, 6363–6365.
6. Vesely, J.; Ibrahem, I.; Zhao, G.-L.; Rios, R.; Cordova, A. Angew. Chem., Int. Ed.
2007, 46, 778–781.
7. For reviews on organocatalysts, see: (a) Pellissier, H. Tetrahedron 2007, 63,
9267–9331; (b) Kotsuki, H.; Ikishima, H.; Okuyama, A. Heterocycles 2008, 75,
493–529; Kotsuki, H.; Ikishima, H.; Okuyama, A. Heterocycles 2008, 75, 757–
797; (c) Mielgo, A.; Palomo, C. Chem. Asian J. 2008, 3, 922–948;.
acetate = 4/1) to give aziridine 8f (56.8 mg, 97%) as a yellow oil: ½a D21
ꢁ
+95.5
(c0.54, CHCl3); IR (neat) 1727, 1532, 1351, 1155 cmꢀ1 1H NMR (400 MHz,
;
CDCl3) d 1.50 (9H, s), 3.31 (1H, dt, J = 1.1, 2.4 Hz), 3.94 (1H, d, J = 2.2 Hz), 7.56
(1H, dt, J = 1.1, 8.8 Hz), 7.67 (1H, dd, J = 1.1, 7.7 Hz), 8.19–8.21 (2H, m), 9.49
(1H, dd, J = 1.1, 3.3 Hz); 13C NMR (100 MHz, CDCl3) d 27.8, 44.3, 49.9, 83.4,
121.4, 123.5, 129.7, 132.5, 137.2, 148.4, 157.6, 193.2; HRMS (FAB, NPOE) calcd
for C14H17N2O5 293.1137 (M+H+), found 293.1158. The enantiomeric excess
was determined after conversion into the corresponding methyl ester 9f. To a
stirred solution of 8f (51.0 mg, 0.17 mmol) and sodium cyanide (17.3 mg,
0.35 mmol) in methanol (0.87 mL) at 0 °C was added activated manganese
dioxide (255 mg). After stirring the mixture at 0 °C for 40 min, the reaction
mixture was diluted with ethyl acetate and filtered through a pad of Celite. The
filtrate was concentrated in vacuo. The residue was diluted with ether, washed
with saturated aqueous ammonium chloride and brine, dried over sodium
sulfate, filtered, and concentrated in vacuo. The residue was purified by silica
gel chromatography (n-hexane/ethyl acetate = 9/1) to give aziridine methyl
8. For recent examples, see: (a) Hara, S.; Makino, K.; Hamada, Y. Pept. Sci. 2005
2006, 39–42; (b) Hara, S.; Makino, K.; Hamada, Y. Tetrahedron Lett. 2006, 47,
1081–1085; (c) Makino, K.; Jiang, H.; Suzuki, T.; Hamada, Y. Tetrahedron:
Asymmetry 2006, 17, 16441649; (d) Yoshitomi, Y.; Makino, K.; Hamada, Y. Org.
Lett. 2007, 9, 2457–2460; (e) Hara, S.; Nagata, E.; Makino, K.; Hamada, Y. Pept.
Sci. 2007 2008, 27–30.
ester 9f (25.7 mg, 46%, 99% ee, dr >99/1) as a colorless oil: ½a D19
ꢁ
+45.4 (c1.05,
CHCl3); IR (neat) 1729, 1532, 1439, 1350, 1208, 1149 cmꢀ1 1H NMR (400 MHz,
;
9. Carpino, L. A. J. Am. Chem. Soc. 1960, 82, 3133–3135.
CDCl3) d 1.49 (9H, s), 3.09 (1H, d, J = 2.4 Hz), 3.84 (3H, s), 3.93 (1H, d, J = 2.2 Hz),
7.54 (1H, t, J = 7.7 Hz), 7.67 (1H, dt, J = 1.1, 7.7 Hz), 8.16–8.20 (2H, m); 13C NMR
(100 MHz, CDCl3) d 27.9, 43.6, 44.3, 52.9, 82.8, 121.5, 123.3, 129.6, 132.6, 137.7,
148.5, 157.7, 167.2; HRMS (FAB, NBA) calcd for C15H18N2NaO6 345.1063
(M+Na+), found 345.1086. HPLC analysis: CHIRALCEL OD-H, (n-hexane/i-
PrOH = 90/10, 1.0 mL/min), tR = 10.7 min (minor) and 13.6 min (major).
10. For aziridinations using N-arenesulfonyloxycarbamates, see: (a) Lwowski, W.;
Mairich, T. J. J. Am. Chem. Soc. 1965, 87, 3630–3637; (b) Banks, M. R.; Blake, A. J.;
Cadogan, J. I. G.; Dawson, I. M.; Gosney, I.; Grant, K. J.; Gaur, S.; Hodgson, P. K.
G.; Knight, K. S.; Smith, G. W. Tetrahedron 1992, 48, 7979–8006; (c) Fioravanti,
S.; Morreale, A.; Pellacani, L.; Tardella, P. A. Synthesis 2001, 13, 1975–1978; (d)
Fioravanti, S.; Morreale, A.; Pellacani, L.; Tardella, P. A. Eur. J. Org. Chem. 2003,