Samarium diiodide-promoted electrophilic amination of ketone enolates: efficient synthesis of quaternary carbon-containing α-aminated ketones

Article abstract of DOI:10.1016/j.tetlet.2008.07.123

An efficient and practical electrophilic amination method that allows the preparation of useful quaternary carbon-containing α-aminoketones was developed. The reaction proceeds regiospecifically via a samarium enolate intermediate at room temperature in the presence of mild reducing agent SmI₂. Unlike the most reported lithium enolate cases, this new amination method does not require the use of strong base such as BuLi or LDA.

Full text of DOI:10.1016/j.tetlet.2008.07.123

Tetrahedron Letters 49 (2008) 5807–5809
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Tetrahedron Letters
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Samarium diiodide-promoted electrophilic amination of ketone enolates:
efficient synthesis of quaternary carbon-containing
a-aminated ketones
a,
Xing-Wen Sun a, Wei Wang a, Ming-Hua Xu a,b, , Guo-Qiang Lin
*
*
a Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China
b Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient and practical electrophilic amination method that allows the preparation of useful quater-
nary carbon-containing -aminoketones was developed. The reaction proceeds regiospecifically via a
samarium enolate intermediate at room temperature in the presence of mild reducing agent SmI2. Unlike
the most reported lithium enolate cases, this new amination method does not require the use of strong
base such as BuLi or LDA.
Received 5 June 2008
Revised 18 July 2008
Accepted 23 July 2008
Available online 26 July 2008
a
Ó 2008 Elsevier Ltd. All rights reserved.
The electrophilic amination of carbanionic species is an
important C–N bond formation approach that allows the prepara-
tion of a wide range of aminated compounds.1 Over the past years,
many electrophilic aminating reagents have been employed,
including sulfonylazides,2 sulfonyloxycarbamates,3 hydroxylamine
derivatives,4 azodicarboxylates,5 oxaziridines,6 1-chloro-1-nitroso
compounds,7 and arylazo tosylate.8 Among them, di-tert-butylazo-
dicarboxylate (DTBAD) appears one of the most general and prac-
to useful
containing
a
a
-aminated ketones. Moreover, quaternary carbon-
-aminoketones may also be constructed by this way
(Scheme 1). Herein, we report our results. This is also the first
example of SmI2-promoted electrophilic amination of ketone
enolate.
First, we examined the reaction of 2-methoxy-2-phenyl-cyclo-
hexanone (1a) with di-tert-butylazodicarboxylate (DTBAD) in the
presence of SmI2 (Scheme 2). A procedure similar to that reported
by Molander16 and Takeuchi17 was applied to check the potential
of our consideration. To our delight, when the reaction was per-
þ
tical electrophilic NH2 equivalents owing to its commercial
availability, high stability, and remarkable reactivity.
a-Aminoketones are versatile precursors of many physiologi-
formed at 0 °C in THF for 15 min, formation of the desired a-ami-
cally important compounds and useful intermediates for organic
synthesis.9 These importances have stimulated the effort to devel-
op new and improved synthetic strategies; asymmetric synthesis
nation product 2a was indeed found, but the yield was very low
(23%, Table 1, entry 1). A similar yield was obtained when the reac-
tion time was prolonged to 1 h (entry 2). The reduction product of
2-methoxy-2-phenyl-cyclohexanone (1a) was obtained as major
product in about 75% yield in both cases.
To find appropriate conditions, more reaction factors were con-
sidered and investigated. When the reaction substrate 1a was first
stirred with SmI2 for an hour before the addition of the aminating
reagent DTBAD, the reaction gave good yield of 80% (entry 3). This
result suggests the samarium enolate formation is the key to
increase the reaction yield. As the reaction temperature increased
to room temperature, the yield further increased (84%, entry 4).
Gratifyingly, a dramatic improvement of the yield (94%) was
achieved by employing 2 equiv of HMPA as additive18 (entry 5).
of optically active
a-aminoketones is of particular interest in
recent years.10 Among the methods developed, electrophilic
amination of enolates is one of the most important and general
way, and many examples of amination of lithium enolates,11
enamines,12 and enolsilanes13 have been documented. To the best
of our knowledge, there has been no report concerning the electro-
philic amination of samarium enolates. In the last two decades,
SmI2 has played an important role in organic synthesis.14 Our
interest in SmI2-mediated reactions15 led us to explore the possi-
bility of the electrophilic amination of samarium enolates.
Previously, Molander16 and Takeuchi17 have demonstrated that
samarium enolates of ketones could be formed regiospecifically
from the corresponding
mediated reaction. Thus, we envisioned if the mild electrophilic
-amination of -heterosubstituted ketones could be carried out
a-heterosubstituted ketones by the SmI2-
O
OSm
O
SmI2
R
X
HNR'R''
NR'R''
R
R
a
a
?
using appropriate aminating agent in the presence of SmI2, leading
R = aromatic or aliphatic
HNR'R'' = aminating reagent
X = OMe, OTs, OTMS, Br, Cl,
* Corresponding authors. Tel./fax: +86 21 5080 7388 (M.-H.X.).
E-mail address: xumh@mail.sioc.ac.cn (M.-H. Xu).
Scheme 1. Reaction proposal.
0040-4039/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2008.07.123

5808
X.-W. Sun et al. / Tetrahedron Letters 49 (2008) 5807–5809
Table 2
Electrophilic amination of
O
O
a
-heterosubstituted ketones with DTBADa
DTBAD
OMe
Ph
Ph
NBoc
NHBoc
Yieldb (%)
94
SmI2 /THF
Entry
1
Substrate
Product
O
O
Ph
Ph
1a
2a
Scheme 2. Amination of substrate 1a with DTBAD.
NHBoc
1a
1b
1c
1d
1e
2a
2b
2c
2a
2a
N
OMe
Boc
O
O
Ph
Table 1
Ph
2
3
4
5
87
83
92
89
NHBoc
Initial examination of the amination conditions
N
OMe
Boc
Entry
Procedurea
Temp
Time
Yieldc (%)
O
O
1
2
3
A
A
B
B
B
0 °C
0 °C
0 °C
rt
15 min
1 h
1 h
1 h
1 h
23
25
80
84
94
Ph
Ph
NHBoc
NBoc
OMe
4
5b
rt
O
O
O
O
Ph
N
a
Ph
Procedure A: a solution of ketone 1a and DTBAD in THF was added to the
solution of SmI2. Procedure B: a solution of ketone 1a was first added to the solution
of SmI2, the mixture was stirred for 30 min, and then DTBAD was added.
NHBoc
Br
Boc
b
Two equivalents of HMPA were added as additive.
Isolated yield.
c
Ph
N
Ph
NHBoc
Cl
Boc
The detailed experimental procedure used in entry 5 of Table 1
is described below. Under nitrogen, to a solution of freshly made
SmI2 (1 mmol) in THF (5 mL) was added HMPA (0.17 mL, 1 mmol).
After the mixture was stirred at room temperature for 15 min, sub-
strate 1a (102 mg, 0.5 mmol) in freshly distilled THF (3 mL) was
added and the stirring continued for an additional 30 min. DTBAD
(138 mg, 0.6 mmol) in THF (2 mL) was then added, and the reac-
tion mixture was stirred for 1 h. Subsequently, the reaction mix-
ture was quenched with saturated Na2S2O3 aqueous solution. The
aqueous layer was separated and extracted with ether. The com-
bined organic layer was washed successively with water, brine,
and dried over Na2SO4, and concentrated under vacuum. The crude
product was purified by column chromatography on silica gel to
give aminated ketone 2a in 94% yield.
Cl
Cl
O
O
O
O
O
O
6
7
8
1f
2f
95
93
98
OMe
OMe
OMe
N
N
N
NHBoc
Boc
Br
Br
1g
1h
2g
2h
NHBoc
Boc
Me
Me
NHBoc
Boc
Following the optimal reaction conditions, a variety of
a-het-
OMe
OMe
O
O
O
O
erosubstituted ketone substrates were tested for the -amination.
a
9
1i
2i
85
The experimental results are summarized in Table 2. As expected,
the reaction was found very effective for a wide range of substrates
OMe
N
NHBoc
Boc
including both cyclic and acyclic
cases, the -amination products could be obtained cleanly in satis-
factory yields.19 In addition to six membered
-methoxy-cyclo-
hexanone substrates, -methoxy substituted cyclopentanone and
cycloheptanone are also successfully aminated (entries 1–3).
Moreover, the reactions can be performed smoothly when -halo-
a-substituted ketones. In most
a
Bn
Bn
NHBoc
10
11
12
1j
2j
67
94
91
93
a
N
OMe
Boc
a
O
O
a
NHBoc
1k
1l
2k
2l
substituted substrates are used (entries 4, 5, 11 and 12). In entries
6-9, 2-methoxy-2-phenyl-cyclohexanone (1a) derivatives having
both electron-withdrawing and electron-donating substituents
on the benzene ring gave the corresponding products in excellent
yields. When substrates 1j was employed, lower yield (67%) was
observed (entry 10). This result indicates that an aromatic substi-
N
Br
Boc
O
O
Br
Ph
N
NHBoc
Boc
tuent such as phenyl group at the
useful but not necessary for the reaction. For acyclic substrates,
as shown in entries 12–13, it was found that -heterosubstituted
a-position of carbonyl is very
NHBoc
O
BocN
Ph
a
13
1m
2m
Ph
ketones 1l–m could be easily aminated and gave amination
products 2l–m in over 90% yields, indicating a mild and readily
preparation of structurally interesting quaternary carbon-contain-
O
O
a
All reactions were carried out in THF using the optimized conditions.
Isolated yield.
b
ing
In summary, we have developed an efficient and practical elec-
trophilic amination approach for the preparation of useful quater-
nary carbon-containing -aminoketones. The reaction can be
a-aminoketone analogues.
a
lithium enolate cases, this new method does not require the use
of strong base such as BuLi or LDA. Attempts toward the asymmet-
ric version of the reaction as well as the extension of this method
are currently underway.
performed under very simple and mild reaction conditions. It pro-
ceeds regiospecifically via a samarium enolate intermediate in the
presence of mild reducing agent SmI2; unlike the most reported

X.-W. Sun et al. / Tetrahedron Letters 49 (2008) 5807–5809
5809
15. (a) Xu, M.-H.; Wang, W.; Lin, G.-Q. Org. Lett. 2000, 2, 2229; (b) Xu, M.-H.; Wang,
W.; Xia, L.-J.; Lin, G.-Q. J. Org. Chem. 2001, 66, 3953; (c) Wang, W.; Zhong, Y.-W.;
Lin, G.-Q. Tetrahedron Lett. 2003, 44, 4613; (d) Zhong, Y.-W.; Izumi, K.; Xu,
M.-H.; Lin, G.-Q. Org. Lett. 2004, 6, 4747; (e) Zhong, Y.-W.; Xu, M.-H.; Lin, G.-Q.
Org. Lett. 2004, 6, 3953; (f) Huang, L.-L.; Xu, M.-H.; Lin, G.-Q. J. Org. Chem. 2005,
70, 529; (g) Zhong, Y.-W.; Dong, Y.-Z.; Fang, K.; Xu, M.-H.; Lin, G.-Q. J. Am. Chem.
Soc. 2005, 127, 12956; (h) Zhu, C.; Shi, Y.; Xu, M.-H.; Lin, G.-Q. Org. Lett. 2008,
10, 1243. For a samarium enolate example: (i) Wang, W.; Xu, M.-H.; Lei, X.-S.;
Lin, G.-Q. Org. Lett. 2000, 2, 3773.
Acknowledgments
Financial support from the National Natural Science Foundation
of China (20402018, 20721003), the Chinese Academy of Sciences,
the Major State Basic Research Development Program (2006CB-
806106), and the Shanghai Rising-Star Program (05QMX1467) is
acknowledged.
16. Molander, G. A.; Hahn, G. J. Org. Chem. 1986, 51, 1135.
17. Nakamura, Y.; Takeuchi, S.; Ohgo, S.; Yamaoka, M.; Yoshida, A.; Mikami, K.
Tetrahedron 1999, 55, 4595.
References and notes
18. For HMPA effect in SmI2 chemistry, see: (a) Otsubo, K.; Inanaga, J.; Yamaguchi,
M. Tetrahedron Lett. 1986, 27, 5763; (b) Shabangi, M.; Sealy, J. M.; Flowers, R. A.,
II. Tetrahedron Lett. 1998, 39, 4429; (c) Hou, Z.; Wakatsuki, Y. J. Chem. Soc.,
Chem. Commun. 1994, 1205; (d) Enemaerke, R. J.; Hertz, T.; Skrydstrup, T.;
Daasbjerg, K. Chem. Eur. J. 2000, 6, 3747.
1. For several review articles: (a) Erdik, E.; Ay, M. Chem. Rev. 1989, 89, 1947; (b)
Mulzer, J. Organic Synthesis Highlights; Wiley-VCH: Weinheim, 1991; 45; (c)
Greck, C.; Genet, J. P. Synlett 1997, 741; (d) Genet, J. P.; Greck, C.; Lavergne, D. In
Modern Amination Methods. Ricci, A., Ed.; Wiley-VCH: Weinheim, 2000; p 65;
(e) Dembech, P.; Seconi, G.; Ricci, A. Chem. Eur. J. 2000, 6, 1281; (f) Greck, C.;
Drouillat, B.; Thomassigny, C. Eur. J. Org. Chem. 2004, 1377; (g) Erdik, E.
Tetrahedron 2004, 60, 8747.
2. (a) Harmon, R. E.; Wellman, G.; Gupta, S. K. J. Org. Chem. 1973, 38, 11; (b) Evans,
D. A.; Britton, T. C.; Ellman, J. A.; Dorrow, R. L. L. J. Am. Chem. Soc. 1990, 112,
4011.
3. (a) Lwowski, W.; Maricich, J. M. J. Am. Chem. Soc. 1965, 87, 3630; (b) Felice, E.;
Fioravanti, S.; Pellacani, L.; Tardella, P. A. Tetrahedron Lett. 1999, 40, 4413.
4. (a) Greck, C.; Bischoff, L.; erreira, F.; Genet, J. P. J. Org. Chem. 1995, 60, 7010; (b)
Bernardi, P.; Dembech, P.; Fabbri, G.; Ricci, A.; Seconi, G. J. Org. Chem. 1999, 64,
641; (c) Berman, A. M.; Johnson, J. S. J. Am. Chem. Soc. 2004, 126, 5680; (d)
Campbell, M. J.; Johnson, J. S. Org. Lett. 2007, 9, 1521.
19. Characterization data for products 2a–m: Compound 2a: 1H NMR (300 MHz,
CDCl3) d 1.43 (br s, 9H), 1.48 (br s, 9H), 1.26–1.83 (m, 2H), 2.06–2.19 (m, 2H),
2.38–2.47 (m, 2H), 2.83–3.08 (m, 2H), 5.92 (s, 1H), 7.27–7.41 (m 5H) ppm; FT-
IR (KBr) m ; ESI-MS: 427.1
3278, 1724, 1368, 1245, 1161, 698, 581 cmꢀ1
(M++Na), HRMS (ESI) calcd for C22H32N2O5Na: 427.2203; found, 427.2201;
Anal. Calcd for C22H32N2O5: C, 65.32; H, 7.97; N, 6.93. Found: C, 65.09; H, 8.03;
N, 6.70. Compound 2b: 1H NMR (300 MHz, CDCl3) d 1.45 (br s, 9H), 1.49 (br s,
9H), 1.36–2.64 (m, 6H), 5. 91 (6.09) (s, 1H), 7.24–7.51 (m, 5H) ppm; FT-IR (KBr)
m
3340, 1750, 1730, 1715, 1496, 1366, 1257, 1181, 1150, 754 cmꢀ1; ESI-MS:
413.2 (M++Na); Anal. Calcd for C21H30N2O5: C, 64.59; H, 7.74; N, 7.17. Found: C,
64.70; H, 7.90; N, 7.05. Compound 2c: 1H NMR (300 MHz, CDCl3) d 1.45 (br s,
9H), 1.49 (br s, 9H), 1.33–2.64 (m, 10H), 5.95 (6.11, 6.16) (s, 1H), 7.34–7.61 (m
5. (a) Carpino, L. A.; Terry, P. H.; Crowley, D. J. J. Org. Chem. 1961, 26, 4336; (b)
Lenarsic, R.; Kocevar, M.; Polane, S. J. Org. Chem. 1999, 64, 2558; (c) Harris, J. M.;
Bolessa, E. A.; Mendonca, A. J.; Feng, S.-C.; Vederas, J. C. J. Chem. Soc., Perkin
5H) ppm; FT-IR (KBr) m 3301, 2980, 2935, 1715, 2865, 1722, 1368, 1162, 749,
700 cmꢀ1
;
ESI-MS: 441.2 (M++Na); HRMS (ESI) calcd for C23H34N2O5Na:
441.2385; found, 441.2359. Compound 2f: 1H NMR (300 MHz, CDCl 3) d 1.43
Trans.
1
1995, 1945; (d) Meseguer, M.; Moreno-Mañas, M.; Vallribera, A.
(br s, 9H), 1.45 (br s, 9H), 1.43-2.97 (m, 8H), 5.91 (6.08, 6.46) (s, 1H), 7.11–7.44
Tetrahedron Lett. 2000, 41, 4093.
(m, 4H) ppm; FT-IR (KBr) m 3238, 3161, 2981, 1715, 1701, 1496, 1160, 1016,
6. (a) Andreae, S.; Schmitz, E. Synthesis 1991, 327; (b) Shustov, G. V.; Kadorkina, G.
K.; Varlamov, S. V.; Kachanov, A. V.; Kostyanovsky, R. G.; Rauk, A. J. Am. Chem.
Soc. 1992, 114, 1616; (c) Hannachi, J. C.; Vidal, J.; Mulatier, J. C.; Collet, A. J. Org.
Chem. 2004, 69, 2367; (d) Armstrong, A.; Edmonds, I. D.; Swarbrick, M. E.;
Treweeke, N. R. Tetrahedron 2005, 61, 8423.
7. (a) Oppolzer, W.; Tamura, O. Tetrahedron Lett. 1990, 31, 991; (b) Oppolzer, W.;
Tamura, O.; Sundarababu, G.; Signer, M. J. Am. Chem. Soc. 1992, 114, 5900.
8. (a) Sapountzis, I.; Knochel, P. Angew. Chem., Int. Ed. 2004, 43, 897; (b) Sinha, P.;
Kofink, C. C.; Knochel, P. Org. Lett. 2006, 8, 3741.
829, 806 cmꢀ1; ESI-MS: 427.1(M++Na); HRMS (ESI) Calcd for C22H31N2O5ClNa:
461.1818; found, 461.1814; Anal. Calcd for C23H31N2ClO5: C, 60.20; H, 7.12; N,
6.38. Found: C, 60.48; H 7.18; N 6.27. Compound 2g: 1H NMR (300 MHz, CDCl3)
d 1.42 (br s, 18H), 1.40–2.98 (m, 8H), 5.94 (6.11, 6.49) (s, 1H), 7.13 (d, 2H,
J = 6.9 Hz), 7.34–7.45 (m, 2H) ppm; ESI-MS: 441.2(M++Na), HRMS (ESI) calcd
for C22H31BrN2O5Na: 505.1309; found, 505.1309. Anal. Calcd for C22H31BrN2O5:
C, 54.66; H, 6.46; N, 5.80; Br, 16.53. Found: C, 55.24; H, 6.58; N, 5.54; Br, 16.19.
Compound 2h: 1H NMR (300 MHz, CDCl3) d 1.41 (br s, 9H), 1.47 (br s, 9H), 1.26–
2.04 (m, 6H), 2.34 (s, 3H), 3.25 (d, 2H, J = 9.0 Hz), 7.19 (m, 4H) ppm; FT-IR (KBr)
9. Mayer, D., fourth ed.. In Houben Weyl, Methods of Organic Chemistry; Müller, E.,
Ed.; Thieme Medical Publishers, 1977; vol. 7/2c, p 2253.
m
3240, 3163, 2980, 2944, 2870, 1715, 1702, 1016, 790, 613 cmꢀ1; ESI-MS:
441.2(M++Na); HRMS (ESI) calcd for C23H34N2O5Na: 441.2354; found,
457.2360; Anal. Calcd for C23H34N2O5: C, 66.00; H, 8.19; N, 6.69. Found: C,
65.90; H, 8.18; N, 6.61. Compound 2i: 1H NMR (300 MHz, CDCl3) d 1.43 (s, 9H),
1.47 (s, 9H), 1.75–2.99 (m, 8H), 3.09 (s, 3H) , 5.99 (6.14, 6.21) (s, 1H), 6.73 (d,
10. For recent examples: (a) List, B. J. Am. Chem. Soc. 2002, 124, 5656; (b) Bogevig,
A.; Juhl, K.; Kumaragurubaran, N.; Zhuang, W.; Jørgensen, K. A. Angew. Chem.,
Int. Ed. 2002, 41, 1790; (c) Duthaler, R. O. Angew. Chem., Int. Ed. 2003, 42, 975;
(d) Dessole, G.; Bernardi, L.; Bonini, B. F.; Capitò, E.; Fochi, M.; Herrera, R. P.;
Ricci, A.; Cahiez, G. J. Org. Chem. 2004, 69, 8525; (e) Xu, X.; Yabuta, T.; Yuan, P.;
Takemoto, Y. Synlett 2006, 137; (f) Thomassigny, C.; Prim, D.; Greck, C.
Tetrahedron Lett. 2006, 47, 1117; (g) Kang, Y. K.; Kim, D. Y. Tetrahedron Lett.
2006, 47, 4565; (h) Terada, M.; Nakano, M.; Ube, H. J. Am. Chem. Soc. 2006, 128,
16044; (i) Liu, T.-Y.; Cui, H.-L.; Zhang, Y.; Jiang, K.; Du, W.; He, Z.-Q.; Chen, Y.-C.
Org. Lett. 2007, 9, 3671. For a related, minireview see: (j) Janey, J. M. Angew.
Chem., Int. Ed. 2005, 44, 4292.
2H, J = 8.8 Hz), 7.19 (d, 2H, J = 8.8 Hz) ppm; FT-IR (KBr)
m 3349, 3065, 2996,
2929, 2859, 2832, 1763, 1454, 1434, 1333, 1284 , 1080, 1061, 1035, 996, 829,
806 cmꢀ1; HRMS (ESI) calcd for C23H34N2O6Na: 457.2379; found, 457.2363.
Compound 2j: 1H NMR (300 MHz, CDCl3) d 1.39 (s, 9H), 1.45 (s, 9H), 1.75–2.98
(m, 10H), 5.99 (6.16) (s, 1H), 7.01–7.387 (m, 5H) ppm; FT-IR (KBr)
2938, 1751, 1724, 1603, 1368, 758, 705 cmꢀ1
HRMS (ESI) calcd for
23H34N2O5Na: 441.2374; found, 441.2360. Compound 2k: 1H NMR
m 3359, 2979,
;
C
(300 MHz, CDCl3) d 1.41 (s, 9H), 1.49 (s, 9H), 1.25–1.38 (m, 4H), 2.95–3.09 (s,
11. Selected examples: (a) Trimble, L. A.; Vederas, J. C. J. Am. Chem. Soc. 1986, 108,
6397; (b) Estermann, H.; Seebach, D. Helv. Chim. Acta 1988, 71, 1824; (c)
Enders, D.; Poiesz, C.; Joseph, R. Tetrahedron: Asymmetry 1998, 9, 3709; (d)
Page, P. C. B.; McKenzie, M. J.; Allin, S. M.; Buckle, D. R. Tetrahedron 2000, 56,
9683; (e) Evans, D. A.; Britton, T. C.; Dorow, R. L.; Dellaria, J. F. J. Am. Chem. Soc.
1986, 108, 6395.
3H), 6.57 (6.63) (s, 1H), 7.18–7.35 (m, 3H), 7.42–7.47 (m, 1H) ppm; FT-IR (KBr)
m
3324, 2978, 2939, 1738, 1703, 1685, 1602, 1505, 1367, 741, 601 cmꢀ1; ESI-
MS: 413.2 (M++Na); HRMS (ESI) calcd for C21H30N2O5Na: 413.2068; found,
413.2047; Anal. Calcd for C21H30N2O5: C, 64.59; H, 7.74; N, 7.17. Found: C,
64.85; H, 7.76; N, 7.12. Compound 2l: 1H NMR (300 MHz, CDCl3) d 1.21–1.49
(m, 4H), 1.50 (s, 18H), 1.53–1.66 (m, 2H), 2.03–2.28 (m, 4H), 5.93 (6.09, 6.13) (s,
12. (a) Gmeiner, P.; Bollinger, B. Tetrahedron 1994, 50, 10909; (b) Enders, D.;
Joseph, R.; Poiesz, C. Tetrahedron 1998, 54, 10069.
13. (a) Gennari, C.; Colombo, L.; Bertolini, G. J. Am. Chem. Soc. 1986, 108, 6394; (b)
Evans, D. A.; Johnson, D. S. Org. Lett. 1999, 1, 595.
14. For review articles on the application of SmI2 in organic synthesis, see: (a)
Molander, G. A. Chem. Rev. 1992, 92, 29; (b) Molander, G. A.; Harris, C. R. Chem.
Rev. 1996, 96, 307; (c) Molander, G. A.; Harris, C. R. Tetrahedron 1998, 54, 3321;
(d) Skrydstrup, T. Angew. Chem., Int. Ed. 1997, 36, 345; (e) Krief, A.; Laval, A. M.
Chem. Rev. 1999, 99, 745; (f) Kagan, H. B. Tetrahedron 2003, 59, 10351; (g)
Edmonds, D. J.; Johnston, D.; Procter, D. J. Chem. Rev. 2004, 104, 3371; (h)
Gopalaiah, K.; Kagan, H. B. New J. Chem. 2008, 32, 607.
1H), 7.39–7.55 (m, 3H), 8.05–8.10 (br s, 2H) ppm; FT-IR (KBr) m 3356, 3065,
2973, 2938, 1745, 1685, 1503, 1159, 882, 705 cmꢀ1; ESI-MS: 441.2 (M++Na);
HRMS (ESI) calcd for C23H34N2O5Na: 441.2347; found, 441.2360; Anal. Calcd
for C23H34N2O5: C, 66.00; H, 8.19; N, 6.69. Found: C, 66.21; H, 8.14; N, 6.54.
Compound 2m: 1H NMR (300 MHz, CDCl3) d 1.44–1.49 (br, 18H), 2.10 (s, 3H),
6.12 (s, 1H), 7.22–7.48 (m, 8H), 8.17 (d, J = 10.0 Hz, 2H) ppm; FT-IR (KBr)
m
3316, 3065, 2981, 2934, 1712, 1598, 1369, 1156, 962, 699 cmꢀ1; ESI-MS: 463.2
(M++Na); HRMS (ESI) calcd for C25H32N2O5Na: 463.2185; found, 463.2203;
Anal. Calcd for C25H32N2O5: C, 68.16; H, 7.32; N, 6.36. Found: C, 68.09; H, 7.40;
N, 6.31.