Stereoselective Lewis base-catalyzed asymmetric hydrosilylation of α-acetamido-β-enamino esters: Straightforward approach for the construction of α,β-diamino acid derivatives

Article abstract of DOI:10.1002/adsc.201300184

The Lewis base-organocatalyzed asymmetric hydrosilylation of α-acetamido-β-enamino esters was investigated. Among various chiral Lewis base catalysts, a novel catalyst derived from L-serine was found to be the most efficient one which can promote the reaction to afford a series of α,β-diamino acid derivatives with high yields (up to 99%), excellent enantioselectivities (up to 98% ee) and moderate diastereoselectivities (up to 80:20 dr). The absolute configuration of one of the products was determined by the X-ray crystallographic analysis. In addition, the mechanism and the transition state of the reaction were proposed. Copyright

Full text of DOI:10.1002/adsc.201300184

COMMUNICATIONS
DOI: 10.1002/adsc.201300184
Stereoselective Lewis Base-Catalyzed Asymmetric
Hydrosilylation of a-Acetamido-b-enamino Esters:
Straightforward Approach for the Construction of
a,b-Diamino Acid Derivatives
Yan Jiang,a,b Xing Chen,a,b Xiao-Yan Hu,a,b Chang Shu,a,b Yong-Hong Zhang,a,b
Yong-Sheng Zheng,a,b Chun-Xia Lian,a Wei-Cheng Yuan,a and Xiao-Mei Zhanga,*
a
Key Laboratory for Asymmetric Synthesis and Chiraltechnology of Sichuan Province, Chengdu Institute of Organic
Chemistry, Chinese Academy of Sciences, Chengdu 610041, Peopleꢀs Republic of China
Fax : (+86)-28-8525-7883; e-mail: xmzhang@cioc.ac.cn
University of Chinese Academy of Sciences, Beijing 100049, Peopleꢀs Republic of China
b
Received: February 28, 2013; Revised: April 23, 2013; Published online: && &&, 0000
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201300184.
Abstract: The Lewis base-organocatalyzed asym-
metric hydrosilylation of a-acetamido-b-enamino
esters was investigated. Among various chiral Lewis
base catalysts, a novel catalyst derived from l-
serine was found to be the most efficient one which
can promote the reaction to afford a series of a,b-
diamino acid derivatives with high yields (up to
99%), excellent enantioselectivities (up to 98% ee)
and moderate diastereoselectivities (up to 80:20
dr). The absolute configuration of one of the prod-
ucts was determined by the X-ray crystallographic
analysis. In addition, the mechanism and the transi-
tion state of the reaction were proposed.
ing with this method. In 2001, Robinson and co-work-
ers reported the Rh-catalyzed asymmetric hydrogena-
tion
of
a,b-diamidopropenoate
and
a,b-
diamidobutenACHTUNGTREGoNNUN ate through which they obtained chiral
a,b-diaminopropanoic acid derivatives and a,b-diami-
nobutanoic acid derivatives in good ee values (>
95%).[8] However, the generality of the reaction has
not been examined. In addition, the organocatalytic
reduction of a-amido-b-enamino ester has not been
reported yet.
Over the past decade, the chiral Lewis base-cata-
lyzed asymmetric hydrosilylation of C=N bonds has
become an efficient method to obtain chiral amines
and amino acids.[9,10] Our group has been actively en-
gaged in research on chiral Lewis base-organocata-
lyzed hydrosilylation of a wide range of C=N double
bond compounds.[10n–s] Recently, we demonstrated
a highly diastereoselective and enantioselective hy-
drosilylation of a-acetoxy-b-enamino esters through
which various valuable a-hydroxy-b-amino esters
Keywords: amino acids; asymmetric catalysis; hy-
drosilylation; Lewis bases
Optically active a,b-diamino acids are important were prepared efficiently.[10q] Inspired by our success
structural components present in many natural prod- on the hydrosilylation of a-heteroatom substituted b-
ucts, synthetic peptides and therapeutically useful enamino esters, we attempted to extend this method-
compounds.[1] Consequently, considerable research ef- ology to the transformation of a-amido-b-enamino
forts have been devoted to the asymmetric synthesis esters to a,b-diamino acid derivatives. Thus a-acetam-
of chiral a,b-diamino acids.[2] Up to now, the synthe- ido-b-enamino esters (1) were designed, synthesized
ses of chiral a,b-diamino acids mainly focus on asym- and subjected to the Lewis base-catalyzed asymmetric
metric aza-Mannich reactions,[3] aza-Henry reac- hydrosilylation. The reactions proceeded smoothly to
tions,[4] asymmetric diamination,[5] ring opening of give the chiral a,b-diamino acid derivatives (2) with
chiral aziridines[6] and other transformations.[7]
high yields (up to 99%), excellent enantioselectivities
Among various synthetic approaches, the direct cat- (up to 98% ee) and moderate diastereoselectivities
alytic asymmetric hydrogenation of a-amido-b-enami- (up to 80:20 dr) (Scheme 1).
no esters is an elegant and efficient strategy to con-
During our ongoing research on the Lewis base-cat-
struct chiral a,b-diamino acids. However, to the best alyzed hydrosilylation of C=N double bond com-
of our knowledge, there are only a few examples deal- pounds, we have developed several kinds of highly
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1
ÞÞ
These are not the final page numbers!

Yan Jiang et al.
COMMUNICATIONS
Table 1. Screening of chiral Lewis base catalysts in the asym-
metric hydrosilylation of a-acetamido-b-enamino ester 1a.[a]
Scheme 1. Asymmetric hydrosilylation of a-acetamido-b-en-
amino esters (1).
Entry Cat* Yield [%][b] syn:anti[c] ee [%][d] syn, anti
active and selective chiral picolinamide Lewis base
catalysts 3–5 (Figure 1). Moreover, we designed and
synthesized a kind of novel catalyst 6 analogous to 5
which delivered good results in the hydrosilylation of
a-acetoxy-b-enamino esters.[10q] Catalysts 6a–6c were
prepared from l-serine via facile steps.[10s] Compared
to 5, 6 contains one more aryl group at C-2 of the
ring, which makes it bulkier so that it might be more
stereoselective in hydrosilylation.
All of these chiral Lewis bases were evaluated in
the hydrosilylation of a-acetamido-b-enamino ester
1a in 1,2-dichloroethane at 08C. The results are sum-
marized in Table 1. Catalyst 3[10n] delivered very poor
diastereoselectivity as well as enantioselectivity
(Table 1, entry 1). Although good diastereoselectivity
was observed for catalyst 4,[10p] the ee value of the
major diastereomer was very poor (Table 1, entry 2).
When 5a was employed, the syn-diastereomer was ob-
tained with a good ee value of 90%, however, almost
1
2
3
4
5
6
7
8
9
3
4
98
96
96
89
85
92
98
96
90
20:80
4:96
21, 57
40, 6
90, 20
49, 8
62, 5
82, 3
95, 31
92, 25
93, 37
5a
5b
5c
5d
6a
6b
6c
51:49
20:80
17:83
33:67
53:47
54:46
35:65
[a]
Unless otherwise specified, the reactions were carried
out on a 0.15-mmol scale with 2.0 equiv. of HSiCl3 in
1.5 mL of ClCH2CH2Cl.
[b]
[c]
Isolated yield based on 1a.
The relative comfiguration of 2a was determined by com-
parison of the vicinal coupling constants (see the Sup-
porting Information). The dr value of 2a was determined
by chiral HPLC analysis.
[d]
The ee values were determined by chiral HPLC.
the same yield of the anti-diastereomer was generated stable under the reaction conditions and we can re-
in very low enantioselectivity (Table 1, entry 3). Cata- cover the catalyst after the reaction. Although the
lysts 5b–5d resulted in higher dr values but very poor diastereoselectivity is not satisfactory yet, 6a was de-
ee values for the major diastereomer (Table 1, en- termined as the optimal catalyst and employed in fur-
tries 4–6). Catalysts 6a–6c exhibited better enantiose- ther investigations.
lectivities (Table 1, entries 7–9) whereby 6a gave the
In order to improve the results, the other conditions
major diastereomer with up to 95% ee (Table 1, were modified. First, several solvents were tested. The
entry 7). The acetonide function of the catalysts 6a is reaction in dichloromethane did not give the product
with a better dr value (Table 2, entry 2). Surprisingly,
it was found that the reaction in chloroform gave only
a trace of the product (Table 2, entry 3). The reason
has not been found out yet. To our delight, the reac-
tion in THF resulted in an evidently higher dr value
and the ee value of the major diastereomer was not
affected (Table 2, entry 4). Perhaps the hydrogen
bonding of THF with the the a-acetamide group in
the substrate can diminish the intramolecular hydro-
gen bonding of the substrate (see Scheme 3 below),
and thus reduce the probability of generation of the
anti-product. Therefore, THF was selected as the opti-
mal solvent for the reaction. Afterwards, when the re-
action was conducted at À108C, a higher dr value and
a slightly higher ee value were obtained (Table 2,
entry 5). Further decreasing the temperature to
À208C did not improve the result any more (Table 2,
entry 6). Therefore, À108C was determined as the op-
timal temperature of the reaction. When the reaction
was conducted in diluted solution, the dr value in-
creased obviously, however, the ee value of the major
Figure 1. Chiral Lewis base organocatalysts 3–6 evaluated in
this study.
2
asc.wiley-vch.de
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
These are not the final page numbers!

Stereoselective Lewis Base-Catalyzed Asymmetric Hydrosilylation of a-Acetamido-b-enamino Esters
Table 2. Modification of the conditions for the asymmetric hydrosilylation of 1a.[a]
Entry
Solvent
Temperature [oC]
Yield [%][b]
syn:anti[c]
ee [%][d] syn, anti
1
2
3
4
ClCH2CH2Cl
CH2Cl2
CHCl3
THF
THF
THF
0
0
0
0
À10
À20
À10
À10
98
97
trace
94
98
99
77
77
53:47
47:53
–
66:34
73:27
73:27
82:18
70:30
95, 31
95, 33
–
94, 34
96, 26
96, 16
48, 31
64, 16
5
6
7[e]
8[f]
THF
THF
[a]
Unless otherwise specified, the reactions were carried out on a 0.15-mmol scale with 2.0 equiv. of HSiCl3 and 10 mol% of
6a in 1.5 mL of the solvent.
Isolated yield based on 1a.
[b]
[c]
The relative comfiguration of 2a was determined by comparison of the vicinal coupling constants (see the Supporting In-
formation). The dr value of 2a was determined by chiral HPLC analysis.
The ee values were determined by using chiral HPLC analysis.
3 mL of THF were used.
[d]
[e]
[f]
5 mol% of 6a were used.
diastereomer dropped sharply (Table 2, entry 7). De- Z ratios of the substrates and the results, it can be
creasing the catalyst loading to 5 mol% also caused concluded that the E/Z ratios do not correlate with
a dramatic reduction in the ee value of the major dia- the stereoselectivities.
stereomer (Table 2, entry 8).
Afterwards, the major isomer of product 2g was
Having established the optimal conditions, the subjected to cyclization with thiophosgene to generate
scope of the reaction was investigated. In the pres- the cyclic product 7 (Scheme 2). The absolute configu-
ence of 10 mol% of catalyst 6a, various a-acetamido- ration of 7 was unambiguously confirmed as (4R,5S)
b-enamino esters were hydrosilylated in THF at by the X-ray crystallographic analysis.[11] Thus the ab-
À108C. The results are summarized in Table 3. Gener- solute configuration of 2g was determined as (2R,3S)
ally, moderate dr values were obtained for all of the accordingly.
reactions. Good enantioselectivities for the major iso-
In this study, the diastereocontrol is somewhat
mers were observed with b-phenyl and b-para- or b- lower than those of a-aryl, a-alkyl, and a-OAc sub-
meta-substituted-phenyl substrates (Table 3, entries 1– strates reported previously.[10g,q] We reasoned that the
8). The electronic property of the substituents exhibit- hydrogen of the a-acetamide group in the substrate
ed little effect on the results. However, we failed to might be in charge of this result. As can be seen in
synthesize the b-ortho-substituted-phenyl substrates Scheme 3, the enamine tautomer isomerizes to gener-
to test the effect of ortho-substitution. b-2-Naphthyl ate an E-imine tautomer and a Z-imine tautomer.
substrate 1i also delivered good enantioselectivity for Generally, formation of the E-imine is much easier.
the major diastereomer (Table 3, entry 9). The b-2- However, in this case, the Z-imine can be stabilized
furyl substrate 1j gave a slightly lower ee value for the by hydrogen bonding between the hydrogen of the a-
major diastereomer (Table 3, entry 10). As for b-alkyl acetamide group and the nitrogen atom of the imine
substrates, the ee values decreased obviously. b- so that considerable amount of Z-imine can be gener-
Methyl substrate 1k generated the major diastereo- ated. For the E-imine tautomer, as described by
[10g]
ˇ
mer in only moderate ee value (Table 3, entry 11) and Malkov and Kocovsky et al.,
the ester carbonyl
b-benzyl substrate 1l afforded even lower enantiose- and the imine group are held together either by hy-
lection for the major diastereomer (Table 3, entry 12). drogen bonding (in the protonated form, the proton
This suggested that the b-aryl ring might have an might be generated from the reaction of trichlorosi-
arene-arene interaction with the catalyst so that good lane and traces of water in the solvent) or by chela-
enantioselections could be obtained. In contrast there tion to silicon, thus it undergoes the hydrosilylation to
is no arene-arene interaction between b-alkyl sub- provide a syn-product. While, for the Z-imine tauto-
strate and the catalyst, therefore, poor enantioselec- mer, the acetamide group and the imine group are
tivities were observed. In addition, comparing the E/ held together by intramolecular hydrogen bonding
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
3
ÞÞ
These are not the final page numbers!

Yan Jiang et al.
COMMUNICATIONS
Table 3. Asymmetric hydrosilylation of a-acetamido-b-enamino esters 1a–l under the optimal conditions.[a]
Entry
1
R
E/Z[b]
Yield [%][c]
syn:anti[d]
ee [%][e] syn, anti
1
1a
1b
1c
1d
1e
1f
1g
1h
1i
Ph
4.6/1
3.5/1
3.3/1
4.3/1
5.2/1
6.1/1
5.7/1
4.8/1
4.6/1
2.3/1
2.8/1
3.0/1
98
99
98
93
98
88
89
98
97
97
98
98
73:27
71:29
71:29
66:34
75:25
80:20
67:33
70:30
67:33
65:35[h]
71:29[h]
72:28[h]
96, 26
96, 25
96, 25
96, 17
95, 30
98, 34
95, 50
96, 26
94, –[g]
90, 59
80, 35
62, 25
2[e]
3
4-MeC6H4
4-MeOC6H4
4-BnOC6H4
4-FC6H4
4-BrC6H4
3-ClC6H4
3,4-(MeO)2C6H3
2-naphthyl
2-furanyl
Me
4
5
6[e]
7[e]
8
9
10
11[f]
12[f]
1j
1k
1l
Bn
[a]
Unless otherwise specified, the reactions were carried out on a 0.15-mmol scale with 2.0 equiv. of HSiCl3 and 10 mol% of
6a in 1.5 mL of THF.
The E/Z ratios were determined by H NMR spectroscopy.
Isolated yield based on 1.
[b]
[c]
[d]
1
The relative comfigurations of 2a–2i were determined by X-ray crystallographic analysis and comparison of the vicinal
coupling constants (see the Supporting Information). The dr values were determined by chiral HPLC analysis.
The ee values were determined by chiral HPLC.
4.0 equiv. of HSiCl3 were used.
The ee value of the anti-diastereomer was not determined.
The relative configurations cannot be determined.
[e]
[f]
[g]
[h]
and the reaction gives an anti-product. Hence, it is
not surprising that the reaction cannot result in good
Scheme 2. Cyclization of 2g with thiophosgene and the crys-
tal determination of its absolute configuration.
Scheme 3. Proposed mechanism of the generation of syn-
and anti-products.
4
asc.wiley-vch.de
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
These are not the final page numbers!

Stereoselective Lewis Base-Catalyzed Asymmetric Hydrosilylation of a-Acetamido-b-enamino Esters
and dried over anhydrous Na2SO4 and the solvents were
evaporated. Purification by column chromatography (silica
gel, hexane/EtOAc=1:1) afforded the diastereomers. The dr
values and the ee values were determined using established
HPLC techniques with chiral stationary phases.
Scheme 4. Proposed transition state for the asymmetric hy-
drosilylation of a-acetamido-b-enamino esters.
Acknowledgements
We are grateful for the financial support from National Sci-
ences Foundation of China (20972155, 21172217) and Na-
tional Basic Research Program of China (973 Program)
(2010CB833300).
diastereoselectivity. We tried to improve the diaste-
reoselectivity by replacing the acetamide group by an
N,N-disubstituted group. However, we failed to pre-
pare such a substrate.
Finally, a plausible transition state for the reaction
has been proposed. As can be seen in Scheme 4,
Cl3SiH coordinates to the catalyst at the place remote
from the diphenyl groups. From the transition state, it
is easy to understand that the (R)-E-imine undergoes
the reaction preferentially. The (R)-E-imine is activat-
ed by a proton. The imine group and the ester car-
bonyl are held together by hydrogen bonding or by
chelation to silicon. Meanwhile an arene-arene inter-
action between the b-aryl group of the substrate and
the pyridine ring of the catalyst fixes the transition
state. Hence, the hydride attacks the imine from the
Si face to generate the (2R,3S)-product.
In summary, we have developed a stereoselective
hydrosilylation of a-acetamido-b-enamino esters cata-
lyzed by a novel Lewis base derived from l-serine.
This transformation enables us to prepare various
enantioenriched a-acetamido-b-amino esters in good
yields, good enantioselectivities and moderate diaste-
reoselectivities. Afterwards, one of the products was
cyclized with thiophosgene and the absolute configu-
ration of the resulted cyclic compound was deter-
mined by the X-ray crystallographic analysis. Accord-
ingly the absolute configuration of the product was
determined. The mechanism and the transition state
of the reaction have been proposed. Further work is
ongoing to explore new applications of this methodol-
ogy.
References
[1] a) J. J. Corrigan, N. G. Srinivasan, Biochemistry 1966, 5,
1185–1190; b) H. Umezawa, K. Maeda, T. Takeuchi,
Y. J. Okami, J. Antibiot. 1966, 19, 200–209; c) B. W. By-
croft, D. Cameran, L. R. Croft, A. Hassanali-Walji,
A. W. Johnson, T. Webb, Nature 1971, 231, 301–302;
d) C. S. Evans, M. Y. Qureshi, E. A. Bell, Phytochemis-
try 1977, 16, 565–570; e) H. Umezawa, Y. Muraoka, A.
Fujii, H. Naganawa, T. Takita, J. Antibiot. 1980, 33,
1079–1082; f) G. J. Shaw, P. J. Ellingham, A. Bingham,
G. J. Wright, Phytochemistry 1982, 21, 1635–1637; g) T.
Yamamoto, K. Yoneda, E. Ueta, T. Osaki, Jpn. J. Phar-
macol. 2001, 87, 41–50; h) S. Vos, D. J. Berrisford, J. M.
Avis, Biochemistry 2002, 41, 5383–5396; i) F. M. Kong,
G. T. Carter, J. Antibiot. 2003, 56, 557–564; j) U. Galm,
M. H. Hager, S. G. V. Van Lanen, J. Ju, J. S. Thorson, B.
Shen, Chem. Rev. 2005, 105, 739–758; k) U. Galm, E.
Wendt-Pienkowski, L. Y. Wang, N. P. George, T. J. Oh,
F. Yi, M. F. Tao, J. M. Coughlin, B. Shen, Mol. Biosyst.
2009, 5, 77–90; l) M. Strieker, M. A. Marahiel, Chem-
BioChem 2009, 10, 607–616.
[2] For reviews, see: a) R. G. Arrayꢂs, J. C. Carretero,
Chem. Soc. Rev. 2009, 38, 1940–1948; b) J. Wang, L.
Zhang, H. L. Jiang, H. Liu, Curr. Pharm. Des. 2010, 16,
1252–1259; c) A. Viso, R. F. de La Pradilla, M. Tortosa,
A. Garcꢃa, A. Flores, Chem. Rev. 2011, 111, Pr1–Pr42.
[3] For selected examples, see: a) L. Bernardi, A. S. Goth-
elf, R. G. Hazell, K. A. Jørgensen, J. Org. Chem. 2003,
68, 2583–2591; b) A. Okada, T. Shibuguchi, T. Ohshi-
ma, H. Masu, K. Yamaguchi, M. Shibasaki, Angew.
Chem. 2005, 117, 4640–4643; Angew. Chem. Int. Ed.
2005, 44, 4564–4567; c) M. M. Salter, J. Kobayashi, Y.
Shimizu, S. Kobayashi, Org. Lett. 2006, 8, 3533–3536;
d) G. A. Cutting, N. E. Stainforth, M. P. John, G.
Kociok-Kçhn, M. C. Willis, J. Am. Chem. Soc. 2007,
129, 10632–10633; e) X. X. Yan, Q. Peng, Q. Li, K.
Zhang, J. Yao, X. L. Hou, Y. D. Wu, J. Am. Chem. Soc.
2008, 130, 14362–14363; f) J. Hernꢂndez-Toribio, R.
Gꢄmez Arrayꢂs, J. C. Carretero, J. Am. Chem. Soc.
2008, 130, 16150–16151; g) D. Uraguchi, Y. Ueki, T.
Ooi, J. Am. Chem. Soc. 2008, 130, 14088–14089; h) S.
Kobayashi, R. Yazaki, K. Seki, Y. Yamashita, Angew.
Chem. 2008, 120, 5695–5697; Angew. Chem. Int. Ed.
2008, 47, 5613–5615; i) Z. Chen, H. Morimoto, S. Mat-
sunaga, M. Shibasaki, J. Am. Chem. Soc. 2008, 130,
Experimental Section
General Procedure for Enantioselective Hydro-
silylation of a-Acetamido-b-enamino Esters 1a–1l
A solution of trichlorosilane (31 mL, 0.3 mmol, 2.0 equiv.) in
120 mL of THF was added to a stirred solution of the corre-
sponding a-acetamido-b-enamino ester (0.15 mmol) and the
catalyst (0.015 mmol) in THF (1.5 mL) at À108C. The mix-
ture was stirred at the same temperature until the reaction
was completed. Then the reaction was quenched with a satu-
rated aqueous solution of NaHCO3 and was extracted with
EtOAc. The combined organic layer was washed with brine
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
5
ÞÞ
These are not the final page numbers!

Yan Jiang et al.
COMMUNICATIONS
2170–2171; j) D. Uraguchi, K. Koshimoto, T. Ooi, J.
Am. Chem. Soc. 2008, 130, 10878–10879; k) H. Van
Nguyen, R. Matsubara, S. Kobayashi, Angew. Chem.
2009, 121, 6041–6043; Angew. Chem. Int. Ed. 2009, 48,
5927–5929; l) L. Li, M. Ganesh, D. Seidel, J. Am.
Chem. Soc. 2009, 131, 11648–11649; m) D. J. Shang,
Y. L. Liu, X. Zhou, X. H. Liu, X. M. Feng, Chem. Eur.
J. 2009, 15, 3678–3681; n) H. L. Zhang, S. Syed, C. F.
Barbas, Org. Lett. 2010, 12, 708–711; o) X. D. Liu, L. J.
Deng, X. X. Jiang, W. J. Yan, C. L. Liu, R. Wang, Org.
Lett. 2010, 12, 876–879; p) G. Liang, M. C. Tong, H. Y.
Tao, C. J. Wang, Adv. Synth. Catal. 2010, 352, 1851–
1855; q) X. H. Chen, S. X. Dong, Z. Qiao, Y. Zhu,
M. S. Xie, L. L. Lin, X. H. Liu, X. M. Feng, Chem. Eur.
J. 2011, 17, 2583–2586; r) A. D. Melhado, G. W. Amar-
ante, Z. J. Wang, M. Luparia, F. D. Toste, J. Am. Chem.
Soc. 2011, 133, 3517–3527; s) S. H. Shi, F. P. Huang, P.
Zhu, Z. W. Dong, X. P. Hui, Org. Lett. 2012, 14, 2010–
2013; t) T. Arai, A. Mishiro, E. Matsumura, A. Awata,
M. Shirasugi, Chem. Eur. J. 2012, 18, 11219–11222;
u) T. Kano, R. Sakamoto, M. Akakura, K. Maruoka, J.
Am. Chem. Soc. 2012, 134, 7516–7520; v) E. Hernando,
R. G. Arrayas, J. C. Carretero, Chem. Commun. 2012,
48, 9622–9624.
duction of Olefins, Ketones and Imines, in: Enantiose-
lective Organocatalysis, (Ed.: P. I. Dalko), Wiley-VCH,
Weinheim, 2007, p 391; c) S. E. Denmark, G. L. Beut-
ner, Angew. Chem. 2008, 120, 1584–1663; Angew.
Chem. Int. Ed. 2008, 47, 1560–1638; d) S. Guizzetti, M.
Benaglia, Eur. J. Org. Chem. 2010, 5529–5541; e) A.
Weickgenannt, M. Oestreich, Chemcatchem 2011, 3,
1527–1529; f) S. Jones, C. J. A. Warner, Org. Biomol.
Chem. 2012, 10, 2189–2200.
[10] For selected examples, see: a) F. Iwasaki, O. Onomura,
K. Mishima, T. Kanematsu, T. Maki, Y. Matsumura,
Tetrahedron Lett. 2001, 42, 2525–2527; b) O. Onomura,
Y. Kouchi, F. Iwasaki, Y. Matsumura, Tetrahedron Lett.
2006, 47, 3751–3754; c) A. V. Malkov, A. Mariani, K. N.
ˇ
MacDougall, P. Kocovsky, Org. Lett. 2004, 6, 2253–
2256; d) A. V. Malkov, A. J. P. S. Liddon, P. Ramꢃrez-
ˇ
Lꢄpez, L. Bendovꢂ, D. Haigh, P. Kocovsky, Angew.
Chem. 2006, 118, 1460–1463; Angew. Chem. Int. Ed.
ˇ
2006, 45, 1432–1435; e) A. V. Malkov, S. Stoncius, K. N.
ˇ
MacDougall, A. Mariani, G. D. McGeoch, P. Kocovsky,
Tetrahedron 2006, 62, 264–284; f) A. V. Malkov, S. Ston-
ˇ
ˇ
cius, P. Kocovsky, Angew. Chem. 2007, 119, 3796–3798;
Angew. Chem. Int. Ed. 2007, 46, 3722–3724; g) A. V.
Malkov, S. Stoncius, K. Vrankova, M. Arndt, P. Kocov-
sky, Chem. Eur. J. 2008, 14, 8082–8085; h) A. V.
Malkov, K. Vrankova, S. Stoncius, P. Kocovsky, J. Org.
Chem. 2009, 74, 5839–5849; i) Z. Y. Wang, X. X. Ye,
S. Y. Wei, P. C. Wu, A. J. Zhang, J. Sun, Org. Lett. 2006,
8, 999–1001; j) D. Pei, Z. Y. Wang, S. Y. Wei, Y. Zhang,
J. Sun, Org. Lett. 2006, 8, 5913–5915; k) Y. C. Xiao, C.
Wang, Y. Yao, J. Sun, Y. C. Chen, Angew. Chem. 2011,
123, 10849–10852; Angew. Chem. Int. Ed. 2011, 50,
10661–10664; l) X. J. Wu, Y. Li, C. Wang, L. Zhou,
X. X. Lu, J. A. Sun, Chem. Eur. J. 2011, 17, 2846–2848;
m) X. W. Liu, Y. Yan, Y. Q. Wang, C. Wang, J. Sun,
Chem. Eur. J. 2012, 18, 9204–9207; n) H. J. Zheng, J. G.
Deng, W. Q. Lin, X. M. Zhang, Tetrahedron Lett. 2007,
48, 7934–7937; o) H. J. Zheng, W. B. Chen, Z. J. Wu,
J. G. Deng, W. Q. Lin, W. C. Yuan, X. M. Zhang, Chem.
Eur. J. 2008, 14, 9864–9867; p) Z. Y. Xue, Y. Jiang,
X. Z. Peng, W. C. Yuan, X. M. Zhang, Adv. Synth.
Catal. 2010, 352, 2132–2136; q) Y. Jiang, X. Chen, Y. S.
Zheng, Z. Y. Xue, C. Shu, W. C. Yuan, X. M. Zhang,
Angew. Chem. 2011, 123, 7442–7445; Angew. Chem.
Int. Ed. 2011, 50, 7304–7307; r) X. Chen, Y. S. Zheng,
C. Shu, W. C. Yuan, B. Liu, X. M. Zhang, J. Org. Chem.
2011, 76, 9109–9115; s) X. Chen, X. Y. Hu, C. Shu,
Y. H. Zhang, Y. S. Zheng, Y. Jiang, W. C. Yuan, B. Liu,
X. M. Zhang, Org. Biomol. Chem. 2013, 11, 3089–3093;
t) S. Guizzetti, M. Benaglia, S. Rossi, Org. Lett. 2009,
11, 2928–2931; u) S. Guizzetti, M. Benaglia, M. Bon-
signore, L. Raimondi, Org. Biomol. Chem. 2011, 9,
739–743.
[4] a) K. R. Knudsen, T. Risgaard, N. Nishiwaki, K. V.
Gothelf, K. A. Jørgensen, J. Am. Chem. Soc. 2001, 123,
5843–5844; b) A. Singh, R. A. Yoder, B. Shen, J. N.
Johnston, J. Am. Chem. Soc. 2007, 129, 3466–3467;
c) A. Singh, J. N. Johnston, J. Am. Chem. Soc. 2008,
130, 5866–5867; d) M. Rueping, A. P. Antonchick, Org.
Lett. 2008, 10, 1731–1734.
[5] a) H. Han, J. Yoon, K. D. Janda, J. Org. Chem. 1998,
63, 2045–2048; b) D. D. Hennings, R. M. Williams, Syn-
thesis 2000, 1310–1314; c) K. MuÇiz, M. Nieger, Chem.
Commun. 2005, 2729–2731.
[6] a) F. M. Rossi, E. T. Powers, R. Yoon, L. Rosenberg, J.
Meinwald, Tetrahedron 1996, 52, 10279–10286; b) T. H.
Chuang, K. B. Sharpless, Org. Lett. 1999, 1, 1435–1437;
c) T. H. Chuang, K. B. Sharpless, Org. Lett. 2000, 2,
3555–3557; d) X. Y. Hu, X. Y. Yang, M. Cheng, Q.
Zhang, W. Wei, J. X. Ji, Synth. Commun. 2012, 42,
3403–3412.
[7] a) Y. Park, S. Kang, Y. J. Lee, T. S. Kim, B. S. Jeong,
H. G. Park, S. S. Jew, Org. Lett. 2009, 11, 3738–3741;
b) J. Jiang, H. D. Xu, J. B. Xi, B. Y. Ren, F. P. Lv, X.
Guo, L. Q. Jiang, Z. Y. Zhang, W. H. Hu, J. Am. Chem.
Soc. 2011, 133, 8428–8431; c) C. K. De, N. Mittal, D.
Seidel, J. Am. Chem. Soc. 2011, 133, 16802–16805;
d) M. S. Valle, M. F. Saraiva, P. Retailleau, M. V. deAl-
meida, R. H. Dodd, J. Org. Chem. 2012, 77, 5592–5599.
[8] a) A. J. Robinson, C. Y. Lim, J. Org. Chem. 2001, 66,
4141–4147; b) A. J. Robinson, P. Stanislawski, D. Mul-
holland, J. Org. Chem. 2001, 66, 4148–4152.
[9] For reviews on Lewis base catalysis and Lewis base cat-
[11] CCDC 926418 (7) contains the supplementary crystal-
lographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
alytic asymmetric hydrosilylations of C=N double
ˇ
´
bonds, see: a) P. Kocovsky, A. V. Malkov, Chiral Lewis
Bases as Catalysts, in: Enantioselective Organocatalysis,
(Ed.: P. I. Dalko), Wiley-VCH, Weinheim, 2007, p 255;
b) H. B. Kagan, Organocatalytic Enantioselective Re-
6
asc.wiley-vch.de
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
These are not the final page numbers!

COMMUNICATIONS
Stereoselective Lewis Base-Catalyzed Asymmetric
Hydrosilylation of a-Acetamido-b-enamino Esters:
Straightforward Approach for the Construction of a,b-
Diamino Acid Derivatives
7
Adv. Synth. Catal. 2013, 355, 1 – 7
Yan Jiang, Xing Chen, Xiao-Yan Hu, Chang Shu,
Yong-Hong Zhang, Yong-Sheng Zheng, Chun-Xia Lian,
Wei-Cheng Yuan, Xiao-Mei Zhang*
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
7
ÞÞ
These are not the final page numbers!