Methylsulfonyl-based sulfamide-amine alcohol as a ligand for enantioselective alkynylation of aldehydes

Article abstract of DOI:10.1016/S1872-2067(10)60106-4

Chiral methylsulfonyl-based sulfamide-amine alcohol (SAA) ligands were synthesized from commercially available starting materials in two simple steps. Methylsulfonyl-based SAA ligands catalyzed the asymmetric alkynylation of various aldehydes using alkyny

Full text of DOI:10.1016/S1872-2067(10)60106-4

CHINESE JOURNAL OF CATALYSIS
Volume 31, Issue 9, 2010
Online English edition of the Chinese language journal
RESEARCH PAPER
Cite this article as: Chin J Catal, 2010, 31: 1098–1102.
Methylsulfonyl-Based Sulfamide-Amine Alcohol as a Ligand
for Enantioselective Alkynylation of Aldehydes
JIN Wei, HUANG Yongbo, WAN Boshun*
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
Abstract: Chiral methylsulfonyl-based sulfamide-amine alcohol (SAA) ligands were synthesized from commercially available starting
materials in two simple steps. Methylsulfonyl-based SAA ligands catalyzed the asymmetric alkynylation of various aldehydes using al-
kynylzinc to provide chiral propargyl alcohols with moderate to good enantioselectivity up to 83% ee.
Key words: sulfamide-amine alcohol; enantioselective addition; alkynylation; aldehyde
The catalytic enantioselective addition of terminal alkynes
to aldehydes is a very useful method for the synthesis of chiral
propargyl alcohols, which are important versatile building
blocks of many biologically active compounds and natural
products [1–4]. In recent years, chiral ligands, such as
N-methyl ephedrine [5,6], sulfonamide alcohol [7,8], BINOL
and its derivatives [9–12], have successfully been used in this
reaction. However, Ti(O-iPr)4 or other metal species are usu-
ally necessary in most of these catalytic systems [13–17]. On
the other hand [18–32], efficient ligands that can be prepared
from cheap and easily available starting materials in a few
synthetic steps and that are designed for facile structural
variations are still particularly useful. The design of chiral
ligands is the key to new enantioselective catalysts from a
practical viewpoint [33,34]. We have reported a series of chiral
p-tolyl sulfonyl (Ts)-based sulfamide-amine alcohol (SAA)
ligands for asymmetric diethylzinc addition to aldehydes
without the use of a titanium complex [35]. We also found that
Ts-based and trifluoromethanesulfonyl (Tf)-based SAA were
also effective for the asymmetric alkynylation of carbonyl
compounds [36–38]. In order to understand the electronic and
steric effects of chiral SAA on asymmetric alkynylation of
aldehydes and as part of extending the application of our SAA
ligands, we report methylsulfonyl (Ms)-based SAA catalyzed
enantioselective alkynylation of aldehydes under very mild
conditions without using moisture sensitive Ti(O-iPr)4 and
Zn(OTf )2.
1 Experimental
1.1 Typical procedure for the preparation of Ms-based
SAA (4a)
Methanesulfonyl chloride (1.7 ml, 22 mmol) was added
dropwise over 1.5 h to (S)-alaninol (1.37 g, 10 mmol) and
triethylamine (2.8 ml, 20 mmol) in dry CH2C12 (60 ml) under
argon at –20 °C. Stirring was continued at this temperature for
an additional 30 min, after which the flask was kept at –30 °C
overnight. The cold solution was then washed with 0.1 mol/L
HC1 (10 ml × 2) and saturated aqueous NaHCO3 (15 ml). The
organic phase was dried (MgSO4) and the solvent evaporated to
leave the corresponding aziridine (6) as a white solid. Without
purification, the aziridine and (–)-ephedrine were dissolved in
dry acetonitrile (60 ml) and the mixture was stirred under
reflux for 2 d. The solvent was evaporated under reduced
pressure. The residue was purified by column chromatography
to give the pure ligand. When the R group was changed to
benzyl or methyl group, the triethylamine was changed to
4-dimethylaminopyridine (DMAP) and K2CO3, respectively,
and the solvent was changed to acetonitrile. The spectral data
of Ms-based ligands are listed below.
N-[(R)-2-[[(1R,2S)-1-hydroxy-1-phenylpropan-2-yl]
(methyl)amino]-1-phenylethyl]methanesulfonamide (4a):
white solid, 41% yield. mp: 127–128 °C; 1H NMR: δ 1.09 (d, J
= 6.4 Hz, 3H), 2.07 (s, 3H), 2.409 (s, 3H), 2.48 (dd, J = 12 Hz,
Received date: 2 February 2010.
*Corresponding author. Tel: +86-411-84379260; Fax: +86-411-84379223; E-mail: bswan@dicp.ac.cn
Foundation item: Supported by the National Basic Research Program of China (973 Program, 2010CB833300).
Copyright © 2010, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier BV. All rights reserved.
DOI: 10.1016/S1872-2067(10)60106-4

JIN Wei et al. / Chinese Journal of Catalysis, 2010, 31: 1098–1102
1H), 2.67 (dd, J = 4.4 Hz, 1H), 2.84 (dt, J = 6.4 Hz, 1H), 4.38
Under argon, the chiral ligand (10 mol%, 0.025 mmol) was
mixed with dry n-hexane (1.0 ml) at room temperature and
stirred for 10 min. Then Et2Zn (10 wt% in n-hexane, 0.9 ml)
and phenylacetylene (54 μl, 0.5 mmol) were added by a sy-
ringe. After the mixture was stirred at room temperature for
another 1 h, aldehyde (0.25 mmol) was added. The resulting
mixture was stirred for 24 h at room temperature. Then the
reaction was quenched with aqueous HCl (5%) and the mix-
ture was extracted with ether (6 ml). The combined organic
layer was washed with brine, dried over Na2SO4, and concen-
trated under vacuum. The residue was purified by flash col-
umn chromatography to give the product.
(dd, J = 4.4 Hz, 1H), 4.67 (d, J = 6.4 Hz, 1H), 7.26–7.42 (m,
10H); 13C NMR: δ 10.52, 35.42, 42.01, 55.46, 62.00, 65.86,
75.69, 126.31, 127.55, 127.91, 128.32, 128.86, 128.92, 139.98,
143.49.
N-[(R)-2-[[(1S,2S)-1-hydroxy-1-phenylpropan-2-yl]
(methyl)amino]-1-phenylethyl]methanesulfonamide (4b):
white solid, 31% yield. mp: 162–163 °C; 1H NMR: δ 0.65 (d, J
= 6.8 Hz, 3H), 2.36 (m, 4H), 2.54 (d, J = 6.4 Hz, 1H), 2.61 (s,
3H), 2.73 (dd, J = 9.6 and 12.8 Hz, 1H), 4.24 (d, J = 9.6 Hz,
1H), 4.58 (dd, J = 6.4 and 9.2 Hz, 1H), 7.22–7.41 (m, 10H); 13
C
NMR: δ 8.40, 37.29, 42.10, 56.10, 58.71, 66.07, 74.96, 127.14,
127.52, 127.15, 128.49, 129.23, 140.24, 141.93.
1,3-Diphenylprop-2-yn-1-ol (7a). Retention time, tmajor
11.6 min and tminor = 21.1 min.
=
N-[(S)-2-[[(1R,2S)-1-hydroxy-1-phenylpropan-2-yl]
(methyl)amino]-1-phenylethyl]methanesulfonamide (4c):
white solid, 25% yield. mp: 110–112 °C; 1H NMR: δ 0.97 (d, J
= 6.8 Hz, 3H), 2.24 (s, 2H), 2.37 (s, 3H), 2.49 (dd, J = 4.8 and
12.8 Hz, 1H), 2.63 (dd, J = 12.8 and 10 Hz, 1H), 2.88 (m, J =
6.8 and 5.6, 1H), 4.45 (dd, J = 10 and 4.8 Hz, 1H), 4.64 (d, J =
5.6 Hz, 1H), 7.25–7.45 (m, 10H); 13C NMR: δ 8.95, 39.36,
41.94, 55.74, 58.92, 64.22, 76.84, 126.77, 127.50, 127.82,
128.26, 128.71, 128.94, 140.26, 143.07.
1-(2-Methylphenyl)-3-phenylprop-2-yn-1-ol (7b). Reten-
tion time, tmajor = 9.3 min and tminor = 21.1 min. 1H NMR: δ 2.45
(s, 3H), 2.58 (s, 1H), 5.78 (s, 1H), 7.17–7.29 (m, 6H),
7.42–7.45 (m, 2H), 7.69–7.70 (m, 1H); 13C NMR: δ 19.1, 63.0,
86.6, 88.8, 122.7, 126.4, 126.7, 128.4, 128.6, 128.7, 130.9,
131.9, 136.2, 138.5.
1-(3-methylphenyl)-3-phenylprop-2-yn-1-ol (7c) [14].
Retention time, tmajor = 10.6 min and tminor = 25.7 min.
N-[(S)-2-[[(1S,2S)-1-hydroxy-1-phenylpropan-2-yl]
(methyl)amino]-1-phenylethyl]methanesulfonamide (4d):
white solid, 20% yield. mp: 149–151 °C; 1H NMR: δ 0.67 (d, J
= 6.8 Hz, 3H), 2.42 (dd, J = 12.8 and 6.0 Hz, 1H), 2.37 (s, 3H),
2.56–2.59 (m, 1H), 2.61 (s, 3H), 2.75 (dd, J = 9.2 and 12.8 Hz,
1H), 4.25 (d, J = 9.6 Hz, 1H), 4.59 (dd, J = 6.0 and 9.2 Hz, 1H),
7.30–7.41 (m, 10H); 13C NMR: δ 8.41, 37.37, 42.11, 56.07,
58.66, 65.97, 75.00, 127.14, 127.51, 128.15, 128.50, 129.01,
129.23, 140.19, 141.91.
1-(3-Methoxyphenyl)-3-phenylprop-2-yn-1-ol
(7d).
Retention time, tmajor = 16.8 min and tminor = 29.6 min. 1H NMR:
δ 2.52 (s, 1H), 3.80 (s, 3H), 5.64 (m, 1H), 6.86–6.88 (m, 1H),
7.16–7.19 (m, 2H), 7.29–7.31 (m, 4H), 7.44–7.47 (m, 2H); 13
C
NMR: δ 55.5, 65.1, 86.7, 88.9, 112.3, 114.3, 119.2, 122.6,
128.5, 128.8, 129.9, 131.9, 142.4, 160.0.
1-(4-Methoxyphenyl)-3-phenylprop-2-yn-1-ol
(7e).
Retention time, tmajor = 15.1 min and tminor = 30.4 min. 1H NMR:
δ 3.39 (s, 1H), 3.84 (s, 3H), 5.96 (s, 1H), 6.88–7.01 (m, 2H),
N-[(R)-1-[[(1R,2S)-1-hydroxy-1-phenylpropan-2-yl]
(methyl)amino]propan-2-yl]methanesulfonamide (5): white
solid, 41% yield. mp: 124–125 °C; 1H NMR: δ 0.70 (d, J = 4.8
and 6.4 Hz, 3H), 1.22 (dd, J = 12.8 and 6.4 Hz, 3H), 2.20–2.24
(m, 1H), 2.33 (d, J = 5.2 Hz, 3H), 2.49 (dd, J = 8.8 and 12.8 Hz,
1H), 2.59–2.65 (m, 1H), 3.03 (d, J = 4 Hz, 3H), 3.60 (d, J = 6
Hz, 1H), 4.26 (dd, J = 4.4 and 9.6 Hz, 1H), 7.24–7.35 (m, 5H);
13C NMR: δ 7.96, 20.41, 37.91, 41.92, 48.02, 58.39, 65.93,
75.03, 127.51, 128.12, 128.51, 141.84.
7.28–7.32 (m, 4H), 7.46–7.49 (m, 2H), 7.65–7.68 (m, 1H); 13
C
NMR: δ 55.3, 60.7, 85.6, 88.8, 110.8, 120.6, 127.7, 128.1,
128.2, 129.5, 131.5, 156.5.
1-(3-Fluorophenyl)-3-phenylprop-2-yn-1-ol (7f). Reten-
tion time, tmajor = 9.2 min and tminor = 27.3 min. 1H NMR: δ
2.621 (s, 1H), 5.67 (s, 1H), 7.00–7.02 (m, 1H), 7.29–7.36 (m,
6H), 7.45–7.47 (m, 2H); 13C NMR: δ 64.6, 87.1, 88.3, 113.8,
114.0, 116.4, 115.6, 128.6, 129.0, 130.3, 132.0, 143.0, 164.0.
1-(4-Fluorophenyl)-3-phenylprop-2-yn-1-ol (7g) [14].
Retention time, tmajor = 9.0 min and tminor = 26.2 min.
1-(4-chlorophenyl)-3-phenylprop-2-yn-1-ol (7h). Reten-
tion time, tmajor = 9.4 min and tminor = 29.0 min. 1H NMR: δ 2.78
(s, 1H), 5.63 (s, 1H), 7.27–7.35 (m, 5H), 7.43–7.45 (m, 2H),
7.50–7.52 (m, 2H); 13C NMR: δ 64.5,87.1, 88.4, 122.3, 128.3,
128.5, 128.9, 131.1, 131.9, 134.3, 139.2.
N-[(R)-1-[[(1R,2S)-1-hydroxy-1-phenylpropan-2-yl]
(methyl)amino]-3-phenylpropan-2-yl]methanesulfonamide
(6): white solid, 48% yield. mp: 104–105 °C; 1H NMR: δ 0.74
(d, J = 6.8 Hz, 3H), 2.30 (s, 3H), 2.36 (s, 3H), 2.56–2.68 (m,
3H), 2.71 (dd, J = 2.4 and 6.8 Hz, 1H), 3.06 (dd, J = 4.4 and 14
Hz, 1H), 3.71 (m, 1H), 4.31 (d, J = 9.6 Hz, 1H), 7.22–7.41 (m,
10H); 13C NMR: δ 8.18, 36.66, 40.16, 41.11, 55.54, 59.91,
66.66, 75.22, 127.07, 127.64, 128.09, 128.53, 128.91, 129.85,
138.34, 141.74.
1-(3,5-Dichlorophenyl)-3-phenylprop-2-yn-1-ol (7i). Re-
tention time, tmajor = 6.6 min and tminor = 29.6 min. 1H NMR: δ
3.02 (s, 1H), 5.59 (s, 1H), 7.27–7.35 (m, 4H), 7.42−7.45 (m,
4H); 13C NMR: δ 63.9, 87.5, 87.6, 121.9, 125.3, 128.0, 128.6,
129.1, 132.0, 135.3, 143.9.
1.2 Typical procedure for asymmetric addition of
phenylacetylene to aldehydes
1-(3-Trifluoromethylphenyl)-3-phenylprop-2-yn-1-ol
(7j). Retention time, tmajor = 7.6 min and tminor = 36.7 min. 1H

JIN Wei et al. / Chinese Journal of Catalysis, 2010, 31: 1098–1102
NMR: δ 2.70 (s, 1H), 5.73 (s, 1H), 7.23–7.35 (m, 3H),
Table 1 Asymmetric alkynylation of benzaldehyde catalyzed by
7.45–7.51 (m, 3H), 7.58–7.60 (m, 1H), 7.77–7.79 (m, 1H), 7.87
(s, 1H); 13C NMR: δ 64.6, 87.5, 88.1, 122.2, 123.7,125.4,
128.6, 129.1, 129.3, 130.3,131.0, 131.3, 132.0, 141.2.
1-(4-Trifluoromethylphenyl)-3-phenylprop-2-yn-1-ol
(7k). Retention time, tmajor = 8.4 min and tminor = 42.0 min. 1H
NMR: δ 2.56 (s, 1H), 5.74 (s, 1H), 7.25–7.37 (m, 3H),
7.45–7.47 (m, 2H), 7.64–7.74 (m, 4H); 13C NMR: δ 64.6, 87.5,
88.1, 122.2, 125.8, 127.2, 128.6, 129.1, 132.0, 144.6.
1-(1-Naphthyl)-3-phenylprop-2-yn-1-ol (7l) [14]. Reten-
tion time, tmajor = 17.1 min and tminor = 36.6 min.
Ms-based SAA
O
H
OH
Ligand
Et2Zn
+
Ph
*
Ph
Ph
H
Ph
eeb (%)
65
Entry
Ligand
4a
Yielda (%)
1
2
3
4
5
6
99
96
80
99
78
79
4b
4c
33
9
4d
5
45
3
6
31
Reaction conditions: phenylacetylene:Et2Zn:aldehyde:ligand = 2.0:2.2:1:
0.1, toluene 1 ml, rt, 24 h.
2 Results and discussion
aIsolated yield.
bDetermined by HPLC on a Chiracel OD-H column.
As shown in Scheme 1, in the traditional method [39], the
chiral amino alcohols (1) first reacted with two equivalent
methanesulfonyl chloride to afford substituted derivatives (2).
Treatment with NaH resulted in N-methanesulfonyl aziridine
(3). In this work, 1 was reacted with methanesulfonyl chloride
to give 3 directly, and then without purification, reacted with
natural chiral (–)-ephedrine or (+)-pseudoephedrine to give
the corresponding Ms-based SAA ligands (4) in two simple
steps. The Ms-based SAA ligands are cheap and very stable in
air.
phenyl to methyl or benzyl group led to less enantioselectivity
(Table 1, entries 5 and 6). Clearly, 4a was an effective chiral
ligand for this asymmetric reaction.
To improve the enantioselectivity, the reaction conditions
were optimized using benzaldehyde as the substrate (Table 2).
The reactions were strongly influenced by the amount of
ligand, reaction temperature, and solvent. At room tempera-
ture, increasing the amount of ligand 4a to 20 mol% did not
improve the selectivity, while decreasing the amount of 4a to
5 mol% gave a chiral product with only 43% ee (Table 2,
entries 1–3). Lower reaction temperatures did not improve the
enantioselectivities (Table 2, entries 4 and 5). When the reac-
tion was carried out in THF, low ee values were obtained
(Table 2, entry 6). However, there was no enhancement in
The enantioselective addition of alkynylzinc to benzalde-
hyde was first examined in the presence of 0.1 equivalent chiral
Ms-based SAA ligand in toluene. As shown in Table 1, the
matching of the stereogenic centers and substituent on the
ligands had a large effect on the reaction. 4a was more effec-
tive than 4b, 4c, and 4d, which have the same substituent as
4a (Table 1, entries 1–4). Changing the substituent from
R
o
CH Cl , -20
C
2
2
MsO
NHMs
R = Ph, base: Et3N, solvent: CH2Cl2
R = Me, base: K2CO3, solvent: CH3CN
R = Bn, base: DMAP, solvent: CH3CN
THF NaH
2
M
sCl
Et N
3
Me
R
(-)-ephedrine
or (+)-pseudoephedrine
R
Ph
R
MsCl, base
solvent
N
N
CH CN, reflux
3
HO
NH2
OH
NHMs
Ms
1
4
3
Me
N
Me
Me
Ph
Ph
Ph
NHMs
Ph
Ph
Ph
Ph
N
N
Yield
OH
OH
NHMs
OH
NHMs
4a 41%
4b 31%
4c 25%
4d 20%
4a
4c
4b
Me
Me
Me
5
6
41%
48%
Ph
Ph
Ph
Me
N
N
N
Ph
NHMs
OH
NHMs
OH
NHMs
OH
4d
6
5
Scheme 1. Synthesis of Ms-based SAA.

JIN Wei et al. / Chinese Journal of Catalysis, 2010, 31: 1098–1102
Table 2 Optimization of reaction conditions
O
H
OH
Ph
Ph
NMs
4a
Et2Zn
+
Ph
N
*
Ph
Ph
H
active
nucleophile
Zn
Et
Ph
ee (%)
O
Et Zn
Content of 4a
Yield
(%)
66
O
t/oC
Solvent
active
electrophile
Entry
H
(mol%)
5
Ph
1
2
3
4
5
6
7
8
9
rt
rt
toluene
toluene
toluene
toluene
toluene
THF
43
65
65
54
31
40
70
62
62
10
99
Ph
20
rt
98
Scheme 2. Proposed transition states of the reaction.
10
0
98
10
–20
rt
98
moisture sensitive Ti(O-iPr)4 and Zn(OTf)2, which were
needed in the literature [5–12,18–21].
10
50
10
rt
n-hexane
DCM
78
10
rt
53
10
rt
Et2O
99
3
Conclusions
Reaction conditions are the same as in Table 1 except for the solvent and
reaction temperature.
New convenient chiral Ms-based SAA ligands were pre-
pared from commercially available starting materials in two
simple steps. Ms-based SAA 4a catalyzed the asymmetric
alkynylation of aromatic aldehydes with up to 83% ee. The
cheap Ms-based SAA 4a is a practical laboratory ligand for
the enantioselective alkynylation of aromatic aldehydes under
very mild conditions that do not need moisture sensitive
Ti(O-iPr)4 and Zn(OTf)2.
enantioselectivity when dichloromethane (DCM) and Et2O was
used as the solvent (Table 2, entries 8 and 9). The best ee of
70% was obtained in n-hexane (Table 2, entry 7).
Having optimized the asymmetric alkynylation of benzal-
dehyde with phenylacetylene using 4a, we decided to screen
various aldehydes. As can be seen from the summarized results
in Table 3, 4a was efficient for all of the aromatic aldehydes
studied. Propargylic alcohols were obtained with up to 83% ee
and up to 91% yield.
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