Stereoselective cyclopropanation of 3-aryl-2-phosphonoacrylates induced by the (-)-8-phenylmenthyl group as a chiral auxiliary

Article abstract of DOI:10.1016/S0040-4039(01)01116-9

The cyclopropanation of (-)-8-phenylmenthyl (E)-3-aryl-2-phosphonoacrylates with dimethyloxosulfonium methylide and diazomethane afforded the corresponding trans cyclopropane derivatives with high diastereoselectivity as the major diastereomer. The high selectivity is understandable in terms of the π-π interaction between the phenyl ring of the chiral auxiliary and the acrylate moiety.

Full text of DOI:10.1016/S0040-4039(01)01116-9

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 42 (2001) 5891–5895
Stereoselective cyclopropanation of 3-aryl-2-phosphonoacrylates
induced by the (−)-8-phenylmenthyl group as a chiral auxiliary
Ryukichi Takagi, Minoru Nakamura, Miki Hashizume, Satoshi Kojima and Katsuo Ohkata*
Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama,
Higashi-Hiroshima 739-8526, Japan
Received 23 April 2001; revised 20 June 2001; accepted 25 June 2001
Abstract—The cyclopropanation of (−)-8-phenylmenthyl (E)-3-aryl-2-phosphonoacrylates with dimethyloxosulfonium methylide
and diazomethane afforded the corresponding trans cyclopropane derivatives with high diastereoselectivity as the major
diastereomer. The high selectivity is understandable in terms of the p–p interaction between the phenyl ring of the chiral auxiliary
and the acrylate moiety. © 2001 Elsevier Science Ltd. All rights reserved.
Many phosphonate derivatives have been applied to the
areas of agricultural chemistry, owing to their biologi-
cal activity.1 Much effort has been directed toward the
synthesis of 1-aminocyclopropanecarboxylic acid
derivatives2 because of their biological activity3 and the
potential use in conformationally restricted peptides.4
The synthesis of cyclopropane phosphonic acid deriva-
tives has widely been investigated.5
paper, we describe the p-differentiational cyclopropana-
tion of 3-aryl-2-diethylphosphonoacrylates by means of
the (−)-8-phenylmenthyl group.
(E)-, (Z)-3-Aryl-2-phosphonoacrylates 1a–c were pre-
pared by the titanium mediated Knoevenagel condensa-
tion of (−)-8-phenylmenthyl diethylphosphonoacetate
with the corresponding aryl aldehydes with high
stereoselectivity (Scheme 1).9 The condensation reaction
of the diethylphosphonoacetate with aryl aldehydes in
the presence of N-methylmorpholine (NMM)/TiCl4
gave Knoevenagel products 1a–c having the thermody-
namically more stable (E)-geometry.9b The thermody-
namically less stable (Z)-isomers Z-1a–c were obtained
by the reaction of the diethylphosphoate with aryl
aldehydes in the presence of ClTi(OiPr)3/Et3N at low
temperature (−78°C).9a,10
Recently, we have investigated the asymmetric induc-
tion in the formation of cyclic compounds by means of
the (−)-8-phenylmenthyl group as a chiral auxiliary.6
Various types of asymmetric reactions using the (−)-8-
phenylmenthyl group as a chiral auxiliary have been
investigated and the reaction proceeded with consider-
ably high stereoselectivity.7,8 The high stereoselectivity
has been attributed to the differentiation of the p-faces
induced by the (−)-8-phenylmenthyl group. In this
Me
(EtO)2P(O)
CO2R*
H
(EtO)2P(O)
CO2R*
Ar
RCHO
(EtO)2P(O)
CO2R*
Knoevenagel
condensation reaction
R* =
Ar
Z-1a-c
H
O
E-1a-c
Me
Me
Ph
1a : Ar = C6H5
1b : Ar = p-MeOC6H4
1c : Ar = p-ClC6H4
Scheme 1. Reagents and conditions: For E-1a–c: TiCl4 (2 equiv.), NMM (10 equiv.), THF. For Z-1a–c: Ti(OiPr)3Cl (2 equiv.),
Et3N (10 equiv.), THF.
Keywords: activated cyclopropane; 8-phenylmenthyl; diastereoselective.
* Corresponding author. Tel.: +81-824-24-7432; fax: +81-824-0747; e-mail: ohkata@sci.hiroshima-u.ac.jp
0040-4039/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(01)01116-9

5892
R. Takagi et al. / Tetrahedron Letters 42 (2001) 5891–5895
diastereomers of the pyrazolines 3a–c could not be
separated. However, the relative configuration of the
pyrazolines could be determined by the coupling con-
stant (3JCP) in 13C NMR spectra between the ipso-car-
bon of the aryl ring and the phosphorus. The
1,3-dipolar cycloaddition reaction of E-1a–c with dia-
The cyclopropanation of 1a–c with dimethyloxosulfo-
nium methylide was examined (Scheme 2). All four
diastereomers of 2a–c were separated by HPLC, respec-
tively. The relative configuration of the diastereomers
was assigned by the coupling constant (3JCP) between
the ipso-carbon of the aryl group and the phosphorus.
Table 1 shows the results of the cyclopropanation
reaction of 1a–c with dimethyloxosulfonium methylide.
The reaction of E-1a–c at 25°C afforded preferentially
the trans isomers (Table 1, entries 1–3). The
diastereoselectivity in the cyclopropanation was moder-
ate (40–49% de) for the cis isomers 2a–c and consider-
ably high (80–86% de) for the trans isomers 2a–c. The
cyclopropanation of Z-1a–c in DMSO at 25°C gave
mixtures of cis and trans cyclopropanation derivatives
2a–c (Table 1, entries 4–6). The diastereoselectivity in
the reactions were from low to fair (17–58% de).
Table 2. The formation of pyrazolines by the reaction of
1a–c with CH2N2
Entry
Substrate
Product
trans:cisa
% dea
trans
cis
1
2
3
E-1a
E-1b
E-1c
3a
3b
3c
1:–
1:–
10:1
84
85
80
–
–
43
4
5
6
Z-1a
Z-1b
Z-1c
3a
3b
3c
1:28
1:1.2
1:2.8
\90
76
80
25
40
56
Next, the cyclopropanation reaction of 1a–c with excess
diazomethane was examined (Scheme 3). Treatment of
1a–c in Et2O at 0–25°C with diazomethane afforded a
mixture of D1-pyrazoline derivatives 3a–c (Table 2). The
a The ratios were determined by integral values of 31P NMR.
Ar
CO2R*
Ar
H
P(O)(OEt)2
CO2R*
P(O)(OEt)2
H
(EtO)2P(O)
Ar
CO2R*
Me3S(O)+I-
cis-I-2a-c
2a-c
trans-I-
NaH, DMSO
CO2R*
H
a : Ar = C6H5
b : Ar = p-MeOC6H4
c : Ar = p-ClC6H4
P(O)(OEt)2
H
E- and Z-1a-c
Ar
P(O)(OEt)2
CO2R*
trans-II-2a-c
Ar
R* = (-)-8-phenylmenthyl
cis-II-2a-c
Scheme 2.
Table 1. The cyclopropanation of 1a–c with dimethyloxosulfonium methylide
Entry
Substrate
Product
Yield (%)
trans:cis
% dea
trans
cis
1
2
3
E-1a
E-1b
E-1c
2a
2b
2c
69
96
93
7.8:1
1.7:1
1.8:1
86
83
80
46
49
40
4
5
6
Z-1a
Z-1b
Z-1c
2a
2b
2c
91
97
73
1:1.3
1:1.1
1.1:1
35
35
58
17
20
21
a The ratios were determined by integral values of the cyclopropyl proton in 1H NMR.
N
N
N
N
Ar
H
P(O)(OEt)2
Ar
Ar
H
P(O)(OEt)2
CO2R*
cis-I-2a-c
CO2R*
P(O)(OEt)2
trans-I-3a-c
Ar
H
CO2R*
P(O)(OEt)2
O
O
P
CO2R*
cis-I-3a-c
H
CH2N2
hv
OEt
OEt
trans-I-2a-c
R*O
N
N
N
N
H
Ar
H
CO2R*
H
P(O)(OEt)2
CO2R*
H
Ar
P(O)(OEt)2
CO2R*
trans-II-3a-c
H
Ar
CO2R*
E-, Z-1a-c
Ar
P(O)(OEt)2
Ar
P(O)(OEt)2
cis-II-3a-c
cis-II-2a-c
trans-II-2a-c
Scheme 3.

R. Takagi et al. / Tetrahedron Letters 42 (2001) 5891–5895
Table 3. The cyclopropanation of 1a–c with CH2N2 via pyrazolines
5893
Entry
Substrate
Product
Yield (%)a
trans:cisb
% de
trans
cis
1
2
3
E-1a
E-1b
E-1c
2a
2b
2c
59
62
32
25:1
15:1
6:1
87
87
93
0
0
29
4
5
6
Z-1a
Z-1b
Z-1c
2a
2b
2c
28
41
48
1:2.5
1.1:1
1:2
66
88
83
50
45
46
a The yields were calculated from 1a–c.
b The ratios were determined by integral values of 1H NMR.
zomethane proceeded with high stereoselectivity and
the trans pyrazoline derivatives trans-3a–c were pref-
erentially obtained as the major diastereomer (Table
2, entries 1–3). The reaction of Z-1a–c with diazo-
methane gave the cis pyrazolines cis-3a–c as the
major diastereomers (Table 2, entries 4–6). The
diastereoselectivity of the cis pyrazolines 3a–c was
low.
The photolysis of the pyrazolines 3a–c which were
obtained by the reaction of 1a–c with diazomethane
gave cyclopropane derivatives 2a–c.11 Table 3 shows
the results of the cyclopropanation via the pyrazoli-
nes. The trans cyclopropane derivatives 2a–c were
preferentially obtained with high diastereoselectivity in
the cyclopropanation of E-1a–c via pyrazolines (Table
3, entries 1–3). The cyclopropanation of Z-1a–c via
pyrazolines gave mixtures of cis- and trans-
diastereomers of which ratios were ca. 1:1 (Table 3,
entries 4–6). The diastereomeric ratios of the cis
diastereomers were very low and those of the trans
diastereomers were high.
Figure 1. Ball–stick drawing of the X-ray structure of trans-
II-2b.
In the cyclopropanation using both dimethyloxosulfo-
nium methylide and diazomethane, the geometric
ratios (cis/trans) of cyclopropanation derivatives 2a–
c13 generated by the reaction with E-1a–c were higher
than that of Z-1a–c. This indicates that the trans
isomers were obtain in order to avoid the repulsion
between the aryl ring and the phosphonate moiety in
the intermediates B and C.
trans-II-2b turned out to be crystalline and was sub-
jected to X-ray structural analysis (Fig. 1). The abso-
lute stereochemistry was determined to be (1S,2R) as
shown in Fig. 1. On the basis of this observation, the
absolute stereochemistry of the major products (trans-
II and cis-I) was presumed to be as shown in Scheme
4.
In conclusion, we have shown that the cyclopropana-
tion reaction of (E)-3-aryl-2-phosphonoacrylates using
the (−)-8-phenylmenthyl group as a chiral auxiliary
gives the trans cyclopropane derivatives with high
diastereoselectivity. The high diastereoselectivity can
be attributed to the high p-face differentiation of the
acrylate moiety by the face-to-face interaction with
the phenyl ring of the chiral auxiliary.
The high diastereoselectivity in the reaction of E-1a–c
with both oxosulfonium methylide and diazomethane
is understandable in terms of p–p interaction between
the phenyl ring of the chiral auxiliary and the acry-
late moiety (Scheme 4).12 In this conformation, it is
considered that the phenyl group of the chiral auxil-
iary is suitably positioned to block the depicted back
face of the acrylate moiety and induce the reagents
(dimethyloxosulfonium methylide and diazomethane)
to approach from the Re-face. The reagents attack
Z-1a–c from both the Re- and the Si-face of the
acrylate moiety and the cyclopropanation of Z-1a–c
Acknowledgements
NMR measurements were carried out on JEOL GSX-
270 and LA-500 instruments, and HRMS measure-
ments on a JEOL SX-102A spectrometer at the
Instrument Center for Chemical Analysis, Hiroshima
University.
afforded
cyclopropane
derivatives
with
low
diastereoselectivity.

5894
R. Takagi et al. / Tetrahedron Letters 42 (2001) 5891–5895
CH3
H3C
CH3
CH3
O
O
Ar
H
P(O)(OEt)2
CO2R*
CH3
Ar
O
Ar
O
CH3
Re-face attack
H
O
(EtO)2(O)P
(EtO)2(O)P
Me
trans-II
(1S,2R)-trans-2a-c
S
or
X
H2C N N
H2C Me
A
E-1a-c
CH3
CH3
H3C
CH3
CH3
O
O
CH3
Si-face attack
Re-face attack
Ph
O
Ph
O
H
Ar
H
P(O)(OEt)2
CO2R*
Ar
Ar X
(EtO)2(O)P
(EtO)2(O)P
cis-I
(1S,2S)-cis-2a-c
B
Z-1a-c
CH3
H3C
CH3
R* = (-)-8-phenylmenthyl
O
X
H
H
CO2R*
P(O)(OEt)2
Ph
O
O
Me
Ar
X =
or
cis-II
(1R,2R)-cis-2a-c
S
N N
Ar
(EtO)2(O)P
Me
C
Scheme 4.
Yoshimura, M.; Ohkata, K. Heterocycles 1997, 45, 2097;
(c) Takagi, R.; Kimura, J.; Shinohara, Y.; Ohba, Y.;
Takezono, K.; Hiraga, Y.; Kojima, S.; Ohkata, K. J.
Chem. Soc., Perkin Trans. 1 1998, 689; (d) Kojima, S.;
Fujitomo, K.; Shinohara, Y.; Shimizu, M.; Ohkata, K.
Tetrahedron Lett. 2000, 41, 9847; (e) Shinohara, Y.;
Ohba, Y.; Takagi, R.; Kojima, S.; Ohkata, K. Heterocy-
cles 2001, 55, 9.
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2JCP=9.6 Hz); 31P NMR (202 MHz, CDCl3) l 21.2;
HRMS (EI) calcd for C30H31O5P M+: 512.2602. Found:
512.2645.
trans-I-2a: 1H NMR (500 MHz, CDCl3) l 0.37 (q, J=
11.9 Hz, 1H), 0.47–0.60 (m, 1H), 0.58 (d, J=6.6 Hz, 3H),
0.64–0.77 (m, 2H), 1.00–1.50 (m, 2H), 1.23 (s, 3H), 1.34
(t, J=7.0 Hz, 3H), 1.34 (s, 3H), 1.49 (t, J=7.1 Hz, 3H),
1.68–1.75 (m, 1H), 1.76–1.82 (m, 1H), 1.82–1.89 (m, 1H),
2.19–2.25 (m, 1H), 3.10–3.17 (m, 1H), 4.15–4.24 (m, 2H),
4.29–4.36 (m, 2H), 4.65 (dt, J=4.5, 10.5 Hz, 1H), 7.06–
7.41 (m, 10H); 13C NMR (125 MHz, CDCl3) l 14.9 (d,
13. NMR spectra data: cis-I-2a: 1H NMR (500 MHz,
CDCl3) l 0.75–0.90 (m, 2H), 0.87 (d, J=6.4 Hz, 3H),
0.97–1.08 (m, 1H), 1.11 (t, J=7.1 Hz, 3H), 1.12 (t, J=7.0
Hz, 3H), 1.33 (s, 3H), 1.43 (m, 1H), 1.46 (s, 3H), 1.52–
1.62 (m, 3H), 1.90–2.00 (m, 3H), 2.74(q, J=8.9 Hz, 1H),
3.65–3.78 (m, 3H), 3.85–3.93 (m, 1H), 5.00 (td, J=4.6,
10.8 Hz, 1H), 7.18–7.34 (m, 10H); 13C NMR (125 MHz,
3
3
2JCP=2.4 Hz), 16.2 (d, JCP=7.1 Hz), 16.6 (d, JCP=7.2
1
Hz), 21.4, 22.7, 27.4, 29.3 (d, JCP=184.7 Hz), 30.8, 31.0,
3
3
CDCl3) l 16.2 (d, JCP=5.3 Hz), 16.3 (d, JCP=3.8 Hz),
31.5, 34.1, 40.5, 41.3, 50.1, 62.3 (d, 2JCP=4.5 Hz), 62.4
(d, 2JCP=3.6 Hz), 76.8, 125.3, 125.9 (×2), 127.9 (×2),
128.1 (×2), 128.4, 129.4 (×2), 133.8 (d, 3JCP=1.8 Hz),
150.1, 166.0 (d, 2JCP=6.3 Hz); 31P NMR (202 MHz,
CDCl3) l 23.4; HRMS (EI) calcd for C30H31O5P M+:
512.2602. Found: 512.2709.
2
17.1 (d, JCP=2.0 Hz), 21.7 (×2), 25.0, 27.0, 29.0, 29.1 (d,
1JCP=197.7 Hz), 31.2 (×2), 33.4 (d, JCP=2.0 Hz), 34.4,
2
2
2
40.6, 41.7, 50.5, 61.6 (d, JCP=5.9 Hz), 62.6 (d, JCP=5.9
Hz), 75.8, 125.4, 125.6, 127.3, 127.7 (×2), 128.1 (×2),
3
2
130.0, 134.7 (d, JCP=4.5 Hz), 150.8, 169.1 (d, JCP=8.6
Hz); 31P NMR (202 MHz, CDCl3) l 21.5; HRMS (EI)
calcd for C30H31O5P M+: 512.2602. Found: 512.2684.
cis-II-2a: 1H NMR (500 MHz, CDCl3) l 0.75–0.90 (m,
1H), 0.88 (d, J=6.6 Hz, 3H), 0.98–1.12 (m, 1H), 1.08 (t,
J=7.1 Hz, 3H), 1.09 (t, J=7.0 Hz, 3H), 1.24–1.28 (m,
1H), 1.27 (s, 3H), 1.38 (s, 3H), 1.41–1.48 (m, 2H), 1.53–
1.62 (m, 2H), 1.62–1.67 (m, 1H), 1.92–1.98 (m, 1H),
2.00–2.08 (m, 1H), 2.63 (q, J=8.2 Hz, 1H), 3.60–3.70 (m,
1H), 3.78–3.92 (m, 3H), 5.00 (td, J=4.6, 10.7 Hz, 1H),
7.40–7.80 (m, 1H), 7.19–7.34 (m, 9H); 13C NMR (125
MHz, CDCl3) l 16.1 (d, 3JCP=3.7 Hz), 16.2 (d, 3JCP=1.8
Hz), 17.9 (d, 2JCP=2.1 Hz), 21.8, 25.4, 27.1, 28.3, 28.9 (d,
trans-II-2a: 1H NMR (500 MHz, CDCl3) l −0.04 (q,
J=13.1 Hz, 1H), 0.55–0.64 (m, 2H), 0.62 (d, J=6.8 Hz,
3H), 0.78–0.88 (m, 2H), 1.00 (s, 3H), 1.19 (s, 3H), 1.35–
1.45 (m, 3H), 1.39 (t, J=7.1 Hz, 3H), 1.44 (t, J=7.0 Hz,
3H), 1.52–1.58 (m, 1H), 1.70–1.76 (m, 1H), 2.98 (ddd,
J=8.4, 8.4, 17.0 Hz, 1H), 4.24 (dq, J=7.2, 14.5 Hz, 2H),
4.31 (dq, J=7.2, 14.5 Hz, 2H), 4.53 (td, J=4.1, 10.8 Hz,
1H), 7.15–7.32 (m, 10H); 13C NMR (125 MHz, CDCl3) l
15.6 (d, 2JCP=1.9 Hz), 16.5 (d, 3JCP=6.7 Hz), 16.6 (d,
1
3JCP=6.7 Hz), 21.4 (×2), 26.0, 26.7, 26.9, 28.8 (d, JCP
=
2
191.0 Hz), 30.9 (d, JCP=17.2 Hz), 34.3, 39.7, 40.0, 50.1,
62.5 (d, 2JCP=5.5 Hz), 62.7 (d, 2JCP=6.5 Hz), 75.7,
125.2, 125.5 (×2), 127.4, 128.0 (×2), 128.2 (×2), 129.5
(×2), 134.6 (d, JCP=1.8 Hz), 151.4, 166.1 (d, JCP=8.6
Hz); 31P NMR (202 MHz, CDCl3) l 24.1; HRMS (EI)
calcd for C30H31O5P M+: 512.2692. Found: 512.2698.
2
1JCP=198.0 Hz), 31.4 (×2), 31.8 (d, JCP=3.9 Hz), 34.4,
40.2, 41.8 (×2), 49.9, 61.7 (d, 2JCP=5.6 Hz), 62.1 (d,
2JCP=6.9 Hz), 76.4, 125.4, 125.5. 127.0, 127.7 (×2), 128.1,
130.0 (×2), 135.3 (d, 3JCP=6.4 Hz), 150.8, 169.2 (d,
3
2
.