Lewis acid mediated reactions of cyclopropyl aryl ketones with arylaldehydes, facile preparation of 2-(2-hydroxyethyl)-1,3-diarylpropenones

Article abstract of DOI:10.1016/j.tet.2004.12.028

In the presence of Lewis acid TMSOTf, ring-opening reaction of aryl cyclopropyl ketone with arylaldehyde took place under mild conditions to give 2-(2-hydroxyethyl)-1,3-diarylpropenone in good yield. By protection of hydroxy group with triethylsilyl group (TES), the corresponding ring-opened product 7 was obtained in high yield with good geometrical selectivity.

Full text of DOI:10.1016/j.tet.2004.12.028

Tetrahedron 61 (2005) 1893–1901
Lewis acid mediated reactions of cyclopropyl aryl ketones with
arylaldehydes, facile preparation of
2-(2-hydroxyethyl)-1,3-diarylpropenones
*
Min Shi, Yong-Hua Yang and Bo Xu
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu,
Shanghai 200032, China
Received 9 November 2004; revised 29 November 2004; accepted 1 December 2004
Available online 11 January 2005
Abstract—In the presence of Lewis acid TMSOTf, ring-opening reaction of aryl cyclopropyl ketone with arylaldehyde took place under
mild conditions to give 2-(2-hydroxyethyl)-1,3-diarylpropenone in good yield. By protection of hydroxy group with triethylsilyl group
(TES), the corresponding ring-opened product 7 was obtained in high yield with good geometrical selectivity.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
drug-like heterocyclic libraries (isoxazolines,6a,b tetra-
hydropyrimidines,6a,b dihydropyrimidiones,6c pyrimi-
dines,6c pyridine,6c,d benzothiazepines,6e pyrazoles,6c
pyrazolones,6f dihydropyran-2-ones,6g and pyrazolines6h).
Olsson also achieved central cyclic or a,b-enone core
products from a-substituted a,b-enone compounds through
combinatorial scaffold approaches.3h Herein we present a
Lewis acid mediated ring-opening reaction of arylcarbonyl
activated cyclopropanes (monoactivated cyclopropane)
with arylaldehydes under mild conditions which gives
a-substituted a,b-enone compounds in good yields.
Cyclopropane derivatives, as versatile building blocks have
been more than laboratory curiosities for quite some time.1
In order to activate strained three-membered ring, electron-
donating or accepting substituents are generally involved in
their reactions to make polar processes more favorable.
However, cyclopropane involved synthetically useful
reactions frequently contains two activating groups.2 The
ring-opening reactions of monoactivated cyclopropane
derivatives are in general sluggish due to their low
reactivities. So far several examples have been reported
under severe conditions either assisted by stronger nucleo-
philes such as IK and stronger Lewis acids such as TiCl4, or
assisted by the b-effect of silicon atom of trimethylsilyl
group (Scheme 1).3 Therefore, it is necessary to develop a
method for the ring-opening reaction of simple mono-
activated cyclopropane derivatives under mild conditions.
2. Results and discussion
As a first try, we searched for a protocol of the reaction of
phenyl cyclopropyl ketone 1a with 4-chlorobenzaldehyde
2a mediated by a variety of Lewis acids in dichloromethane
(DCM). We found that TfOH (1.0 equiv) or TMSOTf
(1.0 equiv) can effectively promoted this reaction to give
a,b-enone 3a as mixtures of Z- and E-isomers in moderate
yield along with a trace amount of [3C2] cycloaddition
products 4a and 5a in which product 5a was determined as a
dimer of 3a (Table 1, entries 2 and 5) by spectroscopic data
and NOESY spectrum (see Supporting information). Other
Lewis acids such as BF3$OEt2, Cu(OTf)2, AgOTf,
Zn(OTf)2, Zr(OTf)4 and other metal triflates did not
promote this reaction. Using 1,2-dichloroethane (DCE) as
solvent at higher temperature (60 8C to reflux), the yield of
3a was raised to 66% at 60 8C and 81% under reflux in the
presence of TMSOTf (1.0 equiv) (Table 1, entries 7–8). In
a,b-Enones represent a common feature in many useful
reactions,3d for example, Diels–Alder reactions,4a Stetter
reaction,4b Michael additions,4c Baylis–Hillman reactions,4d
4e
Julia-Colonna epoxidatons, and Robinson annulations.4f
´
Furthermore, in addition to possessing cytotoxic activities
and anticancer properties (Chalcones),5 a,b-enones are
frequently used as branching points for the creation of
Keywords: Cyclopropyl aryl ketones; Monoactivated cyclopropane; Lewis
acid; TMSOTf; TESOTf; Ring-opening reaction; 2-(2-Hydroxyethyl)-1,3-
diarylpropenone.
* Corresponding author. Tel.: C86 21 64163300x3421; fax: C86 21
64166128; e-mail: mshi@pub.sioc.ac.cn
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.12.028

1894
M. Shi et al. / Tetrahedron 61 (2005) 1893–1901
Scheme 1. Ring-opening reaction of monoactivitated cyclopropane assisted by IK and TiCl4, or assisted by the b-effect of silicon atom.
Table 1. Reaction of phenyl ketone 1a and 4-chlorobenzaldehyde 2a mediated by various Lewis acids
Entry
Lewis acid
Solvent
Temp.
Yield/[%]a
Yield/[%]a
3a (Z/E)
5a
1
2
3
4
5
6b
7
8
9
BF3 OEt2
TfOH
TfOH
DCM
DCM
DCE
DCE
DCM
DCM
DCE
DCE
DCE
r.t.
r.t.
60 8C
Reflux
r.t.
9 (0/100)
0
57 (15/85)
61 (16/84)
79 (45/55)
59 (25/75)
10 (0/100)
66 (18/82)
81 (31/69)
54 (19/81)
Trace
Trace
Trace
Trace
0
Trace
Trace
13
TfOH
TMSOTf
TMSOTf
TMSOTf
TMSOTf
TESOTf
r.t.
60 8C
Reflux
Reflux
a Isolated yields, sterochemistry is determined by NOESY spectrum.
b TMSOTf (0.2 equiv).
addition, 3a was also isolated in 61% at 60 8C and 79%
under reflux in the presence of TfOH (1.0 equiv), respect-
ively (Table 1, entries 3–4). Catalytic amounts of TMSOTf
did not effectively promote this reaction (Table 1, entry 6).
TESOTf was proven not as effective as TMSOTf (Table 1,
entry 9).
hydroxy group in the presence of lutidine to give the
corresponding product 7d in 60% yield. Interestingly, 7d
was predominantly obtained as E-configuration under this
conditions (Scheme 3).
The reaction of a variety of aryl cyclopropyl ketones with
various arylaldehydes was carried out in the presence of
TESOTf. The corresponding a,b-enones 7 were obtained
exclusively in good to high yields in all cases as
E-dominated configuration. The results are summarized in
Table 3. In this reaction, R1 and R2 could be various
substituted aromatic and heterocyclic groups (Table 3,
entries 1–10).
We next carried out the reactions of a variety of aryl
cyclopropyl ketones with various arylaldehydes under the
optimized reaction conditions. In all of the cases we
examined, a,b-enones 3 were dominantly formed along
with dimers 5.7 The results are summarized in Table 2
which indicates that a,b-enones 3, in some cases, were
obtained in low yields because of the formation of dimers 5,
and the cleanly isolated products 3 will also immediately
become mixtures of 3 and 5 due to the equilibrium shown in
Scheme 2.
Concerning the formation of 7-E, we have observed that 3-E
is isolated as a major product in reaction mixtures (Table 2)
and compounds 3 and 5 are formed in equilibrium under
ambient atmosphere as shown in Scheme 2. Interestingly,
using compound 4a as starting material, g-hydroxy ketone
3a was obtained in the presence of TMSOTf under reflux in
DCE to give 68% isolated yield as mixtures of Z- and
E-isomers (Scheme 4). This result suggests that trace
amount of product 4a is the active intermediate in this
reaction. Therefore, we believe that the transformation of
3-Z and 3-E proceeds through intermediate 4 (Scheme 5). In
any sense, 3-Z suffers from severe steric interaction between
In order to avoid the dimerization of 3, we decide to protect
the hydroxy group. As shown in Scheme 3, after the Lewis
acid mediated reaction was finished, we utilized isocyanato-
benzene and TESOTf to protect the hydroxy group,
respectively. The corresponding carbamate 6 was obtained
in 50% yield as mixtures of Z- and E-isomers. We were
delighted to find that the subsequent use of TESOTf twice
could efficiently promote this reaction and trap the formed

M. Shi et al. / Tetrahedron 61 (2005) 1893–1901
1895
Table 2. Reaction of arylaldehydes with various arylcarbonyl activated
cyclopropanes
Table 3. Reaction of aryl cyclopropyl ketone 1 with various arylaldehydes
2 in the presence of TESOTf
Entry
R1
R2
Yield/[%]a
7 (Z/E)
1
2
3
4
5
6
7
8
1a, C6H5
1a, C6H5
1a, C6H5
1a, C6H5
1a, C6H5
1b, p-FC6H4
1c, p-MeC6H4
1d, m,m-(Me)2C6H3
1e, p-MeOC6H4
1f, 2-thiophenyl
2a, p-ClC6H4
2e, C6H5
7a, 75 (0/100)
7b, 62 (0/100)
7c, 81 (0/100)
7d, 60 (1/99)b
7e, 69 (1/100)b
7f, 73 (0/100)
7g, 93 (0/100)
7h, 87 (0/100)
7i, 74 (0/100)
7j, 79 (0/100)
Entry
R1
R2
Yield/[%]a
3 (Z/E)
2f, p-MeC6H4
2g, p-MeOC6H4
2h, 2-furanyl
2f, p-MeC6H4
2f, p-MeC6H4
2f, p-MeC6H4
2f, p-MeC6H4
2f, p-MeC6H4
1
2
3
4
5
6
7
8
1a, C6H5
1a, C6H5
1a, C6H5
1a, C6H5
1a, C6H5
1a, C6H5
1a, C6H5
1b, p-FC6H4
1c, p-MeC6H4
1d, m,m-(Me)2C6H3
1e, p-MeOC6H4
1e, p-MeOC6H4
1f, 2-thiophenyl
2b, p-FC6H4
2c, m-ClC6H4
2d, p-BrC6H4
2e, C6H5
2f, p-MeC6H4
2g, p-MeOC6H4
2h, 2-furanyl
2a, p-ClC6H4
2a, p-ClC6H4
2a, p-ClC6H4
2a, p-ClC6H4
2d, p-BrC6H4
2a, p-ClC6H4
3b, 53 (17/83)
3c, 49 (26/74)
3d, 35 (0/100)
3e, 55 (30/70)
3f, 62 (0/100)b
3g, 23 (20/80)b
3h, 31 (0/100)b
3i, 42 (0/100)
3j, 88 (24/76)
3k, 53 (0/100)
3l, 84 (43/56)
3m, 77 (23/77)
3n, 55 (18/82)
9
10
a Isolated yields.
b Determined by 1H NMR spectroscopic data.
9
10
11
12
13
a Isolated yields, sterochemistry of 3a and 3m is determined by NOESY,
the remaining compounds were tentatively assigned according to the
general trend.
1
b Determined by H NMR spectroscopic data.
Scheme 4. Preparation of g-hydroxyl ketone 3a from compound 4a in the
presence of TMSOTf.
Scheme 2. Dimerization of 3.
Scheme 5. Formation route of 7-E in the reaction mixtures.
Scheme 3. Selection of the protection of hydroxy group.
R1 and R2, and thus, 3-E was formed in a thermo-
dynamically favored way (Scheme 5). At any rate, the
reversibility of the conjugate addition of an alcohol affected
the geometrical selectivity in this reaction and give the
thermodynamically stable 3-E exclusively. Therefore,
the enhanced stereochemistry could be explained by the
equilibrium shown in Scheme 5 in which the thermo-
dynamically favored major isomer 3-E reacts with TESOTf
to give 7-E in the presence of lutidine. Namely, the
equilibrium leans to the formation of 7-E in the presence of
TESOTf and lutidine (Scheme 5). The dimerization of 3-E
partially take places to afford the sterically demanding
dimer 5 as shown in Scheme 3 (compound 5a has been
isolated in enough purity).
At room temperature, Bu4NF can easily cleave triethylsilyl
group from 7a-E to give 2-(2-hydroxyethyl)-1,3-diaryl-
propenone 3a in high yield. Since equilibrium shown in
Scheme 5 exists, mixtures of Z- and E-isomers were
obtained with ratio of 8/92 at the beginning (Scheme 6).

1896
M. Shi et al. / Tetrahedron 61 (2005) 1893–1901
Analytical Concept mass spectrometer (EI), Bruker FT
mass spectrometer (ESI), and IonSpec 4.7 Tesla FFMS
(MALDI). Organic solvents used were dried by standard
methods when necessary. Commercially obtained reagents
were used without further purification. All reactions were
monitored by TLC with Yinlong GF254 silica gel coated
plates. Flash column chromatography was carried out using
300–400 mesh silica gel at increased pressure.
Scheme 6. Deprotection of 7a-E.
4.2. General procedure for the reactions of cyclopropyl
aryl ketones with arylaldehyde
Under argon atmosphere, the mixture of cyclopropyl aryl
ketone (1, 0.5 mmol), arylaldehyde (2, 0.5 mmol) and
TMSOTf (1.0 equiv) was dissolved in 1,2-dichloroethane
(DCE, 1.5 mL) and the reaction mixture was refluxed for
10 h. The reaction solution was cooled to room temperature
and then quenched by the addition of aqueous NaHCO3
solution. The reaction mixture was washed with H2O
(50 mL) and extracted by dichloromethane (3!15 mL) and
dried over anhydrous MgSO4. The solvent was removed
under reduced pressure and the residue was purified by a
silica gel column chromatography using petroleum ether/
ethyl acetate (10/1) as an eluent to give ring-opened product
2-(2-hydroxyethyl)-1,3-diarylpropenone 3 as an oily
product.
Scheme 7. The plausible reaction mechanism in the reaction of
aryladehydes with arylcarbonyl activated cyclopropane mediated by
Lewis acid.
Further store under ambient atmosphere will be
accompanied by the formation of dimer 5. Therefore, the
products 3 should be used for the next reaction immediately
because of their labilities.
Under argon atmosphere, the mixture of cyclopropyl aryl
ketone (1, 0.5 mmol), arylaldehyde (2, 0.5 mmol) and
TESOTf (1.0 equiv) was dissolved in 1,2-dichloroethane
(DCE, 1.5 mL) and the reaction mixture was refluxed for
10 h. The reaction solution was cooled to room temperature,
then lutidine (480 mL, 4.0 mmol) and TESOTf (216 mL,
1.0 mmol) were added subsequently and the reaction
solution was stirred for another 2 h. The solvent was
removed under reduced pressure and the residue was
purified by a silica gel column chromatography using
petroleum ether as an eluent to give the product 1,3-diaryl-
2-(2-triethylsilanyloxyethyl)propenone 7 as an oily product.
Based on the above results, a plausible reaction mechanism
is proposed in Scheme 7. In the presence of Lewis acid, the
attack of carbonyl oxygen atom of arylaldehyde to three-
membered ring of cyclopropyl aryl ketone 1 gives enolate
oxonium ion A, which produces the key intermediate 4
through intramolecular aldol reaction, as a [3C2] cyclo-
addition product. 2-(2-Hydroxyethyl)-1,3-diarylpropenone
3 is formed through proton transfer of the intermediate B
derived from 4 in the presence of Lewis acid. Overall, this
reaction is facile process for the preparation of 2-(2-
hydroxyethyl)-1,3-diarylpropenones.
4.3. The reaction of cyclopropyl phenyl ketone with
4-methoxyphenylaldehyde 2g or Furanylaldehyde 2h
3. Conclusion
Aldehyde 2g or 2h (0.5 equiv) was added dropwise to a
refluxing mixture of phenyl cyclopropyl ketone and
TESOTf (1.0 equiv) for 1 h. Then the reaction solution
was stirred under reflux for another 2 h. The reaction was
cooled to room temperature and then was quenched by the
addition of aqueous NaHCO3 solution. The reaction mixture
was washed with H2O (50 mL) and extracted by dichloro-
methane (3!15 mL) and dried over anhydrous MgSO4. The
solvent was removed under reduced pressure and the residue
was purified by a silica gel column chromatography using
petroleum as an eluent to give product 3g (23%) or 3h
(31%) as a red oily product.
In conclusion, we have found that Lewis acid TMSOTf can
effectively mediate the ring-opening reaction of cyclopropyl
aryl ketones with arylaldehydes to give the products 2-(2-
hydroxyethyl)-1,3-diarylpropenones 3 along with dimers 5.
The products 3 are labile compounds because of the
subsequent rapid dimerization. The subsequent twice use
of Lewis acid TESOTf gives hydroxyl group protected
products 7 with high geometrical selectivities (predomi-
nantly E configuration) in good yields.
4. Experimental
4.4. The procedure of desilylation of compound 7a
4.1. General methods
Bu4NF$3H2O (236 mg, 0.74 mmol) was added to a solution
of
oxyethyl)propenone 7a (150 mg, 0.37 mmol) in THF
(10 mL) and the reaction mixture was stirred at room
temperature for 10 h. Then the solvent was removed under
3-(4-chlorophenyl)-1-phenyl-2-(2-triethylsilanyl-
1H and 13C NMR spectra were recorded at 300 and 75 MHz
respectively. Mass spectra were recorded by EI, SCI and
ESI methods, and HRMS was measured on Kratos

M. Shi et al. / Tetrahedron 61 (2005) 1893–1901
1897
reduced pressure and the residue was purified by a silica gel
column chromatography using petroleum ether/ethyl acetate
(10/1) as an eluent to give product 3a-E (94 mg) and 3a-E
(8 mg) as red oil.
Ar), 7.47 (tt, JZ7.5 Hz, JZ1.2 Hz, 1H, Ar), 7.78 (dd, JZ
6.6 Hz, JH-FZ1.5 Hz, 2H, Ar); MS (EI) m/z: 270 (MC, 9),
241 (23), 240 (66), 239 (46), 133 (64), 109 (17), 105 (100),
77 (99), 51 (32); HRMS (EI) Calcd. for C17H15O2F:
270.1056, Found: 270.1077.
4.4.1. E-3-(4-Chlorophenyl)-2-(2-hydroxyethyl)-1-phe-
nylpropenone (3a-E). This compound was obtained as a
red oil, yield: 80 mg, 56%. IR (CH2Cl2): n 1014, 1045,
1093, 1179, 1246, 1316, 1374, 1447, 1490, 1578, 1595,
4.4.5. E-3-(3-Chlorophenyl)-2-(2-hydroxyethyl)-1-phe-
nylpropenone (3c-E). Only the mixture of 3c-E and the
dimer were obtained as a red oil, yield: 51 mg, 36%. IR
(CH2Cl2): n 1028, 1055, 1080, 1158, 1227, 1265, 1283,
1428, 1447, 1475, 1563, 1594, 1649, 1721, 2853, 2924,
1
1646, 1736, 2931, 3060, 3462 cmK1; H NMR (300 MHz,
CDCl3, TMS): d 2.82 (s, 1H, OH), 2.96 (t, JZ6.3 Hz, 2H,
CH2), 3.85 (t, JZ6.3 Hz, 2H, CH2), 7.15 (s, 1H, CH), 7.35
(d, JZ8.7 Hz, 2H, Ar), 7.36 (dt, JZ6.6 Hz, JZ7.2 Hz, 2H,
Ar), 7.45 (dt, JZ1.5 Hz, JZ6.6 Hz, 2H, Ar), 7.56 (tt, JZ
7.2 Hz, JZ1.5 Hz, 1H, Ar), 7.78 (d, JZ8.7 Hz, 2H, Ar); 13C
NMR (75 MHz, CDCl3, TMS): d 31.0, 61.4, 128.3, 128.8,
129.73, 130.5, 132.3, 133.5, 134.7, 137.9, 139.2, 142.1,
199.9; MS (EI) m/z: 288 (3), 286 (MC, 9), 256 (38), 255
(27), 221 (22), 115 (55), 105 (87), 77 (100), 51 (33); HRMS
(EI) Calcd. for C17H15O2Cl: 286.0761, Found: 286.0764.
1
3061, 3493 cmK1; H NMR (300 MHz, CDCl3, TMS): d
2.97 (t, JZ6.6 Hz, 2H, CH2), 3.88 (t, JZ6.6 Hz, 2H, CH2),
7.13 (s, 1H, CH), 7.30 (t, JZ8.1 Hz, 1H, Ar), 7.32 (dt, JZ
1.2 Hz, JZ7.5 Hz, 2H, Ar), 7.41 (s, 1H, Ar), 7.47 (dt, JZ
6.3 Hz, JZ7.5 Hz, 2H, Ar), 7.58 (tt, JZ6.3 Hz, JZ1.2 Hz,
1H, Ar), 7.81 (d, JZ8.1 Hz, 2H, Ar); MS (EI) m/z: 288 (4),
286 (MC, 12), 257 (21), 256 (19), 221 (14), 115 (53), 105
(76), 86 (26), 77 (100), 51 (38), 49 (20); HRMS (EI) Calcd.
for C17H15O2Cl: 286.0761, Found: 286.0786.
4.4.2. Z-3-(4-Chlorophenyl)-2-(2-hydroxyethyl)-1-phe-
nyl-propenone (3a-Z). This compound was obtained as a
red oil, yield: 36 mg, 25%. IR (CH2Cl2): n 1013, 1048,
1092, 1176, 1234, 1265, 1312, 1378, 1404, 1449, 1491,
1579, 1594, 1653, 1720, 2927, 3059, 3429 cmK1; 1H NMR
(300 MHz, CDCl3, TMS): d 2.72 (dt, JZ0.9 Hz, JZ6.0 Hz,
2H, CH2), 3.82 (t, JZ6.0 Hz, 2H, CH2), 6.81 (s, 1H, CH),
7.03 (d, JZ7.5 Hz, 2H, Ar), 7.06 (dt, JZ5.7 Hz, JZ7.5 Hz,
2H, Ar), 7.34 (tt, JZ5.7 Hz, JZ1.5 Hz, 2H, Ar), 7.48 (tt,
JZ1.5 Hz, JZ7.5 Hz, 1H, Ar), 7.88 (d, JZ7.5 Hz, 2H, Ar);
13C NMR (75 MHz, CDCl3, TMS): d 39.8, 61.3, 128.4,
128.5, 128.7, 129.5, 129.8, 131.5, 133.6, 133.8, 135.2,
138.9, 200.9; MS (EI) m/z: 288 (1), 286 (MC, 4), 257 (21),
255 (22), 221 (21), 115 (28), 105 (100), 77 (67), 51 (16);
HRMS (EI) Calcd. for C17H15O2Cl: 286.0761, Found:
286.0767.
4.4.6. Z-3-(3-Chlorophenyl)-2-(2-hydroxyethyl)-1-phe-
nylpropenone (3c-Z). This compound was obtained as a
red oil, yield: 18 mg, 13%. IR (CH2Cl2): n 1046, 1080,
1177, 1235, 1377, 1449, 1466, 1564, 1579, 1594, 1655,
1
1720, 2851, 2924, 2956, 3412 cmK1; H NMR (300 MHz,
CDCl3, TMS): d 2.73 (dt, JZ0.9 Hz, JZ6.0 Hz, 2H, CH2),
3.83 (t, JZ6.0 Hz, 2H, CH2), 6.81 (s, 1H, CH), 6.99 (t, JZ
8.1 Hz, 1H, Ar), 7.02 (dt, JZ1.2 Hz, JZ7.5 Hz, 2H, Ar),
7.11 (s, 1H, Ar), 7.33 (dt, JZ6.3 Hz, JZ7.5 Hz, 2H, Ar),
7.47 (tt, JZ6.3 Hz, JZ1.2 Hz, 1H, Ar), 7.87 (d, JZ8.1 Hz,
2H, Ar); MS (EI) m/z: 288 (2), 286 (MC, 5), 257 (29), 256
(64), 221 (27), 115 (39), 105 (100), 77 (82), 43 (23); HRMS
(EI) Calcd. for C17H15O2Cl: 286.0761, Found: 286.0783.
4.4.7. E-3-(4-Bromophenyl)-2-(2-hydroxyethyl)-1-phe-
nylpropenone (3d-E). This compound was obtained as a
red oil, yield: 57 mg, 35%. IR (CH2Cl2): n 1010, 1040,
1073, 1159, 1178, 1261, 1282, 1317, 1380, 1447, 1487,
1585, 1597, 1645, 2252, 2884, 2927, 3061, 3443 cmK1; 1H
NMR (300 MHz, CDCl3, TMS): d 2.91 (s, 1H, OH), 2.96 (t,
JZ6.3 Hz, 2H, CH2), 3.86 (t, JZ6.3 Hz, 2H, CH2), 7.14 (s,
1H, CH), 7.31 (d, JZ8.4 Hz, 2H, Ar), 7.44–7.59 (m, 5H,
Ar), 7.78 (d, JZ8.4 Hz, 2H, Ar); 13C NMR (75 MHz,
CDCl3, TMS): d 31.0, 61.4, 123.0, 128.3, 129.7, 130.7,
131.7, 132.3, 133.9, 137.8, 139.2, 142.3, 200.0; MS (EI)
m/z: 315 (27), 313 [(M-17)C, 27], 128 (13), 115 (17), 105
(100), 77 (44); HRMS (MALDI) Calcd. for C17H15O2BrC
H: 331.0334, Found: 331.0337.
4.4.3. E-3-(4-Fluorophenyl)-2-(2-hydroxyethyl)-1-phe-
nylpropenone (3b-E). Only the mixture of 3b-E and the
dimer were obtained as a red oil, yield: 59 mg, 44%. IR
(CH2Cl2): n 1054, 1098, 1159, 1177, 1229, 1265, 1292,
1307, 1379, 1447, 1508, 1578, 1600, 1646, 1720, 2887,
2927, 3058, 3472 cmK1 1H NMR of 3b-E (300 MHz,
;
CDCl3, TMS): d 2.98 (t, JZ6.0 Hz, 2H, CH2), 3.88 (t, JZ
6.0 Hz, 2H, CH2), 7.05 (dd, JZ8.1 Hz, JH-FZ8.9 Hz, 2H,
Ar), 7.12 (dt, JZ5.7 Hz, JZ7.5 Hz, 2H, Ar), 7.19 (s, 1H,
CH), 7.46 (dt, JZ5.7 Hz, JZ0.9 Hz, 2H, Ar), 7.56 (tt, JZ
7.2 Hz, JZ0.9 Hz, 1H, Ar), 7.78 (dd, JZ8.1 Hz, JH-F
Z
3.3 Hz, 2H, Ar); MS (EI) m/z: 270 (MC, 7), 239 (22), 133
(66), 105 (74), 77 (100), 57 (45), 51 (62), 49 (84), 43 (83);
HRMS (EI) Calcd. for C17H15O2F: 270.1056, Found:
270.1079.
4.4.8. E-2-(2-Hydroxyethyl)-1,3-diphenylpropenone
(3e-E). This compound was obtained as a red oil, yield:
48 mg, 38%. IR (CH2Cl2): n 1002, 1027, 1054, 1159, 1177,
1265, 1319, 1379, 1447, 1492, 1577, 1597, 1464, 2885,
2926, 3026, 3057, 3443 cmK1; 1H NMR (300 MHz, CDCl3,
TMS): d 3.00 (t, JZ6.3 Hz, 2H, CH2), 3.88 (t, JZ6.3 Hz,
2H, CH2), 7.24 (s, 1H, CH), 7.37–7.56 (m, 8H, Ar), 7.80 (d,
JZ7.2 Hz, 2H, Ar); 13C NMR (75 MHz, CDCl3, TMS): d
31.1, 61.8, 128.3, 128.6, 128.8, 129.2, 129.8, 132.2, 135.1,
138.1, 138.7, 143.9, 200.4; MS (EI) m/z: 252 (MC, 2), 234
(4), 222 (13), 115 (12), 105 (49), 86 (67), 84 (100), 77 (31);
HRMS (EI) Calcd. for C17H16O2: 252.1150, Found:
252.1160.
4.4.4. Z-3-(4-Fluorophenyl)-2-(2-hydroxyethyl)-1-phe-
nylpropenone (3b-Z). This compound was obtained as a
red oil, yield: 12 mg, 9%. IR (CH2Cl2): n 1047, 1160, 1177,
1229, 1290, 1312, 1449, 1508, 1579, 1600, 1653, 2852,
2924, 3062, 3433 cmK1 1H NMR (300 MHz, CDCl3,
;
TMS): d 2.31 (s, 1H, OH), 2.72 (dt, JZ0.9 Hz, JZ6.0 Hz,
2H, CH2), 3.82 (t, JZ6.0 Hz, 2H, CH2), 6.79 (dd, JZ
6.6 Hz, JH-FZ8.4 Hz, 2H, Ar), 6.84 (s, 1H, CH), 7.09 (dt,
JZ7.2 Hz, JZ7.5 Hz, 2H, Ar), 7.32 (dt, JZ1.2, 7.2 Hz, 2H,

1898
M. Shi et al. / Tetrahedron 61 (2005) 1893–1901
4.4.9. Z-2-(2-Hydroxyethyl)-1,3-diphenylpropenone
(3e-Z). This compound was obtained as a red oil, yield:
21 mg, 17%. IR (CH2Cl2): n 1047, 1176, 1235, 1379, 1449,
CDCl3, TMS): d 31.1, 61.4, 115.5 (d, JC-FZ21.8 Hz), 128.8,
130.5, 132.4 (d, JC-FZ9.1 Hz), 133.3, 134.0 (d, JC-F
3.0 Hz), 134.8, 139.1, 141.6, 165.3 (d, JC-FZ253.1 Hz),
198.5; MS (EI) m/z: 306 (1), 304 (MC, 3), 287 (2), 274 (15),
239 (22), 149 (10), 123 (100), 115 (17), 95 (43), 86 (19), 84
(30), 75 (12); HRMS (MALDI) Calcd. for C17H15O2ClFC
H: 305.0745, Found: 305.0740.
Z
1
1597, 1655, 2855, 2927, 3435 cmK1; H NMR (300 MHz,
CDCl3, TMS): d 2.74 (t, JZ5.7 Hz, 2H, CH2), 3.84 (t, JZ
5.7 Hz, 2H, CH2), 6.89 (s, 1H, CH), 7.09–7.14 (m, 5H, Ar),
7.33 (dt, JZ7.2 Hz, JZ8.4 Hz, 2H, Ar), 7.46 (tt, JZ1.5 Hz,
JZ7.2 Hz, 1H, Ar), 7.90 (dt, JZ1.5 Hz, JZ8.4 Hz, 2H,
Ar).
4.4.14. E-3-(4-Chlorophenyl)-2-(2-hydroxyethyl)-1-p-
tolylpropenone (3j-E). Only the mixture of 3j-E and
dimer were obtained as a red oil, yield: 115 mg, 77%. IR
(CH2Cl2): n 1013, 1055, 1092, 1157, 1180, 1261, 1282,
1312, 1377, 1406, 1490, 1606, 1645, 2886, 2924, 3029,
4.4.10. E-2-(2-Hydroxyethyl)-1-phenyl-3-p-tolylprope-
none (3f). Only the mixture of 3f-Z, 3f-E and the dimer
were obtained as a red oil, yield: 82 mg, 62%. IR (CH2Cl2):
n 1043, 1113, 1159, 1177, 1265, 1319, 1380, 1447, 1511,
1578, 1643, 1716, 2886, 2924, 3026, 3057, 3459 cmK1; 1H
NMR of 3f-E (300 MHz, CDCl3, TMS): d 2.38 (s, 3H, CH3),
3.03 (t, JZ6.3 Hz, 2H, CH2), 3.91 (t, JZ6.3 Hz, 2H, CH2),
7.08 (s, 1H, CH), 7.15 (dt, JZ6.6 Hz, JZ7.2 Hz, 2H, Ar),
7.30 (d, JZ7.2 Hz, 1H, Ar), 7.41 (dt, JZ1.5 Hz, JZ7.2 Hz,
2H, Ar), 7.56 (tt, JZ1.5 Hz, JZ6.6 Hz, 1H, Ar), 7.78 (d,
JZ7.2 Hz, 2H, Ar); MS (EI) m/z: 266 (MC, 3), 248 (2), 236
(18), 233 (12), 221 (22), 122 (27), 105 (100), 77 (57), 51
(12); HRMS (MALDI) Calcd. for C18H18O2CH: 267.1386,
Found: 267.1378.
1
3468 cmK1; H NMR (300 MHz, CDCl3, TMS): d 2.42 (s,
1H, CH3), 2.95 (t, JZ6.0 Hz, 2H, CH2), 3.84 (t, JZ6.0 Hz,
2H, CH2), 7.12 (s, 1H, CH), 7. 25 (d, JZ7.8 Hz, 2H, Ar),
7.36 (s, 4H, Ar), 7.71 (d, JZ7.8 Hz, 2H, Ar); MS (EI) m/z:
302 (2), 300 (MC, 6), 285 (4), 271 (14), 255 (46), 119 (88),
115 (19), 91 (50), 84 (100), 49 (18), 47 (20); HRMS
(MALDI) Calcd. for C18H17ClO2CH: 301.0995, Found:
301.0999.
4.4.15. Z-3-(4-Chlorophenyl)-2-(2-hydroxyethyl)-1-p-
tolylpropenone (3j-Z). This compound was obtained as a
red oil, yield: 16 mg, 11%. IR (CH2Cl2): n 1014, 1043,
1092, 1177, 1237, 1377, 1407, 1491, 1604, 1655, 1712,
2840, 2924, 3030, 3425 cmK1; 1H NMR (300 MHz, CDCl3,
TMS): d 2.42 (s, 3H, CH3), 2.70 (t, JZ5.7 Hz, 2H, CH2),
3.81 (t, JZ5.7 Hz, 2H, CH2), 6.75 (s, 1H, CH), 7.04–7.10
(m, 4H, Ar), 7.14 (d, JZ8.1 Hz, 2H, Ar), 7.61 (d, JZ
8.1 Hz, 2H, Ar); 13C NMR (75 MHz, CDCl3, TMS): d 21.7,
39.8, 61.3, 128.4, 128.8, 129.5, 129.6, 129.7, 130.9, 133.4,
133.9, 138.9, 145.0, 200.6; MS (EI) m/z: 302 (1), 300 (MC,
3), 285 (2), 270 (23), 257 (19), 255 (53), 119 (100), 115
(26), 65 (26); HRMS (MALDI) Calcd. for C18H17ClO2C
Na: 323.0815, Found: 323.0820.
4.4.11. E-2-(2-Hydroxyethyl)-3-(4-methoxyphenyl)-1-
phenylpropenone (3g). Only the mixture of 3g-Z, 3g-E
and the dimer were obtained as a red oil, yield: 40 mg, 28%,
1
Z/EZ20/80 (determined by H NMR spectroscopic data).
IR (CH2Cl2): n 1032, 1070, 1115, 1159, 1177, 1252, 1385,
1421, 1450, 1464, 1511, 1604, 1643, 1716, 2837, 2933,
1
3058, 3507 cmK1; H NMR of 3g-E (300 MHz, CDCl3,
TMS): d 3.05 (t, JZ6.3 Hz, 2H, CH2), 3.83 (s, 3H, OCH3),
3.92 (t, JZ6.3 Hz, 2H, CH2), 6.93 (d, JZ8.4 Hz, 1H, Ar),
7.22 (s, 1H, CH), 7.41–7.48 (m, 5H, Ar), 7.77 (d, JZ8.4 Hz,
2H, Ar); MS (EI) m/z: 282 (MC, 6), 265 (1), 252 (10), 233
(7), 221 (13), 121 (13), 115 (12), 105 (100), 103 (15), 78 (9),
77 (63); HRMS (EI) Calcd. for C18H18O3: 282.1256, Found:
282.1262.
4.4.16. E-3-(4-Chlorophenyl)-1-(3,5-dimethylphenyl)-2-
(2-hydroxyethyl)propenone (3k-E). This compound was
obtained as a red oil, yield: 83 mg, 53%. IR (CH2Cl2): n
1013, 1048, 1093, 1207, 1299, 1315, 1381, 1439, 1490,
1602, 1643, 2921, 3445 cmK1; 1H NMR (300 MHz, CDCl3,
TMS): d 2.36 (s, 6H, CH3), 2.96 (t, JZ6.0 Hz, 2H, CH2),
3.85 (t, JZ6.0 Hz, 2H, CH2), 7.16 (s, 1H, CH), 7.19 (s, 1H,
Ar), 7.33–7.40 (m, 6H, Ar); 13C NMR (75 MHz, CDCl3,
TMS): d 21.1, 31.0, 61.4, 127.4, 128.7, 130.5, 133.6, 133.9,
134.6, 137.9, 138.0, 139.3, 142.0, 200.3; MS (EI) m/z: 316
(4), 314 (MC, 11), 285 (22), 269 (31), 261 (13), 255 (4), 159
(14), 133 (100), 115 (29), 105 (63), 91 (50), 84 (48), 79 (29),
77 (29); HRMS (MALDI) Calcd. for C19H19ClO2CNa:
337.0971, Found: 337.0973.
4.4.12. 3-Furan-2-yl-2-(2-hydroxyethyl)-1-phenylprope-
none (3h). Only the mixture of 3h-Z, 3h-E and the dimmer
were obtained as a red oil, yield: 28 mg, 23%, E/ZZ7/93
(determined by 1H NMR spectroscopic data). IR (CH2Cl2):
n 1022, 1155, 1178, 1220, 1266, 1317, 1369, 1421, 1448,
1616, 1643, 1717, 2929, 3055, 3420 cmK1; 1H NMR of 3h-
E (300 MHz, CDCl3, TMS): d 3.17 (t, JZ6.3 Hz, 2H, CH2),
3.94 (t, JZ6.3 Hz, 2H, CH2), 6.63 (d, JZ3.6 Hz, 1H, Ar),
6.48 (dd, JZ3.6 Hz, JZ7.8 Hz, 1H, CH), 6.96 (s, 1H, CH),
7.28–7.74 (m, 5H, Ar), 8.11 (d, JZ7.8 Hz, 1H, Ar); MS (EI)
m/z: 242 (MC, 5), 212 (12), 122 (49), 105 (100), 86 (16), 84
(25), 77 (68), 51 (34), 50 (15); HRMS (MALDI) Calcd. for
C15H15O3CH: 243.1022, Found: 243.1023.
4.4.17. E-3-(4-Chlorophenyl)-2-(2-hydroxyethyl)-1-(4-
methoxyphenyl)propenone (3l-E). Only the mixture of
3l-E and the dimer were obtained as a red oil, yield: 76 mg,
48%. IR (CH2Cl2): n 1013, 1030, 1092, 1170, 1254, 1310,
1375, 1420, 1441, 1463, 1490, 1509, 1573, 1598, 1641,
4.4.13. E-3-(4-Chlorophenyl)-1-(4-fluorophenyl)-2-(2-
hydroxyethyl)propenone (3i-E). This compound was
obtained as a red oil, yield: 64 mg, 42%. IR (CH2Cl2): n
1013, 1056, 1093, 1156, 1232, 1281, 1308, 1375, 1407,
1491, 1506, 1597, 1648, 2887, 2928, 3481 cmK1; 1H NMR
(300 MHz, CDCl3, TMS): d 2.96 (t, JZ6.3 Hz, 2H, CH2),
3.87 (t, JZ6.3 Hz, 2H, CH2), 7.11 (s, 1H, CH), 7.14 (dd, JZ
8.7 Hz, JH-FZ8.7 Hz, 2H, Ar), 7.38 (s, 4H, Ar), 7.78 (dd,
JZ8.7 Hz, JH-FZ5.7 Hz, 2H, Ar); 13C NMR (75 MHz,
1713, 2840, 2934, 3053, 3446 cmK1 1H NMR of 3l-E
;
(300 MHz, CDCl3, TMS): d 2.96 (t, JZ6.0 Hz, 2H, CH2),
3.86 (t, JZ6.0 Hz, 2H, CH2), 3.90 (s, 3H, OCH3), 6.97 (d,
JZ9.0 Hz, 2H, Ar), 7. 10 (s, 1H, CH), 7.39 (s, 4H, Ar), 7.87
(d, JZ9.0 Hz, 2H, Ar); MS (EI) m/z: 318 (4), 316 (MC, 11),
287 (35), 286 (17), 285 (18), 257 (13), 255 (34), 251 (7), 135

M. Shi et al. / Tetrahedron 61 (2005) 1893–1901
1899
(100), 115 (10), 77 (11); HRMS (EI) Calcd. for
C18H17ClO3: 316.0866, Found: 316.0855.
1092, 1248, 1279, 1352, 1378, 1410, 1490, 1513, 1593,
1625, 2924, 3088, 3308 cmK1; 1H NMR (300 MHz, CDCl3,
TMS): d 2.73 (t, JZ6.3 Hz, 2H, CH2), 3.84 (t, JZ6.3 Hz,
2H, CH2), 6.77 (s, 1H, CH), 6.94 (dd, JZ4.8 Hz, JZ3.6 Hz,
1H, Ar), 7.13 (s, 4H, Ar), 7.51 (dd, JZ3.6 Hz, JZ0.9 Hz,
2H, Ar), 7.60 (dd, JZ4.8 Hz, JZ0.9 Hz, 2H, Ar); 13C NMR
(75 MHz, CDCl3, TMS): d 39.7, 61.4, 128.4, 128.5, 129.8,
131.5, 133.7, 133.9, 135.1, 135.6, 139.0, 142.8, 192.8; MS
(EI) m/z: 294 (1), 292 (MC, 2), 262 (21), 247 (2), 239 (3),
227 (20), 211 (2), 149 (8), 139 (78), 115 (14), 111 (100), 75
(29); HRMS (MALDI) Calcd. for C15H13O2SClCNa:
315.0222, Found: 315.0227.
4.4.18. Z-3-(4-Chlorophenyl)-2-(2-hydroxyethyl)-1-(4-
methoxyphenyl)propenone (3l-Z). This compound was
obtained as a red oil, yield: 57 mg, 36%. IR (CH2Cl2): n 1014,
1030, 1092, 1169, 1252, 1313, 1376, 1421, 1442, 1462, 1491,
1509, 1572, 1598, 1648, 1712, 2841, 2933, 3054, 3449 cmK1
;
1H NMR (300 MHz, CDCl3, TMS): d 2.68 (t, JZ6.0 Hz, 2H,
CH2), 3.80 (t, JZ6.0 Hz, 2H, CH2), 3.81 (s, 3H, OCH3), 6.72
(s, 1H, CH), 6.81 (d, JZ8.7 Hz, 2H, Ar), 7.07(s, 4H, Ar), 7.87
(d, JZ8.7 Hz, 2H, Ar);MS(EI)m/z:318(2), 316(MC, 4), 287
(18), 286 (25), 285 (12), 257 (11), 255 (27), 251 (6), 135 (100),
115 (23), 92 (24), 84 (54), 77 (37); HRMS (EI) Calcd. for
C18H17ClO3: 316.0866, Found: 316.0870.
4.4.23. [2-(4-Chlorophenyl)-tetrahydrofuran-3-yl]phe-
nylmethanone (4a). This compound was obtained as a red
oil. IR (CH2Cl2): n 1014, 1067, 1089, 1180, 1216, 1280,
1363, 1410, 1448, 1491, 1580, 1597, 1680, 2871, 2926,
4.4.19. E-3-(4-Bromophenyl)-2-(2-hydroxyethyl)-1-(4-
methoxyphenyl)propenone (3m-E). Only the mixture of
3m-E and the dimer were obtained as a red oil, yield:
107 mg, 59%. IR (CH2Cl2): n 1009, 1030, 1073, 1170, 1253,
1282, 1308, 1487, 1509, 1598, 1640, 2839, 2933, 3052,
1
3058 cmK1; H NMR (300 MHz, CDCl3, TMS): d 2.24–
2.35 (m, 1H, CH2), 2.42–2.55 (m, 1H, CH2), 3.82–3.90 (m,
1H, CH), 4.04–4.11 (m, 1H, CH2), 4.22–4.30 (m, 1H, CH2),
5.26 (d, JZ7.2 Hz, 1H, CH), 7.28 (s, 4H, Ar), 7.43 (t, JZ
7.5 Hz, 2H, Ar), 7.56 (t, JZ7.5 Hz, 1H, Ar), 7.84 (d, JZ
7.5 Hz, 2H, Ar); 13C NMR (75 MHz, CDCl3, TMS): d 32.2,
54.8, 68.4, 82.3, 127.2, 128.4, 128.5, 128.7, 133.3, 133.4,
136.3, 140.1, 199.5; MS (EI) m/z: 288 (5), 286 (MC, 14),
258 (61), 257 (74), 223 (2), 181 (11), 146 (27), 139 (17), 105
(100), 77 (54); HRMS (EI) Calcd. for C17H15O2Cl:
286.0755, Found: 286.0727.
1
3444 cmK1; H NMR (300 MHz, CDCl3, TMS): d 2.93 (t,
JZ6.0 Hz, 2H, CH2), 3.82 (t, JZ6.0 Hz, 2H, CH2), 3.87 (s,
3H, OCH3), 6.94 (d, JZ9.0 Hz, 2H, Ar), 7. 05 (s, 1H, CH),
7.30 (d, JZ8.7 Hz, 4H, Ar), 7.51 (d, JZ8.7 Hz, 2H, Ar),
7.51 (d, JZ9.0 Hz, 2H, Ar); MS (EI) m/z: 362 (7), 360 (MC,
7), 344 (2), 331 (27), 301 (20), 263 (11), 251 (7), 161 (8),
135 (100), 115 (16), 77 (17); HRMS (MALDI) Calcd. for
C18H18BrO3CH: 361.0440, Found: 361.0426.
4.4.24. 3-(4-Chlorophenyl)-1-phenyl-2-(2-triethylsilanyl-
oxyethyl)propenone (7a). This compound was obtained as
a red oil, yield: 150 mg, 75%. IR (CH2Cl2): n 1015, 1046,
1092, 1229, 1260, 1282, 1315, 1386, 1413, 1447, 1458,
1490, 1596, 1650, 1705, 2875, 2910, 2955 cmK1; 1H NMR
(300 MHz, CDCl3, TMS): d 0.58 (q, JZ8.4 Hz, 6H, CH2,),
0.93 (t, JZ8.4 Hz, 9H, CH2), 2.96 (t, JZ6.3 Hz, 2H, CH2),
3.86 (t, JZ6.3 Hz, 2H, CH2), 7.13 (s, 1H, CH), 7.34 (d, JZ
6.9 Hz, 2H, Ar), 7.42–7.54 (m, 5H, Ar), 7.79 (d, JZ6.9 Hz,
2H, Ar); 13C NMR (75 MHz, CDCl3, TMS): d 4.3, 6.7,
31.1,, 61.0, 128.1, 128.5, 129.7, 130.7, 131.9, 133.9, 134.41,
138.5, 139.6, 141.7, 198.9; MS (EI) m/z: 400 (MC, 1), 371
(99), 307 (6), 269 (10), 233 (21), 139 (61), 125 (29), 117
(79), 105 (90), 77 (100); Anal. Calcd. for C23H29ClO2Si: C,
68.89, H, 7.29%; Found: C, 69.20, H, 7.37%.
4.4.20. Z-3-(4-Bromophenyl)-2-(2-hydroxyethyl)-1-(4-
methoxyphenyl)propenone (3m-Z):. This compound was
obtained as a pale-yellow oil, yield: 32 mg, 18%. IR
(CH2Cl2): n 1009, 1029, 1073, 1167, 1247, 1314, 1376,
1421, 1487, 1509, 1572, 1597, 1649, 2840, 2932, 2961,
1
3412 cmK1; H NMR (300 MHz, CDCl3, TMS): d 2.69 (t,
JZ5.7 Hz, 2H, CH2), 3.80 (t, JZ5.7 Hz, 2H, CH2), 3.82 (s,
3H, OCH3), 6.71 (s, 1H, CH), 6.83 (d, JZ8.7 Hz, 2H, Ar),
7.01(d, JZ8.7 Hz, 2H, Ar), 7.24 (d, JZ8.4 Hz, 2H, Ar),
7.88 (d, JZ8.4 Hz, 2H, Ar); 13C NMR (75 MHz, CDCl3,
TMS): d 39.7, 61.2, 66.4, 114.0, 121.6, 128.0, 130.0, 130.5,
131.3, 131.9, 134.3, 139.1, 161.2, 199.5; MS (EI) m/z: 362
(5), 360 (MC, 5), 332 (31), 299 (29), 263 (5), 251 (9), 161
(9), 135 (100), 115 (20), 77 (20); HRMS (MALDI) Calcd.
for C18H18BrO3CH: 361.0440, Found: 361.0425.
4.4.25. 1,3-Diphenyl-2-(2-triethylsilanyloxyethyl)prope-
none (7b). This compound was obtained as a red oil,
yield: 114 mg, 62%. IR (CH2Cl2): n 1016, 1047, 1094, 1178,
1231, 1263, 1320, 1379, 1414, 1448, 1494, 1577, 1597,
4.4.21. E-3-(4-Chlorophenyl)-2-(2-hydroxyethyl)-1-thio-
phen-2-yl-propenone (3n-E). This compound was obtained
as a red oil, yield: 66 mg, 45%, IR (CH2Cl2): n 1013, 1051,
1092, 1231, 1262, 1258, 1309, 1353, 1413, 1490, 1513, 1621,
1650, 2875, 2955, 3026, 3060, 3516 cmK1 1H NMR
;
1
1712, 1884, 2926, 3053, 3448 cmK1; H NMR (300 MHz,
(300 MHz, CDCl3, TMS): d 0.58 (q, JZ8.4 Hz, 6H, CH2),
0.93 (t, JZ8.4 Hz, 9H, CH2), 3.10 (t, JZ6.6 Hz, 2H, CH2),
3.87 (t, JZ6.6 Hz, 2H, CH2), 7.20 (s, 1H, CH), 7.32–7.41
(m, 5H, Ar), 7.51–7.55 (m, 3H, Ar), 7.80 (d, JZ8.4 Hz, 2H,
Ar); 13C NMR (75 MHz, CDCl3, TMS): d 4.3, 6.7, 31.1,
61.1, 128.1, 128.3, 128.5, 129.3, 129.7, 131.8, 135.4, 138.5,
138.9, 143.1, 199.2; MS (EI) m/z: 366 (MC, 1), 337 (100),
319 (2), 259 (6), 234 (26), 217 (12), 203 (7), 129 (10), 115
(34), 105 (38), 77 (33); HRMS (ESI) Calcd. for
C23H30O2SiCH: 367.2093, Found: 367.2091.
CDCl3, TMS): d 2.94 (t, JZ6.3 Hz, 2H, CH2), 3.84 (t, JZ
6.3 Hz, 2H, CH2), 7.16 (t, JZ4.8 Hz, 1H, Ar), 7.37–7.44 (m,
5H, Ar), 7.71–7.46 (m, 2H, Ar); 13C NMR (75 MHz, CDCl3,
TMS): d 31.6, 61.3, 127.9, 128.8, 130.5, 133.5, 134.4, 134.5,
134.6, 139.2, 139.4, 143.3, 191.0; MS (EI) m/z: 294 (2), 292
(MC, 6), 262 (30), 247 (3), 239 (9), 227 (31), 211 (5), 149 (12),
115 (24), 111 (100), 84 (46); HRMS (MALDI) Calcd. for
C15H14O2SClCH: 293.0403, Found: 293.0393.
4.4.22. Z-3-(4-Chlorophenyl)-2-(2-hydroxyethyl)-1-thio-
phen-2-yl-propenone (3n-Z). This compound was obtained
as a red oil, yield: 15 mg, 10%, IR (CH2Cl2): n 1013, 1050,
4.4.26. 1-Phenyl-3-p-tolyl-2-(2-triethylsilanyloxyethyl)-
propenone (7c). This compound was obtained as a red

1900
M. Shi et al. / Tetrahedron 61 (2005) 1893–1901
oil, yield: 154 mg, 81%. IR (CH2Cl2): n 1018, 1047, 1094,
1178, 1232, 1264, 1290, 1320, 1379, 1414, 1448, 1458,
1511, 1578, 1598, 1647, 1719, 2876, 2912, 2954, 3025,
3509 cmK1; 1H NMR (300 MHz, CDCl3, TMS): d 0.60 (q,
JZ7.8 Hz, 6H, CH2), 0.95 (t, JZ7.8 Hz, 9H, CH2), 2.39 (s,
3H, CH3), 3.03 (t, JZ6.3 Hz, 2H, CH2), 3.89 (t, JZ6.3 Hz,
2H, CH2), 7.20 (s, 1H, CH), 7.22 (d, JZ7.2 Hz, 2H, Ar),
7.43–7.55 (m, 5H, Ar), 7.79 (d, JZ7.2 Hz, 2H, Ar); 13C
NMR (75 MHz, CDCl3, TMS): d 4.3, 6.8, 21.3, 31.1, 61.1,
128.1, 19.1, 129.4, 129.7, 131.7, 132.5, 138.0, 138.8, 138.8,
143.8, 199.3; MS (EI) m/z: 380 (MC, 1), 351 (100), 335 (5),
259 (11), 248 (28), 233 (28), 216 (7), 143 (7), 115 (31), 105
(39), 77 (27); HRMS (ESI) Calcd. for C24H32O2SiCH:
381.2250, Found: 381.2236.
142.8, 165.0 (d, JC-FZ251.9 Hz), 197.8; MS (EI) m/z: 398
(MC, 1), 369 (100), 353 (2), 303 (11), 266 (24), 251 (26),
234 (5), 143 (11), 95 (32), 87 (37), 75 (31); Anal. Calcd. for
C24H31FO2Si: C, 72.32, H, 7.84%;Found: C, 72.27, H, 7.75%.
4.4.30. 1,3-Di-p-tolyl-2-(2-triethylsilanyloxyethyl)prope-
none (7 g). This compound was obtained as a red oil, yield:
186 mg, 94%, Z/EZ0/100. IR (CH2Cl2): n 1018, 1046,
1093, 1180, 1232, 1263, 1291, 1319, 1378, 1413, 1458,
1510, 1608, 1645, 2875, 2911, 2954, 3026 cmK1; 1H NMR
(300 MHz, CDCl3, TMS): d 0.60 (q, JZ7.8 Hz, 6H, CH2),
0.96 (t, JZ7.8 Hz, 9H, CH2), 2.39 (s, 3H, CH3), 2.43 (s, 3H,
CH3), 3.02 (t, JZ6.6 Hz, 2H, CH2), 3.88 (t, JZ6.6 Hz, 2H,
CH2), 7.18 (s, 1H, CH), 7.20 (d, JZ8.1 Hz, 2H, Ar), 7.26 (d,
JZ8.1 Hz, 5H, Ar), 7.46 (d, JZ8.1 Hz, 2H, Ar), 7.72 (d,
JZ8.1 Hz, 2H, Ar); 13C NMR (75 MHz, CDCl3, TMS): d
4.3, 6.7, 21.3, 21.5, 31.3, 61.2, 128.7, 129.1, 129.4, 129.9,
132.7, 136.0, 138.2, 138.6, 142.4, 142.8, 199.0; MS (EI)
m/z: 394 (MC, 1), 365 (100), 349 (18), 273 (15), 262 (38),
247 (62), 215, (10), 143 (15), 129 (19), 119 (76), 91 (64), 75
(44); Anal. Calcd. for C25H34O2Si: C, 76.09, H, 8.68%;
Found: C, 76.23, H, 8.43%.
4.4.27. 3-(4-Methoxyphenyl)-1-phenyl-2-(2-triethyl-
silanyloxyethyl)propenone (7d). This compound was
obtained as a red oil, yield: 119 mg, 60%. IR (CH2Cl2): n
1034, 1177, 1255, 1034, 1319, 1379, 1417, 1447, 1459,
1511, 1577, 1604, 1642, 1720, 2876, 2911, 2955, 3448 cmK1
;
1H NMR (300 MHz, CDCl3, TMS): d 0.50 (q, JZ8.4 Hz, 6H,
CH2), 0.88 (t, JZ8.4 Hz, 9H, CH2), 2.96 (t, JZ6.3 Hz, 2H,
CH2), 3.76 (s, 3H, OCH3), 3.82 (t, JZ6.3 Hz, 2H, CH2), 6.85
(d, JZ7.2 Hz, 2H, Ar), 7.19 (s, 1H, CH), 7.34–7.48 (m, 5H,
Ar), 7.67 (d, JZ7.2 Hz, 2H, Ar); 13C NMR (75 MHz, CDCl3,
TMS): d 4.3, 6.7, 31.1, 55.2, 61.2, 113.8, 127.9, 128.0, 129.5,
131.2, 131.5, 136.8, 139.0, 143.9, 160.0, 199.3; MS (EI) m/z:
396 (MC, 4), 367 (86), 335 (3), 264 (33), 259 (12), 233 (38),
221 (8), 159 (14), 115 (36), 105 (100), 87 (37), 77 (64); Anal.
Calcd. for C24H32O3Si: C, 72.68, H, 8.13%; Found: C, 72.83,
H, 8.15%.
4.4.31. 1-(3,5-Dimethylphenyl)-3-p-tolyl-2-(2-triethyl-
silanyloxyethyl)propenone (7 h). This compound was
obtained as a red oil, yield: 178 mg, 87%. IR (CH2Cl2): n
1016, 1067, 1094, 1206, 1241, 1265, 1303, 1320, 1381,
1415, 1458, 1511, 1603, 1646, 2876, 2913, 2955, 3032 cmK1
;
1H NMR (300 MHz, CDCl3, TMS): d 0.51 (q, JZ8.1 Hz, 6H,
CH2), 0.86 (t, JZ8.1 Hz, 9H, CH2), 2.26 (s, 6H, CH3), 2.28 (s,
3H, CH3), 2.92 (t, JZ6.6 Hz, 2H, CH2), 3.77 (t, JZ6.6 Hz,
2H, CH2), 7.08 (d, JZ7.8 Hz, 2H, Ar), 7.10 (s, 1H, CH), 7.12
(s, 2H, Ar), 7.37 (d, JZ7.8 Hz, 2H, Ar); 13C NMR (75 MHz,
CDCl3, TMS): d 4.3, 6.8, 21.2, 21.3, 31.1, 61.2, 127.4, 129.1,
129.4, 132.7, 133.3, 137.7, 138.3, 138.6, 139.0, 143.3, 199.8;
MS (EI) m/z: 408 (MC, 1), 379 (100), 363 (14), 287 (16), 276
(33), 261 (52), 244 (8), 229 (10), 143 (11), 133 (46), 115 (56),
105 (71), 87 (13); Anal. Calcd. for C26H36O2Si: C, 76.42, H,
8.88%; Found: C, 76.50, H, 8.75%.
4.4.28. 3-Furan-2-yl-1-phenyl-2-(2-triethylsilanyloxy-
ethyl)propenone (7e). This compound was obtained as a
red oil, yield: 123 mg, 69%. IR (CH2Cl2): n 1005, 1072,
1271, 1317, 1447, 1615, 1645, 1721, 2877, 2912, 2955,
3415 cmK1; 1H NMR (300 MHz, CDCl3, TMS): d 0.53 (q,
JZ8.1 Hz, 6H, CH2), 0.88 (t, JZ8.1 Hz, 9H, CH2), 3.12 (t,
JZ6.6 Hz, 2H, CH2), 3.79 (t, JZ6.6 Hz, 2H, CH2), 6.44
(dd, JZ1.8 Hz, JZ3.0 Hz, 1H, Ar), 6.62 (d, JZ3.0 Hz, 1H,
Ar), 6.87 (s, 1H, CH), 7.38 (dt, JZ7.5 Hz, JZ7.2 Hz, 2H,
CH), 7.47 (t, JZ7.5 Hz, 1H, Ar), 7.49 (s, 1H, Ar), 7.63 (d,
JZ7.2 Hz, 2H, Ar); 13C NMR (75 MHz, CDCl3, TMS): d
4.3, 6.7, 31.8, 61.6, 112.2, 115.6, 128.1, 129.3, 130.0, 131.4,
134.6, 138.6, 144.5, 151.1, 198.6; MS (EI) m/z: 356 (MC,
9), 327 (100), 259 (5), 224 (39), 195 (7), 165 (11), 117 (54),
105 (60), 87 (53), 77 (68); Anal. Calcd. for C21H28O3Si: C,
70.74, H, 7.92%; Found: C, 70.74, H, 8.13%.
4.4.32. 1-(4-Methoxyphenyl)-3-p-tolyl-2-(2-triethyl-
silanyloxyethyl)propenone (7i). This compound was
obtained as a pale-yellow oil, yield: 151 mg, 74%, Z/EZ
0/100. IR (CH2Cl2): n 1031, 1047, 1093, 1140, 1171, 1254,
1290, 1319, 1378, 1416, 1459, 1509, 1574, 1600, 1642,
2875, 2954, 3032 cmK1 1H NMR (300 MHz, CDCl3,
;
TMS): d 0.53 (q, JZ7.5 Hz, 6H, CH2), 0.89 (t, JZ7.5 Hz,
9H, CH2), 2.32 (s, 3H, CH3), 2.97 (t, JZ6.6 Hz, 2H, CH2),
3.90 (s, 3H, OCH3), 3.80 (t, JZ6.6 Hz, 2H, CH2), 6.88 (d,
JZ8.1 Hz, 2H, Ar), 7.08 (s, 1H, CH), 7.14 (d, JZ7.5 Hz,
2H, Ar), 7.40 (d, JZ8.1 Hz, 2H, Ar), 7.79(d, JZ7.5 Hz, 2H,
Ar); 13C NMR (75 MHz, CDCl3, TMS): d 4.2, 6.7, 21.2,
31.5, 55.3, 61.1, 113.2, 129.0, 129.3, 131.1, 132.0, 132.7,
138.2, 138.3, 141.4, 162.7, 198.0; MS (EI) m/z: 410 (MC,
1), 381 (100), 365 (6), 349 (8), 289 (14), 278 (34), 263 (58),
135 (71), 115 (53), 103 (29), 87 (59), 75 (58); Anal. Calcd.
for C25H34O3Si: C, 73.13, H, 8.35%; Found: C, 73.13, H,
8.48%.
4.4.29. 1-(4-Fluorophenyl)-3-p-tolyl-2-(2-triethylsilanyl-
oxyethyl)propenone (7f). This compound was obtained as a
red oil, yield: 145 mg, 73%, Z/EZ0/100. IR (CH2Cl2): n
1015, 1045, 1094, 1155, 1186, 1231, 1262, 1292, 1319,
1378, 1409, 1458, 1505, 1598, 1648, 2876, 2912, 2955,
3026 cmK1; 1H NMR (300 MHz, CDCl3, TMS): d 0.57 (q,
JZ7.5 Hz, 6H, CH2), 0.92 (t, JZ7.5 Hz, 9H, CH2), 2.38 (s,
3H, CH3), 3.00 (t, JZ6.6 Hz, 2H, CH2), 3.85 (t, JZ6.6 Hz,
2H, CH2), 7.12 (s, 1H, CH), 7.12 (dd, JZ8.4 Hz, JH-F
Z
8.4 Hz, 2H, Ar), 7.20 (d, JZ7.8 Hz, 2H, Ar), 7.44 (d, JZ
7.8 Hz, 2H, Ar), 7.82 (dd, JZ8.4 Hz, JH-FZ5.4 Hz, 2H,
Ar); 13C NMR (75 MHz, CDCl3, TMS): d 4.3, 6.7, 21.3,
31.3, 61.1, 115.1 (d, JC-FZ21.9 Hz), 129.1, 129.4, 132.3 (d,
JC-FZ8.6 Hz), 132.5, 134.9 (d, JC-FZ3.0 Hz), 138.2, 138.7,
4.4.33. 1-Thiophen-2-yl-3-p-tolyl-2-(2-triethylsilanyl-
oxyethyl)propenone (7j). This compound was obtained as
a pale-yellow oil, yield: 152 mg, 79%, Z/EZ0/100. IR
(CH2Cl2): n 1018, 1054, 1094, 1186, 1232, 1264, 1291,

M. Shi et al. / Tetrahedron 61 (2005) 1893–1901
1901
1317, 1353, 1378, 1414, 1457, 1512, 1627, 2875, 2914,
Supplementary data
1
2954, 3024 cmK1; H NMR (300 MHz, CDCl3, TMS): d
0.55 (q, JZ8.4 Hz, 6H, CH2), 0.90 (t, JZ8.4 Hz, 9H, CH2),
2.39 (s, 3H, CH3), 2.98 (t, JZ6.6 Hz, 2H, CH2), 3.83 (t, JZ
6.6 Hz, 2H, CH2), 7.12 (dd, JZ4.8 Hz, JZ3.9 Hz, 1H, Ar),
7.21 (d, JZ8.1 Hz, 2H, Ar), 7.40 (s, 1H, CH), 7.47 (d, JZ
8.1 Hz, 2H, Ar), 7.65–7.68 (m, 2H, Ar); 13C NMR (75 MHz,
CDCl3, TMS): d 4.3, 6.7, 21.3, 31.7, 61.2, 127.6, 129.1,
129.4, 132.6, 133.4, 133.8, 138.4, 138.6, 140.7, 144.1,
196.6; MS (EI) m/z: 386 (MC, 1), 357 (100), 341 (7), 254
(16), 239 (21), 205 (43), 187 (8), 177 (18), 111 (89), 105
(23), 87 (43), 75 (28); HRMS (ESI) Calcd. for C22H30O02-
SSiCH: 387.1814, Found: 387.1818.
Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/j.tet.2004.
12.028
References and notes
1. (a) Reissig, H.-U.; Zimmer, R. Chem. Rev. 2003, 103, 1151–1196.
(b) Paquette, L. A. Chem. Rev. 1986, 86, 733–750. (c) Wong,
H. N. C.; Hon, M. Y.; Tse, C.-W.; Yip, Y.-C. Chem. Rev. 1989, 89,
165–198. (d) de Meijere, A.; Wessjohamm, L. Synlett 1990,
20–32. (e) Kulinkovich, O. G. Russ. Chem. Rev. 1993, 62,
839–850. (f) Kulinkovich, O. G. Polish. J. Chem. 1997, 849–882.
(g) Wenkert, E. Acc. Chem. Res. 1980, 13, 27–31. (h) Wenkert, E.
Heterocycles 1980, 14, 1703–1708. (i) Seebach, D. Angew.
Chem. 1979, 91, 259–278. (j) Angew. Chem., Int. Ed. 1979, 18,
239–258. (k) Reiser, O. Chem. Rev. 2003, 103, 1603–1624.
2. Danishefsky, S. Acc. Chem. Res. 1979, 12, 66–72.
4.4.34. 2-{2-[3-(4-Chlorobenzylidene)-2-phenyltetra-
hydrofuran-2-yloxy]ethyl}-3-(3-chlorophenyl)-1-phenyl-
propenone (5a). This compound was obtained as a red oil.
IR (CH2Cl2): n 1013, 1056, 1091, 1158, 1210, 1264, 1313,
1372, 1405, 1432, 1447, 1490, 1578, 1594, 1651, 1734,
1
1903, 1963, 2886, 2928, 3058 cmK1; H NMR (300 MHz,
CDCl3, TMS): d 2.85–2.90 (m, 2H, CH2), 3.00–3.11 (m, 2H,
CH2), 3.52–3.59 (m, 1H, CH2), 3.69–3.77 (m, 1H, CH2),
4.03–4.11 (m, 1H, CH2), 4.23–4.30 (m, 1H, CH2), 6.14 (s,
1H, CH), 7.04 (s, 1H, CH), 7.08 (d, JZ8.7 Hz, 2H, Ar), 7.23
(d, JZ8.7 Hz, 2H, Ar), 7.31–7.50 (m, 11H, Ar, CH), 7.55
(d, JZ6.9 Hz, 2H, Ar), 7.78 (d, JZ6.9 Hz, 2H, Ar); 13C
NMR (75 MHz, CDCl3, TMS): d 28.6, 30.1, 60.6, 66.1,
108.8, 124.1, 126.4, 128.1, 128.3, 128.3, 128.6, 128.8,
129.7, 129.7, 130.7, 132.0, 132.6, 133.8, 134.4, 136.3,
136.1, 139.3, 139.9, 140.9, 143.6, 198.5; MS (EI) m/z: 287
(2), 285 [(M-269)C, 6], 271 (21), 269 (60), 256 (4), 115
(10), 105 (100), 77 (47); Anal. Calcd. for C34H28Cl2O3: C,
73.51, H, 5.08%; Found: C, 73.52, H, 5.15%.
3. (a) Han, Z.; Uehira, S.; Tsuritani, T.; Shinokubo, H.; Oshima, K.
Tetrahedron 2001, 57, 987–995. (b) Yadav, V. K.;
Balamurugan, R. Org. Lett. 2003, 5, 4281–4284. (c) Bertozzi,
F.; Gustafsson, M.; Olsson, R. Org. Lett. 2002, 4, 3147–3150.
(d) Bertozzi, F.; Gustafsson, M.; Olsson, R. Org. Lett. 2002, 4,
4333–4336. (e) Ichiyanagi, T.; Kuniyama, S.; Shimizu, M.;
Fujisawa, T. Chem. Lett. 1997, 1149–1150. (f) Enholm, E. J.;
Jia, Z. J. J. Org. Chem. 1997, 62, 5248–5249. (g) Enholm, E. J.;
Jia, Z. J. J. Org. Chem. 1997, 62, 9159–9164. (h) Bertozzi, F.;
Gundersen, B. V.; Gustafsson, M.; Olsson, R. Org. Lett. 2003, 5,
1551–1554.
4. (a) Oppolzer, W. In Trost, B. M., Fleming, I., Eds.; Comprehen-
sive organic synthesis; Pergamon: New York, 1991; Vol. 5,
pp 315–399. (b) Stetter, H.; Kuhlman, H.; Haese, W. Org. Synth.
1987, 65, 26. (c) Sundararajan, G.; Pragbaran, N. Org. Lett. 2001,
3, 389–392. (d) Li, G.; Gao, J.; Wei, H.-X.; Enright, M. Org. Lett.
2000, 2, 617–620. (e) Berkessel, A.; Gasch, N.; Glaubitz, K.;
Koch, C. Org. Lett. 2001, 3, 3839–3842. (f) Tai, C.-L.; Ly,
T.W.J.-D.; Shia, K.-S.; Liu, H.-J. Synlett 2001, 214–217.
5. (a) Dimmock, J. R.; Kandepu, N. M.; Hetherington, M.; Quail,
J. W.; Pugazhenthi, U.; Sudom, A. M.; Chamankhah, M.; Rose,
P.; Allen, T. M.; Halleran, S.; Clerq, E. D.; Balzarini, J. J. Med.
Chem. 1998, 41, 1014–1026. (b) Ei-Subbagh, H. I.; Abu-Zaid,
S. M.; Mahran, M. A.; Badria, F. A.; Al-Obaid, A. M. J. Med.
Chem. 2000, 43, 2915–2921.
4.4.35. Phenyl-carbamic acid 3-benzoyl-4-(4-methoxy-
phenyl)-but-3-enyl ester (6). Only the mixture of 6-Z and
6-E was obtained as a red oil, yield: 100 mg, 50%.; 1H NMR
of 6-E (300 MHz, CDCl3, TMS): d 3.20 (t, JZ6.9 Hz, 2H,
CH2), 3.81 (s, 3H, OCH3), 4.30 (t, JZ6.0 Hz, 2H, CH2),
6.57 (s, 1H, NH), 6.92 (d, JZ9.0 Hz, 2H, Ar), 7.04 (t, JZ
7.2 Hz, 2H, Ar), 7.23 (s, 1H, CH), 7.25–7.33 (m, 4H, Ar),
7.41–7.46 (m, 4H, Ar), 7.51–7.53 (m, 1H, Ar), 7.73 (d, JZ
9.0 Hz, 2H, Ar); MS (EI) m/z: 296 [(M-105)C, 1], 264 (89),
249 (5), 233 (20), 221 (6), 205 (9), 159 (27), 105 (100), 77
(62); HRMS (EI) Calcd. for C25H23NO4: 401.1627, Found:
401.1650.
5. Supporting information
6. (a) Powers, D. G.; Casebier, D. S.; Fokss, D.; Ryan, W. J.;
Troth, J. R.; Coffen, D. L. Tetrahedron 1998, 54, 4085–4096.
(b) Fokss, D.; Ryan, W. J.; Casebier, D. S.; Coffen, D. L.
Tetrahedron Lett. 1998, 39, 2235–2238. (c) Marzinzik, A. L.;
Felder, E. R. J. Org. Chem. 1998, 63, 723–727. (d) Gordeev,
M. F.; Patel, D. V.; Wu, J.; Gordon, E. M. Tetrahedron Lett.
1996, 37, 4643–4646. (e) Micheli, F.; Degiorgis, F.; Feriani, A.;
Paio, A.; Pozzan, A.; Zarantonello, P.; Seneci, P. J. Comb.
Chem. 2001, 3, 224–228. (f) Grosche, P.; Holtzel, A.; Walk,
T. B.; Trautwein, A. W.; Jung, G. Synthesis 1999, 1961–1970.
(g) Katritzky, A. R.; Denisko, O. V. J. Org. Chem. 2002, 67,
3104–3108. (h) Bauer, U.; Egner, B. J.; Nilsson, I.; Berghult, M.
Tetrahedron Lett. 2004, 41, 2713–2717.
1
The Noesy spectrum of 3a-Z and the H and 13C NMR
spectra of 5a are included in Supporting information. This
material is available free of charge via the Internet website.
Acknowledgements
We thank the State Key Project of Basic Research (Project
973) (No. G2000048007), Shanghai Municipal Committee
of Science and Technology, Chinese Academy of Sciences
(KGCX2-210-01), and the National Natural Science
Foundation of China for financial support (20025206,
203900502, and 20272069).
7. In all of the cases shown in Table 2, none of the cyclized product
4 was detected.