Unexpected catalyst for Wittig-type and dehalogenation reactions

Article abstract of DOI:10.1021/jo025693b

A novel catalyst 2 for Wittig-type and dehalogenation reactions was developed. In the presence of triphenyl phosphite, a wide variety of aldehydes could react with α-bromoacetates to afford α,β-unsaturated esters or ketones in high yields with excellent E-stereoselectivity when 1-2 mol % of compound 2 was used. Compound 2 was also an effective catalyst for reductive dehalogenation of α-bromocarbonyl compounds. The mechanisms for the above reactions were also proposed.

Full text of DOI:10.1021/jo025693b

Un exp ected Ca ta lyst for Wittig-Typ e a n d Deh a logen a tion
Rea ction s
Zheng-Zheng Huang and Yong Tang*
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry,
354 Fenglin Lu, Shanghai 200032, China
tangy@pub.sioc.ac.cn
Received March 8, 2002
A novel catalyst 2 for Wittig-type and dehalogenation reactions was developed. In the presence of
triphenyl phosphite, a wide variety of aldehydes could react with R-bromoacetates to afford R,â-
unsaturated esters or ketones in high yields with excellent E-stereoselectivity when 1-2 mol % of
compound 2 was used. Compound 2 was also an effective catalyst for reductive dehalogenation of
R-bromocarbonyl compounds. The mechanisms for the above reactions were also proposed.
In tr od u ction
compound 25,6 was obtained (Scheme 1). Thus, we as-
sumed initially that compound 2 was an inactive species
and its formation would lead to the loss of activity of
dibutyl telluride in the catalytic cycle. This assumption
could also explain the deactivation of the recovered PEG-
telluride.6 To verify this assumption, we tried a catalytic
reaction of 4-chlorobenzaldehyde with bromoacetate us-
ing compound 2 instead of Bu2Te. Unexpectedly, the
reaction proceeded well and afforded the desired product
in 31% yield (eq 1). Further studies showed that the
odorless compound 2 was also an excellent catalyst for
the Wittig-type reaction. In this paper, we report Wittig-
type olefination and dehalogenation reactions catalyzed
by compound 2.
Much attention has been paid to the development of
catalytic reactions in the past decades. Although the
Wittig reaction and its variants have been extensively
studied and are used as one of the most important
synthetic methods for construction of carbon-carbon
double bonds,1 research on the catalytic olefination
processes is still in its infancy. In the literature, Huang
et al. reported the first example of a catalytic Wittig-type
reaction by use of 20 mol % tributylarsine or dibutyl
telluride in 1989.2 To the best of our knowledge, no more
reports appeared until last year. In our continuing
studies on ylides in organic synthesis,3 we found that
PEG-telluride4 is a better catalyst for Witttig-type reac-
tions than nBu2Te or nBu3As and the catalyst loading
could be reduced to 2 mol %. To investigate the mecha-
nism of the aforementioned reaction, the telluronium salt
1 was synthesized. Surprisingly, salt 1 decomposed
quickly in the presence of water and a stable, odorless
(1) (a) Hoffmann, R. W. Angew. Chem., Int. Ed. 2001, 40 (8), 1411.
(b) Maryanoff, B. E.; Reitz, A. B. Chem. Rev. 1989, 89, 863. (c) Nicolaou,
K. C.; Ha¨rter, M. W.; Gunzner, J . L.; Nadin, A. Liebigs Ann./ Recueil
1997, 1283 and references therein. (d). Kolodiazhnyi, O. I. Phosphorus
Ylides: Chemistry and Application in Organic Synthesis; Wiley-VCH:
New York, 1999. (e) Forsyth, C. J .; Ahmed, F.; Cink, R. D.; Lee, C. S.
J . Am. Chem. Soc. 1998, 120, 5597. (f) Smith, A. B., III; Beauchamp,
T. J .; LaMarche, M. J .; Kaufman, M. D.; Qiu, Y.; Arimoto, H.; J ones,
D. R.; Kobayshi, K. J . Am. Chem. Soc. 2000, 122, 8654. (g) White, J .
D.; Carter, R. G.; Sundermann, K. F.; Wartmann, M. J . Am. Chem.
Soc. 2001, 123, 5407.
Resu lts a n d Discu ssion
Ca ta lytic Wittig-Typ e Rea ction . After the observa-
tion that compound 2 could catalyze a Wittig-type reac-
tion, we optimized the reaction conditions to improve its
catalytic efficiency. It was found that when P(OPh)3 was
used as the reducing reagent instead of NaHSO3, the
olefination reaction of p-chlorobenzaldehyde afforded the
corresponding product in excellent yield in the presence
of 1 mol % compound 2 (entry 4, Table 1).
(2) (a) Shi, L.; Wang, W.; Wang, Y.; Huang, Y.-Z. J . Org. Chem. 1989,
54, 2028. (b). Li, S.-W. Ph.D. Thesis, Shanghai Institute of Organic
Chemistry, 1990.
(3) (a) Huang, Y.-Z.; Tang, Y.; Zhou, Z.-L.; Huang, J .-L. J . Chem.
Soc., Chem. Commun. 1993, 7. (b) Huang, Y.-Z.; Tang, Y.; Zhou, Z.-L.;
Xia, W.; Shi, L.-P. J . Chem. Soc., Perkin Trans. 1 1994, 893. (c) Tang,
Y.; Huang, Y.-Z.; Dai, L.-X.; Chi, Z.-F.; Shi, L.-P. J . Org. Chem. 1996,
61, 5762. (d) Tang, Y.; Huang, Y.-Z.; Dai, L.-X.; Sun, J .; Xia, W. J .
Org. Chem. 1997, 62, 954. (e) Tang, Y.; Chi, Z.-F.; Huang, Y.-Z.; Dai,
L.-X.; Yu, Y.-H. Tetrahedron 1996, 52, 8747. (f) Huang, Y.-Z.; Tang,
Y.; Zhou, Z.-L. Tetrahedron 1998, 54, 1667. (g) Ye, S.; Yuan, L.; Huang,
Z.-Z.; Tang, Y.; Dai, L.-X. J . Org. Chem. 2000, 65, 6257. (h) Ye, S.;
Tang, Y.; Dai, L.-X. J . Org. Chem. 2001, 66, 5717.
(5) (a) This compound may be toxic. (b) Zhou, Z.-L.; Shi, L.-L.;
Huang, Y.-Z. Synth. Commun. 1991, 21, 1027.
(6) Huang, Z.-Z.; Ye, S.; Xia, W.; Yu, Y.-H.; Tang, Y. J . Org. Chem.
2002, 67, 3096.
(4) Huang, Z.-Z.; Ye, S.; Xia, W.; Tang, Y. Chem. Commun. 2001,
1384.
10.1021/jo025693b CCC: $22.00 © 2002 American Chemical Society
Published on Web 07/02/2002
5320
J . Org. Chem. 2002, 67, 5320-5326

Wittig-Type and Dehalogenation Reactions
SCHEME 1
TABLE 1. Da ta for Wittig-Typ e Rea ction s Ca ta lyzed by Com p ou n d 2a
a
Reaction conditions: aldehyde (0.50 mmol); bromide (0.70 mmol); P(OPh)3 (0.90 mmol); K2CO3 (0.65 mmol); compound 2 (0.01 mmol);
toluene (2 mL). Isolated yield. c 69% of p-chlorobenzaldehyde can be recovered.
b
To determine the generality, a variety of structurally
different aldehydes and bromides were employed in this
reaction (Table 1). It was found that both aliphatic and
aromatic aldehydes worked well with high stereoselec-
tivity in good to excellent yields. As shown in Table 1,
various aromatic aldehydes (entries 1-7, 14), as well as
a heteroaromatic aldehyde (entry 8, Table 1), gave
excellent yields with nearly exclusive E-stereoselectivity,
which was comparable to typical Wittig reactions of
stablized ylides. Aliphatic aldehydes, such as cyclo-
J . Org. Chem, Vol. 67, No. 15, 2002 5321

Huang and Tang
SCHEME 2
hexanecarboxaldehyde and decyl aldehyde (entries 9, 10)
also participated in this reaction to give the correspond-
ing olefins in good yields. trans-Cinnamic aldehyde (entry
11) could be highly stereoselectively converted to the
corresponding diene ester in high yield. Other bromides,
such as tert-butyl bromoacetate and ω-bromoaceto-
phenone (entries 12, 13), were also investigated in this
reaction condition. Both of them reacted readily with
p-chlorobenzaldehyde to afford the corresponding prod-
ucts in excellent yields. A controlled experiment showed
that no Wittig-type olefination product was formed in the
absence of catalyst 2 (entry 15). It is worth noting that
base was necessary for this reaction. In the absence of
K2CO3, aldehyde was recovered quantitatively (eq 2).
SCHEME 3
Mech a n ism . To understand the catalytic process in
detail, we first examined the reaction in the absence of
aldehyde and bromide. It was found that compound 2
could be converted readily into Bu2Te when a mixture of
compound 2 (0.1 mmol), P(OPh)3 (0.2 mmol), and K2CO3
(0.5 mmol) in toluene was heated in an 80 °C oil bath
(Scheme 2, eq 3). Additionally, we found that telluronium
salt 1 could react directly with aldehyde to afford the
R,â-unsaturated ketone, as described by Huang et al.7
In this reaction, compound 2 was also isolated (Scheme
2, eq 4).
SCHEME 4
According to the above observations, together with the
mechanism suggested by Huang,2 two mechanisms shown
in Scheme 3 are probably operative in this reaction. In
mechanism I, compound 2 was first reduced to dibutyl
telluride (8), which reacted with bromide to form tellu-
ronium salt 1. Salt 1 reacted directly with aldehyde to
afford the desired olefin 5 and recycled compound 2 to
complete the catalytic cycle. Another path maybe proceed
via an ylide route. Reaction of dibutyl telluride with
bromoacetate yielded salt 1. Salt 1, followed by depro-
tonation, reacted with aldehyde to afford compound 5 and
tellurium oxide 7. Compound 7 was readily reduced by
P(OPh)3 to regenerate dibutyl telluride (Scheme 3).
Ca ta lytic Deh a logen a tion . During our preparation
of compound 2 by hydrolysis of telluronium salt 1,
acetophenone was detected (Scheme 1). On the basis of
this finding, together with the above-described catalytic
process, we designed the catalytic cycle in Scheme 4 and
found that the dehalogenation reaction catalyzed by
compound 2 worked well.8
reaction was base-dependent (entries 1-5, Table 2). And
NaHCO3 was the most appropriate one. Although THF,
acetone, CH3CN, and H2O could be used as the reaction
solvents (entries 8-13), the best one was a mixture of
DMF and water. Without compound 2, the dehalogena-
tion reaction was exceedingly slow (entry 22, Table 2).
After optimization of the reaction conditions (entries 6-7,
14-21), the most efficient one was the use of P(OPh)3 as
the reducing agent, a mixture of DMF and H2O (6/0.5,
v/v) as the solvent, and 1 mol % of compound 2 as the
catalyst.
In the presence of 1 mol % compound 2, when NaHSO3
was used as the reducing agent, the dehalogenation
(7) Huang, X.; Xie, L.; Wu, H. Tetrahedron Lett. 1987, 28, 801.
(8) For selected references for reductive dehalogenation of R-bromo-
carbonyl compounds, see: (a) Barrero, A. F.; Alvarez-Manzaneda, E.
J .; Chahboun, R.; Meneses, R.; Romera, J . L. Synlett 2001, 485. (b)
Park, L.; Keum, G.; Kang, S. B.; Kim, K. S.; Kim, Y. J . Chem. Soc.,
Perkin Trans. 1 2000, 4462. (c) Ranu, B. C.; Dutta, P.; Sarkar, A. J .
Chem. Soc., Perkin Trans. 1 1999, 1139. (d) Han, Y.; Huang, Y.-Z.
Tetrahedron Lett. 1998, 7751. (e) Zhang, J .; Saito, S.; Takahashi, T.;
Koizumi, T. Heterocycles 1997, 45, 575. (f) Schultz, E. K. V.; Harpp,
D. N. Synthesis 1998, 1137. (g) Chatgilialoglu, C.; Guerra, M.; Guerrini,
A.; Seconi, G.; Clark, K. B.; Griller, D.; Kanabus-Kaminska, J .;
Martinho-Simo˜es, J . A. J . Org. Chem. 1992, 57, 2427.
As shown in Table 3, this catalytic system was proved
to be highly efficient for dehalogenation of R-bromo-
carbonyl compounds. A variety of 2-bromo-substituted
phenylethanones were readily reduced in high to excel-
lent yields (entries 1-5, 11, Table 3). It is worth noting
that not only R-bromo ketones but also R-chloro ketones
worked well (entry 10, Table 3). gem-R-Dibromides and
di-tert-butyl 2-bromomalonate also provided the desired
5322 J . Org. Chem., Vol. 67, No. 15, 2002

Wittig-Type and Dehalogenation Reactions
TABLE 2. Effects of Rea ction Con d ition s on Deh a logen a tion
entry
reducing agent
catal (mol %)
solvent (v/v)
temp (°C)
base
yielda (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
NaHSO3
NaHSO3
NaHSO3
NaHSO3
NaHSO3
NaHSO3
NaHSO3
NaHSO3
NaHSO3
NaHSO3
NaHSO3
NaHSO3
NaHSO3
P(OPh)3
P(OPh)3
P(OPh)3
P(OPh)3
P(OPh)3
P(OPh)3
P(OPh)3
P(OPh)3
P(OPh)3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
THF/H2O (2/0.04)
THF/H2O (2/0.04)
THF/H2O (2/0.04)
THF/H2O (2/0.04)
THF/H2O (2/0.04)
THF/H2O (2/0.04)
THF/H2O (2/0.04)
CH3CN/H2O (2/0.04)
DMF/H2O (2/0.04)
acetone/H2O (2/0.04)
acetone/H2O (2/0.04)
DMF/H2O (1/1)
H2O
DMF/H2O (1/1)
H2O/DMF (2/2)
H2O/DMF(4/4)
H2O/DMF (6/6)
H2O/DMF (6/0.5)
H2O
80
80
80
80
80
50
23
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
K2CO3
KHCO3
Na2CO3
22
23
11
44
5
NaHCO3
LiOH‚H2O
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
10
4
15
36
14
15
55
29
77
82
88
99
99
75
58
13
<5
1
1
1
0.5
0.1
0
H2O/DMF (6/0.5)
H2O/DMF (6/0.5)
H2O/DMF (6/0.5)
a
GC yield.
J ) 7.2 Hz, 2H), 7.65 (t, J ) 7.4 Hz, 1H), 7.52 (t, J ) 7.7 Hz,
2H), 4.48 (s, 2H), 3.22-3.07 (m, 4H), 1.89-1.79 (m, 4H), 1.47-
1.35 (m, 4H), 0.92 (t, J ) 7.3 Hz, 6H). 13C NMR (75 MHz,
CDCl3): 194.9, 135.1, 134.1, 128.9, 128.7, 34.2, 27.7, 27.6, 24.4,
13.1 ppm. 125Te NMR (CDCl3/Me2Te): δ 551.191. MS (ESI):
m/z 363.1 [(Bu2)Te+CH2(CO)Ph (130Te)], 361.1 [(Bu2)Te+CH2-
(CO)Ph (128Te)], 359.1 [(Bu2)Te+CH2(CO)Ph (126Te)]. IR (KBr):
products in high yields (entries 7-9, 12, Table 1).
However, 2-bromocamphor failed (entry 6), most probable
owing to the steric hindrance that retarded the formation
of telluronium salt.
Con clu sion
ν ) 2962, 1662, 742, 690, 588 cm-1. Anal. Calcd for C16H25
-
A novel catalyst for Wittig-type and dehalogenation
reactions was developed. Compared to the other catalysts
previously reported, this catalyst showed its advantages
in its stability, lack of odor, and high catalytic efficiency.
The catalytic Wittig-type reaction shown here had a wide
scope of suitable substrates. Most of them gave the
corresponding Wittig-type products in excellent yields
and high E-stereoselectivity. The catalytic dehalogena-
tion reaction presents a mild reducing process with high
catalytic efficiency. This method represents a method for
the selective cleavage of C-X bond in the presence of
other functional groups.
BrOTe: C, 43.59; H, 5.72; Br, 18.12. Found: C, 43.38; H, 5.57;
Br, 17.50.
A mixture of compound 1 (0.2433 g, 1.0 mmol) and water
(0.02 mL) in CH2Cl2/ THF (0.5 mL/0.5 mL) was stirred at room
temperature overnight. The yield of acetophenone was deter-
mined by GC (mesitylene as internal standard). Yield: 100%.
The reaction mixture was filtered, and the filtrate was
concentrated. The residue was washed with ether to give the
compound 25,6 as white crystals. Yield: 307.8 mg (94%). Mp:
136-138 °C. 1H NMR (300 MHz, CDCl3/TMS): δ 3.48 (br, 4H),
3.10 (br, 4H), 2.10-1.92 (m, 8H), 1.58-1.47 (m, 8H), 1.00 (t, J
) 7.3 Hz, 12H). 13C NMR (75 MHz, CDCl3): 43.3, 27.2, 24.5,
13.6 ppm. MS (ESI): m/z 261.1 [(Bu2)Te+(OH) (130Te)], 259.1
[(Bu2)Te+(OH)
( (
128Te)], 257.1 [(Bu2)Te+(OH) 126Te)]. IR
(KBr): ν ) 2961, 1464, 632, 439 cm-1. Anal. Calcd for C16H36
-
Exp er im en ta l Section
Br2OTe2: C, 29.14; H, 5.50; Br, 24.23. Found: C, 29.21; H,
5.75; Br, 24.27.
All reaction flasks and equipment for catalytic Wittig type
reactions were dried for several hours prior to use, and all
reactions were carried out under nitrogen. Aldehydes, bro-
mides, and P(OPh)3, as well as the solvents, were purified
according to the standard method before use.
(A) Typ ica l P r oced u r e for Ca ta lytic Wittig-Typ e Rea c-
tion s. A mixture of catalyst 2 (6.6 mg, 0.01 mmol), bromide
(0.30 mmol), and P(OPh)3 (0.23 mL, 0.88 mmol) in toluene (1.5
mL) was stirred at 80 °C for 5 min, and then K2CO3 (89.8 mg,
0.65 mmol) was added. The resulting suspension was stirred
for 1 min, followed by addition of a mixture of aldehyde (0.5
mmol) and bromide (0.40 mmol) in toluene (0.5 mL) in portions
within 3.5 h. After the reaction was completed (monitored by
P r ep a r a tion of Com p ou n d 2. A mixture of n-butyl
telluride (454.8 mg, 1.88 mmol) and ω-bromoacetophenone
(431.0 mg, 2.16 mmol) was stirred at room temperature for 5
h. The resulting white solid was collected and washed with
ether to afford the white powder 1.7,14 Yield: 823.0 mg (99%).
1
(11) (a). Hollowood, J .; J ansen, A. B. A.; Southgate, P. J . J . Med.
Chem. 1967, 10, 863. (b). Rich, D. H.; Dhaon, M. K. Tetrahedron. Lett.
1983, 1671.
Mp: 93 °C (dec). H NMR (300 MHz, CDCl3/TMS): δ 8.21 (d,
(9) Ogata, M.; Matsumoto, H.; Kida, S.; Shimizu, S.; Tawara, K.;
Kawamura, Y. J . Med. Chem. 1987, 30, 1497.
(10) Uemura, S.; Fukuzawa, S. J . Chem. Soc., Perkin, Trans. 1 1986,
1983.
(12) Aston, J . G.; Newkirk, J . D.; Dorsky, J .; J enkins, D. M. J . Am.
Chem. Soc. 1942, 64, 1413.
(13) Philip, K.; Bosco, D.; J ohn, V. Tetrahedron 2001, 57, 8047.
(14) Huang, X.; Xie, L.; Wu, H. J . Org. Chem. 1988, 53, 4862.
J . Org. Chem, Vol. 67, No. 15, 2002 5323

Huang and Tang
TABLE 3. Deh a logen a tion Rea ction s Ca ta lyzed by Com p ou n d 2
a
b
Isolated yield. GC yields are given in parentheses. The bromide can be recovered quantitatively.
TLC), the mixture was filtered rapidly through a glass funnel
with a thin layer of silica gel (ethyl acetate as the elution).
The filtrate was concentrated, and the residue was purified
by flash column chromatography to afford the desired product.
MHz, CDCl3/TMS) δ 7.70 (d, J ) 15.9 Hz, 1H), 7.55-7.52 (m,
2H), 7.40-7.38 (m, 3H), 6.45 (d, J ) 15.9 Hz, 1H), 4.27 (q, J
) 7.1 Hz, 2H), 1.35 (t, J ) 7.1 Hz, 3H).
E t h yl (E)-3-(4-m et h ylp h en yl)p r op -2-en oa t e2a (R 1
)
Eth yl (E)-3-p h en ylp r op -2-en oa te2a (R1 ) C6H5, R2
)
p-CH3C6H4, R2 ) OEt, 5b): yield 94.0 mg (99%); E/Z > 99:1;
OEt, 5a ): yield 88.9 mg (100%); E/Z > 99:1; 1H NMR (300
5324 J . Org. Chem., Vol. 67, No. 15, 2002
1H NMR (300 MHz, CDCl3/TMS) δ 7.59 (d, J ) 15.9 Hz, 1H),

Wittig-Type and Dehalogenation Reactions
7.41 (d, J ) 7.9 Hz, 2H), 7.18 (d, J ) 7.9 Hz, 2H), 6.32 (d, J )
15.9 Hz, 1H), 3.50 (q, J ) 7.0 Hz, 2H), 2.37 (s, 3H), 1.33 (t, J
) 7.0 Hz, 3H).
99:1; 1H NMR (300 MHz, CDCl3/TMS) δ 7.99 (d, J ) 15.9 Hz,
1H), 7.51 (dd, J ) 8.0, 1.7 Hz, 1H), 7.35 (td, J ) 7.8, 1.8 Hz,
1H), 6.99-6.90 (m, 2H), 6.52 (d, J ) 16.2 Hz, 1H), 4.26 (q, J
) 7.1 Hz, 2H), 3.89 (s, 3H), 1.34 (t, J ) 7.2 Hz, 3H).
(B) Typ ica l P r oced u r e for Deh a logen a tion Rea ction s.
To a mixture of catalyst 2 (6.6 mg, 0.01 mol) and bromide (1.0
mmol) in DMF/H2O (0.5 mL/6.0 mL) was added P(OPh)3 (0.36
mL, 1.4 mmol). The mixture was stirred at 80 °C for 5 min,
and then NaHCO3 (0.1680 g, 2.0 mmol) was added. The
resulting suspension was stirred for 1 h. After the reaction
was completed it was analyzed with GC (mesitylene as the
internal standard) or the mixture was filtered rapidly through
a glass funnel with a thin layer of silica gel (ethyl acetate for
elution). The filtrate was concentrated, and the residue was
purified by flash column chromatography to afford the desired
product.
E t h yl (E)-3-(4-m et h oxyp h en yl)p r op -2-en oa t e4 (R 1
)
p-CH3OC6H4, R2 ) OEt, 5c): yield 97.6 mg (94%); E/Z > 99:
1; 1H NMR (300 MHz, CDCl3/TMS) δ 7.64 (d, J ) 16.0 Hz,
1H), 7.47 (d, J ) 6.8 Hz, 2H), 6.90 (d, J ) 6.8 Hz, 2H), 6.31 (d,
J ) 16.0 Hz, 1H), 4.25 (q, J ) 7.2 Hz, 2H), 3.83 (s, 3H), 1.33
(t, J ) 7.2 Hz, 3H).
E t h yl (E)-3-(4-Ch lor op h en yl)p r op -2-en oa t e2a (R 1
)
p-ClC6H4, R2 ) OEt, 5d ). A 1 mol % amount of the catalyst
was used. Yield: 95.9 mg (91%). E/Z > 99:1. 1H NMR (300
MHz, CDCl3/TMS): δ 7.64 (d, J ) 16.0 Hz, 1H), 7.46 (d, J )
6.7 Hz, 2H) 7.36 (dd, J ) 6.7 Hz, 2H), 6.41 (d, J ) 16.1 Hz,
1H), 4.27 (q, J ) 7.1 Hz, 2H), 1.34 (t, J ) 7.1 Hz, 3H).
E t h yl (E)-3-(3-ch lor op h en yl)p r op -2-en oa t e13 (R 1
)
Deh a logen a tion of 2-br om o-1-p h en yleth a n on e: GC
yield 99%.
m -ClC6H4, R2 ) OEt, 5e): yield 104.1 mg (99%); E/Z > 99:1;
1H NMR (300 MHz, CDCl3/TMS) δ 7.61 (d, J ) 16.5 Hz, 1H),
7.51 (s, 1H), 7.40-7.06 (m, 3H), 6.43 (d, J ) 15.9 Hz, 1H),
4.27 (q, J ) 7.1 Hz, 2H), 1.34 (t, J ) 7.3 Hz, 3H).
Deh a logen a tion of 2-Br om o-1-(4-m eth ylp h en yl)eth a -
n on e. The 2-bromo-1-(4-methylphenyl)ethanone substrate was
synthesized (94% yield) according to the literature.9 1H NMR
(300 MHz, CDCl3/TMS): δ 7.88 (d, J ) 8.4 Hz, 2H), 7.31 (d, J
) 8.4 Hz, 2H), 4.43 (s, 2H), 2.42 (s, 3H).
E t h yl (E)-3-(2-ch lor op h en yl)p r op -2-en oa t e2a (R 1
)
o-ClC6H4, R2 ) OEt, 5f): yield 103.0 mg (98%); E/Z > 99:1;
1H NMR (300 MHz, CDCl3/TMS) δ 8.09 (d, J ) 15.9 Hz, 1H),
7.63-7.60 (m, 1H), 7.43-7.31 (m, 1H), 7.31-7.26(m, 2H), 6.43
(d, J ) 15.9 Hz, 1H), 4.28 (q, J ) 7.1 Hz, 2H), 1.35 (t, J ) 7.0
Hz, 3H).
Deh a logen a tion : yield 111.0 mg (83%). 1H NMR for
4-methylphenylethanone (300 MHz, CDCl3/TMS): δ 7.86 (d,
J ) 8.4 Hz, 2H), 7.26 (d, J ) 7.8 Hz, 2H), 2.58 (s, 3H), 2.41 (s,
3H).
Eth yl (E)-3-(4-tr iflu or om eth ylp h en yl)p r op -2-en oa te4
(R1 ) p-CF 3C6H4, R2 ) OEt, 5g): yield 118.5 mg (97%); E/Z
Deh a logen a tion of 2-Br om o-1-(4-m eth oxyp h en yl)eth a -
n on e. The 2-bromo-1-(4-methoxyphenyl)ethanone substrate
was synthesized (80% yield) according to the literature.9 1H
NMR (300 MHz, CDCl3/TMS): δ 7.98 (d, J ) 8.7 Hz, 2H), 6.97
(d, J ) 8.4 Hz, 2H), 4.41 (s, 2H), 3.89 (s, 3H).
1
> 99:1; H NMR (300 MHz, CDCl3/TMS) δ 7.70 (d, J ) 16.1
Hz, 1H), 7.64 (s, 4H), 6.51 (d, J ) 16.1 Hz, 1H), 4.27 (q, J )
7.1 Hz, 2H), 1.35 (t, J ) 7.1 Hz, 3H).
Eth yl (E)-3-(2-fu r yl)p r op -2-en oa te2a (R1 ) fu r yl, R2
)
Deh a logen a tion : yield 129.4 mg (86%). 1H NMR for
4-methoxyphenylethanone (300 MHz, CDCl3/TMS): δ 7.95 (d,
J ) 8.4 Hz, 2H), 6.94 (d, J ) 7.8 Hz, 2H), 3.88 (s, 3H), 2.56 (s,
3H).
OEt, 5h ): yield 82.9 mg (100%); E/Z > 99:1; 1H NMR (300
MHz, CDCl3/TMS) δ 7.48 (d, J ) 1.4 Hz, 1H), 7.43 (d, J )
15.7 Hz, 1H), 6.60 (d, J ) 3.3 Hz, 1H), 6.47 (dd, J ) 1.7, 3.3
Hz, 1H), 6.32 (d, J ) 15.7 Hz, 1H), 4.25 (q, J ) 7.1 Hz, 2H),
1.32 (t, J ) 7.1 Hz, 3H).
Deh a logen a tion of 2-Br om o-1-(4-ch lor op h en yl)eth a -
n on e. The solvent used was H2O/DMF ) 6 mL/1 mL. Yield of
Eth yl (E)-3-cycloh exylp r op -2-en oa te2a (R1 ) C6H11, R2
) OEt, 5i): reaction scale 1.0 mmol; yield 146.6 mg (80%);
1
dehalogenation: 107.5 mg (70%). H NMR (300 MHz, CDCl3/
1
TMS) for 4-chlorophenylethanone: δ 7.91 (d, J ) 8.4 Hz, 2H),
7.44 (d, J ) 8.7 Hz, 2H), 2.60 (s, 3H).
E/Z > 99:1; H NMR (300 MHz, CDCl3/TMS) δ 6.92 (dd, J )
6.9, 15.8 Hz, 1H), 5.77 (dd, J ) 15.8, 1.0 Hz, 1H), 4.19 (q, J )
7.1 Hz, 2H), 2.20-2.15 (m, 1H), 1.78-1.64 (m, 4H), 1.36-1.12
(m, 9H).
Deh a logen a t ion of 2-Br om o-1-(4-n it r op h en yl)et h a -
n on e. A 2 mol % amount of the catalyst was used. The solvent
1
Eth yl (E)-d od ec-2-en oa te4 (R1 ) CH3(CH2)8, R2 ) OEt,
used was H2O/THF ) 6 mL/1 mL. Yield: 101.0 mg (61%). H
1
NMR (300 MHz, CDCl3/TMS) for 4-nitrophenylethanone: δ
8.33 (d, J ) 9.0 Hz, 2H), 8.12 (d, J ) 9.0 Hz, 2H), 2.69 (s, 3H).
Deh a logen a t ion of Di-ter t-b u t yl 2-Br om om a lon a t e.
The di-tert-butyl 2-bromomalonate substrate was synthesized
(40% yield) according to the literature.11 1H NMR (300 MHz,
CDCl3/TMS): δ 4.67 (s, 1H), 1.50 (s, 18H).
5j): reaction scale 1.0 mmol; yield 182.6 mg (80%); H NMR
(300 MHz, CDCl3/TMS) δ 6.97 (dt, J ) 15.7, 6.9 Hz, 1H), 5.81
(dt, J ) 15.7, 1.4 Hz, 1H), 4.18 (q, J ) 7.1 Hz, 2H), 2.23-2.15
(m, 2H), 1.47-1.27 (m, 17H), 0.88 (t, J ) 6.7 Hz, 3H).
Eth yl (E,E)-5-ph en ylpen t-2, 4-dien oate2a (R1 ) C6H5CHd
CH, R2 ) OEt, 5k ): yield 100.1 mg (98%); E/Z > 96:4; 1H
NMR (300 MHz, CDCl3/TMS) for trans isomer δ 7.49-7.38 (m,
3H), 7.38-7.30 (m, 3H), 6.90-6.87 (m, 2H), 5.99 (d, J ) 15.2
Hz, 1H), 4.23 (q, J ) 7.1 Hz, 2H), 1.32 (t, J ) 7.1 Hz, 3H); 1H
NMR (300 MHz, CDCl3/TMS) for cis isomer δ 8.21-8.11(m,
1H), 7.54-7.46 (m, 2H), 7.38-7.26 (m, 3H), 6.90-6.71 (m, 2H),
5.73 (d, J ) 11.6 Hz, 1H), 4.23 (q, J ) 7.1 Hz, 2H), 1.34 (t, J
) 7.3 Hz, 3H).
Deh a logen a tion . A 5 mol % amount of the catalyst was
used. Yield: 175.0 mg (81%). 1H NMR (300 MHz, CDCl3/
TMS): δ 3.19 (s, 2H), 1.48 (s, 18H).
Deh a logen a tion of 2,2-Dibr om op h en yleth a n on e. The
2,2-dibromophenylethanone substrate was synthesized (43%
yield) according to the literature as a byproduct.12 1H NMR
(300 MHz, CDCl3/TMS): δ 8.10-8.07 (m, 2H), 7.65-7.62 (m,
1H), 7.55-7.52 (m, 2H), 6.72 (s, 1H). 13C NMR (75 MHz,
CDCl3): 185.8, 134.3, 130.6, 129.5, 128.8, 39.7 ppm. IR (film):
ν ) 1694.36, 1592.45, 800.91 cm-1. MS (EI) [m/z (rel intensity)]:
280 (0.23), 278 (0.47), 276 (0.24), 105 (100).
ter t-Bu tyl (E)-3-(4-ch lor op h en yl)p r op -2-en oa te4 (R1
)
p-ClC6H4, R2 ) OBu t, 5l): yield 237.5 mg (93%); E/Z > 99:1;
1H NMR (300 MHz, CDCl3/TMS) δ 7.53 (d, J ) 15.9 Hz, 1H),
7.44 (d, J ) 7.0 Hz, 2H), 7.34 (d, J ) 7.0 Hz, 2H), 6.34 (d, J )
15.8 Hz, 1H), 1.53 (s, 9H).
Deh a logen a tion : GC yield 90%.
(E)-3-(4-Ch lor op h en yl)-1-p h en ylp r op -2-en on e2a (R 1)
p-ClC6H4, R2 ) P h , 5m ): yield: 116.2 mg (95%); E/Z > 89:
Deh a logen a tion of 2,2-Dibr om o-1-(4-m eth oxyp h en yl)-
eth an on e. The 2,2-dibromo-1-(4-methoxyphenyl)ethanone sub-
strate was synthesized (13% yield) according to the literature
as a byproduct.9 1H NMR (300 MHz, CDCl3/TMS): δ 8.09 (d,
J ) 9.3 Hz, 2H), 6.98 (d, J ) 9.3 Hz, 2H), 6.67 (s, 1H), 3.90 (s,
3H). 13C NMR (75 MHz, CDCl3): 184.6, 164.5, 132.1, 123.2,
114.2, 55.7, 40.1 ppm. IR (film): ν ) 1677.74, 1600.78, 845.56,
809.69 cm-1. MS (EI) [m/z (rel intensity)]: 310 (1.86), 308
(3.63), 306 (1.97) 135 (100).
1
11; H NMR (300 MHz, CDCl3/TMS) for trans isomer δ 8.02
(d, J ) 8.5 Hz, 2H), 7.69 (d, J ) 15.7 Hz, 1H), 7.59-7.48 (m,
6H), 7.39 (d, J ) 8.4 Hz, 2H); 1H NMR (300 MHz, CDCl3/TMS)
for cis isomer δ 7.98-7.94 (m, 2H), 7.55-7.52 (m, 2H), 7.45-
7.36 (m, 3H); 7.26-7.21 (m, 2H); 6.95 (d, J ) 12.8 Hz, 1H),
6.68 (d, J ) 12.9 Hz, 1H).
E t h yl (E)-3-(2-m et h oxyp h en yl)p r op -2-en oa t e13 (R 1
o-CH3OC6H4, R2 ) OEt, 5n ): yield 199.2 mg (97%); E/Z >
)
Deh a logen a tion : yield 134.5 mg (90%).
J . Org. Chem, Vol. 67, No. 15, 2002 5325

Huang and Tang
Deh a logen a tion of 2-Ch lor o-1-(4-m eth oxyp h en yl)eth a -
n on e. This reaction was carried out in H2O/DMF ) 6 mL/1
mL for 5 h by using 5 mol % catalyst. Yield: 133.7 mg (89%).
Deh a logen a tion of 2-Br om o-1-p h en ylp r op a n on e. The
2-bromo-1-phenylpropanone substrate was synthesized (1.5
equiv of bromine, glacial acetic acid, 55% yield) according to
the literature.10 1H NMR (300 MHz, CDCl3/TMS): δ 8.04 (d,
J ) 6.9 Hz, 2H), 7.61 (t, J ) 7.4 Hz, 1H), 7.52-7.47 (m, 2H),
5.31 (q, J ) 6.7 Hz, 1H), 1.91 (t, J ) 6.6 Hz, 3H).
(d, J ) 7.5 Hz, 2H), 7.59 (t, J ) 7.4 Hz, 1H), 7.50-7.45 (m,
2H), 2.76 (s, 3H). 13C NMR (75 MHz, CDCl3): 188.1, 133.4,
131.5, 131.2, 127.8, 57.8, 37.6 ppm. IR (film): ν ) 1679.79,
1593.76, 804.79 cm-1. MS (EI) [m/z (rel intensity)]: 294 (0.36),
292 (0.69), 290 (0.37), 105 (100).
Deh a logen a tion : yield 115.6 mg (86%). A 5 mol % amount
of the catalyst was used.
Deh a logen a tion : yield 115.6 mg (86%); 1H NMR (300 MHz,
CDCl3/TMS) δ 7.99-7.96 (m, 2H), 7.59-7.54 (m, 1H), 7.50-
7.44 (m, 2H), 3.02 (q, J ) 7.2 Hz, 2H), 1.24 (t, J ) 7.2 Hz,
3H).
Ack n ow led gm en t. We are grateful for the financial
support from the National Natural Sciences Foundation
of China, the State Key Project of Basic Research
(Project 973, No. 2000 48007), and the “Hundred
Scientists Program” from the Chinese Academy of
Sciences.
Deh a logen a tion of 2,2-Dibr om o-1-p h en ylp r op a n on e.
The 2,2-dibromo-1-phenylpropanone substrate was synthesized
(1.5 equiv of bromine, glacial acetic acid, 40% yield) according
to the literature.10 1H NMR (300 MHz, CDCl3/TMS): δ 8.41
J O025693B
5326 J . Org. Chem., Vol. 67, No. 15, 2002