Wittig-type olefination catalyzed by PEG-telluride

Article abstract of DOI:10.1021/jo025586h

Soluble poly(ethylene glycol) (PEG)-supported telluride 2 was designed and synthesized for catalytic Wittig-type reactions. It was found that the catalytic loading could be reduced from 20 to 2 mol % by the introduction of PEG (even to 0.5 mol % when some telluride salts were used as the catalyst). Under the catalytic reaction conditions, a wide variety of aldehydes with different structures could react with bromoacetate to afford β-substituted or α,β-disubstituted unsaturated esters in high yields with excellent E-stereoselectivity. The modified process, by using sodium bisulfite instead of triphenyl phosphite, represented a very simple product isolation procedure. The roles of PEG for promoting the ylide formation and stabilizing the catalytic species were disclosed. The mechanism was also studied.

Full text of DOI:10.1021/jo025586h

3096
J . Org. Chem. 2002, 67, 3096-3103
Wittig-Typ e Olefin a tion Ca ta lyzed by P EG-tellu r id e
Zheng-Zheng Huang, Song Ye, Wei Xia, Yi-Hua Yu, 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 February 4, 2002
Soluble poly(ethylene glycol) (PEG)-supported telluride 2 was designed and synthesized for catalytic
Wittig-type reactions. It was found that the catalytic loading could be reduced from 20 to 2 mol %
by the introduction of PEG (even to 0.5 mol % when some telluride salts were used as the catalyst).
Under the catalytic reaction conditions, a wide variety of aldehydes with different structures could
react with bromoacetate to afford â-substitutited or R,â-disubstituted unsaturated esters in high
yields with excellent E-stereoselectivity. The modified process, by using sodium bisulfite instead
of triphenyl phosphite, represented a very simple product isolation procedure. The roles of PEG
for promoting the ylide formation and stabilizing the catalytic species were disclosed. The mechanism
was also studied.
Sch em e 1
In tr od u ction
In 1953, Wittig and his co-worker discovered the ylide
olefination reaction between diphenyl ketone and phos-
phonium ylide.1 To date, modifications of this reaction
are the most powerful approaches in constructing carbon-
carbon double bonds due to its unambiguous positioning
and good stereoselectivity of the double bond.2 From the
view of atom economy, however, it is not a perfect
reaction.3 For example, only the methylene group is used,
and a large amount of triphenylphosphine oxide is
produced as waste in the reaction of methylene triphen-
ylphosphine with aldehyde (Scheme 1). Because triphen-
ylphosphine oxide is hard to reduce, this drawback also
limits its further applications in organic synthesis. Thus,
chemists are interested in developing catalytic process
of this reaction, but few examples have been successful.
The first example of catalytic Wittig-type reactions
appeared in 1989, in which Huang et al. found tributyl-
arsine could be used as the catalyst in the presence of
triphenyl phosphite.4 Later, they described the catalytic
ylide olefination, epoxidation, and cyclopropanation reac-
tions mediated by n-butyl telluride or isobutyl telluride.5
Unfortunately, 20 mol % of the catalyst should be used
for both reactions described above. Reduction of the
amount of catalyst means low yield even if the reaction
time was prolonged.6 Compared to other catalytic reac-
tions, needless to say, the low catalytic efficiency and the
use of triphenyl phosphite are the two serious drawbacks.
To develop catalytic ylide olefinations for practical use
remains a challenge. In our continuing studies on the
application of ylides in organic synthesis,7 we focused on
the catalytic efficiency of ylide olefinations and com-
municated a modified catalytic ylide process, in which
only 2 mol % of PEG-telluride was used.8 In this paper,
we report the possible mechanism, modification, scope,
and limitations of these reactions in detail.
Resu lts a n d Discu ssion
Ca ta lyst Design a n d Syn th esis. By analysis of the
corresponding mechanism reported (Scheme 2), probably
the formation of ylide is the rate-determining step in the
catalytic ylide olefination.6 Improving the rate of ylide
generation may essentially speed up this catalytic cycle.
Thus, we designed PEG-telluride as the catalyst for the
following considerations. First, the PEG may interact
with potassium ion, like crown ether,9 by self-assembling
* To whom correspondence should be addressed. Fax: 86-21-
64166128.
(1) Wittig, G.; Geissler, G. Liebigs Ann. Chem. 1953, 580, 44.
(2) (a) Hoffmann, R. W. Angew. Chem., Int. Ed. 2001, 40, 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.
(3) Trost, B. M. Science 1991, 254(5037), 1471.
(4) Shi, L.; Wang, W.; Wang, Y.; Huang, Y.-Z. J . Org. Chem. 1989,
54, 2028.
(5) (a). Huang, Y.-Z. Shi, L.-L.; Li, S.-W.; Wen, X.-Q. J . Chem. Soc.,
Perkin Trans. 1 1989, 2397. (b). Zhou, Z.-L.; Shi, L.-L.; Huang, Y.-Z.
Tetrahedron Lett. 1990, 31, 7657. (c). Huang, Y.-Z.; Tang, Y.; Zhou,
Z.-L.; Xia, W.; Shi, L.-P. J . Chem. Soc., Perkin Trans. 1 1994, 893.
(6) Li, S.-W. Ph.D. Thesis, Shanghai Institute of Organic Chemistry,
1990.
(7) (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.
(8) Huang, Z.-Z.; Ye, S.; Xia, W.; Tang. Y. Chem. Commun. 2001,
1384.
(9) Maynard, H. D.; Grubbs, R. H. Macromolecules 1999, 32, 6917.
10.1021/jo025586h CCC: $22.00 © 2002 American Chemical Society
Published on Web 03/30/2002

Wittig-Type Olefination Catalyzed by PEG-telluride
J . Org. Chem., Vol. 67, No. 9, 2002 3097
Ta ble 1. Effects of Rea ction Con d ition s on th e Ca ta lytic
Ylid e Olefin a tion of p-Ch lor oben za ld eh yd e w ith Eth yl
Br om oa ceta tea
F igu r e 1.
catalyst
T
yield
(%)
entry loadingb
solvent
base
(°C) methodc
Sch em e 2
1d
2
3
4
5
10
10
10
10
10
10
10
THF/H2O
THF
CH2Cl2
ethyl ether K2CO3
butyl ether K2CO3
toluene
petroleum
ether
K2CO3
K2CO3
K2CO3
80
80
80
80
80
80
80
1
1
1
1
1
1
1
58
66
58
31
32
70
39
6
7
K2CO3
K2CO3
8
9
10
10
10
10
10
10
10
10
10
10
10
10
5
hexane
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
K2CO3
DBU
KHCO3
KOH
80
80
80
80
80
80
80
110
50
80
80
80
80
80
80
80
80
80
80
1
1
1
1
1
1
1
1
1
1
2
2
2
2
3
4
5
5
6
47
0
22
22
59
70
76
96
35
70
100
92
80
73
83
94
88
97
98
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Na2CO3
K2CO3
Cs2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Sch em e 3
2.5
1.3
1.3
1.3
1
2
2
to form a half-open crown ether as shown in Figure 1.
PEG would be proposed not only to play a role as a phase-
transfer catalyst but also to increase the basicity of
potassium carbonate in the reaction system. And thus,
it is expected to accelerate the reaction of ylide formation
and to enhance the catalytic activity. Second, soluble PEG
is being developed as an alternative matrice for organic
synthesis owing to the advantages of homogeneous
solution chemistry with those of solid-phase methods.10
The soluble PEG-supported telluride catalyst could be
recoverable easily and be reusable.
The PEG-supported telluride 2 was readily available
from poly(ethylene glycol) in two steps as shown in
Scheme 3. Tosylation11 of PEG (#4000) in anhydrous CH2-
Cl2 in the presence of Et3N at room temperature for 12 h
afforded compound 1 in 99% yield. Treatment of com-
pound 1 with BuTeLi, generated in situ in anhydrous
THF at -78 °C, followed by precipitation with diethyl
ether, afforded PEG-supported telluride 2 in 83% yield.
Effects of Rea ction Con d ition s. We first tried the
olefination of p-chlorobenzaldehyde and ethyl bromo-
acetate in the presence of 10 mol % of PEG-telluride 2
under the optimized reaction condition mediated by nBu2-
Te.5 It was disappointing that this reaction gave the
product in 58% yield (entry 1, Table 1). It was found that,
as shown in Table 1, the reaction could be carried out in
a wide variety of solvents such as THF, hexane, and ethyl
ether, etc. The best ones were THF, CH2Cl2, and toluene
probably due to good solubility of the PEG-supported
telluride 2 in these solvents (entries 2, 3, and 6, Table
1).
a
b
Please see the Experimental Section. Catalytic loading (mol
%). c Isolated yields.
KOH, and Na2CO3 could be used as the bases (entries
10, 11, and 12, Table 1), the best ones were K2CO3 and
Cs2CO3 (entries 13 and 14, Table 1). Further studies
showed that the reaction temperature strongly influenced
the yield of olefin. As shown in Table 1, an almost
quantitative yield of olefin 5a was obtained at 110 °C
while 35% yield was isolated at 50 °C (entries 15 and
16, Table 1).
Surprisingly, we found that the addition sequence of
reactants affected the yields dramatically. Only 70% yield
of compound 5a was isolated when p-chlorobenzaldehyde
was added before the addition of PEG-telluride (entry 17,
Table 1). However, quantitative yield was obtained if the
aldehyde was added after PEG-telluride (entry 18, Table
1) at the same reaction conditions. It is worthy to note
that, by the using of method 2, this reaction also gave
73% yield even if the amount of PEG-telluride 2 was
reduced from 10 mol % to 1.3 mol % (entry 21, Table 1).
In this reaction, interestingly, we got a byproduct 6,12
which may be formed from ethyl bromoacetate and
P(OPh)3. This finding meant that the side reaction
consumed the bromide 4a .
Several kinds of base, including weak organic base
(entry 9, Table 1), were examined in the reactions when
toluene was employed as the solvent. Although KHCO3,
Thus, we tried to add ethyl bromoacetate or the
aldehyde or the mixture of these two starting materials
in portions to reduce their decomposition. It is pleasant
(10) Wentworth, P.; J anda, K. D. Chem. Commun. 1999, 1917.
(11) Zhao, X.; J anda, K. D. Tatrahedron Lett. 1997, 38, 5437.

3098 J . Org. Chem., Vol. 67, No. 9, 2002
Huang et al.
Ta ble 2. Olefin a tion of Ald eh yd es Ca ta lyzed by
P EG-Su p p or ted Tellu r id e
Ta ble 3. Effects of Rea ction Con d ition s on th e Ca ta lytic
Ylid e Olefin a tion of p-Ch lor oben za ld eh yd e w ith
Br om oa ceta te Usin g Na HSO3 a s th e Red u cin g Agen ta
entry base (equiv)
solvent
T (°C) yield (%)
1
2
3
4
5
6
7
8
9
K2CO3 (2)
K2CO3 (2)
Na2CO3 (2) THF/H2O (4/0.1)
KHCO3 (2) THF/H2O (4/0.1)
K2CO3 (2)
K2CO3 (2)
K2CO3 (2)
K2CO3 (1.6) THF/H2O (4/0.1)
K2CO3 (1.2) THF/H2O (4/0.07)
THF/H2O (4/0.1)
THF/H2O (4/0.1)
80
80
80
80
80
80
80
80
80
50
80
80
82
66b
25
33
80
73
7c
77
47
50
75
70
THF/H2O (4/0.07)
THF/H2O (4/0.04)
THF
10
11
12
K2CO3 (2)
K2CO3 (2)
K2CO3 (2)
THF/H2O (4:0.1)
THF/toluene/H2O (3:1:0.1)
THF/H2O (8:0.1)
a
b
5 mol % of the catalyst was used except as noted. 2 mol % of
the catalyst was used in this reaction. c Bu4NBr was added.
dehyde (entry 5, Table 2) was less active, it still worked
well when 5 mol % of catalyst 2 was employed. Func-
tionalized and unfunctionalized aliphatic aldehydes with
different structures were also available in this reaction
to give the corresponding olefins in moderate yields with
high stereoselectivity except entry 10 (entries 7-10,
Table 2). Importantly, when only 0.5% mol of the corre-
sponding salt was taken as the catalyst instead of PEG-
telluride, this olefination reaction could also give 94%
yield (entry 11, Table 2).
a
b
Isolated yields. The ratio of E/Z isomers was determined by
1H NMR. c 5 mol % catalyst used. 0.5 mol % of the salt 16
d
([C2H5O2C(Bu)Te-PEG-Te(Bu)CO2C2H5]2+2Br-) was used.
Ylid e Olefin a tion Ca ta lyzed by P EG-Su p p or ted
Tellu r id e in th e P r esen ce of Na HSO3. To make this
reaction practical, we took our efforts to use inorganic
reducing reagents instead of P(OPh)3. First, we tried
NaHSO3 as the reducing agent, and it was found that
only trace product 5a was detected when this reaction
was carried out in toluene, whether in the presence of a
trace of water or not. Fortunately, 82% yield could be
achieved in THF/trace H2O in the reaction of p-chloro-
benzaldehyde with ethyl bromoacetate in the presence
of NaHSO3 when 5 mol % of PEG-telluride 2 was used.
Reduction of the catalyst loading resulted in low yield
(entry 2, Table 3).
to find that the side reaction could be inhibited more or
less (entries 22, 23, and 24, Table 1) by this method. Even
in the presence of 1 mol % of PEG-telluride 2, 88% yield
of compound 5a was isolated (entry 24, Table 1). Further
studies showed that method 6 was the best one and was
easily reproducible. In this method, the mixture of PEG-
telluride 2, ethyl bromoacetate (0.45 mmol), and P(OPh)3
was stirred in toluene at 80 °C for 5 min, and then the
K2CO3, the mixture of p-chlorobenzaldehyde (1.0 mmol),
and the rest bromide were added (entry 26, Table 1).
Ylid e Olefin a tion of Ald eh yd es w ith Eth yl Br o-
m oa ceta te Ca ta lyzed by P EG-Su p p or ted Tellu r id e
in th e P r esen ce of P (OP h )3. To determine the general-
ity of this reaction, a variety of structurally different
aldehydes were employed. Some results are summarized
in Table 2, with the optimized condition of Table 1.
It was found that both aliphatic and aromatic alde-
hydes worked well with high stereoselectivity in reason-
able yields. In most cases, traditional E-stereoselectivity
was maintained compared with typical Wittig reactions
of stable ylides. Aromatic aldehydes with an electron-
withdrawing group (entries 1 and 3, Table 2) or a weak
electron-donating group (entry 4, Table 2) in the para
positon as well as the heteroaromatic aldehyde (entry 6,
Table 2) were the most suitable substrates. All of them
can afford the desired products in excellent yields with
high stereoselectivity. Although aromatic aldehyde with
a strong electron-donor group such as p-methoxybezal-
In these reactions, unexpectedly, trace of compound 7
was isolated and was characterized as the following
structure.
This result suggested that the product 5a was hydro-
lyzed under these reaction conditions and thus lowered
the yield.
To inhibit this side reaction and improve the yield, we
tried to use weaker bases (entries 3 and 4, Table 3) or
reduce the amount of potassium carbonate (entries 8 and
9, Table 3) and water (entries 5 and 6, Table 3), but no
good results were obtained. Attempts to use TBAB
instead of water as the phase-transfer catalyst (entry 7,
Table 3) or to lower the reaction temperature and so on
(entries 10, 11, and 12, Table 3) failed too. Finally, we
(12) The reaction afforded compound 6 in 15% yield. 1H NMR (300
MHz, CDCl3/TMS): δ 7.33-7.26 (m, 2H), 7.02-6.97 (m, 1H), 6.93-
6.90 (m, 2H), 4.62 (s, 2H), 4.28 (q, J ) 7.1 Hz, 2H), 1.30 (t, J ) 7.1 Hz,
3H). IR (film): ν ) 2900, 1760, 1601, 1199, 1089, 755, 691 cm-1. GC/
MS (m/e): 180 (M+), 77 (100).

Wittig-Type Olefination Catalyzed by PEG-telluride
J . Org. Chem., Vol. 67, No. 9, 2002 3099
Ta ble 4. Olefin a tion of Ald eh yd es Ca ta lyzed by
P EG-Su p p or ted Tellu r id e in th e P r esen ce of Na HSO3
Ta ble 5. Com p a r ison s betw een P EG-Te a n d n Bu 2Tea
a
yield
cat.
co-
catalyst
other
of 6 yieldc
entry (mol %)
solvent
reagentb
(%)
(%)
1
2
3
4
Bu2Te (4) toluene
Bu2Te (4) toluene
P(OPh)3
P(OPh)3 18-crown-6 69
P(OPh)3 54
trace 69
(68)d
98
2 (2)
toluene
Bu2Te (2) THF/H2O NaHSO3
(4/0.03)
(12)d
5
2 (1)
THF/H2O NaHSO3
(4/0.03)
81
a
The other reaction conditions: when R ) C2H5, K2CO3 (1.3
mmol), P(OPh)3 (1.4 mmol), toluene (4 mL), 80 °C, aldehyde (1.0
mmol), ethyl bromoacetate (1.6 mmol); when R ) tC4H9, K2CO3 (2
mmol), NaHSO3 (1.6 mmol),THF/H2O (4/0.07), aldehyde (1.0
b
mmol); tert-butyl bromoacetate (1.2 mmol). 0.6 equiv of 18-
d
crown-6 was used. c Isolated yield. Determined by GC.
catalyst could be recovered in 100% yield by filtering off
the solid of the reaction mixture, followed by addition of
ether and collection of the precipitate. The recovered
catalyst could be used in the second run but only 69%
yield was obtained probably due to the decomposition of
PEG-telluride during the catalytic olefination.13
Th e Roles of P EG. By the introduction of the PEG-
chain, we successfully reduced the amount of telluride
from 20 into 2 mol % in the catalytic ylide olefination.
To understand the role of PEG-chain in this reaction, we
compared Bu2Te-catalyzed with PEG-telluride 2 cata-
lyzed olefination reaction in the presence of P(OPh)3 in
detail. It was found that only a trace of compound 6 was
formed when Bu2Te was used. Under the same condi-
tions, however, 69% yield of compound 6 was isolated in
the presence of 18-crown-6 (entry 2, Table 5). When PEG-
telluride was used instead of Bu2Te and 18-crown-6, 54%
yield of compound 6 was afforded. These results sug-
gested that PEG, like crown ether, could enhance the
basicity of potassium carbonate probably due to the self-
asembling with potassium ion. This interaction improved
the rate of ylide formation and speeded up the catalytic
cycle.
Further study showed that only 12% conversion was
detected when the amount of n-butyl telluride was
reduced from 4 to 2 mol % in the presence of NaHSO3.
However, the corresponding product was obtained in 81%
yield when 1 mol % of PEG-telluride 2 was used. So, we
proposed that PEG-chain probably also stabilized the
telluronium salt due to the interaction of PEG-oxygen
and tellurium. This may slow the rate of catalyst
deactivation and enhance the catalytic efficiency. To get
further details, we synthesized PEG-like compound 11
as shown in Scheme 4.16
a
Other reaction conditions: K2CO3 (2.0 mmol); NaHSO3 (1.6
mmol); PEG-telluride; THF/H2O ) 4:0.07; reflux, aldehyde (1.0
mmol); tert-butyl bromoacetate (1.2 mmol). Isolated yield. c E/Z
b
ratio was determined by 300 MHz 1H NMR.
chose tert-butyl bromoacetate, which is difficult to hy-
drolyze under these conditions, instead of ethyl ester and
found 99% yield of olefin 8a was reached. Even if 1 mol
% of catalyst was used, the yield was still 81% (entries
1, 2, and 3, Table 4). A variety of structurally different
aldehydes including some functionalized aldehydes such
as epoxy aldehyde (entry 14, Table 4) could react with
tert-butyl bromoacetate in the presence of 2 mol % of
PEG-telluride 2 when using NaHSO3 as the cocatalyst.
As shown in Table 4, NaHSO3 turned out to be another
effective reducing reagent in this catalytic Wittig-type
reaction. It is interesting that the use of NaHSO3
improved the stereoselectivity of the reaction of aldehyde
3j greatly. The ratio (E/Z) of the product was enhanced
from 58/42 (entry 10, Table 3) to 99/1 (entry 12, Table
4). The E/Z selectivity of aldehyde 3i was also improved.
It is noteworthy that the product isolation procedure was
very simple by this modification. After the reaction was
complete, almost pure product could be obtained just by
filtering off the inorganic salts, followed by precipitating
PEG-Telluride 2 in ether.
(13) (a) Detty, M. D. J . Org. Chem. 1980, 45, 274. (b) Drew, H. D.
K. J . Chem. Soc. 1929, 560.
(14) (a) Pauling, L. The Nature of the Chemical Bond, 3rd ed.;
Cornell University: Ithaca, NY, 1960; p 260. (b) Day, R. O.; Holmes,
R. R. Inorg. Chem. 1981, 20, 3071.
(15) Petragnani, N.; Comasseto, J . V. Synthesis 1991, 897.
(16) (a) Morishita, S.; Saito, T.; Hirai, Y.; Shoji, M.; Mishima, Y.;
Kawakami, M. J . Med. Chem. 1988, 31, 1205. (b). The procedure is
similar to the synthesis of compound 2. The product was purified by
distillation under the reduced pressure
Further studies showed that the catalyst could be
recovered quantitatively but lost its activity partially
through multiple cycles. We found 2-furaldehyde (10.85
mmol) reacted with tert-butyl bromoacetate in the pres-
ence of sodium bisulfite to afford the desired product in
90% yield when 2 mol % of PEG-telluride was used. The

3100 J . Org. Chem., Vol. 67, No. 9, 2002
Huang et al.
Sch em e 5
Sch em e 6
Sch em e 7
F igu r e 2. View of the structure of compound 11. Selected the
bond lengths (Å): Te-C(1), 2.098(6); Te-C(10), 2.148(6); Te-
C(16), 2.205(7); O(1)-C(11), 1.292(7); O(1)-C(12), 1.502(8);
O(2)-C(11), 1.190(8); O(3)-C(4), 1.361(7); O(3)-C(3), 1.447-
(8); O(2)-Te, 3.282; O(3)-Te, 2.926.
Sch em e 4
quantitative yield and compound 13 in 94% yield even
at room temperature (Scheme 6). The structure of
compound 13 was determined by NMR, elemental analy-
sis, and X-ray crystal analysis. These results showed that
the trace of acetophenone came from the decomposition
of the corresponding salt, which gave a reasonable
explanation for the recovery PEG-telluride 2 partially
losing the activation as described above.
These results also suggested that there may exist
reaction pathways other than ylide olefination. To dem-
onstrate it, the best way is to inhibit the formation of
ylide as far as possible in this reaction. So, we first
examined the reaction of p-chlorobezenaldehyde with
ethyl bromoacetate or bromoacetophenone in the pres-
ence of stoichiometric PEG-telluride 2 without using
potassium carbonate, separately (Scheme 7).
The ORTEP diagram of its X-ray structure analysis
was shown in Figure 2. The distance of Te-O3 is 2.926
Å, which is shorter than the van der Waals sum of 3.60
Å.14 This result indicated the existence of bonding
interaction between the tellurium and the side-chain
oxygen to make Te atom pseudo six-coordinated. This
interaction of course could make the tellurium compound
stable.
According to our speculation, compound 10 should be
better catalyst for ylide olefination than dibutyltelluride.
Actually, the conversion was improved from 12% to 19%
when 2 mol % of compound 10 was used instead of
n-butyl telluride.
To our surprise, both reactions gave the desired
products although the yields were much lower when
compared with those carried out in the presence of
K2CO3.
In the literature, Huang et al.17 reported that carbeth-
oxydibutyltelluronium bromide could directly react with
aromatic aldehydes to afford a,â-unsaturated esters. They
proposed a six-membered ring transition state to eluci-
date the reaction pathway (Figure 3).
According to the above results, in our reaction, we
proposed that both reaction pathways are compatible as
shown in Scheme 8. The major product was obtained via
ylide route while the trace one was formed via path II.
In mechanism I, the olefination proceeded via a ylide
route. The PEG-supported telluride 2 reacted with bro-
Mech a n ism . In an initial study, we proposed that this
reaction was a typical ylide reaction. In the reaction of
4-chlorobenzaldehyde with ω-bromoacetophenone, how-
ever, we detected a trace of acetophenone. Further study
showed that the telluride 2 could react with ethyl
bromoacetate or bromoacetophenone directly to afford
ethyl acetate and acetophenone separately in the pres-
ence of a trace of water (Scheme 5). They may be
produced from the dehalogenation of the corresponding
bromides by telluride.15
To make it clear, we synthesized compound 12, which
was characterized by X-ray analysis. It was found that
this salt could react with water to give acetophenone in
(17) Huang, X.; Xie, L.; Wu, H. Tetrahedron Lett. 1987, 28, 801.

Wittig-Type Olefination Catalyzed by PEG-telluride
J . Org. Chem., Vol. 67, No. 9, 2002 3101
P r ep a r a t ion of P olym er -Su p p or t ed Ca t a lyst : P r ep -
a r a tion of Com p ou n d 1. To a stirred and chilled solution of
PEG#4000 (30 g, 10 mmol) and triethylamine (50 mL, 360
mmol) in dichloromethane (80 mL) was added p-toluenesul-
fonyl chloride (25 g, 120 mmol) at 0 °C in portions. The
resulting light red slurry was stirred at room temperature for
24 h. The reaction mixture was filtered and washed with CH2-
Cl2. The combined filtrate was concentrated to about 10 mL
and triturated with Et2O (1600 mL). The resulting white solid
was filtered, washed with 2-propanol, and dried in vacuo to
provide compound 1. Yield: 33.0 g (99%). 1H NMR (300 MHz,
CDCl3/TMS): 7.81 (d, J ) 8.0 Hz, 4H), 7.35 (d, J ) 8.0 Hz,
4H), 4.16 (t, J ) 4.8 Hz, 4H), 3.88-3.41 (m, ∼280H), 2.45 (s,
F igu r e 3.
Sch em e 8
6H). IR (KBr): 2887, 1600 cm-1
.
P r ep a r a tion of Com p ou n d 2. To a suspension of Te
(0.1250 g, 48.0 mmol) in THF (250 mL) was added BuLi (43.5
mL in hexane, c ) 1.33 mol/ L) dropwise at 0 °C. After addition,
the light yellow solution was cooled to -78 °C and the solution
of compound 1 (10.03 g, 3.0 mmol) in THF (120 mL) was added.
The resulting light green slurry was stirred for an additional
8 h and then warmed to room temperature. The reaction
mixture was concentrated. The residue was dissolved in CH2-
Cl2, filtered through a glass funnel with a thin layer of Celite,
and washed with CH2Cl2. The combined filtrates were con-
centrated (∼10 mL) and triturated with Et2O (2000 mL). The
resulting white solid was collected, washed with ether, and
dried in vacuo to afford compound 2. Yield: 8.4 g (83%). 1H
NMR (300 MHz, CDCl3/TMS): δ 3.90-3.40 (m, ∼280H), 2.80
(t, J ) 7.6 Hz, 4H), 2.66 (t, J ) 7.4 Hz, 4H), 1.75-1.70 (m,
4H), 1.39-1.36 (m, 4H), 0.92 (t, J ) 7.2 Hz, 6H). IR (KBr):
moacetate to form the corresponding telluronium salt 16.
After deprotonation of salt 16 by K2CO3, followed by the
reaction with aldehyde, the desired alkene was formed.
And the PEG-supported telluride 2 was regenerated by
the reduction of telluride oxide with triphenyl phosphite
or sodium bisulfite. This is also the main pathway in this
reaction. Besides, in mechanism II, the salt 16 could react
with aldehyde directly to afford the desired product but
this way led the decomposition of catalytic telluride
species.
2888, 1113, 529 cm-1 125Te (CDCl3/Me2Te): δ 200.203.
.
Effect of th e Ad d ition Sequ en ce of Rea cta n ts. Meth od
1. The reactants were combined in the following order:
p-chlorobenzaldehyde (1.0 mmol), K2CO3 (1.3 mmol), toluene,
ethyl bromoacetate (1.6 mmol), telluride 2, and P(OPh)3. The
mixture was heated at 80 °C for several hours. Meth od 2.
Method 2 was similar to method 1 but the addition sequence
was changed as follows: telluride 2, toluene, ethyl bromoace-
tate (1.6 mmol), P(OPh)3, K2CO3 (1.3 mmol). and p-chlorobenz-
aldehyde (1.0 mmol). Meth od 3. Method 3 was similar to
method 2, but the ethyl bromoacetate was added in portions
in 4-6 h. Meth od 4. Method 4 was similar to method 2, but
p-chlorobenzaldehyde was added in portions in 4-6 h. Meth od
5. Method 5 was similar to method 2, but the mixture of
p-chlorobenzaldehyde and ethyl bromoacetate was added in
portions in 4-6 h. Meth od 6. Method 6 was similar to method
5, but the mixture of telluride 2, toluene, ethyl bromoacetate,
and P(OPh)3 was stirred at 80 °C for 5 min before the K2CO3
and the mixture of p-chlorobenzaldehyde and ethyl bromoac-
etate was added.
Typ ica l P r oced u r e A. P (OP h )3 a s th e Coca ta lyst. A
mixture of catalyst 2 (0.0680 g, 2 mol %), ethyl bromoacetate
(0.06 mL, 0.5 mmol), and P(OPh)3 (0.36 mL, 1.4 mmol) in
toluene (3.0 mL) was stirred at 80 °C for 10 min, and then
K2CO3 (0.1796 g, 1.3 mmol) was added. The resulting suspen-
sion was stirred for 1 min, followed by addition of a mixture
of aldehyde (1.0 mmol) and ethyl bromoacetate (0.12 mL, 1.1
mmol) in toluene (1.0 mL) in portions in 3.5 h. After the
reaction was completed (monitored by TLC), the mixture was
filtered rapidly through a glass funnel with a thin layer of
silica gel, washed with ethyl acetate. The filtrate was concen-
trated, and the residue was purified by flash column chroma-
tography to afford the desired product.
Con clu sion
In the past decades, highly efficient catalysis has
become one of the most important frontiers in exploratory
organic synthetic research.18 Any catalytic process usu-
ally contains multistep reactions. One of the key points
to improve the turnover number, we think, is to find out
and speed up the rate-determining step. Another key
factor is to stabilize the catalytic species in the catalytic
cycle in case of deactivation of catalyst. Following these
concepts, in this paper, an effective catalytic ylide olefi-
nation were successfully developed by the introduction
of PEG. In which, it involves in simple procedure, mild
reaction conditions, in particular, the use of sodium
bisulfite as cocatalyst. The highly catalytic efficiency,
together with the ability to easily purify the product,
demonstrates our method to be practical for the synthesis
of R,â-unsaturated esters. The extension of our method
to epoxidation, cyclopropanation, and aziridination is in
progress in our laboratory.
Exp er im en ta l Section
Gen er a l Meth od s. All reaction flasks and equipment were
dried for several hours prior to use, and all reactions were
carried out under nitrogen. Solvents and aldehydes were
purified according to standard method. Chemical shifts are
given in ppm relative to internal TMS. The reagents were
purchased from commercial sources and used directly.
Eth yl (E)-3-(4-Ch lor op h en yl)a cr yla te (R ) p-ClC6H4,
5a ). Procedure A. Yield: 206.8 mg (98%). E/Z > 99:1.1H NMR
(300 MHz, CDCl3/TMS): δ 7.64 (d, J ) 16.0 Hz, 1H), 7.46 (dd,
J ) 1.8, 6.7 Hz, 2H),7.36 (dd, J ) 1.8,6.7 Hz, 2H), 6.41 (d, J )
16.0 Hz, 1H), 4.27 (q, J ) 7.1 Hz, 2H), 1.34 (t, J ) 7.1 Hz,
3H).
Eth yl (E)-3-P h en yla cr yla te (R ) C6H5, 5b). Procedure
A. Yield: 171.0 mg (98%). E/Z > 99:1. 1H NMR (300 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).
(18) (a) J acobsen, E. N.; Pfaltz, A.; Yamamoto, H. Comprehensive
Asymmetric Catalysis; Springer: Berlin, 1999. (b) Burke, S. D.;
Danheiser, R. L. Oxidizing and Reducing Agents in Handbook of
Reagents for Organic Synthesis; Paquette, L. A., Ed.; J ohn Wiley &
Son, New York, 1999; Vol. 2. (c) Ojima, I. Asymmetric Synthesis;
VCH: New York, 1993. (d) Santelli, M. Pons, J .-M. Lewis Acid and
Selectivity in Organic Synthesis; CRC Press: Boca RAton, 1995.

3102 J . Org. Chem., Vol. 67, No. 9, 2002
Huang et al.
Eth yl (E)-3-(4-Tr iflu or om eth ylp h en yl)a cr yla te (R )
p-CF 3C6H4, 5c). Procedure A. Yield: 181.3 mg (74%). E/Z >
99:1. 1H 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). 19F NMR (56.4 MHz,
CCl4/CF3COOH): δ -15.0.
Eth yl (E)-3-(p-Tolyl)a cr yla te (R ) p-CH3C6H4, 5d ).
Procedure A Yield: 177.5 mg (93%). E/Z ) 90:10. 1H NMR
(300 MHz, CDCl3/TMS) (for trans isomer): δ 7.59 (d, J ) 15.9
Hz, 1H), 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).
Eth yl (E)-3-(p-An isyl)a cr yla te (R ) p-CH3OC6H4, 5e).
Procedure A. Yield: 208.4 mg (94%). E/Z > 99:1. 5 mol %
catalyst was used. 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).
Eth yl (E)-3-(2-F u r yl)a cr yla te (R ) C4H3O, 5f). Procedure
A. Yield: 160.0 mg (96%). 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).
Eth yl (E,E)-5-P h en ylp en ta -2,4-d ien oa te (R ) C6H5CHd
CH2, 5g). Procedure A. Yield: 150.4 mg (74%). 5 mol %
catalyst was used. E/Z > 99:1. 1H NMR (300 MHz, CDCl3/
TMS): 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).
Eth yl (E)-3-Cycloh exyla cr yla te (R ) C6H11, 5h ). Proce-
dure A. Yield: 128.0 mg (70%). E/Z > 99:1. 1H 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).
Eth yl (E)-d od ec-2-en oa te (R ) CH3(CH2)8, 5i). Procedure
A. Yield: 168.9 mg (74%). E/Z ) 88:12. 1H NMR (300 MHz,
CDCl3/TMS) (for trans isomer): 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 3-(6-Ben zyloxy-2,2-d im eth yltetr a h yd r ofu r o[2,3-
d ][1,3]d ioxol-5-yl)a cr yla te (5j). Procedure A. A 0.5 mmol
portion of the corresponding aldehyde was employed. Yield:
137.9 mg (79%). E/Z ) 58:42. 1H NMR (300 MHz, CDCl3/TMS)
(for trans isomer): δ 7.36-7.26 (m, 5H), 6.96 (dd, J ) 15.9,
5.1 Hz, 1H), 6.17 (dd, J ) 15.8, 1.7 Hz, 1H), 6.00 (d, J ) 3.6
Hz, 1H), 4.81-4.79 (m, 1H), 4.65-4.48 (m, 3H), 4.22 (q, J )
7.1 Hz, 2H), 3.71 (d, J ) 3.0 Hz, 1H), 1.49 (s, 3H), 1.33 (s,
3H), 1.30 (t, J ) 7.2 Hz, 3H). 1H NMR (300 MHz, CDCl3/TMS)
(for cis isomer): δ 7.38-7.21 (m, 5H), 6.39 (dd, J ) 11.9, 6.8
Hz, 1H), 6.01 (d, J ) 3.6 Hz, 1H), 5.91 (dd, J ) 11.6, 1.2 Hz,
1H), 5.63-5.60 (m, 1H), 4.65-4.44 (m, 3H), 4.28 (d, J ) 3.3
Hz, 1H), 4.11 (q, J ) 7.2 Hz, 2H), 1.51 (s, 3H), 1.33 (s, 3H),
1.26 (t, J ) 6.9 Hz, 3H).
TMS): δ 7.73 (d, J ) 16.1 Hz, 1H), 7.48 (d, J ) 7.7 Hz, 2H),
7.38 (d, J ) 7.7 Hz, 2H), 6.50 (d, J ) 16.1 Hz, 1H), 4.74 (s,
2H), 4.26 (q, J ) 7.1 Hz, 2H), 1.31 (t, J ) 7.1 Hz, 3H). 13C
NMR (75 MHz, CDCl3): 167.868, 165.937, 144.758, 136.558,
132.695, 129.402, 129.256, 117.448, 61.513, 60.945, 14.141
ppm. IR (KBr): ν ) 2984, 1743, 1714, 1633, 1591, 1493, 825
cm-1. MS (m/e): 270 (M+(37Cl), 12.25), 268 M+(35Cl), 34.53),
167 (M+(37Cl), 36.68), 165 (M+(35Cl), 100%). HRMS: calcd for
C
13H13ClO4 268.050 24, found 268.048 09.
Typ ica l P r oced u r e B: Na HSO3 a s th e Coca ta lyst. A
mixture of catalyst 2 (0.0680 g, 2 mol %), tert-butyl bromoac-
etate (0.06 mL, 0.4 mmol), and NaHSO3 (0.1664 g, 1.6 mmol)
in THF (3.0 mL) was refluxed for 10 min, and then H2O (0.04
mL) was added. The resulting mixture was stirring for 10 min,
followed by addition of K2CO3 (0.2760 g, 2.0 mmol). After being
stirred for 1 min, to this suspension was added a mixture of
aldehyde (1.0 mmol), tert-butyl bromoacetate (0.12 mL, 0.8
mmol), and water (0.03 mL) in THF (1.0 mL) in portions in
3.5 h. This reaction was quenched by anhydrous MgSO4 after
it was complete (monitored by TLC). The resulting mixture
was filtered rapidly through a glass funnel with a thin layer
of silica gel, washed with ethyl acetate. The combined filtrate
was concentrated, and the residue was purified by flash
column chromatography to afford the desired product.
ter t-Bu tyl (E)-3-(4-Ch lor oph en yl)acr ylate (R ) p-ClC6H4,
8a ). Procedure B. Yield: 237.5 mg (93%). E/Z > 99:1. 1H NMR
(300 MHz, CDCl3/TMS): δ 7.53 (d, J ) 16.0 Hz, 1H), 7.44 (d,
J ) 7.0 Hz, 2H), 7.34 (d, J ) 7.0 Hz, 2H), 6.34 (d, J ) 16.0 Hz,
1H), 1.53 (s, 9H).
ter t-Bu tyl (E)-3-P h en yla cr yla te (R ) C6H5, 8b). Proce-
dure B. Yield: 189.0 mg (92%). E/Z > 99:1. 1H NMR (300 MHz,
CDCl3/TMS): δ 7.60 (d, J ) 16.0 Hz, 1H), 7.53-7.50 (m, 2H),
7.38-7.36 (m, 3H), 6.38 (d, J ) 16.0 Hz, 1H), 1.53 (s, 9H).
ter t-Bu tyl (E)-3-(4-Nitr op h en yl)a cr yla te (R ) p-NO3C6-
H4, 8c). Procedure B. Yield: 191.3 mg (77%). E/Z > 99:1.1H
NMR (300 MHz, CDCl3/TMS): δ 8.24 (d, J ) 20.6 Hz, 2H),
7.67-7.58 (m, 3H), 6.50 (d, J ) 15.9 Hz, 1H), 1.55 (s, 9H).
ter t-Bu tyl (E)-3-(p-Tolyl)a cr yla te (R ) p-CH3C6H4, 8d ).
Procedure B. Yield: 209.9 mg (96%). E/Z ) 94:6. 1H NMR (300
MHz, CDCl3/TMS) (for trans isomer): δ 7.57 (d, J ) 15.9 Hz,
1H), 7.41 (d, J ) 8.1 Hz, 2H), 7.18 (d, J ) 8.1 Hz, 2H), 6.32 (d,
J ) 15.9 Hz, 1H), 2.37 (s, 3H), 1.53 (s, 9H).
ter t-Bu tyl (E)-3-(p-An isyl)a cr yla te (R ) p-CH3OC6H4,
8e). Procedure B. Yield: 203.9 mg (87%). E/Z > 99:1. 5 mol %
catalyst was used. 1H NMR (300 MHz, CDCl3/TMS): δ 7.55
(d, J ) 16.0 Hz, 1H), 7.46 (d, J ) 8.7 Hz, 2H), 6.89 (d, J ) 8.7
Hz, 2H), 6.24 (d, J ) 16.0 Hz, 1H), 3.83 (s, 3H), 1.53 (s, 9H).
ter t-Bu tyl (E)-3-(2-F u r yl)a cr yla te (R ) C4H3O, 8f).
Procedure B. Yield: 171.1 mg (88%). E/Z > 99:1. 1H NMR (300
MHz, CDCl3/TMS): δ 7.45 (s, 1H), 7.33 (d, J ) 15.8 Hz, 1H),
6.57 (d, J ) 3.4 Hz, 1H), 6.44 (dd, J ) 3.4, 1.9 Hz, 1H), 6.25
(d, J ) 15.8 Hz, 1H), 1.52 (s, 9H).
ter t-Bu tyl (E,E)-5-P h en ylp en t-2,4-d ien oa te (R ) C6H5-
CHdCH2, 8g). Procedure B. Yield: 205.3 mg (89%). E/Z >
1
99:1. 5 mol % catalyst was used. H NMR (300 MHz, CDCl3/
P r ep a r a tion of Eth yl (E)-3-(4-ch lor op h en yl)a cr yla te
(R ) p-ClC6H4) in th e P r esen ce of Na HSO3. A mixture of
catalyst 2 (0.1680 g, 5 mol %), bromoacetate (0.06 mL, 0.5
mmol), and NaHSO3 (0.1664 g, 1.6 mmol) and in THF (3.0 mL)
was refluxed for 10 min, and then H2O (0.04 mL) was added.
The resulting mixture was stirred for 10 min, followed by
addition of K2CO3 (0.2760 g, 2.0 mmol). After being stirred
for 1 min, to this suspension was added a mixture of p-
chlorobenzaldehyde (1.0 mmol), ethyl bromoacetate (0.12 mL,
1.1 mmol), and water (0.03 mL) in THF (1.0 mL) in portions
in 3.5 h. The reaction was quenched by anhydrous MgSO4 after
the reaction was complete (monitored by TLC). The resulting
mixture was filtered rapidly through a glass funnel with a thin
layer of silica gel, washed with ethyl acetate. The combined
filtrate was concentrated and the residue was purified by flash
column chromatography to afford the desired product. Yield
for ethyl (E)-3-(4-chlorophenyl)acrylate: 172.6 mg (82%).
E/Z > 99:1. Yield for compound 7: 8.5 mg (3%). E/Z > 99:1.
The product was recrystallized with ethyl acetate/petroleum
ether. Mp: 69-70 °C. Compound 7. 1H NMR (300 MHz, CDCl3/
TMS): δ 7.48-7.20 (m, 6H), 6.87-6.85 (m, 2H), 5.92 (d, J )
15.3 Hz, 1H), 1.51 (s, 9H).
ter t-Bu tyl (E)-3-Cycloh exyla cr yla te (R ) C6H11, 8h ).
Procedure B. Yield: 161.2 mg (76%). E/Z > 99:1. 1H NMR (300
MHz, CDCl3/TMS): δ 6.81 (dd, J ) 15.8, 6.8 Hz, 1H), 5.68 (dd,
J ) 15.8, 1.3 Hz, 1H), 2.11-2.09 (m, 1H), 1.81-1.61 (m, 4H),
1.48 (s, 9H), 1.43-1.07 (m, 6H).
ter t-Bu tyl (E)-Dod ec-2-en oa te (R ) CH3(CH2)8, 8i).
Procedure B. Yield: 214.3 mg (84%). E/Z ) 95:5. Bp: 90 °C/2
mmHg. 1H NMR (300 MHz, CDCl3/TMS) (for trans isomer):
δ 6.86 (dt, J ) 15.5, 7.0 Hz, 1H), 5.74 (d, J ) 15.5 Hz, 1H),
2.16 (q, J ) 7.2 Hz, 2H), 1.49 (s, 9H), 1.47-1.27 (m, 14H), 0.89
(t, J ) 6.5 Hz, 3H). 13C NMR (75 MHz, CDCl3): 166.220,
148.195, 122.930, 79.940, 32.077, 31.895, 29.503, 29.426,
29.308, 29.200, 28.188, 28.123, 22.682, 14.100 ppm. IR (film):
ν ) 2928, 1718, 1368 cm-1. MS (m/e): 255 (0.65), 199 (100).
Anal. Calcd for C16H30O2: C, 75.53; H, 11.89. Found: C, 75.75;
H, 11.74.
ter t-Bu tyl (E)-3-(6-Ben zyloxy-2,2-d im eth yltetr a h yd r o-
fu r o[2,3-d ][1,3]d ioxol-5-yl)a cr yla te (8j). Procedure B. A 0.5

Wittig-Type Olefination Catalyzed by PEG-telluride
J . Org. Chem., Vol. 67, No. 9, 2002 3103
mmol portion of the corresponding aldehyde was employed.
supported telluride 2 (0.1684 g, 0.05 mmol), water (0.003 g,
0.16 mmol), and ω-bromoacetophenone (0.03185 g, 0.16 mmol)
or ethyl bromoacetate (0.018 mL, 0.16 mmol) in toluene (1 mL)
was stirred at 80 °C for 2 h. Mesitylene (0.0120 g, 0.1 mmol)
was added to the reaction mixture as the interal standard.
The reaction mixture was filtered, and the filtrate was
analyzed by GC to afford the yield.
Deh a logen a tion of ω-Br om oa cetop h en on e w ith Di-
bu tyl Tellu r id e. The solution of n-butyl telluride (0.4548 g,
1.88 mmol) and ω-bromoacetophenone (0.4310 g, 2.16 mmol)
was stirred at room temperature for 5 h. The resulting white
solid was washed with ether to afford the desired product 12.
Yield: 823.0 mg (99.5%). The product 12 was recrystallized
from THF. 1H NMR (300 MHz, CDCl3/TMS): δ 8.21 (d, 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 ) 1.7 Hz, 6H). 13C NMR (75 MHz, CDCl3):
δ 194.918, 135.119, 134.128, 128.994, 128.745, 34.199, 27.765,
27.617, 24.457, 13.148 ppm. 125Te (CDCl3/Me2Te): δ 551.191.
MS (ESI): 363.1 [M+(130Te)], 361.1 [M+(128Te)], 359.1 [M+(126Te)].
IR (KBr): ν ) 2962, 1662, 742, 690, 588 cm-1. Anal. Calcd for
C16H25BrOTe: C, 43.59; H, 5.72; Br, 18.12. Found: C, 43.38;
H, 5.57; Br, 17.50.
Yield: 121.9 mg (65%). E/Z > 99:1. The product was recrystal-
1
lized from ethyl acetate/petroleum. Mp: 92-94 °C. H NMR
(300 MHz, CDCl3/TMS): δ 7.37-7.27 (m, 5H), 6.88 (dd, J )
15.7, 5.3 Hz, 1H), 6.09 (dd, J ) 15.8, 1.3 Hz, 1H), 6.00 (m,
1H), 4.78 (s, 1H), 4.66-4.62 (m, 2H), 4.50 (d, J ) 12.1 Hz,
1H), 3.96 (d, J ) 3.2 Hz, 1H), 1.50 (s, 9H), 1.33 (s, 6H). 13C
NMR (75 MHz, CDCl3): 165.275, 140.132, 137.247, 128.654,
128.535, 128.214, 128.065, 127.812, 125.370, 111.921, 105.104,
83.134, 82.923, 80.448, 79.594, 72.295. 28.188, 26.880, 26.288
ppm. IR (KBr): ν ) 2981, 2935, 1714, 1662, 1028, 699 cm-1
.
MS (m/e): 361 (M - 15), 91 (100). Anal. Calcd for C21H28O6:
C, 67.00; H, 7.50. Found: C, 66.92; H, 7.39.
ter t-Bu tyl (E,E)-3-[2-(2-ter t-Bu toxycar bon ylvin yl)ph en -
yl]a cr yla t e (8k ). Procedure B. A 0.5 mmol portion of the
corresponding aldehyde was used. Other conditions: tert-butyl
acetate (0.18 mL, 1.2 mmol), NaHSO3 (0.1664 g, 1.6 mmol),
K2CO3 (0.2764 g, 2.0 mmol), PEG-supported telluride 2 (0.0337
g, 0.01 mmol), THF/H2O (2 mL/0.04 mL). Yield: 120.8 mg
1
(73%). H NMR (300 MHz, CDCl3/TMS): δ 7.94 (d, J ) 15.8
Hz, 2H), 7.92-7.54 (m, 2H), 7.38-7.35 (m, 2H), 6.27 (d, J )
15.8 Hz, 2H), 1.55(s, 18H).
ter t-Bu tyl 7-Ben zyloxy-(4S,5S)-ep oxy-2(E)-h ep ten oa te
(8l). Procedure B. The aldehyde was synthesized from 2,3-
epoxy-5-benzyloxypentan-1-ol (0.16 mmol) by Swern oxidation.
After the oxidation was complete, the mixture was concen-
trated. The residue was used directly without further purifica-
tion. Yield based on 2,3-epoxy-5-benzyloxypentan-1-ol: 33.7
mg (69%). E/Z > 99:1. 1H NMR (300 MHz, CDCl3/TMS): δ
7.37-7.26 (m, 5H), 6.55 (dd, J ) 15.7, 7.2 Hz, 1H), 6.04 (d,
J ) 15.7 Hz, 1H), 4.52 (s, 2H), 3.61 (t, J ) 6.1 Hz, 2H), 3.25
(d, J ) 7.1 Hz, 1H), 3.06-3.02 (m, 1H), 1.94-1.88 (m, 2H),
1.48 (s, 9H). 13C NMR (75 MHz, CDCl3): 164.952, 143.294,
138.192, 128.444, 127.702, 127.638, 125.804, 80.731, 73.147,
66.624, 59.018, 56.442, 32.458, 28.108 ppm. IR (film): ν )
2927, 1714, 1640, 1162 cm-1. MS (m/e): 247 (M - 57), 91(100).
Th e Roles of P EG. P r ep a r a tion of 11. A solution of butyl
3-phenoxylpropyl telluride16 and tert-butyl bromoacetate (0.40
mL, 2.80 mmol) in THF (0.5 mL) was stirred at 0 °C for 2.5 h.
The reaction mixture was concentrated and dried in vacuo.
The resulting colorless oil was dissolved in tertiary butyl
alcohol (1 mL), and then a solution of sodium tetraphenylbo-
rate (0.6844 g, 2.0 mmol) in tertiary butyl alcohol (10 mL) was
added at room temperature. The suspension was filtered and
washed twice with methanol. The white solid was collected as
the desired product. Yield: 93% (1.4011 g). The product was
recrystallized with CH2Cl2/ethyl acetate/ether at -20 °C. Mp:
127-129 °C. 1H NMR (300 MHz, CDCl3/TMS): δ 7.52 (s, 8H),
7.34-7.28 (m, 2H), 7.08-7.01 (m, 9H), 6.90 (t, J ) 7.1 Hz, 4H),
6.75 (dd, J ) 8.7, 0.9 Hz, 2H), 3.75 (t, J ) 4.1 Hz, 2H), 2.51 (s,
2H), 2.10-2.08 (m, 4H), 1.48 (s, 2H), 1.44 (s, 9H), 1.26-1.22
(m, 4H), 0.83 (t, J ) 7.1 Hz, 3H). 13C NMR (75 MHz, CDCl3):
δ 165.922, 164.223 (q, J ) 48.9 Hz), 156.686, 136.111, 129.765,
125.986, 125.957, 122.077, 114.269, 84.630, 67.068, 27.853,
27.362, 26.064, 25.457, 24.597, 24.226, 22.230, 13.138 ppm.
A mixture of compound 12 (0.1881 g, 0.4 mmol) and water
(0.02 mL) in CH2Cl2/THF (0.5 mL/0.5 mL) was stirred at room
temperature overnight. The yield of aceophenone was deter-
mined by GC (mesitylene as interal standard). Yield: 100%.
The reaction mixture was filtered, and the filtrate was
concentrated. The residue was washed with ether to give
compound 13 as a white solid. Yield: 117.5 mg (94%). 1H NMR
(300 MHz, CDCl3/TMS): δ 3.48 (br, 4H), 3.10 (br, 4H), 2.02-
2.00 (m, 8H), 1.57 (q, J ) 7.4 Hz, 8H), 1.00 (t, J ) 1.3 Hz,
12H). 13C NMR (75 MHz, CDCl3): δ 43.2917, 27.2311, 24.5575,
13.6348 ppm. MS (ESI): 261.1 [M+(130Te)], 259.1 [M+(128Te)],
257.1 [M+(126Te)]. IR (KBr): ν ) 2961, 1464, 632, 439 cm-1
.
Anal. Calcd for C16H36Br2OTe2: C, 29.14; H, 5.50; Br, 24.23.
Found: C, 29.31; H, 5.75; Br, 24.27.
On e-P ot Rea ction of p-Ch lor oben za ld eh yd e, P EG-
Su p p or ted Tellu r id e 2, ω-Br om oa cetop h en on e or Eth yl
Br om oa ceta te. A solution of PEG-supported telluride 2
(0.1684 g, 0.05 mmol), p-chlorobenzaldehyde (0.014 g, 0.1
mmol), and ω-bromoacetophenone (0.0320 g, 0.16 mmol) or
ethyl bromoacetate (0.018 mL, 0.16 mmol) in toluene (1 mL)
was stirred at 80 °C for 2 h. After the reaction was complete,
the reaction mixture was filtered, and the filtrate was analyzed
by GC to give the yields (mesitylene was used as internal
reference).
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
(PROJ ECT 973, No.2000 48007), and the “Hundred
Scientist Program” from the Chinese Academy of Sci-
ences.
IR (KBr): ν ) 1719, 1601, 1589, 1579, 1236, 709, 604 cm-1
.
Anal. Calcd. for C43H51BO3Te: C, 68.47; H, 6.82. Found: C,
68.32; H, 6.80.
Mech a n ism Resea r ch . Deh a logen a tion of ω-Br om o-
a cetop h en on e a n d Eth yl Br om oa ceta te w ith P EG-Su p -
p or ted Tellu r id e Com p ou n d 2. The solution of PEG-
Su p p or tin g In for m a tion Ava ila ble: Crystal structure
data of compounds 11-13. This material is available free of
charge via the Internet at http://pubs.acs.org.
J O025586H