DMP-mediated one-pot oxidative olefination of silyl ethers

Article abstract of DOI:10.1016/j.tet.2005.04.021

Silyl ethers of arylic, allylic, propargylic and unactivated alcohols could be deprotected and oxidized with Dess-Martin periodinane, and the resulting aldehydes could be directly converted to the corresponding α,β- unsaturated esters in one pot with stabilized phosphoranes. Good selectivities were achieved upon a variety of protecting groups of alcohol by using this method. Other advantages of the protocol included simplicity of operations and high efficiency, as well as good to excellent yields.

Full text of DOI:10.1016/j.tet.2005.04.021

Tetrahedron 61 (2005) 5818–5821
DMP-mediated one-pot oxidative olefination of silyl ethers
*
Guisheng Deng, Baihua Xu and Chunyu Liu
College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081, People’s Republic of China
Received 18 March 2005; revised 6 April 2005; accepted 9 April 2005
Abstract—Silyl ethers of arylic, allylic, propargylic and unactivated alcohols could be deprotected and oxidized with Dess–Martin
periodinane, and the resulting aldehydes could be directly converted to the corresponding a,b-unsaturated esters in one pot with stabilized
phosphoranes. Good selectivities were achieved upon a variety of protecting groups of alcohol by using this method. Other advantages of the
protocol included simplicity of operations and high efficiency, as well as good to excellent yields.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
One-pot methods have broadly been applied in organic
synthesis. Syntheses of a,b-unsaturated esters using one-pot
methodologies have been attracted attentions due to their
widely potential applications in organic chemistry. For
instance, one-pot oxidative olefination of alcohol using
active manganese dioxide as an oxidant in the presence of
Wittig reagents has been studied extensively (Scheme 1).1–4
In those procedures, the resulting aldehydes by the
Scheme 2.
and evades liability to oligomerisation, facile hydration,
acerial oxidation, polymerization5 or isomerization.6
oxidation of alcohols can be trapped in situ immediately
by Wittig reagents to afford the corresponding olefins.
Exploration of other one-pot transformations of various
2. Results and discussion
substrates to a,b-unsaturated esters still keeps attractive
today. In principle, all the precursors, which can be
converted to the aldehydes, are able to apply in the methods
to generate a,b-unsaturated esters in one pot.
Initially, the reactions were performed under the conditions
similar to the reported cases using active manganese
dioxide.1–4 However, no reactions occurred when the silyl
ethers were treated under the same conditions. Obviously,
active manganese dioxide is not able to remove silyl ether
protecting groups in the first step. To accomplish this one-
pot transformation, it is crucial to choose an appropriate
reagent, which can deprotect silyl ethers and immediately
oxidize the resulting alcohols to the corresponding alde-
hydes. Many reagents are potentially suitable to meet these
requirements in the literature.7 The oxidants that can
oxidatively deprotect silyl ethers would be preferred to
this transformation. However, these oxidants may encounter
the difficulties due to their sensitivities to the Wittig
reagents under strong acidic and strong oxidative con-
ditions. With these considerations, Dess–Martin
periodinane (DMP), a mild oxidant used for the deprotec-
tion–oxidation reaction of silyl ethers,8 was examined for
this purpose.
Scheme 1.
In this paper, we report a new one-pot transformation of
silyl ethers to a,b-unsaturated esters (Scheme 2). In our
initial plan, deprotection of silyl ethers, oxidation of the
resulting alcohols and subsequent Wittig reaction to trap the
in situ generated aldehydes were combined into a one-step
operation. Such a transformation is particularly advan-
tageous because it avoids the isolations of intermediate
alcohols and aldehydes, reduces the volatility and toxicity,
Keywords: Silyl ether; Unsaturated ester; Wittig reaction; Dess–Martin
periodinane; One-pot method.
*
Corresponding author. E-mail: gsdeng@hunnu.edu.cn
To our delight, Dess–Martin periodinane was proved to be
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.04.021

G. Deng et al. / Tetrahedron 61 (2005) 5818–5821
5819
efficient in the procedure without any additives. Treatment
of a mixture of silyl ethers 1 and ylide 3 in dichloromethane
with DMP 2 at room temperature afforded a,b-unsaturated
esters 4, which were predominantly trans-isomers as
expected (Scheme 3). The results were summarized in
Table 1.
product as compared with the case using (2Z)-1,4-buten-diol
as the substrate.2a,4d
Unactivated silyl ethers, such as alkylic examples, were also
proved to be successful (entries 7–9 in Table 1). The
examined deprotection–oxidation–Wittig reactions of
Me3Si ethers of 1,2- and 1,3-diols both gave the expected
products (entries 10 and 11 in Table 1). In contrast, the
sequential oxidation–Wittig reactions of 1,2- and 1,3-diols
were reported to give the cleavage products.2a,9
Scheme 3.
t
Both of THP and BuMe2Si were examined as protection
As shown in Table 1, the one-pot sequential deprotection–
oxidation–Wittig reaction of more active silyl ethers, such
as arylic, vinylic and alkynylic silyl ethers, generated a,b-
unsaturated esters in 84–94% yields (entries 1–4 in Table 1).
The trans-vinylic silyl ether was converted to 4-trans,
2-trans-unsaturated ester (entry 3 in Table 1); while the cis-
vinylic silyl ether gave 4-cis, 2-trans-unsaturated ester
under the same conditions (entry 4 in Table 1). This
indicated the configuration of the cis-vinylic silyl ether was
remained without any isomerization. However, it was found
by us that the stepwise deprotection–oxidation of the cis-
allylic silyl ether and followed by Wittig reaction
predominately gave the (4E,2E)-isomer under the same
conditions. This was easily explained by rapid isomerization
of the resulted cis-enals.6 Extension of the methodology to
disilyl ethers derived from (Z)-1,4-buten-diol and 1,4-
butynyl-diol was also successful, affording the correspond-
ing double and symmetrical adducts (entries 5 and 6 in
Table 1). Pre-existing Z-alkene geometry of silyl ether
derived from (2Z)-1,4-buten-diol was preserved into its
groups of hydroxyls to replace Me3Si group. The cases with
tBuMe2Si ethers underwent the same reaction as those with
TMS ethers (entry 12 in Table 1); however, the derivatives
protected with THP could not proceed the same reaction
(entries 12 and 13 in Table 1).
Further investigations showed that the arylic, vinylic,
alkynylic and alkylic TMS and/or TBDMS ethers, etc.,
could be deprotected using 1 equiv of acetic acid, however,
the derivatives with THP group could not deprotected under
the same conditions.
High-valent iodine-mediated cleavage of the oxygen–silyl
linkage has been reported. For example, silyl protecting
groups can be cleaved by sodium periodate10 and o-iodoxy-
benzoic acid (IBX).11 The former reaction went to
completion when NaIO4 was used in 1.1–2.5 mol ratio.
The latter reaction was performed when IBX was used in
0.5–1.5 mol ratio. It is noteworthy that these reactions are
not catalytic. Accordingly, the reaction would require
Table 1. DMP-mediated one-pot oxidative olefination of silyl ethers
Entry
1
Silyl ether 1
Product 4
a,
Reaction time, yield, (selectivity)a
a, PhCH2OSiMe3
20 h, 94%, (E:ZZ20:1)
2
b,
2.5 d, 87%, (E:ZZ9:1)
b,
c,
3
4
2.5 d, 90%, (2E,4E:2Z,4EZ10.5:1)
3 d, 84%, (2E,4Z:2Z,4ZZ8:1)
c,
d,
d,
e,
f,
5
6
7
8
3 d, 65%, (2E,4Z,6E:2Z,4Z,6EZ3.6:1)
2 d, 78%, (2E,6E:2Z,6EZ5:1)
3 d, 48%, (2E,5E:2Z,5EZ4:1)
75 h, 60%, (E:ZZ5.5:1)
e,
f,
g,
g,
h,
i,
h,
9
i, CH3(CH2)6OSiMe3
3 d, 70%, (E:ZZ4.5:1)
10
3 d, 60%, (2E,4E:2Z,4EZ5:1)
j,
k,
l,
j,
11
12
3 d, 40%, (2E,5E:2Z,5EZ3.3:1)
3 d, 62%, (E:ZZ7:1)
k,
l,
13
3 d, 65%, (E:ZZ6:1)
m,
m,
a The ratios were determined by 1H NMR.

5820
G. Deng et al. / Tetrahedron 61 (2005) 5818–5821
2 equiv of DMP, at least 1.5 equiv to carry out this one-pot
transformation. However, the experiments showed that only
1 equiv of DMP was enough to finish the above sequential
reactions. This suggested that the desilylation process was
probably not mediated by DMP except the starting stage. A
reasonable explanation was that Dess–Martin periodinane
(DMP) 2 or trace amount of acetic acid in available
commercial source started the deprotection of silyl ethers 1
to form the corresponding alcohols 5. The resulting alcohols
5 could be oxidized by Dess–Martin periodinane 2 to
generate the corresponding aldehydes 6 and 2 equiv of
acetic acid.12 The aldehydes 6 were trapped immediately in
situ with Wittig reagent 3 to give the a,b-unsaturated esters
4 (Scheme 4). With those newly produced acetic acid, the
cycle of deprotection of silyl ethers 1 maintained. There-
fore, the reaction did not require additional DMP for
desilylation once it started.
3.1. General procedure
Silyl ether 1d (0.317 g, 2 mmol) and methyl triphenyl-
phosphoranylideneacetate (0.868 g, 2.6 mmol) were dis-
solved in anhydrous CH2Cl2 (30 mL). Dess–Martin
periodinane (1.70 g, 4 mmol) was added in 3–5 portions
over 16–24 h to the reaction mixture. After stirring for 64 h
at room temperature, Et2O (30 mL) and saturated aqueous
NaHCO3 (20 mL) were added. After stirring for another
10 min, the mixture was filtered; the organic layer was
separated and concentrated under reduced pressure. The
residue was purified by chromatography on silica gel by
eluting with 15:1 petroleum ether–Et2O to give methyl
(2E,4Z)-2,4-heptadienoate 4d (0.235 g, 84%) as a colourless
oil.4d dH (CDCl3, 300 MHz) 0.83 (t, JZ7.1 Hz, 3H), 2.09–
2.19 (m, 2H), 3.73 (s, 3H), 5.77 (d, JZ15.6 Hz, 1H), 6.03–
6.16 (m, 2H), 7.21–7.30 (m, 1H). nmax (KBr) 2953, 2924,
2854, 1719, 1666, 1638, 1463, 1377, 1274, 1178 cmK1
.
3.1.1. Ethyl (2E)-3-phenylpropenoic acid 4a. A colourless
oil3 was obtained in 94% yield. dH (CDCl3, 300 MHz) 1.34
(t, JZ7.2 Hz, 3H), 4.27 (q, JZ7.2 Hz, 2H), 6.44 (d, JZ
15.9 Hz, 1H), 7.32–7.60 (m, 5H), 7.69 (d, JZ15.9 Hz, 1H).
nmax (KBr) 3029, 2925, 2854, 1716, 1663, 1578, 1496, 1449,
1367, 1270, 1175, 1040 cmK1
.
Scheme 4.
3.1.2. Methyl (2E)-2-hepten-4-ynoate 4b. A colourless
oil15 was obtained in 87% yield. dH (CDCl3, 300 MHz) 0.86
(t, JZ7.3 Hz, 3H), 2.39 (dq, JZ7.3, 2.1 Hz, 2H), 3.76 (s,
3H), 6.15 (d, JZ15.9 Hz, 1H), 6.77 (dt, JZ15.9, 2.1 Hz,
1H). nmax (KBr) 2953, 2924, 2854, 2217, 1730, 1666, 1625,
The generation rates of aldehydes 6 may be controlled by
deprotection of silyl ethers 1. The resulting aldehydes 6
were trapped before they were isomerized and/or decom-
posed. Therefore, the pre-existing Z-alkene geometry was
retained (entry 5 in Table 1). In addition, the hydroxyl
groups protected with THP remained as the protected form
in the products because the corresponding deprotections
could not occur under such conditions (entries 12 and 13 in
Table 1). The actual mechanism is still unclear.
1462, 1377, 1274, 1159, 962, 700 cmK1
.
3.1.3. Methyl (2E,4E)-2,4-octadienoate 4c. A colourless
oil16 was obtained in 90% yield. dH (CDCl3, 300 MHz) 0.92
(t, JZ7.2 Hz, 3H), 1.40–1.52 (m, 2H), 2.12–2.18 (m, 2H),
3.74 (s, 3H), 5.79 (d, JZ15.6 Hz, 1H), 6.12–6.23 (m, 2H),
7.23–7.31 (m, 1H). nmax (KBr) 2953, 2925, 2854, 1725,
In summary, a new one-pot oxidative olefination of silyl
ethers using DMP was investigated for the first time. This
protocol proved to be a useful and efficient method to
directly convert the silyl ethers to corresponding a,b-
unsaturated esters, and presented a significant expansion of
the exiting methods.2–4 The geometry of olefins retained
during the reaction and the problems like oxidative cleavage
of diols were not observed.2a,9 Potential uses of this
methodology in the multi-step synthesis of complex
compounds and natural products are under investigation in
our laboratory.
1665, 1646, 1462, 1377, 1275, 1141, 999, 701 cmK1
.
3.1.4. Dimethyl (2E,4Z,6E)-2,4,6-octatrienedioate 4e.
White crystals4d were obtained in 65% yield, mp 112–
116 8C. dH (CDCl3, 300 MHz) 3.79 (s, 6H), 6.02 (d, JZ
15.3 Hz, 2H), 6.35–6.45 (m, 2H), 7.77–7.85 (m, 2H). nmax
(KBr) 2919, 2850, 1708, 1624, 1464, 1367, 1318, 1270,
1164, 1025, 982, 727 cmK1
.
3.1.5. Dimethyl (2E,6E)-2,6-octadien-4-ynedioate 4f.
White crystals4d were obtained in 78% yield, mp 106–
110 8C. dH (CDCl3, 300 MHz) 3.76 (s, 6H), 6.29 (dd, JZ
16.8, 2.0 Hz, 2H), 6.87 (dd, JZ16.8, 2.0 Hz, 2 Hz). nmax
(KBr) 2924, 2853, 2200, 1715, 1610, 1467, 1317, 1273,
3. Experimental
1167, 978 cmK1
.
IR spectra were recorded on a Nicolet 370 FT-IR. 1H NMR
spectra were performed on Varian YH 300 in CDCl3
solution using tetramethylsilane as an internal standard.
Dichloromethane was distilled before use from calcium
hydride. Other solvents were distilled prior to use. Organic
extracts were concentrated using a rotary evaporator at
below 50 8C. Melting points were uncorrected. Silyl
ethers,13 Wittig reagents14 and Dess–Martin periodinane
(DMP)12 were prepared according to the known procedures.
In addition, DMP was obtained from commercial source.
3.1.6. Methyl (2E,5Z)-2,5-octadienoate 4g. Yellow
crystals4d were obtained in 48% yield, mp 86–90 8C. dH
(CDCl3, 300 MHz) 1.07 (t, JZ7.5 Hz, 3H), 1.89–2.02 (m,
2H), 2.61–2.68 (m, 2H), 3.79 (s, 3H), 6.25 (d, JZ15.0 Hz,
1H), 6.46 (d, JZ15.0 Hz, 1H), 7.18–7.34 (m, 2H). nmax
(KBr) 2922, 2853, 1704, 1600, 1463, 1377, 1283, 1159, 973,
722 cmK1
.
3.1.7. Ethyl (2E)-2-decen-5-ynoate 4h. A colourless oil17

G. Deng et al. / Tetrahedron 61 (2005) 5818–5821
5821
Chem. 1997, 62, 9376–9378. (b) Crich, D.; Mo, X. Synlett
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was obtained in 60% yield. dH (CDCl3, 300 MHz) 0.96 (t,
JZ7.3 Hz, 3H), 1.09–1.14 (m, 4H), 1.29 (t, JZ7.2 Hz, 3H),
2.33 (t, JZ7.5 Hz, 2H), 4.03–4.13 (m, 2H), 4.20 (q, JZ
7.2 Hz, 2H), 5.82 (d, JZ15.6 Hz, 1H), 6.97 (dt, JZ15.6,
7.1 Hz, 1H). nmax (KBr) 2927, 2855, 2350, 1726, 1662,
3. Shuto, S.; Niizuma, S.; Matsuda, A. J. Org. Chem. 1998, 63,
4489–4493.
1462, 1377, 1275, 1176, 941, 702 cmK1
.
4. (a) Reid, M.; Rowe, D. J.; Taylor, R. J. K. Chem. Commun.
2003, 2284–2285. (b) Blackburn, L.; Wei, X.; Taylor, R. J. K.
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5. Darkins, P.; McCarthy, N.; Mckervey, M. A.; Ye, T. Chem.
Commun. 1993, 1222–1223.
3.1.8. Methyl (2E)-2-nonenoate 4i. A colourless oil18 was
obtained in 70% yield. dH (CDCl3, 300 MHz) 0.88 (t, JZ
7.1 Hz, 3H), 1.29–1.45 (m, 8H), 2.16–2.23 (m, 2H), 3.73 (s,
3H), 5.82 (d, JZ15.9 Hz, 1H), 6.98 (dt, JZ15.9, 7.2 Hz,
1H). nmax (KBr) 2955, 2928, 2857, 1724, 1656, 1600, 1466,
1379, 1266, 1169, 978 cmK1
.
6. (a) Thomas, D. A.; Warburton, W. K. J. Chem. Soc. 1965,
2988. (b) Xiao, W. Y.; Prestwich, G. D. Synth. Commun. 1990,
20, 3125.
3.1.9. Diethyl (2E,4E)-2,4-hexadienoate 4j. White crystals
were obtained in 60% yield, mp 57–59 8C (lit.2a 57–59 8C).
dH (CDCl3, 300 MHz) 1.30 (t, JZ7.1 Hz, 6H), 4.23 (q, JZ
7.1 Hz, 4H), 6.21 (dd, JZ11.6, 3.0 Hz, 2H), 7.33 (dd, JZ
11.6, 3.0 Hz, 2H). nmax (KBr) 2924, 2853, 1670, 1609, 1462,
7. (a) Chandrasekhar, S.; Mohanty, P. K.; Takhi, M. J. Org.
Chem. 1997, 62, 2628–2629. (b) Chang, S.; Lee, N. H.;
Jacobsen, E. N. J. Org. Chem. 1993, 58, 6939–6941. (c) Astles,
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1246, 1160, 1032, 863, 728 cmK1
.
3.1.10. Diethyl (2E,5E)-2,5-heptadienedioate 4k. A
yellow oil19 was obtained in 40% yield. dH (CDCl3,
300 MHz) 1.29 (t, JZ7.2 Hz, 6H), 2.44–2.50 (m, 2H),
4.18 (q, JZ7.2 Hz, 4H), 5.92 (d, JZ15.8 Hz, 2H), 6.97 (dt,
JZ15.8, 7.2 Hz, 2H). nmax (KBr) 2981, 2937, 1721, 1655,
8. (a) Oskooie, S. H. A.; Heravi, M. M.; Sarmad, N.; Saednia, A.;
Ghassemzadeh, M. Indian J. Chem., Sect. B: Org. Chem. Incl.
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1467, 1369, 1271, 1167, 1046, 979, 711 cmK1
.
3.1.11. Ethyl (2E)-4-[(tetrahydro-2H-pyran-2-yl)oxy]-2-
butenoate 4l or 4m. A yellow oil20 was obtained in 62 and
65% yields, respectively. dH (CDCl3, 300 MHz) 1.29 (t, JZ
7.2 Hz, 3H), 1.50–1.83 (m, 6H), 2.48–2.54 (m, 2H), 3.46–
3.53 (m, 2H), 3.81–3.88 (m, 2H), 4.20 (q, JZ7.2 Hz, 2H),
4.59 (t, JZ3.8 Hz, 1H), 5.90 (d, JZ15.8 Hz, 1H), 6.99 (dt,
JZ15.8, 7.0 Hz, 1H). nmax (KBr) 2925, 2855, 1725, 1655,
10. Wang, M.; Li, C.; Yin, D.; Liang, X.-T. Tetrahedron Lett.
2002, 43, 8727–8729.
11. Wu, Y.; Huang, J.-H.; Shen, X.; Hu, Q.; Tang, C.-J.; Li, L.
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1464, 1367, 1298, 1262, 1176, 1036, 980, 870 cmK1
.
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Acknowledgements
We are grateful for financial support from the Education
Department of Hunan Province (Grant No. 03C247).
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