Catalytic allylation of hydrates of α-keto aldehydes and glyoxylates with allyltrimethylsilane using non-fluorine-containing sulfonic acids as catalysts

Article abstract of DOI:10.1002/hc.1081

Methanesulfonic acid, aromatic sulfonic acids, and 10-camphorsulfonic acid have been used as catalysts in allylation of hydrates of α-keto aldehydes 1a-d and glyoxylates 1e-f with allyltrimethylsilane 2 to afford the corresponding homoallylic alcohols 4a-

Full text of DOI:10.1002/hc.1081

Heteroatom Chemistry
Volume 12, Number 6, 2001
Catalytic Allylation of Hydrates of -Keto
Aldehydes and Glyoxylates with
Allyltrimethylsilane Using
Non-Fluorine-Containing Sulfonic Acids
as Catalysts
Ming Wen Wang, Yong Jun Chen, and Dong Wang
Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080,
P. R. China; Fax: 8610-62559373; E-mail: dwang70118@yahoo.com
Received 5 March 2001; revised 3 April 2001
triflate [4], trimethylsilyl triflate (TMSOTf) [5], a su-
ABSTRACT: Methanesulfonic acid, aromatic sul-
peracid TfOH+2 B(OTf)4 (prepared from BBr3 and
TfOH) [6], and a Bro¨nsted acid HN(SO2F)2 [7].
fonic acids, and 10-camphorsulfonic acid have been
used as catalysts in allylation of hydrates of
-
The strong electron-withdrawing fluorine atom con-
tained in these catalysts appears to be very important
for the catalytic capability. A question arises whether
reagents without a fluorine substituent could also
catalyze the Hosomi-Sakurai reaction. On the other
hand, since allyltrimethylsilane is likely hydrolyzed
under acidic conditions [8], a Bro¨nsted acid has been
used only a few times as a catalyst for the addition
of allylsilane to carbonyl compounds [7]. Herein, we
wish to report the results on the allylation of aldehy-
des with allyltrimethylsilane (Hosomi-Sakurai reac-
tion) catalyzed by non-fluorine-containing sulfonic
acids, including methanesulfonic acid, aromatic sul-
fonic acids, and 10-camphorsulfonic acid.
keto aldehydes 1a–d and glyoxylates 1e–f with al-
lyltrimethylsilane 2 to afford the corresponding ho-
moallylic alcohols 4a–e in good yields. Two plausible
mechanisms of sulfonic acid–catalyzed allylation re-
actions with an allysilane are discussed. 2001 John
Wiley & Sons, Inc. Heteroatom Chem 12:534–538, 2001
C
INTRODUCTION
The allylation of carbonyl compounds with an al-
lylsilane under Lewis acid conditions (the Hosomi-
Sakurai reaction [1]) has been extensively used for
the formation of carbon–carbon bonds in organic
synthesis [2]. This reaction can be promoted by sto-
ichiometric amounts of a conventional Lewis acid
such as TiCl4, SnCl4, and AlCl3 and catalyzed by var-
ious species, such as fluoride ions [3], lanthanide
RESULTS AND DISCUSSION
Methanesulfonic Acid as a Catalyst
The allylation reactions of hydrates of -keto aldehy-
des (1b–d) and glyoxylates (1e–f) with allyltrimethyl-
silane 2 in the presence of a catalytic amount (10 mol
%) of methanesulfonic acid (MsOH) (3) were carried
out in dichloromethane (Scheme 1) at room temper-
For preliminary report, see: Wang, M. W.; Chen, Y. J.; Wang, D.
Synlett 2000, 385–387.
Correspondence to: Dong Wang.
Contract Grant Sponsor: National Natural Science Foundation
of China (298720041).
ature for a given time to afford the corresponding
-
Contract Grant Sponsor: Chinese Academy of Sciences.
2001 John Wiley & Sons, Inc.
c
keto (4a–c) and -ester (4d,e) homoallylic alcohols
534

Catalytic Allylation of Hydrates of -Keto Aldehydes and Glyoxylates 535
O
O
10 mol% cat.
R
SiMe3
+
R
CHX2
OH
2
1a R = Ph, X2 = O
1b R = Ph, X = OH
1c R = p-MeOPh, X = OH
1d R = p-HOPh, X = OH
1e R = BuO, X = OH
1f R = menthylO, X =OH
4a R = Ph
4b R = p-MeOPh
4c R = p-HOPh
4d R = BuO
4e R =menthylO
SiMe
_
3
O2N
+
O
OSO Me
2
SO3SiMe3
SO3SiMe3 H3C
SO3SiMe3
R
H
O
9a
7
9c
9b
SCHEME 1
in yields of 62–74% (Table 1). The reactions show
very good chemoselectivity with the retention of keto
and ester carbonyl groups. In the case of ( )-menthyl
glyoxylate 1f [9], the diastereomeric excess (de) of
the product 4e is 13%, determined by diastereomeric
protons in 1H NMR spectra.
0.38, assigned to silylmethyl protons of trimethylsilyl
methanesulfonate (5, TMSOMs) ([10]: 0.4) appears
soon, and this clearly supports the in situ formation
of protodesilylation product 5 in the course of the
reaction. Furthermore, the allylation reaction of 1b
with 2 using 5 as a catalyst, which was prepared by
the reaction of 3 with chlorotrimethylsilane, gave 4a
in a comparable yield 65% (entry 2 vs. 1). It is in-
teresting to note from the results that the in situ–
generated TMSOMs from mixing 2 with 3 retains
catalytic capability even in the case of the substrates
With regard to the results of the MsOH-catalyzed
Hosomi-Sakurai reaction, we became inquisitive as
to whether MsOH would be an actual catalyst itself.
When the reaction mixture of 2 and 3 is monitored
1
by H NMR spectroscopy, a new up-field peak at
TABLE 1 Methanesulfonic Acid–Catalyzed Allylation of 1a–fa
Entry
Substrate
Catalyst
Amount of cat. (mol %)
Temp. ( C)
Time (h)
Product
Yieldb (%)
1
2
3
4
5
6
7
8
1b
1b
1a
1c
1d
1e
1f
3
5
3
3
3
3
3
6
10
10
10
10
10
10
10
20
25
25
25
25
25
25
25
40
12
12
10
12
12
8
4a
4a
4a
4b
4c
4d
4e
4a
66
65
62
63
70
74
72
54
15
10
1b
aSolvent: CH2Cl2.
bIsolated yield.

536 Wang, Chen, and Wang
bearing active protons of a hydroxyl group. How-
ever, decomposition or deactivation of the conven-
tional moisture-sensitive Lewis acid catalysts might
occur by using the same substrates. Corresponding
to aldehyde hydrate 1b, adehyde 1a, prepared by de-
hydration of 1b by distillation under P2O5, has sim-
ilar reactivity in the methanesulfonic acid catalyzed
allylation reactions (entry 3 vs. 1). In the reaction
mixture of 1b with 2, the formation of 1a was ob-
served. It is suggested that there might be an equi-
librium between 1a and 1b in the reaction media,
and the formed 1a is activated by in situ-generated
TMSOMs and reacts with 2, driving the equilibrium
to the side of the aldehyde 1a. Thus, similar to the
plausible mechanism for the TMSOTf catalyzed re-
action, suggested by Davis [6b], the catalyzed ally-
lation reaction of aldehyde hydrates with 2 in the
presence of 3 could be assumed to involve the in situ
generation of the oxonium cation 7 with counterion
MsO . The catalytic function of MsOH 3 performs
by producing an actual catalyst, TMSOMs.
of 8a, 8b, or 8c respectively with 2 were observed.
The chemical shift at 0.36 is assigned to the TMS
proton of trimethylsilyl benzenesulfonate 9a ([12]:
0.39), that at 0.37 is assigned to trimethylsilyl p-
toluenesulfonate 9b ([12]: 0.38), and that at 0.44 is
assigned to trimethylsilyl m-nitrobenzenesulfonate
9c. By using 9a as a catalyst, the allylation of
1b proceeds smoothly giving the corresponding
homoallylic alcohol 4a in 69% yield. However, other
types of organic acids, such as benzoic acid and
heptanoic acid, were not effective in this reaction
at all, with starting materials being recovered. The
aromatic sulfonic acid–catalyzed allylation of alde-
hydes with 2 also seemed to be effected by the
protodesilylation intermediates of 2 with sulfonic
acid.
10-Camphorsulfonic Acid as a Catalyst
10-Camphorsulfonic acid (CSA), (10) has been
used extensively in synthetic organic chemistry as an
acid catalyst [13]. By using a catalytic amount of 10
(10 mol %), the reactions of 1b–f with 2 in acetoni-
trile at room temperature proceeded smoothly to af-
ford the products 4a–e in yields of 64–78% (Table 3).
The allylation of aldehyde hydrate 1a, catalyzed by
10, also gave 4a in good yield (68%) (entry 1). The
hydroxyl group in each substrate does not need to
be protected. Even in the presence of traces of wa-
ter, (CH3CN/H2O [50:1 to 20:1]), the CSA-catalyzed
allylation reactions still proceeded smoothly (entries
3, 7, and 8). In order to examine the mechanism of
the CSA-catalyzed allylation reaction, the following
experiments were carried out: (1) after stirring of the
mixture of 10 with 2 for 6 hours, no 1H NMR peak of
the corresponding TMS proton was detected, and the
starting material 10 was recovered; (2) in the pres-
ence of 2,6-di-tert-butyl-4-methylpyridine (15 mol %)
[14], a known proton scavenger, the CAS-catalyzed
allylation reaction does not proceed at all; (3) the
reaction of 10 with chlorotrimethylsilane gave com-
plicated products, but no formation of the corres-
ponding TMSOCSA compound was detected. It is
In comparison, a catalytic amount of trifluo-
romethanesulfonic acid (TfOH), (6) [11] was used as
a catalyst in the reaction of 1b with 2. It was found
that stronger reaction conditions (reaction tempera-
ture 40 C; 20 mol % of catalyst) were required, and
a relatively low yield of product (45%) was obtained.
Aromatic Sulfonic Acids as Catalysts
The reactions of -keto aldehyde hydrate 1b with 2
in the presence of aromatic sulfonic acids, includ-
ing benzenesulfonic acid 8a, p-toluenesulfonic acid
8b, and m-nitrobenzenesulfonic acid 8c were ex-
amined (Table 2). It was found that the aromatic
sulfonic acids 8a–c have a lower catalytic ability
than MsOH 3 under the same reaction conditions.
A higher reaction temperature (40 C) and more cat-
alyst (20 mol %) are required. The substituents on the
benzene ring, either methyl or the nitro group, do not
influence the catalytic ability in the allylation reac-
tion. Similarly, the new up-field peaks of tetramethyl-
silane (TMS) in the 1H NMR spectra of the mixtures
TABLE 2 Aromatic Sulfonic Acid–Catalysed Allylation of 1ba
Entry
Catalyst
Amound of cat. (mol %)
Temp. ( C)
Time (h)
Product
Yieldb (%)
1
2
3
4
8a
8b
8c
9a
20
20
20
20
40
40
40
40
10
10
10
12
3a
3a
3a
3a
45
40
57
64
aSolvent: CH3CN.
bIsolated yield.

Catalytic Allylation of Hydrates of -Keto Aldehydes and Glyoxylates 537
TABLE 3 CSA-Catalyzed Allylation of 1a–ga
Entry
Substrate
Solventb
Temp. ( C)
Time (h)
Product
Yieldc(%)
1
2
3
4
5
6
7
8
9
1a
1b
1a
1c
1d
1e
1e
1e
1f
A
A
B
A
A
A
B
C
A
25
25
25
25
25
25
25
40
25
10
10
10
10
10
6
6
6
8
4a
4a
4a
4b
4c
4d
4d
4d
4e
68
66
52
64
70
78
72
50
61
aCatalytic loading: 10 mol %.
bA:CH3CN, B:CH3CN/H2O (50:1); C: CH3CN/H2O (20:1).
cIsolated yield.
confirmed that CSA does not cause protodesilyla-
tion of allylsilane to give TMSOCSA in the course
of the reaction. Based on these results, the CSA-
catalyzed allylation reaction seems to be through an
H+-catalysis cycle suggested by Davis [6b], and CSA
functions as a Bro¨nsted acid catalyst for the addition
of allylsilane to carbonyl compounds. On the other
hand, by use of (+)-10 as a catalyst, the product of the
allylation is racemic (enantiomeric excess [ee] =
0%), while for chiral glyoxylate, 1f, the de of product
4e is 11% in spite of a good yield 61% (entry 9). The
low diastereoselectivity is reasonable with respect to
the suggested H+-catalysis mechanism.
It can be concluded from the previously
mentioned investigations that the non-fluorine-
containing sulfonic acids also can play a cat-
alytic role in some Lewis acid–catalyzed reaction
systems, while the presence of the strong electron-
withdrawing fluorine atom is not an essential ingre-
dient [15]. The sulfonic acids able to be employed
in the catalytic Hosomi-Sakurai reaction are ex-
tremely cheap and easy to handle and may possi-
bly be applied to other types of Lewis acid–catalyzed
reactions.
[17], while ( )-menthyl glyoxylate 1f was prepared
according to Kornblum’s method [9].
General Procedure
MsOH-Catalyzed Allylation Reaction. To a so-
lution of 2 (1 mmol) in 1 mL of CH2Cl2, MsOH
(0.05 mmol) was added at room temperature. After
the mixture had been stirred for 1 hour, the aldehyde
hydrate (0.5 mmol) was added. The mixture was
stirred for a given reaction time at a given tempera-
ture, treated with brine, and extracted with ether. The
organic layer was dried over anhydrous Na2SO4. The
crude product was purified by flash chromatography
on silica gel to give the corresponding homoallylic
alcohol.
Aromatic Sulfonic Acid-Catalyzed Allylation Reac-
tion. To a solution of 2 (1 mmol) in 1 mL of CH3CN,
an aromatic sulfonic acid (0.05 mmol) was added
at room temperature. After the mixture had been
stirred for 1 hour, aldehyde hydrate (0.5 mmol) was
added. The mixture was stirred for a given reaction
time at a given temperature, treated with brine, and
extracted with ether. The organic layer was dried over
anhydrous Na2SO4. The crude product was purified
by flash chromatography on silica gel to give the cor-
responding homoallylic alcohol.
EXPERIMENTAL
All the chemicals used were reagent grade. IR spec-
tra were recorded by a Perkin-Elmer 782 spectropho-
tometer. 1H and 13C NMR spectra were recorded with
a Varian XL-300 spectrometer. NMR spectra are re-
ported in ppm with respect to TMS. Mass spectra
were taken at 60 eV with an AEI MS-50/PS-30 instru-
ment. Microanalysis was performed on a Calro 1102
Element Analysis instrument. Oxidation of the sub-
stituted acetophenones with selenium dioxide gave
the hydrates of -keto aldehydes 1b–d [16]. The hy-
drate of glyoxylate 1e was prepared according to Ref.
CSA-Catalyzed Allylation Reaction. To a solution
of 2 (1 mmol) and aldehyde hydrate (0.5 mmol) in
1 mL of CH3CN, CSA (0.05 mmol) was added, fol-
lowed by stirring for a given reaction time at a given
temperature. The reaction mixture was treated with
brine and extracted with ether. The organic layer was
dried over anhydrous Na2SO4. The crude product
was purified by flash chromatography on silica gel
to give the corresponding homoallylic alcohol.

538 Wang, Chen, and Wang
Compound 4a [18]: colorless oil, IR: = 3442,
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2900, 1670, 1588, 1440 cm . 1H NMR = 2.34–2.43
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(m, 1H,), 2.68–2.74 (m, 1H), 5.02–5.20 (m, 3H), 5.76–
5.87 (m, 1H), 7.51–7.95 (m, 5H). m/z 176 (M+, 1.0),
135 (M+ 41, 10.7), 105 (100).
Compound 4b [4a]: colorless oil, IR: = 3470,
1
2940, 1670, 1570, 1260, 965 cm . 1H NMR = 2.33–
2.38 (m, 1H), 2.63–2.65 (m, 1H), 3.90 (s, 3H), 5.00–
5.12 (m, 2H), 5.72–5.85 (m, 1H), 6.98 (d, 2H, J = 9
Hz), 7.91 (d, 2H, J = 9 Hz). m/z 206 (M+, 2.5), 135
(100).
Compound 4c [4a]: colorless oil, IR: = 3430,
1
2950, 1660, 1510, 1280, 1070, 960 cm . 1H NMR
=
2.29–2.42 (m, 1H), 4.99–5.16 (m, 2H), 5.74–5.82 (m,
1H), 6.50 (s, 1H), 6.92 (d, 2H, J = 9.0 Hz), 7.88 (d,
2H, J = 9.0 Hz).
Compound 4d: Colorless oil. IR: = 3480, 3070,
1
1
1760, 1635, 1460, 910 cm . H NMR = 0.87 (t,
3H, J = 7.3 Hz, CH3), 1.20–1.50 (m, 2H, CH2), 1.55–
1.70 (m, 2H, CH2), 2.18 (s, 1H, OH), 2.35–2.80 (m,
2H, CH2), 4.12 (dt, 2H, J = 2.0, 6.6 Hz), 4.19 (dd, 1H,
J = 4.8, 6.4 Hz), 5.05–5.22 (m, 2H, CH2), 5.7–5.9 (m,
1H, CH). 13C NMR ␦ = 13.57, 19.01, 30.57, 38.69,
65.52, 69.92, 118.58, 132.48, 174.48. Anal calcd for
C9H16O3: C, 62.76; H, 9.36. Found: C, 62.65; H, 9.27.
Compound 4e: Colorless oil. IR: = 3450 (OH),
[11] TfOH can be used as
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1
1
2900, 1720 (C O), 1620, 1210 cm . H NMR
=
0.71–0.78 (2d, 3H, CH3), 0.80–0.95 (m, 6H), 0.95–2.10
(m, 9H), 2.30–2.64 (m, 2H), 4.24 (dd, 1H, J = 2.0, 6.4
Hz, CH), 4.80 (dt, 1H, J = 4.6, 6.4 Hz, CH), 5.10–
5.25 (m, 2H, CH2), 5.70–5.90 (m, 1H, CH); 13C
NMR = (15.7, 16.2), (20.6, 20.8), 21.9, (22.8, 23.3),
(25.8, 26.2), 31.3, 34.0, (38.6, 38.7), (40.6, 40.8), (46.8,
46.9), (69.6, 70.0), (75.9, 76.1), (118.6, 118.7), (132.3,
132.4), 174.0. The data in parentheses are from two
diastereoisomers. Anal. Calcd. for C15H26O3: C, 70.83;
H, 10.30. Found: C, 70.76; H, 10.28.
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