Indium triflate catalyzed allylation of ketones with diallyldibutyltin

Article abstract of DOI:10.1016/j.tet.2005.08.101

A series of ketones underwent an allylation reaction using diallyldibutyltin in the presence of a catalytic amount of In(OTf)₃. The method was found to be superior to most of the known methods. Thus, a new allyltin reagent Bu₂Sn(allyl)₂/In(OTf)₃ for ketones was developed.

Full text of DOI:10.1016/j.tet.2005.08.101

Tetrahedron 61 (2005) 10930–10934
Indium triflate catalyzed allylation of ketones
with diallyldibutyltin
*
Ling-yan Liu, Long Tang, Lei Yu, Wei-xing Chang and Jing Li
The State Key Laboratory of Elemento-Organic Chemistry, Institute of Elemento-Organic Chemistry, Nankai University, Tianjin 300071,
People’s Republic of China
Received 23 July 2005; revised 26 August 2005; accepted 30 August 2005
Available online 23 September 2005
Abstract—A series of ketones underwent an allylation reaction using diallyldibutyltin in the presence of a catalytic amount of In(OTf)3. The
method was found to be superior to most of the known methods. Thus, a new allyltin reagent Bu2Sn(allyl)2/In(OTf)3 for ketones was
developed.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
ketones compared to the previous only limited to tetra-
allyltin.6,7
Allylation of carbonyl groups by various allylic metals is a
highly efficient tool for the synthesis of homoallylic
alcohols with the formation of a new carbon–carbon
bond.1 Among the various allylic metals, allyltin is an
important reagent with its suitable activity, low cost and
easily available. Diastereoselective and enantioselective
allylation with different allyltin derivatives have been
studied mostly for aldehydes2 but rarely for ketones3,4
since the lower reactivity of carbonyl group in ketones.
2. Results and discussion
Firstly, the effect of the solvents on the reaction of
acetophenone (1 equiv) and diallyldibutyltin (1 equiv) in
the presence of In(OTf)3 (10 mol%) at room temperature
was examined. The results in Table 1 showed that
dichloromethane was a good choice over the other solvents
such as MeCN, ether, THF, toluene, and DMSO.
Recently, it was reported that a combination of zinc triflate
and a base such as 2,6-lutidine or pyridine could catalyze the
allylation of ketones with tetra-allyltin.5 It was described
that allylation of acetophenone with 1 equiv of different
allylstannanes such as tetra-allylatin, diallyldibutyltin, and
allyltributyltin gave 94, 59, and 19% yield of 1-phenyl-1-
methylbut-3-en-1-ol (PMB), respectively, in the presence of
10 mol% Zn(OTf)2 and 10 mol% pyridine. However, zinc
triflate alone was ineffective as only a 16% yield of PMB
was obtained in the case of acetophenone with tetra-allyltin.
While working on the In(OTf)3-catalyzed reactions, we
observed that allylation of acetophenone with diallyldibu-
tyltin afforded PMB in 95% yield. The reaction did not
require any Lewis base as co-catalyst and it could be
extended to the enantioselective version. Herein, we report a
new allylation system for various ketones. Thus, it was
extended to the other allyltin reagent for allylation of
Then different metal triflates (See Table 2) were examined
and the indium triflate gave the best result. Furthermore, we
also investigated the effect of the different amount of
In(OTf)3 on this reaction. The results showed that 10 mol%
catalyst was the best choice for this reaction (Table 3).
Table 1. Effect of different solvents on allylation of acetophenone with
diallyldibutyltin
Entry
Solvent
Yield (%)a
1
2
3
4
5
6
CH2Cl2
MeCN
Et2O
THF
Toluene
DMSO
95
37
81
72
84
61
Keywords: Allylation; Ketone; Diallyldibutyltin; In(OTf)3.
*
Corresponding author. Tel.: C86 22 23503336;
e-mail: lijing@nankai.edu.cn
a Isolated yields.
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.08.101

L. Liu et al. / Tetrahedron 61 (2005) 10930–10934
10931
Table 2. Effect of different triflates’ Lewis acids on allylation of
acetophenone with diallyldibutyltin
Table 4. Allylation of ketones with diallyldibutyltin catalyzed by In(OTf)3
Entry
R1
R2
Yield (%)a
Entry
Lewis acid
Yield (%)a
1
2
3
4
5
6
7
8
Ph
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
Ph
95
81
75
86
66
71
93
90
58
50
—
42
78
1
2
3
4
5
6
7
—
27
95
74
71
89
51
48
p-FC6H4
p-ClC6H4
p-BrC6H4
p-NO2C6H4
m-NO2C6H4
m-BrC6H4
m-CF3C6H4
p-MeC6H4
p-MeOC6H4
p-NH2C6H5
Ph
In(OTf)3
Yb(OTf)3
AgOTf
Y(OTf)3
Cu(OTf)2
Zn(OTf)2
9
a Isolated yields.
10
11
12
13
Table 3. Effect of different In(OTf)3 amount on allylation of acetophenone
with diallyldibutyltin
14
15
82
90
16
17
18
CH2CH2CH3
CH2CH(CH3)2
p-MeOC6H4
CH3
CH3
H
45
27
80
Entry Solvent
Temperature (8C)
Amount of
In(OTf)3 (mol%)
Yield
(%)a
a Isolated yields.
1
2
3
CH2Cl2
CH2Cl2
CH2Cl2
Room temperature
Room temperature
Room temperature
1
5
10
38
68
95
not afford the desired homoallylic alcohol but complicated
products tracing by H NMR (entry 11), the reason for
a Isolated yields.
1
which was not clear at present. Surprisingly, substituent in
the meta-position of the aromatic ring underwent allylation
in higher yield than the corresponding substituent in the
para-position of the aromatic ring (entries 4 and 7, 5 and 6).
In addition, aliphatic ketones afforded the allylation
products in the moderate to good yields (entries 13–17).
Furthermore, benzophenone could also react smoothly
(entry 12) with a moderate yield. To confirm the reaction
system could be applied in aldehyde too, p-anisaldehyde,
which usually showed a relatively lower reactivity for
allylation, was chosen to react with the diallyldibutyltin
under the same conditions. And the homoallylic alcohol was
obtained in 80% yield (entry 18).
In order to ascertain whether both allyl groups could all be
transferred, 1 and 0.5 equiv of diallyldibutyltin were used in
two separate experiments by taking an example of the
acetophenone. It was observed that on use of 0.5 equiv of
the diallyldibutyltin, only 31% yield of the product was
obtained even after 24 h at room temperature. Similar
experiments were carried out with other ketones such as
4-bromo-acetophenone (entry 4) and cycloheptanone (entry
15). The yields of allylated products dropped from 86 to
35% for entry 4 and from 90 to 40% for entry 15,
respectively. Thus, it was concluded that the second allyl
group of diallyldibutyltin was uneasily transferred under the
current reaction condition.
The mechanism of this reaction was preliminarily
studied. According to the previous reports, the Lewis
acids catalyzed the allylation of carbonyl compounds
with allylic metal reagents via an acyclic transition
state.8 Herein, we postulated a possible mechanism of
In a word, the optimized reaction condition was that ketones
were treated with an equal mol of diallyldibutyltin in the
presence of 10 mol% In(OTf)3 in CH2Cl2 at room
temperature for 12 h.
1
this reaction according to the H NMR tracing (Scheme
1). By using p-anisaldehyde as a representative substrate
The extended investigation on different kinds of ketones
with diallyldibutyltin was examined under the optimized
conditions. High yields were obtained in most of the cases
(Table 4).
coordinated with 1 equiv In(OTf)3, we found that the
peak corresponding to this aldehyde proton in H NMR
1
showed a down-field shift (d 9.732–9.872 ppm). This
suggested some evidence of activation of aldehyde by
In(OTf)3.
Arylmethyl ketones bearing an electron-withdrawing group
at the para-position of the aromatic ring gave the
corresponding allylation products in high yields (entries
2–4). Arylmethyl ketones bearing an electron-donor group
such as p-Me or p-MeO gave the products in moderate
yields (entries 9 and 10). Moreover, the former proceeded
much faster by TLC monitoring. Even after stirred for 12 h,
the arylmethyl ketones bearing an EDG at the para-position
could not react completely, as the starting material was
recovered. The p-NH2 substituted phenylmethyl ketone did
In addition, we also selected several typical homoallylic
alcohols to analyze their properties by ESI mass spectro-
metric analysis. As a result, we found that the
molecular ion peaks of the general homoallylic alcohols
were weak and easily decomposed by pulling off water
to turn into the tert-carbonium ions, which were the
highest response peak [(MC1)K18] except for m-trifluoro-
methyl acetophenone.

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L. Liu et al. / Tetrahedron 61 (2005) 10930–10934
resonance is indicated by nH. Coupling constants are
reported as a J value in Hz. Carbon nuclear magnetic
resonance spectra (13C NMR) are reported as d in units of
parts per million (ppm) downfield from SiMe4 (d 0.0) and
relative to the signal of chloroform-d (d 77.03, triplet). Mass
spectrometric analysis was carried out on a ThermoFinnigan
LCQ Advantage LC/MS with an electrospray ionization
mode (ESI).
4.2. Synthesis
Preparation of dibromodiallyltin ((CH2]CHCH2)2SnBr2).
To an oven dried 250 ml four-necked flask equipped with a
magnetic stirring bar, a reflux condenser and a thermometer
was added 150 ml toluene, tin powder (17.8 g, 0.15 mol)
and HgCl2 (0.5 g, 0.002 mol). The mixture was refluxed for
30 min, then cooled to room temperature, triethylamine
(0.275 ml) was added and the mixture was heated until
reflux, and 1-bromopropene (18.2 g, 0.15 mol) was added
dropwise within 30 min. The reaction mixture was kept at
reflux for 3 h and then cooled to room temperature, filtered,
concentrated in vacuo. The residual crude product was
distilled under reduced pressure and resulted in 19.5 g of a
slightly yellow colored oil: bp 70–72 8C/0.5 mmHg, Yield
Scheme 1. Probable acyclic transition-state mechanism.
1
Since all the products were known compounds, only H
NMR and selected 13C NMR and Mass spectra were
determined for confirming the products. And all spectra
were available in the supporting material.
3. Conclusion
1
72%. The oil was analyzed by H NMR.
In summary, we have found that diallyldibutyltin /In(OTf)3
was a novel efficient system for the allylation of ketones
under a mild condition. The reaction did not require any
base as an additive and could be applied for various ketones
with modest to high yields. Further investigation on
diastereo- and enantio-selective allylation is currently in
progress in our laboratory.
Preparation of diallyldibutyltin ((CH2]CHCH2)2SnBu2).
Placed of dry magnesium turnings (5 g, 0.208 mol) and
freshly distilled ether (25 ml) in a 250 ml four-necked flask
equipped with a magnetic stirring bar, a reflux condenser
with a drying tube, a dropping funnel charged with the
solution of n-butyl chloride (19.3 g, 0.208 mol) and ether
(10 ml). After addition of about one third of n-butyl chloride
solution into the flask, a small iodine crystal was added to
the mixture. The reaction started immediately and the color
of iodine disappeared. The remaining n-butyl chloride
solution was added slowly into the reaction mixture with
gentle reflux (about 30 min). When all of the n-butyl
chloride solution was dropped into the flask, the reaction
was continued for an additional 30 min on a heated water
bath until magnesium turning disappeared.
4. Experiment
4.1. General
Experiments involving moisture and/or air sensitive
components were performed in oven-dried glassware.
Commercial solvents and reagents were used without
further purification except petroleum ether, dichloro-
methane, ether were fractionally distilled. Ketones were
used without purification. Analytical thin-layer chromato-
graphy (TLC) was performed using Merck 60 F254 pre-
coated silica gel plate. Subsequent to elution, plates were
visualized using UV radiation (254 nm) on Spectroline
Model ENF-24061/F 254 nm. Further visualization was
possible by staining with acidic solution of ceric molybdate,
followed by heating on a hot plate. Flash chromatography
was performed using Merck silica gel 60 with freshly
distilled solvents. Columns were typically packed as slurry
and equilibrated with the appropriate solvent system prior to
use. Proton nuclear magnetic resonance spectra (1H NMR)
were recorded on a Varian Mercury Plus 400 (1H 400 MHz)
(CDCl3 as solvent). Chemical shifts for 1H NMR spectra are
reported as d in units of parts per million (ppm) downfield
from SiMe4 (d 0.0) and relative to the signal of chloroform-d
(d 7.2600, singlet). Multiplicities were given as: s (singlet);
d (doublet); t (triplet); q (quartet); dd (doublets of doublet);
ddd (doublets of doublets of doublet); dddd (doublets of
doublets of doublets of doublet); dt (doublets of triplet); or
m (multiplets). The number of protons (n) for a given
The resulting Grignard reagent was cooled to room
temperature using a cold water bath. A solution of the
freshly prepared dibromodiallyltin (27.0 g, 0.075 mol) in
10 ml dried ether was added dropwise. The dropping rate
was controlled so that the mixture was refluxed gently. After
the addition was finished, the reaction mixture was refluxed
for further 30 min and then cooled in an ice-bath. Under
constant stirring a solution of 1 N hydrochloride (about
80 ml) was added and the stirring was continued until the
solid was dissolved. The organic layer was separated and the
aqueous layer was extracted for three times with ether (3!
25 ml). The combined organic layers were dried with
anhydrous sodium sulfate, filtered, concentrated in vacuo.
The residual crude product was distilled under reduced
pressure and resulted in 15.26 g of a colorless liquid, Yield
1
63%. The liquid was analyzed by H NMR.
4.2.1. Preparation of 1-phenyl-1-methylbut-3-en-1-ol (1).
To an oven dried 10 ml tube equipped with a magnetic
stirring bar was added acetophenone (60 mg, 0.5 mmol) and
diallyldibutyltin (157 mg, 0.5 mmol), then added In(OTf)3

L. Liu et al. / Tetrahedron 61 (2005) 10930–10934
10933
(28 mg, 0.05 mmol) and dichloromethane (2 ml). The
mixture was stirred for 12 h at room temperature. The
reaction mixture was quenched with 2 ml saturated aqueous
NaHCO3 solution, extracted with ether (3!10 ml), washed
with brine, dried over Na2SO4, filtered and concentrated in
vacuo. The residual crude product was purified via silica gel
chromatography to afford the homoallylic alcohol as a
colorless oil (95% yield). MS: m/zZ162.39 (MC), m/zZ
145.49 [(MC1)K18]; 1H NMR (400 MHz, CDCl3): d 7.45–
7.23 (m, 5H, ArH), 5.66–5.58 (m, 1H, CH), 5.13 (t, JZ
8 Hz, 2H, CH]CH2), 2.71–2.47 (m, 2H, CH2), 2.09 (br,
1H, OH), 1.54 (s, 3H, CH3); 13C NMR (400 MHz, CDCl3): d
30.0, 48.7, 73.9, 119.6, 125.0, 126.9, 128.4, 134.0, 148.0.
5.63–5.55 (m, 1H, CH), 5.17–5.13 (m, 2H, CH]CH2),
2.70–2.49 (m, 2H, CH2), 2.17 (s, 1H, OH), 1.56 (s, 3H, CH3).
4.2.9. 1-p-Methylphenyl-1-methylbut-3-en-1-ol (9).
Homoallylic alcohol 9 was obtained using the same
procedure as 1: colorless oil; MS: m/zZ176.39 (MC),
m/zZ159.58 [(MC1)K18]; 1H NMR (400 MHz, CDCl3): d
7.33–7.15 (m, 4H, ArH), 5.69–5.59 (m, 1H, CH), 5.16–5.11
(m, 2H, CH]CH2), 2.71–2.47 (m, 2H, CH2), 2.35 (s, 3H,
CH3-Ar), 2.02 (br, 1H, OH), 1.54 (s, 3H, CH3); 13C NMR
(400 MHz, CDCl3): d 21.2, 30.1, 48.7, 73.8, 119.4, 125.0,
129.1, 134.1, 136.3, 145.0.
4.2.10. 1-p-Methoxyphenyl-1-methylbut-3-en-1-ol (10).
Homoallylic alcohol 10 was obtained using the same
procedure as 1: colorless oil; 1H NMR (400 MHz,
CDCl3): d 7.35–6.85 (m, 4H, ArH), 5.64–5.58 (m, 1H,
CH), 5.13–5.09 (t, JZ7.6 Hz, 2H, CH]CH2), 3.80 (s, 3H,
CH3O), 2.67–2.44 (m, 2H, CH2), 1.98 (br, 1H, OH), 1.57 (s,
3H, CH3).
4.2.2. 1-p-Fluorophenyl-methylbut-3-en-ol (2). Homo-
allylic alcohol 2 was obtained using the same procedure
as 1: colorless oil; 1H NMR (400 MHz, CDCl3): d 7.41–7.30
(m, 2H, ArH), 7.01 (t, JZ8 Hz, 2H, ArH), 5.63–5.55 (m,
1H, CH), 5.14 (d, JZ12 Hz, 2H, CH]CH2), 2.63–2.45 (m,
2H, CH2), 2.07 (br, 1H, OH), 1.53 (s, 3H, CH3).
4.2.3. 1-p-Chlorophenyl-1-methylbut-3-en-1-ol (3).
Homoallylic alcohol 3 was obtained using the same
procedure as 1: colorless oil; 1H NMR (400 MHz,
CDCl3): d 7.31–7.25 (m, 4H, ArH), 5.53 (s, 1H, CH),
5.24–5.08 (m, 2H, CH]CH2), 2.57–2.41 (m, 2H, CH2),
2.02 (br, 1H, OH), 1.46 (t, JZ4 Hz, 3H, CH3).
4.2.11. 1,1-Diphenyl-1-but-3-en-1-ol (12). Homoallylic
alcohol 12 was obtained using the same procedure as 1:
colorless oil; 1H NMR (400 MHz, CDCl3): d 7.40–7.18 (m,
10H, ArH), 5.63–5.60 (m, 1H, CH), 5.23–5.12 (m, 2H,
CH]CH2), 3.03 (br, 1H, OH), 2.52–2.28 (m, 2H, CH2).
4.2.12. 1-Cyclopentyl-1-but-3-en-1-ol (13). Homoallylic
alcohol 13 was obtained using the same procedure as 1:
colorless oil; 1H NMR (400 MHz, CDCl3): d 5.94–5.84 (m,
1H, CH), 5.15–5.12 (m, 2H, CH]CH2), 2.34–2.16 (t, JZ
7.6 Hz, 2H, CH2), 1.79–1.24 (m, 8H, cyclopentyl).
4.2.4. 1-p-Bromophenyl-1-methylbut-3-en-1-ol (4).
Homoallylic alcohol 4 was obtained using the same
procedure as 1: colorless oil; 1H NMR (400 MHz,
CDCl3): d 7.46–7.29 (m, 4H, ArH), 5.59–5.55 (m, 1H,
CH), 5.14–5.11 (d, JZ12 Hz, 2H, CH]CH2), 2.66–2.44
(m, 2H, CH2), 2.08 (br, 1H, OH), 1.51–1.49 (d, JZ10.8 Hz,
3H, CH3); 13C NMR (400 MHz, CDCl3): d 30.1, 48.5, 73.7,
120.1, 120.8, 127.0, 131.4, 133.4, 146.9.
4.2.13. 1-Cyclohexyl-1-but-3-en-1-ol (14). Homoallylic
alcohol 14 was obtained using the same procedure as 1:
colorless oil; 1H NMR (400 MHz, CDCl3): d 5.93–5.84 (m,
1H, CH), 5.14–5.07 (t, JZ10.4 Hz, 2H, CH]CH2), 2.34–
2.19 (t, JZ6.8 Hz, 2H, CH2), 1.70–1.24 (m, 10H,
cyclohexyl).
4.2.5. 1-p-Nitrophenyl-1-methylbut-3-en-1-ol (5). Homo-
allylic alcohol 5 was obtained using the same procedure as
1: colorless oil; H NMR (400 MHz, CDCl3): d 8.18–7.23
1
(m, 4H, ArH), 5.57–5.55 (m, 1H, CH), 5.16–5.14 (t, JZ
2.8 Hz, 2H, CH]CH2), 2.65–2.51 (m, 2H, CH2), 2.14 (br,
1H, OH), 1.55–1.54 (d, JZ4 Hz, 3H, CH3).
4.2.14. 1-Cycloheptyl-1-but-3-en-1-ol (15). Homoallylic
alcohol 15 was obtained using the same procedure as 1:
colorless oil; 1H NMR (400 MHz, CDCl3): d 5.89–5.85 (m,
1H, CH), 5.15–5.08 (t, JZ10.8 Hz, 2H, CH]CH2), 2.22–
2.15 (t, JZ6.8 Hz, 2H, CH2), 1.63–1.37 (m, 12H,
cycloheptyl); 13C NMR (400 MHz, CDCl3): d 22.6, 30.0,
41.3, 48.1, 75.1, 118.9, 134.3.
4.2.6. 1-m-Nitrophenyl-1-methylbut-3-en-1-ol (6). Homo-
allylic alcohol 6 was obtained using the same procedure as
1: slight yellow oil; H NMR (400 MHz, CDCl3): d 8.32–
1
7.26 (m, 4H, ArH), 5.62–5.56 (m, 1H, CH), 5.17–5.13 (t,
JZ7.6 Hz, 2H, CH]CH2), 2.70–2.51 (m, 2H, CH2), 2.16
(br, 1H, OH), 1.58 (s, 3H, CH3).
4.2.15. 1-Methyl-1-propyl-1-but-3-en-1-ol (16). Homo-
allylic alcohol 16 was obtained using the same procedure as
1: colorless oil; H NMR (400 MHz, CDCl3): d 5.89–5.83
1
4.2.7. 1-m-Bromophenyl-1-methylbut-3-en-1-ol (7).
Homoallylic alcohol 7 was obtained using the same
procedure as 1: colorless oil; 1H NMR (400 MHz,
CDCl3): d 7.60–7.18 (m, 4H, ArH), 5.60–5.56 (m, 1H,
CH), 5.14–5.12 (d, JZ9.2 Hz, 2H, CH]CH2), 2.65–2.44
(m, 2H, CH2), 2.08 (br, 1H, OH), 1.51–1.50 (d, JZ4.8 Hz,
3H, CH3).
(m, 1H, CH), 5.15–5.09 (t, JZ8.4 Hz, 2H, CH]CH2),
2.22–2.20 (d, JZ7.6 Hz, 2H, CH2), 1.57–0.91 (m, 10H,
CH3, C3H7)
4.2.16. 1-Methyl-1-isobutyl-1-but-3-en-1-ol (17). Homo-
allylic alcohol 17 was obtained using the same procedure as
1: colorless oil; H NMR (400 MHz, CDCl3): d 5.88–5.82
1
(m, 1H, CH), 5.14–5.08 (t, JZ9.6 Hz, 2H, CH]CH2), 2.23
(m, 2H, CH2), 1.82–0.95 (m, 12H, CH3, i-C4H9).
4.2.8. 1-m-Trifluoromethylphenyl-1-methylbut-3-en-1-ol
(8). Homoallylic alcohol 8 was obtained using the same
1
procedure as 1: colorless oil; MS: m/zZ230.35 (MC); H
NMR (400 MHz, CDCl3): d 7.73–7.45 (m, 4H, ArH),
4.2.17. 1-p-Methoxylphenyl -1-but-3-en-1-ol (18). Homo-
allylic alcohol 18 was obtained using the same procedure as

10934
L. Liu et al. / Tetrahedron 61 (2005) 10930–10934
1
1: colorless oil; H NMR (400 MHz, CDCl3): d 7.31–7.28
(m, 2H, ArH), 6.91–6.89 (m, 2H, ArH), 5.88–5.75 (m, 1H,
CH]CH2), 5.20–5.13 (m, 2H, CH]CH2), 4.72–4.68 (t,
JZ6.6 Hz, 1H, CH), 3.82 (s, 3H, CH3O), 2.54–2.49 (m, 2H,
CH2), 2.18 (s, 1H, OH).
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Acknowledgements
This work was supported by the NSFC (20372033)
and (20421202) and Science Foundation of Nankai
University.
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Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.tet.2005.08.
101