Organotin perfluorooctanesulfonates as air-stable Lewis acid catalysts: Synthesis, characterization, and catalysis

Article abstract of DOI:10.1002/chem.200501091

The reactions of 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane and di-alkyltin dihalides with silver perfluoro-octanesulfonate provided the corresponding sulfonates as hydrates. The number of water molecules (n) of hydration was dependent on the conditions. The distannoxane derivative was identified as n from 0.5 to 6, while in the hydrated mononuclear species and DMSO complexes n varied widely from 4 to 13. ¹¹⁹Sn NMR spectroscopy and conductivity measurements indicated the ionic dissociation of these compounds in solution. These compounds exhibited unusually high solubility in polar organic solvents. The ionic dissociation together with facile hydration probably causes the unusual solubility. The Lewis acidity of these compounds was found to be high among organotin derivatives on the basis of ESR spectra of Superoxide/ metal-ion complexes. In contrast to well-known organotin Inflates, these compounds suffered no hydrolysis upon storage in open air. The high catalytic activity of the distannoxane 1 was exemplified for various carboncarbon bond-forming reactions, such as Mukaiyama-aldol as well as -Michael reactions and allylation of aldehydes.

Full text of DOI:10.1002/chem.200501091

DOI: 10.1002/chem.200501091
Organotin Perfluorooctanesulfonates as Air-Stable Lewis Acid Catalysts:
Synthesis, Characterization, and Catalysis
De Lie An,*[a] Zhihong Peng,[a, b] Akihiro Orita,[b] Akinobu Kurita,[b] Sumiyo Man-e,[b]
Kei Ohkubo,[c] Xingshu Li,[b] Shunichi Fukuzumi,*[c] and Junzo Otera*[b]
Abstract: The reactions of 1,3-dichloro-
1,1,3,3-tetrabutyldistannoxane and di-
alkyltin dihalides with silver perfluoro-
octanesulfonate provided the corre-
sponding sulfonates as hydrates. The
number of water molecules (n) of hy-
dration was dependent on the condi-
tions. The distannoxane derivative was
identified as n from 0.5 to 6, while in
the hydrated mononuclear species and
cated the ionic dissociation of these
compounds in solution. These com-
pounds exhibited unusually high solu-
bility in polar organic solvents. The
ionic dissociation together with facile
hydration probably causes the unusual
solubility. The Lewis acidity of these
compounds was found to be high
among organotin derivatives on the
basis of ESR spectra of superoxide/
metal-ion complexes. In contrast to
well-known organotin triflates, these
compounds suffered no hydrolysis
upon storage in open air. The high cat-
alytic activity of the distannoxane 1
was exemplified for various carbon–
carbon bond-forming reactions, such as
Mukaiyama–aldol as well as -Michael
reactions and allylation of aldehydes.
Keywords: EPR spectroscopy
homogeneous catalysts Lewis
acids · NMR spectroscopy · tin
·
DMSO complexes
n varied widely
·
from 4 to 13. 119Sn NMR spectroscopy
and conductivity measurements indi-
Introduction
ity, on the other hand, often causes failure in the carbon–
carbon bond formation. Hence, the increase of the Lewis
acidity of organotin compounds is of prime importance to
expand the scope of their synthetic utility. One method is to
attach electron-withdrawing group(s) on tin. Guided by this
postulate, we previously disclosed that organotin triflates
served to catalyze carbon–carbon bond-forming reactions
like Mukaiyama–aldol and –Michael reactions in a highly
chemoselective manner.[3] However, their hygroscopic
nature did not allow us to fully characterize these com-
pounds despite strong demands for detailed information
about such synthetically useful class of organotin com-
pounds. Recently, we reported in a preliminary form that
1,3-bis(perfluorooctanesulfonato)-1,1,3,3-tertabutyldistan-
noxane (1) is air-stable and acidic enough to catalyze, for
the first time for this class of compounds, various carbon–
carbon bond-forming reactions with stannyl and silyl nucleo-
philes.[4] Hence, we have investigated relevant organotin per-
fluorooctanesulfonates. In this paper, we put forth a full ac-
count of synthesis and characterization of these compounds.
Furthermore, their catalytic activities are assessed in
carbon–carbon bond-forming reactions.
A number of organotin compounds serve as Lewis acid cata-
lysts in organic synthesis.[1] Normally, their Lewis acidity is
mild so that high chemoselectivity could be attained in vari-
ous functional group transformations.[2] The mild Lewis acid-
[a] Prof. Dr. D. L. An, Z. Peng
Department of Chemistry
College of Chemistry and Chemical Engineering
Hunan University, Changsha 410082 (China)
Fax : (+86)731-882-7944
E-mail: deliean@sina.com
[b] Z. Peng, Prof. Dr. A. Orita, A. Kurita, S. Man-e, X. Li,
Prof. Dr. J. Otera
Department of Applied Chemistry
Okayama University of Science, Rida-cho
Okayama 700-0005 (Japan)
Fax : (+81)86-256-4292
E-mail: otera@high.ous.ac.jp
[c] Dr. K. Ohkubo, Prof. Dr. S. Fukuzumi
Department of Material and Life Science
Graduate School of Engineering, Osaka University
SORST, Japan Science and Technology Agency (JST)
Suita, Osaka 565-0871 (Japan)
Fax: (81)6-6879-7370
E-mail: fukuzumi@chem.eng.osaka-u.ac.jp
1642
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Chem. Eur. J. 2006, 12, 1642 – 1647

FULL PAPER
Results and Discussion
cies in CH3CN on the basis of conductivity measurements.
The hydration number of 1 is variable depending on the
conditions. 1H NMR spectroscopy (in dry CD3CN) proved
that the freshly prepared sample after recrystallization from
EtOAc/hexane (1:3) contained approximately one H2O mol-
ecule per each tin atom (n=4); the water content increased
Synthesis: The synthesis of 1 is straightforward (Scheme 1).
[5]
Treatment of (ClBu SnOSnBu2Cl)2 with four equivalents
2
of AgOSO2C8F17 (AgOPf) in acetone afforded 1 in a hydrat-
1
up to n= ꢀ6 (on the basis of H NMR spectroscopy) upon
standing in open air. Pumping in vacuo for two days at
room temperature caused partial dehydration giving rise to
nꢀ0.5. Elemental analysis of this sample was consistent
with this composition.
Mononulcear compounds 3–5
were prepared analogously by
treatment of R2SnCl2 (R=Bu,
Me, Ph) with two equivalents of
AgOPf in acetone (Scheme 3).
These compounds were also ob-
tained as hydrates, but the hy-
dration number varied widely
from 4 to 13 depending on the
conditions. Although the parent
Scheme 3. Synthesis of diorga-
peaks corresponding to 3 and 4
were confirmed by ESI-MS, no
reliable combustion analyses
notin
nates.
perfluorooctanesulfo-
were attained for these compounds. We therefore trans-
formed the hydrated species to DMSO adducts. Addition of
four equivalents of DMSO to a solution of 3–5 in diethyl
ether afforded [R2Sn(DMSO)4]2+·2OPfÀ, 6–8, which gave
correct analytical data.
As seen from Schemes 1 and 2, the perfluorooctanesulfo-
nate anion reacts with (ClBu2SnOSnBu2Cl)2 quite differently
from the triflate anion. The skeletal change to 2 with the
latter anion is induced by facile hydrolysis of the putative
bis(triflato)distannoxane, while 1 can resist the hydrolysis
though being hydrated. The analogous facile hydrolysis at-
tacks mononuclear organotin triflates, RnSn(OTf)4Àn, leading
to unidentifiable products, yet the corresponding perfluor-
ooctanesulfonates 3–5 survive the hydrolysis. As such, the
organotin perfluorooctanesulfonates are storable in open
air, offering a great advantage over the organotin triflates
from the operational point of view.
Scheme 1. Synthesis of perfluorooctanesulfonato distannoxane.
ed form (PfOBu2SnOSnBu2OPf)2·nH2O. This stands in
strong contrast with the reaction with AgOSO2CF3
(AgOTf), which resulted in a skeletal change to furnish m-
hydroxo dimers 2 (Scheme 2).[6] Single-crystal X-ray analysis
revealed a neutral structure for the butyl derivative 2a,
while a dicationic structure was found for the tert-butyl and
2-phenylbutyl derivatives, 2b and 2c, respectively. However,
all compounds were found to dissociate into the ionic spe-
Characterization: A 119Sn NMR spectrum of 1 exhibited two
signals at d=À162.5 and À203.0 ppm in [D6]acetone, diag-
nostic of the dimeric formulation,[7] while a single peak was
observed for 3–5 consistent with the mononuclear structure
(Table 1). Upon complexation with DMSO, the d values ex-
perienced low-frequency shifts. The dicationic character of 6
was supported by appearance of its 119Sn NMR signal (d=
Table 1. The 119Sn NMR spectra of organotin perfluorooctanesulfonates
in [D6]acetone.
Compound
d [ppm]
Compound
d [ppm]
1
3
4
5
À162.5, À203.0
À348.9
6
7
8
À338.1
À303.3
À501.3
À324.4
À524.1
Scheme 2. Synthesis of cationic organotin compounds.
Chem. Eur. J. 2006, 12, 1642 – 1647
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1643

J. Otera, D. L. An, S. Fukuzumi et al.
À338.1 ppm) in the same region as that found for [Me2Sn-
(DMSO)4]2+·2Ph4BÀ[8] in [D6]DMSO (d=À336.0 ppm). The
119Sn NMR chemical shift of a dibutyltin dicationic species,
[Bu2Sn(H2O)4]2+·2ClO4À, was estimated by use of Bu2SnO
in aqueous HClO4.[9] The d values were plotted against vari-
ous tin concentrations and extrapolation to the infinite dilu-
tion gave rise to d=À294.0 ppm, which is close to d=
À303.2 ppm of 7, indicative of dicationic nature of this com-
pound. No significant differences in d values between 3–5
and 6–8 suggest that the hydrated compounds also are con-
siderably dissociated into the dicationic species, for example,
[R2Sn(H2O)m]2+·2OPfÀ·nH2O.
Rather unexpectedly, however, the DMSO complexes 6–8
did not give rise to the significant decrease in the DE values.
For example, the DE value of Sc(OTf)3 changed from 1.00
to 0.72 upon complexation with hexamethyl phosphoramide
(HMPA).[11] This may be reminiscent of weaker coordina-
tion of DMSO on the tin than that of HMPA on the scandi-
um.
Another notable feature is unusual solubility of 1 and 3–
5. As given in Table 4, the solubility of these compounds in
acetone, THF, EtOAc, CH3CN, and MeOH is extraordinari-
ly high amounting up to 3251 gLÀ1; it is better to say that
The conductivity measurements are consistent with the
ionic dissociation (Table 2). A substantially large conductivi-
ty was observed for 1 in CH3CN, but the molar conductivity
Table 4. Solubility of organotin perfluorooctanesulfonates in organic sol-
vents at 258C.
Solubility [gLÀ1
]
1
3
4
5
6
7
8
[a]
Table 2. Conductivities of organotin perfluorooctanesulfonates.
acetone
THF
EtOAc
MeOH
CH3CN
Et2O
CH2Cl2
toluene
hexane
3018
2908
1594
2643
1245
108
0
2447
2239
2569
3251
3018
192
0
1745
517
2417
1878
42
88
0
0
0
1973
1323
1155
2317
119
351
0
2123
22
17
2114
1971
0
152
0
1646
81
33
2036
1438
0
21
0
0
98
0
0
1137
54
0
Compound
Conductivity
Compound
Conductivity
[b]
[b]
[mScmÀ1
]
[mScmÀ1
]
1
3
4
5
256.5 (64.1)
129.9 (129.9)
125.5 (125.5)
118.1 (118.1)
6
7
8
2a
218.0 (218.0)
197.1 (197.1)
231.8 (231.8)
165.5 (82.8)
0
0
0
0
0
0
0
0
0
[a] In CH3CN (1.0 mmolLÀ1) at 258C. [b] The value given in parentheses
is the molar conductivity (L) (mScm2 molÀ1).
0
is somewhat smaller than that of well-defined dicationic m-
hydroxo dimer 2a. It follows that 1 is not totally but partial-
ly dissociated into the dicationic species like 1’
(Scheme 1).[10] Mononuclear compounds 3–5 exhibited
larger molar conductivities, the magnitudes of which, howev-
er, are not large enough to assume the dicationic formula-
tion because the corresponding DMSO complexes gave
much greater values. It is reasonably concluded as a whole
that the DMSO complexes 6–8 are virtually dicationic, while
the hydrates species 3–5 are involved in equilibrium be-
tween associated and dissociated forms.
Previously, we advanced that the binding energies (DE
values) of Lewis acid metal atoms with O2CÀ can be correlat-
ed with the Lewis acidity of the metals.[11] Thus, we mea-
sured the DE values of the organotin perfluorooctanesulfo-
nates, which are shown in Table 3 together with those of rel-
evant organotin compounds for comparison. As expected,
compounds 1 and 3–5 exhibited relatively large DE values.
they are miscible with each other to form a slightly viscous
liquid. They exhibit normal solubility in less polar Et2O, but
are not soluble in CH2Cl2, a quite surprising behavior be-
cause this solvent is usually the best solvent for similar orga-
notin compounds. Consistently, they are not soluble in much
less polar toluene and nonpolar hexane. Nevertheless, these
compounds are also hydrophobic as is apparent from their
insolubility in water. The long fluoroalkyl chain in the sulfo-
nate ligand must be responsible for the hydrophobicity. Pre-
sumably, such amphiphilic nature is reflected on the unusual
solubility in the polar organic solvents. Upon dissolving the
organotin compounds in polar solvents, the solvent mole-
cules can approach the coordination sphere of the tin to re-
place the hydrated water on account of the compatibility be-
tween them, and the resulting solvated species are highly
soluble in the same polar solvents. By contrast, CH2Cl2 as
well as hydrocarbons cannot have access to the tin atoms
because of interference by the water against these hydro-
phobic solvents. It is concluded therefore that the organotin
perfluorooctanesulfonates are neither hydrophilic nor lipo-
philic in their hydrated form, and accordingly they are not
soluble in both strongly hydrophobic organic solvents and
water. However, the water molecules are readily replaced
by the polar organic solvents to generate the highly soluble
solvated species.
Table 3. gzz and DE values of ESR spectra of O2CÀ/organotin complexes.
Compound
gzz
DE
1
3
4
5
6
7
8
2a
2.0336
2.0333
2.0338
2.0343
2.0335
2.0342
2.0346
2.0595
2.0327
2.0336
0.90
0.90
0.90
0.88
0.90
0.88
0.87
0.49
0.92
0.89
It is reasonable to assume that the solubility decreases by
formation of the highly cationic DMSO complexes. In fact,
the solubility of the hydrated mononuclear species basically
decreases upon formation of the DMSO complexes 6–8. In
particular, conversion of 5 to 8 induced a drastic decrease in
solubility except in MeOH. By contrast, dibutyltin and di-
[a]
[a]
Bu2Sn(OTf)2
(C6F5)2SnBr2
[a] Reference [11].
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ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 1642 – 1647

Organotin Chemistry
FULL PAPER
Table 5. Yields [%] in reactions of benzaldehyde with stannyl and silyl
nucleophiles catalyzed by organotin perfluorooctanesulfonates and 2a.
methyltin derivatives 4 and 5, respectively, exhibited differ-
ent behaviors. The solubility was greatly decreased in THF,
EtOAc, and Et2O, whereas only slightly in acetone, MeOH,
and CH3CN, or even increased occasionally. These com-
pounds became slightly soluble in CH2Cl2 upon complex for-
mation in contrast to the insoluble parent hydrates. The
high solubility of these DMSO complexes might result from
replacement of DMSO with polar solvent molecules. How-
ever, in 1H NMR spectra in [D6]acetone, the S-methyl
proton signals of 6 and 7 experienced strong upfield shifts
Catalyst
Nucleophile
Product
1[a]
3[g]
2a[g]
10
11
12
13
14
18
19
20
21
22
98[b]
81[c]
85[d]
91[e]
95[f]
59[h]
30
27
27
25
90[i]
–
75
64
67
[a] Reaction conditions: substrate (1.0 mmol); nucleophile (1.3 mmol);
catalyst (0.05 mmol); solvent (3.0 mL); RT; 24 h. [b] 10 (0.3 mmol), 1
(0.005 mmol), THF, 12 h. [c] THF, 12 h. [d] THF, 6 h. [e] 1 (0.01 mmol),
MeCN, 2 h. [f] 1 (0.01 mmol), MeCN, 3 h. [g] Reaction conditions: sub-
strate (1.0 mmol); nucleophile (1.3 mmol); Catalyst (0.01 mmol); MeCN
(3 mL); RT; 24 h. [h] 10 (0.3 mmol). [i] 10 (0.3 mmol), 4 h.
(Dd relative to pure DMSO: À0.38 ppm for
6 and
À0.52 ppm for 7). As shown in Table 1, 119Sn NMR spectra
also gave rise to appreciable shifts upon complexation.
These outcomes support the retention of the DMSO coordi-
nation in acetone.
Catalysis: The catalytic activities of 1 and 3 together with m-
hydroxo dimer 2a as a control cationic species were assessed
for various carbon–carbon bond-forming reactions. First, re-
actions of benzaldehyde (9) with nucleophiles, such as tet-
raallyltin (10), enol silyl ethers 11 and 12, and ketene silyl
acetals 13 and 14, were scrutinized (Scheme 4). All reactions
Scheme 5. Reaction of acetophenone, benzaldehyde, and cyclohexenone
with silyl nucleophiles catalyzed by 1.
Table 6. Yields [%] in reaction of 15, 16, and 17 with stannyl and silyl nu-
cleophiles catalyzed by organotin perfluorooctanesulfonates.[a]
Catalyst[b]
Substrate
Nucleophile
Product
1
3
15
10
11
12
13
14
10
11
12
13
14
10
11
13
14
23
87[c]
nr
19[k]
nr
nr
21
20
nr
37
34
21
35
nr
nr
24
25
87[d]
90[e]
nr
Scheme 4. Reaction of benzaldehyde with various nucleophiles catalyzed
by 1.
16
17
25
27
28
29
91[f]
93[f]
50[g]
93[h]
nr
were carried out in the presence of 1 (0.5 mol%) or 3 and
2a (1 mol%), and the yields of the respective reactions are
compiled in Table 5. High yields were constantly attained
with 1, while the other catalysts resulted in much lower
yields. Notably, the solvent, that is, CH3CN, in these reac-
tions was used as received. No dry solvent is needed, be-
cause of tolerance of 1 toward hydrolysis.[12,13] The low activ-
ity of 2a is reasonable in terms of the criterion which we
put forth previously: efficient carbon–carbon bond-forming
reactions are effected by Lewis acid catalysts with the DE
values lager than 0.88.[11] By contrast, rather low activity of
3 cannot be accommodated by this notion. We have no ex-
plicit explanation for this anomaly at present.
30
31
32
71[i]
–
29
25
43
95[j]
[a] Reaction conditions: substrate (1.0 mmol); nucleophile (1.3 mmol);
catalyst (0.01 mmol); CH3CN (3.0 mL); RT; 24 h. [b] nr=no reaction.
[c] 10 (0.4 mmol);
1
(0.05 mmol); THF (3.0 mL). [d] 14 h. [e] 1
(0.02 mmol); 10 h. [f] 13 h. [g] 08C, 16 h. [h] 1 (0.02 mmol); 08C; 8 h. [i] 1
(0.02 mmol); 08C; 16 h. [j] 6 h. [k] 10 (0.4 mmol).
the enol silyl ethers 11 and 12; however, the other reactions
exhibited the similar tendency of the catalytic activity to the
reaction with 9. Probably, the nucleophilicity of the enol
silyl ethers is very strong. Finally, reactions of the acetal and
cyclohexenone substrates 16 and 17 were carried out. No re-
actions occurred with tetraallyltin, which usually exhibits
highest reactivity, whereas high yields were obtained in the
Then, the reactions of other substrates, such as acetophe-
none (15), bezaldehyde dimethyl acetal (16), and cyclohexe-
none (17), were examined under catalysis of 1 and 3
(Scheme 5, Table 6). As expected, acetophenone is less reac-
tive than benzaldehyde and thus no reaction occurred with
Chem. Eur. J. 2006, 12, 1642 – 1647
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1645

J. Otera, D. L. An, S. Fukuzumi et al.
(1.214 g, 2.0 mmol) in acetone (10 mL) was stirred at RTfor 3 h in the
dark. After filtration, the filtrate was evaporated. The crude products
were dissolved in acetone (2 mL), and the solution was added dropwise
to CH2Cl2 (50 mL). Precipitates were separated by filtration and dried in
vacuo. Recrystallization of the solids from AcOEt (4 mL)/hexane
(10 mL) afforded 1 as a hydrate (1.05 g, 71%). 1H NMR (300 MHz,
[D6]acetone): d=0.93 (t, 24H), 1.37–1.41 (m, 16H), 1.63–1.78 (m, 32H),
4.64 ppm (s, 9.8H); 19F NMR (282 MHz, [D6]acetone): d=À79.21 (m,
24F), À112.21 (m, 16F), À118.59 (m, 16F), À119.74 to À119.99 (m, 48F),
À120.85 (m, 16F), À124.27 to À124.37 ppm (m, 16F); 119Sn NMR
(111 MHz, acetone-d6): d=À162.54, À202.95 ppm; IR (Nujol mull): n˜ =
3389, 2959, 2925, 2854, 1634, 1329, 1240, 1153, 1074, 1037, 940, 747,
687 cmÀ1; elemental analysis calcd (%) for C64H76F68O16S4Sn4 (as dihy-
drate): C 25.65, H 2.56; found: C 25.63, H 2.51 (after pumping for
2 days).
other reactions catalyzed by 1, except the reaction of 16
with 13.
Conclusion
The reactions of 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane
and dialkyltin dihalides with silver perfluorooctanesulfonate
provided the corresponding sulfonates as hydrates. The hy-
drated mononuclear species could be converted to DMSO
complexes. 119Sn NMR spectroscopy and conductivity mea-
surements indicated the ionic dissociation of these com-
pounds in solution. The ionic dissociation together with
facile hydration probably causes the unusual solubility. The
Lewis acidity of these compounds was found to be high
among organotin derivatives. In contrast to well-known or-
ganotin triflates, these compounds suffered no hydrolysis
when stored in open air. The high catalytic activity of the
distannoxane 1 was exemplified for various carbon–carbon
bond-forming reactions. The stability and catalytic activity
of organotin perfluorooctanesulfonates will find a wide
range of applications.
Preparation of Bu2Sn(OSO2C8F17)2 (3): An solution of Bu2SnCl2 (304 mg,
1.0 mmol) and silver perfluorooctanesulfonate (1.214 g, 2.0 mmol) in ace-
tone (10 mL) was stirred at RTfor 3 h in the dark. After filtration, the
filtrate was evaporated. The crude products were dissolved in acetone
(2 mL) and the solution was added dropwise to CH2Cl2 (50 mL). Precipi-
tates were separated by filtration and dried in vacuo. Recrystallization of
the solids from AcOEt (8 mL)/hexane (1 mL) afforded 3 as a hydrate
(850 mg, 69%). 1H NMR (300 MHz, [D6]acetone): d=0.94 (t, 6H), 1.37–
1.41 (m, 4H), 1.69–1.80 (m, 8H), 3.52 ppm (s, 6.1H); 19F NMR
(282 MHz, [D6]acetone): d=À79.20 (m, 6F), À112.27 (m, 4F), À118.61
(m, 4F), À119.74 to À119.99 (m, 12F), À120.85 (m, 4F), À124.27 to
À124.37 ppm (m, 4F); 119Sn NMR (111 MHz, [D6]acetone): d=
À348.89 ppm: IR (Nujol mull): n˜ =3357, 2955, 2924, 2853, 1650, 1331,
1203, 1152, 1075, 1038, 942, 706 cmÀ1
; ESI-MS: m/z calcd for
C24H18F34NaO6S2Sn [M+Na]+: 1254.89; found: 1254.42.
Experimental Section
Preparation of compounds Ph2Sn(OSO2C8F17)2 (5) and Me2Sn-
(OSO2C8F17)2 (4): Compounds 4 and 5 were obtained by using a similar
procedure described above for compound 3.
General: All reactions were carried out under an atmosphere of nitrogen
with freshly distilled solvents, unless otherwise noted. Tetrahydrofuran
(THF) was distilled from sodium/benzophenone. Acetonitrile was distil-
led from CaH2. Silica gel (Daiso gel IR-60) was used for column chroma-
tography. NMR spectra were recorded at 258C on JEOL Lambda 300
and JEOL Lambda 500 instruments and calibrated with tetramethylsilane
(TMS) as an internal reference and tetramethylstannane (Me4Sn) as an
external reference. Mass spectra were recorded on Platform II single
quadrupole mass spectrometer (Micromass, Altrinchan, UK). Elemental
analyses were performed by the Perkin–Elmer PE 2400. Conductivity
was measured on HORIBA conductivity meter DS-12.
Data for Ph2Sn(OSO2C8F17)2 (5): Yield: 61%; 1H NMR (300 MHz,
[D6]acetone): d=6.30 (s, 10.8H), 7.51 (m, 6H), 8.02 ppm (m, 4H);
19F NMR (282 MHz, [D6]acetone): d=À79.20 (m, 6F), À112.38 (m, 4F),
À118.62 (m, 4F), À119.75 to À119.99 (m, 12F), À120.84 (m, 4F),
À124.25 to À124.35 ppm (m, 4F); 119Sn NMR (111 MHz, [D6]acetone):
d=À524.07 ppm; IR (Nujol mull): n˜ =3411, 1650, 1332, 1268, 1235, 1204,
1151, 1075, 1037, 939, 695 cmÀ1
.
Data for Me2Sn(OSO2C8F17)2 (4): Yield: 66%; 1H NMR (300 MHz,
[D6]acetone): d=1.32 (s, 6H), 5.91 ppm (s, 5.4H); 19F NMR (282 MHz,
[D6]acetone): d=À79.21 (m, 6F), À112.44 (m, 4F), À118.66 (m, 4F),
À119.75 to À120.00 (m, 12F), À120.86 (m, 4F), À124.27 to À124.39 ppm
(m, 4F); 119Sn NMR (111 MHz, [D6]acetone): d=À324.43 ppm; IR
(Nujol mull): n˜ =3252, 1650, 1328, 1241, 1205, 1152, 1076, 1041, 940,
742 cmÀ1; ESI-MS: m/z calcd for C18H6F34NaO6S2Sn [M+Na]+: 1170.79;
found: 1170.26.
ESR measurements: A quartz ESR tube (4.5 mm i.d.) containing an
oxygen-saturated solution of dimeric 1-benzyl-1,4-dihydronicotinamide
[(BNA)2] in MeCN (1.0”10À3 m) and a Lewis acid (1.0”10À3 m) was irra-
diated in the cavity of the ESR spectrometer with the focused light of a
1000 W high-pressure Hg lamp through an aqueous filter. Dimeric
(BNA)2, which used as an electron donor to reduce oxygen, was prepared
according to the literature.[14–16] The ESR spectra of O2CÀ Lewis acid com-
plexes in frozen MeCN were measured at 143 K with a JEOL X-band
spectrometer (JES-RE1XE) using an attached VT(variable temperature)
apparatus under nonsaturating microwave power conditions. The g values
were calibrated precisely with an Mn2+ marker, which was used as a ref-
erence.
Preparation of Bu2Sn(OSO2C8F17)2(DMSO)4 (6):
A solution of 3
(1.231 mg, 1.0 mmol) and DMSO (313 mg, 4.0 mmol) in Et2O (10 mL)
was stirred at RTfor 1 h in the dark. After filtration, the solids were
washed with AcOEt. Recrystallization of the solids from CH2Cl2/AcOEt
afforded 6 in a pure form (1.36 g, 88%). 1H NMR (300 MHz, [D6]ace-
tone): d=0.91 (t, 6H), 1.36–1.42 (m, 4H), 1.72–1.84 (m, 8H), 2.91 ppm
(s, 24H); 19F NMR (282 MHz, [D6]acetone): d=À79.19 (m, 6F), À112.52
(m, 4F), À118.57 (m, 4F), À119.70 to À119.97 (m, 12F), À120.82 (m,
4F), À124.26 to À124.35 ppm (m, 4F); 119Sn NMR (111 MHz, [D6]ace-
tone): d=À338.05 ppm; IR (Nujol mull): n˜ =2954, 2923, 2854, 1329,
Preparation of C8F17SO3Ag:[17] Commercially available C8F17SO3H was
not pure, but used as received. A suspension of C8F17SO3H (1.00 g; as-
suming it was pure, it corresponded to 2.0 mmol) and Ag2CO3 (331 mg,
1.2 mmol) in water (15 mL) was stirred in the dark at 1008C for 1 h, and
then at RTfor 1 h. After filtration, the solids obtained were washed with
ice-water till the filtrate turned neutral. The solids were dissolved in ace-
tone and filtered. After the filtrate had been evaporated, the crude solids
were subjected to recrystallization from THF (1.5 mL) and Et2O (4 mL)
1258, 1204, 1150, 986, 931 cmÀ1
; elemental analysis calcd (%) for
C32H42F34O10S6Sn: C 24.90, H 2.74; found: C 24.65, H 2.61.
Preparation of compounds Ph2Sn(OSO2C8F17)2(DMSO)4 (8) and
Me2Sn(OSO2C8F17)2(DMSO)4 (7): Compounds 7 and 8 were obtained by
using a similar procedure described above for compound 6.
to afford C8F17SO3Ag in
a
pure form (484 mg, 40%). 19F NMR
Data for Ph2Sn(OSO2C8F17)2(DMSO)4 (8): Yield: 80%; 1H NMR
(300 MHz, [D6]acetone): d=2.98 (s, 24H), 7.51 (m 6H), 7.99 ppm (m,
4H); 19F NMR (282 MHz, [D6]acetone): d=À79.19 (m, 6F), À112.77 (m,
4F), À118.58 (m, 4F), À119.69 to À119.99 (m, 12F), À120.84 (m, 4F),
À124.25 to À124.37 ppm (m, 4F); 119Sn NMR (111 MHz, [D6]acetone):
(282 MHz, [D6]acetone): d=À79.20 (m, 3F), À112.29 (m, 2F), À118.59
(m, 2F), À119.72 to À120.00 (m, 6F), À120.85 (m, 2F), À124.25 to
À124.38 ppm (m, 2F).
Preparation of (PfOBu2SnOSnBu2OPf)2 (1): A solution of (ClBu2SnOSn-
[5]
Bu2Cl)2
(553 mg, 0.5 mmol) and silver perfluorooctanesulfonate
1646
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 1642 – 1647

Organotin Chemistry
FULL PAPER
d=À501.30 ppm; IR (Nujol mull): n˜ =1329, 1243, 1216, 1152, 1023,
942 cmÀ1; elemental analysis calcd (%) for C36H34F34O10S6Sn: C 27.30, H
2.16; found: C 27.43, H 2.23.
2004, p. 621; b) M. Pereyre, J.-P. Quintard, A. Rahm, Tin in Organic
Synthesis, Butterworths, London, 1987.
[2] a) J. Otera, in Advances in Detailed Reaction Mechanisms, Vol. 3
(Ed.: J. M. Coxon), JAI, London, 1994, p. 167; b) J. Otera, in Ency-
clopedia of Reagents for Organic Synthesis, Vol. 2 (Ed.: L. A. Pa-
quette), Wiley, Chichester, 1995, p. 1140; c) O. A. Mascaretti,
R. L. E. Furlꢁn, Aldrichimica Acta 1997, 30, 55; d) J. Otera, Acc.
Chem. Res. 2004, 37, 288.
[3] a) T. Sato, J. Otera, H. Nozaki, J. Am. Chem. Soc. 1990, 112, 901;
b) T. Sato, Y. Wakahara, J. Otera, H. Nozaki, Tetrahedron Lett.
1990, 31, 1581; c) T. Sato, Y. Wakahara, J. Otera, H. Nozaki, S. Fu-
kuzumi, J. Am. Chem. Soc. 1991, 113, 4028; d) T. Sato, Y. Wakahara,
J. Otera, H. Nozaki, Tetrahedron 1991, 47, 9773; e) T. Sato, J. Otera,
H. Nozaki, J. Org. Chem. 1993, 58, 4971.
Data for Me2Sn(OSO2C8F17)2(DMSO)4 (7): Yield: 92%; 1H NMR
(300 MHz, [D6]acetone): d=1.19 (s, 6H), 3.04 ppm (s, 24H); 19F NMR
(282 MHz, [D6]acetone): d=À79.19 (m, 6F), À112.56 (m, 4F), À118.58
(m, 4F), À119.70 to À119.99 (m, 12F), À120.84 (m, 4F), À124.25 to
À124.37 (m, 4F); 119Sn NMR (111 MHz, [D6]acetone): d=À303.29 ppm;
IR (Nujol mull): n˜ =1329, 1283, 1242, 1202, 1151, 1073, 1040, 993,
941 cmÀ1; elemental analysis calcd (%) for C26H30F34O10S6Sn: C 21.40, H
2.07; found: C 21.37, H 1.70.
Determination of a hydration number of 1 (representative): Molecular
sieves (4 Š, 11 g, dried at 1908C for 0.5 h under reduced pressure) were
added to [D3]acetonitrile (25 g), and the mixture was kept under argon
overnight. In this [D3]acetonitrile, water was not detected by 1H NMR
spectroscopy. The dehydrated [D3]acetonitrile (0.6 mL) was added to a
freshly prepared 1 (10 mg, recrystallized from AcOEt/hexane followed
by drying under reduced pressure for 2 h), and the solution was analyzed
by 1H NMR spectroscopy. Based on integrations of CH3 of butyl (d=
0.93 ppm (t, 24H)) and H2O (d=3.66 ppm (s, 8.08H)), a hydration
number was determined to be about 1.01 per each Sn atom.
[4] X. Li, A. Kurita, S. Man-e, A. Orita, J. Otera, Organometallics
2005, 24, 2567.
[5] Commercially available from Aldrich Chemical Co. Inc.
[6] a) K. Sakamoto, Y. Hamada, H. Akashi, A. Orita, J. Otera, Organo-
metallics 1999, 18, 3555; b) K. Sakamoto, H. Ikeda, H. Akashi, T.
Fukuyama, A. Orita, J. Otera, Organometallics 2000, 19, 3242.
[7] a) J. Otera, T. Yano, K. Nakashima, R. Okawara, Chem. Lett. 1984,
2109; b) T. Yano, K. Nakashima, J. Otera, R. Okawara, Organome-
tallics 1985, 4, 1501.
[8] V. G. Kumar Das, W. Kitching, J. Organomet. Chem. 1967, 10, 59.
[9] H. N. Farrer, M. M. McGrady, R. S. Tobias, J. Am. Chem. Soc. 1965,
87, 5019.
According the same procedure, hydration numbers were determined for
the following organotin compounds which had been dried under reduced
pressure overnight and kept in the air (Table 7).
[10] It is not likely that all PfO ligands are dissociated to give highly pos-
itive species, and thus the structure 1’ represents merely one possible
ionic species.
Table 7. Hydration numbers for compounds 1 and 3–5.
Hydration number per Sn atom[a]
[11] K. Ohkubo, S. C. Manson, A. Orita, J. Otera, S. Fukuzumi, J. Org.
Chem. 2003, 68, 4720.
[12] The allylation with 10 catalyzed by HCl in H2O/THF: a) A. Yanagi-
sawa, H. Inoue, M. Morodome, H. Yamamoto, J. Am. Chem. Soc.
1993, 115, 10356; b) A. Yanagisawa, M. Morodome, H. Nakashima,
H. Yamamoto, Synlett 1997, 1309.
[13] Mukaiyama–aldol reactions in water: a) S. Kobayashi, K. Manabe,
Acc. Chem. Res. 2002, 35, 209; b) K. Manabe, S. Kobayashi, Chem.
Eur. J. 2002, 8, 4095, and references therein.
[14] K. Wallenfels, M. Gellerich, Chem. Ber. 1959, 92, 1406.
[15] M. Patz, Y. Kuwahara, T. Suenobu, S. Fukuzumi, Chem. Lett. 1997,
567.
[16] S. Fukuzumi, T. Suenobu, M. Patz, T. Hirasaka, S. Itoh, M. Fujitsu-
ka, O. Ito, J. Am. Chem. Soc. 1998, 120, 8060.
[17] G. M. Whitesides, F. D. Gutowski, J. Org. Chem. 1976, 41, 2882.
[18] Y.-Z. Jin, N. Yasuda, H. Furuno, J. Inanaga, Tetrahedron Lett. 2003,
44, 8765.
5 min
1 day
3 days
(PfOBu2SnOSnBu2OPf)2 (1)
Bu2Sn(OSO2C8F17)2 (3)
Ph2Sn(OSO2C8F17)2 (5)
Me2Sn(OSO2C8F17)2 (4)
0.13
0.24
1.46
1.12
1.28
3.06
11.0
6.70
1.30
3.20
12.7
6.90
[a] After keeping in the air.
Solubility determination of
1 (representative): AcOEt (0.5 mL) was
placed in a test tube; compound 1 was added gradually at RT. When the
amount of added 1 exceeded 797.2 mg, insoluble 1 appeared. Based on
this data, solubility of (C8F17SO3)Bu2SnOSnBu2(OSO2C8F17) was deter-
mined to be 1594 gLÀ1. According to the same procedure, other solubili-
ties were determined.
Allylation of benzaldehyde with 10 catalyzed by
1 (representative):
PhCHO (106 mg, 1.0 mmol) and 10 (85 mg, 0.3 mmol) were added to a
solution of 1 (74 mg, 0.05 mmol) in THF (3 mL), and the mixture was
stirred at RTfor 12 h. After water (2 mL) was added, the mixture was
stirred at RTfor 1 h. After usual workup with AcOEt/water, the com-
bined organic layer was evaporated. The crude product was subjected to
GC analysis to determine a GC yield (98%).
[19] T. Nakagawa, H. Fujisawa, T. Mukaiyama, Chem. Lett. 2003, 32,
462.
[20] J. Chen, K. Sakamoto, A. Orita, J. Otera, Synlett 1996, 877.
[21] J.-X. Chen, J. Otera, Tetrahedron 1997, 53, 14275.
[22] S.-L. Chen, S.-J. Ji, T.-P. Loh, Tetrahedron Lett. 2004, 45, 375.
[23] R. Hamasaki, Y. Chounan, H. Horino, Y. Yamamoto, Tetrahedron
Lett. 2000, 41, 9883.
[24] G. Wenke, E. N. Jacobsen, G. E. Totten, A. C. Karydas, Y. E.
Rhodes, Synth. Commun. 1983, 13, 449.
[25] H. Ishitani, M. Iwamoto, Tetrahedron Lett. 2003, 44, 299.
[26] J.-X. Chen, K. Sakamoto, A. Orita, J. Otera, Tetrahedron 1998, 54,
8411.
[27] K. Saigo, M. Osaki, T. Mukaiyama, Chem. Lett. 1976, 769.
[28] W.-D. Z. Li, X.-X. Zhang, Org. Lett. 2002, 4, 3485.
[29] T.-P. Loh, L.-L. Wei, Tetrahedron 1998, 54, 7615.
[30] T. Inokuchi, Y. Kurokawa, M. Kusumoto, S. Tanigawa, S. Takagishi,
S. Torii, Bull. Chem. Soc. Jpn. 1989, 62, 3739.
Mukaiyama–aldol reaction of benzaldehyde with 11 catalyzed by 1 (rep-
resentative): PhCHO (106 mg, 1.0 mmol) and 11 (250 mg, 1.3 mmol)
were added to a solution of 1 (74 mg, 0.05 mmol) in THF (3 mL), and the
mixture was stirred at RTfor 12 h. After water (2 mL) had been added,
the mixture was stirred at RTfor 1 h. After usual workup with AcOEt/
water, the combined organic layer was evaporated. The crude product
was subjected to column chromatography on silica gel (5:1 hexane/
AcOEt) to afford the desired compound in a pure form (81% yield).
Aldehydes such as benzaldehyde, 15–17 and nucleophiles 10–14 are com-
mercially available. All products have been reported: 18,[18] 19,[19] 20,[20]
21,[21] 22,[22] 23,[23] 24,[20] 25,[24] 26,[25] 27,[26] 28,[27] 29,[28] 30,[29] 31,[30] and
32.[31]
[31] T. Mukaiyama, T. Nakagawa, H. Fujisawa, Chem. Lett. 2003, 32, 56.
[1] a) A. Orita, J. Otera, in Main Group Metals in Organic Synthesis
Vol. 2 (Eds.: H. Yamamoto, K. Oshima), Wiley-VCH, Weinheim,
Received: September 5, 2005
Published online: December 1, 2005
Chem. Eur. J. 2006, 12, 1642 – 1647
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1647