Metal bis(perfluorooctanesulfonyl)amides as highly efficient Lewis acid catalysts for fluorous biphase organic reactions

Article abstract of DOI:10.1016/j.jfluchem.2005.10.017

In fluorous biphase system, metal bis(perfluorooctanesulfonyl)amides are better Lewis acid catalysts than the analogous triflates toward either transesterifications, or direct esterifications, or Friedel-Crafts acylations or Baeyer-Villiger oxidations. These catalysts are selectively soluble in lower fluorous phase and can be recovered simply by phase separation. Furthermore, these catalysts can be reused without decrease of activity in most cases.

Full text of DOI:10.1016/j.jfluchem.2005.10.017

Journal of Fluorine Chemistry 127 (2006) 193–199
www.elsevier.com/locate/fluor
Metal bis(perfluorooctanesulfonyl)amides as highly efficient
Lewis acid catalysts for fluorous biphase organic reactions
*
Xiuhua Hao , Akihiro Yoshida, Joji Nishikido
The Noguchi Institute, 1-8-1 Kaga, Itabashi-ku, Tokyo 173-0003, Japan
Received 15 August 2005; received in revised form 20 October 2005; accepted 24 October 2005
Available online 20 December 2005
Abstract
In fluorous biphase system, metal bis(perfluorooctanesulfonyl)amides are better Lewis acid catalysts than the analogous triflates toward either
transesterifications, or direct esterifications, or Friedel–Crafts acylations or Baeyer–Villiger oxidations. These catalysts are selectively soluble in
lower fluorous phase and can be recovered simply by phase separation. Furthermore, these catalysts can be reused without decrease of activity in
most cases.
#
2005 Elsevier B.V. All rights reserved.
Keywords: Fluorous biphase organic reaction; Lewis acid catalyst; Bis(perfluorooctanesulfonyl)amide; Tin; Hafnium
1
. Introduction
condensation [7] and fluoroalkyldistannoxane-catalyzed FBS
esterification [8–10]. In most cases, however, these works suffer
from one or more constrictions, such as drastic reaction
conditions, tedious work-up procedure or large amount of
catalyst. The main constriction of almost all the existing
methods is that the reuse of catalysts was proved specific only
for a kind of organic reactions, which confined their further
commercial application.
The use of perfluorocarbons as reaction media in Green and
Sustainable Chemistry (GSC) and homogeneous catalysis is a
topic of growing interest [1–3]. In particular, the value of the
phase-separation and catalyst immobilization was well-
recognized, and the concept was extended and developed by
Horv a´ th and R a´ bai in 1994, known as Fluorous Biphase System
(
FBS) [4,5].
On the other hand, the Lewis acid-promoted organic
In 1998, our group synthesized lanthanide (Sc, Yb)
bis(perfluorobutanesulfonyl)amides and tris(perfluorobutane-
sulfonyl)methides, which are active in perfluorinated solvents
such as homogeneous catalysts and were employed for Friedel–
Crafts acylation of anisole, Diels–Alder reaction of 2,3-
dimethylbutadiene and Meerwein–Ponndorf–Verley reduction
[11,12]. However, these complexes failed being used as
fluorous immobilized and recyclable catalysts. This objective
was later reached in 2001 by preparing long-enough bis
(perfluorooctanesulfonyl)amide ligand and the correspo-
nding ytterbium bis(perfluorooctanesulfonyl)amide complex
(Yb[N(C F SO ) ] ). The complex was effective for the
reactions was laid as early as 1890, and they still play
important roles in modern organic chemistry [6]. In most cases,
these reactions are performed by making use of oxophilic Lewis
acids, such as AlCl , TiCl or SnCl . However, at least
3
4
4
stoichiometric quantities of the Lewis acid are required and are
destroyed upon work-up leading to serious problems with
strongly acidic waste streams. Therefore, it is desirable to
develop efficient Lewis acid catalysts for truly catalytic organic
reaction, which can be recycled and reused.
With the increase in environmental concern, some efforts
have been made to develop perfluorinated Lewis acid catalysts
soluble in perfluorocarbons in the last several years, such as 3,5-
bis(perfluorodecyl)phenylboronic acid-catalyzed FBS amide
8
17
2 2 3
fluorous biphase Friedel–Crafts acylation system where the
catalyst can be recycled and reused, but it was only confirmed
with the action of acetic anhydride on the activated arene
anisole [13,14].
In recent communications [15–21], we reported a new
class of metal bis(perfluorooctanesulfonyl)amide complexes,
Hf[N(SO C F ) ] and Sn[N(SO C F ) ] , are versatile
*
Corresponding author. Tel.: +81 3 5248 3596; fax: +81 3 5248 3597.
E-mail address: haoxiuhua@noguchi.or.jp (X. Hao).
2
8
17 2 4
2 8 17 2 4
0022-1139/$ – see front matter # 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2005.10.017

194
X. Hao et al. / Journal of Fluorine Chemistry 127 (2006) 193–199
Lewis acid catalysts in FBS. Herein, the synthesis of
Sn[N(SO C F ) ] and Hf[N(SO C F ) ] complexes is fully
A mixture of the above crude (C F SO ) N HNEt , EtOH
8 17 2 2 3
(612 ml) and H O (68 ml) was introduced into ion exchange
2
2
8
17 2 4
2
8
17 2 4
described, and their catalytic activity was tested and compared
with the activity of the analogous triflates in four reactions:
transesterification, direct esterification, Friedel–Crafts acylation
and Baeyer–Villiger oxidation. In this approach, a key factor is
the use of long-enough perfluorinated –N(SO C F ) ligand
resins column, and the eluate was concentrated under reduced
pressure to give a white solid, which was finally sublimed in
vacuum at 120–160 8C/0.02 mmHg to give white powders of
(C F SO ) NH in 62% yield (42.8 g). Anal. Calcd. for
8
17
2 2
(C F SO ) NH: C, 19.58; F, 65.83. Found: C, 19.60; F,
17
2
8
17 2
8
2 2
1
9
(
not partially fluorinated ligand), whose structural characteristic
65.91. F NMR: d ꢀ126.2, ꢀ121.8, ꢀ114.0, ꢀ81.2.
can coordinate with a variety of metal cations to obtain the
desired Lewisacid catalystswith appropriatecatalytic activity, as
well as the selective immobilization in the fluorous phase.
2.1.2. Tin(IV) bis(perfluorooctanesulfonyl)amide
Sn[N(SO C F ) ]
2
8 17 2 4
A mixture of 1,2-dichloroethane (15 ml) and acetonitrile
(5 ml) was added by HN(SO C F ) (5.9 g, 6.0 mmol) and
2
. Results and discussion
2
8 17 2
tin(IV) acetate (532.3 g, 1.50 mmol), which was stirred
continuously at 50 8C for 15 h (Fig. 1). The reaction mixture
was then cooled to room temperature and perfluorodecane
(20 ml) was added. After the perfluorodecane layer was
evaporated and dried at 80 8C/0.01 mmHg for 8 h, tin(IV)
bis(perfluorooctanesulfonyl)amide complex was therefore
obtained as hygroscopic white powders in 96% yield (5.9 g).
2
.1. Syntheses
2
.1.1. Bis(perfluorooctanesulfonyl)amine (C F SO ) NH
8
17
2 2
The preparation of (C F SO ) NH was performed in three
8
17
2 2
steps.
Step 1: Preparation of perfluorooctanesulfonamide
C F SO NH
Anal. Calcd. for Sn[N(SO
2
C
8
F
17
)
2
]
4
: C, 19.03; Sn, 2.94. Found:
C, 19.10; Sn, 2.91. F NMR: d ꢀ126.1, ꢀ121.2, ꢀ114.2,
81.4.
1
9
8
17
2
2
ꢀ
2.1.3. Hafnium(IV) bis(perfluorooctanesulfonyl)amide
Hf[N(SO C F ) ]
2
8 17 2 4
Anhydrous methanol (10 ml) was added by HN(SO C F )
8 17 2
2
(
5.9 g, 6.0 mmol) and hafnium(IV) chloride (0.5 g, 1.5 mmol),
Perfluorooctanesulfonyl fluoride (36.7 g, 73 mmol) was added
slowlywith stirringto liquid NH (ca. 130 ml), which was chilled
which was stirred continuously at 50 8C for 15 h. After being
cooled to room temperature, the mixture was evaporated and
dried at 80 8C/0.01 mmHg for 16 h to give white powders of
hafnium(IV) bis(perfluorooctanesulfonyl)amide complex in
3
to about ꢀ78 8C by EtOH/dry ice. After the stirring was held at
the constant temperature (ꢀ78 8C) for about 1.5 h, it was then
continued at room temperature for 1.5 h. The resulting white
slurry was acidified to a pH of about 2 with 1 M H SO and then
9
7% yield (6.0 g). Anal. Calcd. for Hf[N(SO C F ) ] : C,
2 8 17 2 4
2
4
1
9
1
8.75; Hf, 4.35. Found: C, 18.65; Hf, 4.33. F NMR: d ꢀ126.2,
extracted into diisopropyl ether (100 ml). The diisopropyl ether
layer was dried with anhydride Na SO , concentrated under
ꢀ
121.1, ꢀ114.2, ꢀ81.5.
2
4
reduced pressure, dried in vacuum at 80 8C/0.01 mmHg for
6 h to give the cream residue of C F SO NH (94% yield).
1
8
17
2
2
Step 2: Preparation of triethylammonium bis(perfluorooc-
tanesulfonyl)amide (C F SO ) N HNEt
8
17
2 2
3
ꢁ
ꢂ
C F SO NH þ C F SO F ꢀ! ðC F SO Þ NHNEt
8
17
2
2
8
17
2
8
17
2 2
3
Et3N
D
Perfluorooctanesulfonyl fluoride (36.0 g, 72 mmol) was added to
a mixture of perfluorooctanesulfonamide (34.4 g, 69 mmol) and
Et N(60 ml).Thismixturewasheatedatrefluxfor23 h,cooledto
3
room temperature, and the resulting biphase system was sepa-
rated. After the upper Et N layer was removed, the lower brown
3
fluorous layer waswashedwith10% HCltoyield the brownsolid,
which was finally dried invacuum at 70 8C/0.01 mmHg for 6 h to
afford (C F SO ) N HNEt as crude form.
8
17
2 2
3
Step 3: Preparation of bis(perfluorooctanesulfonyl)amine
C F SO ) NH
(
8
17
2 2
Fig. 1. MNDO/FF optimized structure of Sn[N(SO
Sn[N(SO CF core part is optimized by the MNDO/AM1 method using
Gaussian-98 and the C 17-chain moiety is optimized by Universal Force Field
with the fixed core geometry.
2 8 17 2
C F ) ]4. The
2
3 2 4
) ]
ꢁ
ꢂ
Amberlite IR-120B column
ðC F SO Þ NHNEt ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ ꢀꢀ ! ðC F SO Þ NH
8
F
8
17
2 2
3
8
17
2 2
EtOH=H2O

X. Hao et al. / Journal of Fluorine Chemistry 127 (2006) 193–199
195
Table 1
Fluorous biphase transesterification
1
a
Yield (%)
b
Selectivity (%)
Entry
2
RCO R
Catalyst
1
2
3
4
5
Sn[N(SO
Sn[N(SO
2
C
C
8
F
F
17
17
2
)
)
2
]
]
4
2
88
84
83
76
65
99
96
96
89
87
2
8
2
Sn(OSO
Hf[N(SO
Hf(OSO
Sc[N(SO
Sc(OSO
Yb[N(SO
Yb(OSO
2
CF
3
)
2
C
8
F
17
)
2
]
4
2
3
CF )
4
6
7
8
9
2
C
8
F
17
)
2
]
3
74
59
55
12
86
87
85
48
2 3
CF )
3
2 8 17 2 3
C F ) ]
2
3 3
CF )
1
1
0
1
Sn[N(SO
2
C
C
8
F
F
17
)
)
2
]
]
4
4
91
90
98
98
Sn[N(SO
2
8
17
2
c
c
1
1
2
3
PhCO CH
2
3
Sn[N(SO
2
C
C
8
F
F
17
)
)
2
]
]
4
4
91
90
98
98
2 2 5
PhCO C H
Sn[N(SO
2
8
17
2
a
b
c
Isolated yields.
Selectivity: mmol product/mmol converted ester.
mol% Sn[N(SO for 24 h.
5
2 8 17 2 4
C F ) ]
2
2
.2. Reactivity
loss of catalytic activity for all of the transesterifications in
Table 1.
.2.1. Transesterification (Table 1)
The catalytic activity of the metal bis(perfluorooc-
2.2.2. Direct esterification (Table 2)
tanesulfonyl)amides was firstly compared with the activity
of the analogous triflates in fluorous biphase transesterifica-
tion of methyl butyrate/n-octanol under the mild conditions
of 80 8C for 15 h (entries 1–9). All of the metal complexes
This catalytic FBS system was also evaluated with the direct
esterification of acetic acid/cyclohexanol under the mild
conditions of 50 8C for 8 h (entries 1–5). Compared with the
above-described transesterification of methyl butyrate/n-octa-
nol, Sn[N(SO C F ) ] (entry 5) could no longer give the best
II
IV
III
III
(
Sn , Hf , Sc , Yb ) with the –N(SO C F ) ligand
2 8 17 2
2 8 17 2 4
(
entries 2, 4, 6 and 8) generally gave better yields than
those with the –OSO CF ligand (entries 3, 5, 7 and 9), but
yield, which was just below Hf[N(SO C F ) ] (entry 1). With
2 8 17 2 4
IV
respect to Hf -based catalysts (entries 1–4), Hf[N(SO
2
2
3
with no significant difference in selectivity except for the
III
C F ) ] showed significantly higher activity than Hf(O-
8 17 2 4
Yb
complex. These results can be attributed to the
SO CF ) , HfCl and HfCl ꢃ2THF, even though the latter ones
2
3 4
4
4
presence of the powerfully electron-withdrawing –N(SO2
C F ) ligand bearing the higher fluorine load on the metal
center [22]. As for M[N(SO C F ) ] (n = 3, 4) complexes,
are well-known efficient catalysts for direct esterification [24].
The efficacy of Hf[N(SO C F ) ] was confirmed for the
8
17 2
2 8 17 2 4
direct esterification of cyclohexanecarboxylic acid/butanol
(entry 6), cyclohexanecarboxylic acid/benzyl alcohol (entries
7) and benzoic acid/butanol (entry 8). Additionally, the
separated fluorous Sn[N(SO C F ) ] phase [25] can be
2
8 17 2 n
IV
the yield and selectivity were in the order of Sn > H-
IV
Hf > Sc > Yb (entries 1, 4, 6 and 8). Accordingly,
III
III
Sn[N(SO C F ) ] (entry 1) was considered to be an
17 2 4
2
8
2 8 17 2 4
excellent catalyst in terms of good yield and excellent
selectivity. In addition, the high catalytic activity of Sn[N
reused in the next reaction more than five times without
depression of catalytic activity for all of the direct esterifica-
tions in Table 2.
(
SO C F ) ] is also applicable to transesterification of
2 8 17 2 4
methyl 3-phenyl propionate/n-octanol (entry 10), methyl
cyclohexanecarboxylate/n-octanol (entry 11), methyl benzo-
ate/n-octanol (entry 12) and ethyl benzoate/n-octanol (entry
2.2.3. Friedel–Crafts acylation (Table 3)
Friedel–Crafts acylation of anisole with acetic anhydride
was carried out in this FBS to investigate the potential of
Hf[N(SO C F ) ] at low catalytic loading (1 mol%). As
1
3).
Moreover, the recyclable performance [23] of Sn[N
SO C F ) ] was also investigated. The fluorous catalytic
2
8 17 2 4
(
described in transesterification and direct esterification,
Hf[N(SO C F ) ] (entry 1) showed significantly higher
activity than Hf(OSO CF ) (entry 2), even though the latter
2
8 17 2 4
phase was directly reused in the next reaction by combining
with another mixture of reactants more than five times without
2
8 17 2 4
2
3 4

196
X. Hao et al. / Journal of Fluorine Chemistry 127 (2006) 193–199
Table 2
Fluorous biphase direct esterification
1
R OH
a
Yield (%)
b
Selectivity (%)
Entry
RCO
2
H
Catalyst
Conditions
1
2
3
4
5
AcOH
Hf[N(SO
2
C
8
F
17
)
2
]
4
50 8C, 8 h
50 8C, 8 h
50 8C, 8 h
50 8C, 8 h
50 8C, 8 h
80
70
22
29
78
99
88
61
60
98
Hf(OSO
2
CF
3
)
4
HfCl
HfCl
4
4
ꢃ2THF
Sn[N(SO
2
C
8
F
17
)
)
2
2
]
]
4
4
6
7
n-C
PhCH
n-C
4
H
9
OH
OH
OH
Hf[N(SO
2
C
8
F
17
70 8C, 15 h
50 8C, 24 h
90 8C, 15 h
92
89
85
97
98
96
2
Hf[N(SO
2
2
C
8
8
F
17
)
)
2
2
]
]
4
4
c
8
PhCO
2
H
4
H
9
Hf[N(SO
C
F
17
a
Isolated yields.
b
c
Selectivity: mmol product/mmol converted carboxylic acid.
In 1,2-dichloroethane (3.0 ml)/perfluorodecalin (3.0 ml) biphase system.
gave a relatively higher activity than the other listed metal
triflates (entries 3–7). As for M(OSO CF ) (n = 3, 4) catalysts,
there was no significant difference in the regioselectivity ( p-
III
regioisomer > 97%) except for Ga catalyst (o/p = 19/81). In
2
3 n
yield (from moderate to low) followed the order of
III
addition, the activity of AlCl3 (entry 8), a well-known
industrially used catalyst for Friedel–Crafts acylation, was
IV
III
III
III
III
Hf > Sc > Ga > Bi ꢄ Yb > Al (entries 2–7), and
Table 3
Fluorous biphase Friedel–Crafts acylation
a,b
Product and yield (%)
c
Entry
ArH
Acylating agent
Ac
Catalyst
Conditions
1
2
3
4
5
2
O
Hf[N(SO
2
C
8
F
17
)
2
]
4
100 8C, 1 h
100 8C, 1 h
100 8C, 1 h
100 8C, 1 h
100 8C, 1 h
1; 80 (0/100)
1; 49 (3/97)
1; 45 (2/98)
1; 42 (19/81)
1; 39 (2/98)
Hf(OSO
Sc(OSO
Ga(OSO
2
CF
CF
CF
CF
3
)
4
2
3 3
)
2
3 3
)
Bi(OSO
2
3 3
)
6
7
8
Yb(OSO
2
CF
CF
3
)
3
100 8C, 1 h
100 8C, 1 h
100 8C, 1 h
1; 16 (3/97)
1; 8 (3/97)
1; 2 (0/100)
Al(OSO
AlCl
2
3
)
3
3
9
(n-C
3
H
7
CO)
2
O
Hf[N(SO
Hf(OSO
2
C
8
F
17
)
)
)
)
2
]
2
]
2
]
2
]
4
4
4
4
90 8C, 1 h
90 8C, 1 h
2; 88 (18/82)
2; 57 (23/77)
1
0
2
CF
3
)
4
1
1
2
(PhCO)
2
O
Hf[N(SO
Hf(OSO
2
C
8
F
17
4
120 8C, 2 h
120 8C, 2 h
3; 90 (3/97)
3; 35 (14/86)
1
2
CF
3
)
1
3
4
Ac
2
O
Hf[N(SO
Hf(OSO
2
C
8
F
17
4
90 8C, 1 h
90 8C, 1 h
4; 91
4; 39
1
2
CF
3
)
1
1
5
6
(n-C
3
H
7
CO)
2
O
Hf[N(SO
Hf(OSO
2
C
8
F
17
4
90 8C, 1 h
90 8C, 1 h
5; 97
5; 66
2
CF
3
)
1
7
8
(PhCO)
2
O
Hf[N(SO
Hf(OSO
2
C
8
F
17
)
2
]
4
110 8C, 2 h
110 8C, 2 h
6; 94
6; 56
1
2
3
CF )
4
a
Acylation products: methoxyacetophenone (1); methoxybutyrophenone (2); methoxybenzophenone (3); 3,4-dimethoxyacetophenone (4); 3,4-dimethoxybutyr-
ophenone (5); 3,4-dimethoxybenzophenone (6).
b
Determined by GC–MS and NMR analysis.
c
Isolated yield after chromatography, with respect to aromatic compound; results in parentheses refer to rations of o/p.

X. Hao et al. / Journal of Fluorine Chemistry 127 (2006) 193–199
197
Table 4
Fluorous biphase Baeyer–Villiger oxidation
a
Yield (%)
b
Selectivity (%)
Entry
Substrate
Product
Catalyst
1
2
3
4
5
Sn[N(SO
Sn[N(SO
2
C
C
8
F
F
17
17
2
)
)
2
]
]
4
2
91
48
37
82
41
99
83
87
92
91
2
8
2
Sn(OSO
Hf[N(SO
Hf(OSO
2
CF
3
)
2
C
8
F
17
)
2
]
4
2
3
CF )
4
6
7
8
9
Sc[N(SO
Sc(OSO
Yb[N(SO
Yb(OSO
2
C
8
F
17
)
2
]
3
53
31
31
19
69
66
73
83
2
3
CF )
3
2 8 17 2 3
C F ) ]
2
3 3
CF )
c
10
2
Sn[N(SO C
8
F
17
)
2
]
4
95
99
a
b
c
Isolated yields.
Selectivity: mmol product/mmol converted ketone.
Reaction was performed in 1,4-dioxane (3.0 ml)/perfluoro(methylcycloexane) (3.0 ml) system, at 50 8C for 1 h.
significantly low under the present mild reaction conditions.
The efficacy of Friedel–Crafts acylation of anisole and o-
dimethoxybenzene with various anhydrides catalyzed by
compared. In Fig. 2, the representative results obtained
from cyclobutanone Baeyer–Villiger oxidation were shown.
It can be found that there was almost no difference for the
formation rate of g-butyrolactone at cycle 1 and 4 within 1 h
reaction time, which confirmed that there was not only no
loss of the catalyst but also no depression of catalytic activity
during the repetition. Accordingly, it can be deduced 99% of
the catalyst should still remain in the fluorous phase even
after the 4th cycle [26]. In fact, the product yield kept a
constant level undering a specific period (e.g. about 1 h for
1
mol% Hf[N(SO C F ) ] was also examined. Inspection
2 8 17 2 4
of the results showed that more electron rich o-dimethox-
ybenzene (entries 13, 15 and 17) underwent acylation more
smoothly than anisole (entries 1, 9 and 11), and produced a
single regioisomer in excellent yields. In all cases,
Hf[N(SO C F ) ] showed a higher activity than Hf(O-
2
8 17 2 4
SO CF ) . Moreover, the recyclable performance of
3 4
2
Hf[N(SO C F ) ] was investigated and showed that the
2
8 17 2 4
catalytic fluorous phase can be reused more than four times for
all of the reactions in Table 3.
2
.2.4. Baeyer–Villiger oxidation (Table 4)
The Baeyer–Villiger oxidation of adamantanone in FBS was
examined to evaluate this FBS. As described in the above
transesterification, direct esterification and Friedel–Crafts
II
IV
III
III
acylation, all of the metal complexes (Sn , Hf , Sc , Yb )
with the –N(SO C F ) ligand (entries 2, 4, 6 and 8) gave
better yield and selectivity than those with the –OSO CF
2
8 17 2
2
3
ligand (entries 3, 5, 7 and 9), but with no significant difference
in selectivity. This ligand effect was further clearly proven by
the Sn-based catalysts: yield and selectivity followed
the order of Sn[N(SO C F ) ] > Sn[N(SO C F ) ] >
2
8
17 2 4
2 8 17 2 2
Sn(OSO CF ) (entries 1–3). In addition, Sn[N(SO C F ) ]
2 8 17 2 4
2
3 2
could be reused more than four times for BV oxidation of
adamantanone and cyclobutanone.
In order to analyze and quantify the catalyst recovery, the
reaction rates (= activity) at different cycle times were
Fig. 2. Lactonization of cyclobutanone catalyzed by Sn[N(SO
2 8 17 2 4
C F ) ] at
different cycles.

198
X. Hao et al. / Journal of Fluorine Chemistry 127 (2006) 193–199
cycle 1 in Fig. 2), which is a criterion for us to determine the
reaction time.
(0.6 ml) was added. After being stirred for 10 min, this mixture
was separated into two liquid phases within 10 s. The upper
toluene phase afforded pure n-octyl butyrate (176.3 mg,
0.9 mmol) by silica gel chromatography and reduced pressure
evaporation, while the lower fluorous phase containing the
catalyst was used in subsequent reactions. To the lower fluorous
phase, toluene (0.4 ml), methyl butyrate (102.1 mg, 1.0 mmol)
and n-octanol (130.2 mg, 1.0 mmol) were added. The other
operations and procedure (e.g. stirring at 80 8C for 15 h, product
separation) were the same as described above for the first cycle.
Such a procedure was repeated further four times. Substantially,
the yields of n-octyl butyrate were 88, 87, 84 and 84% in the
succeeding four times, respectively.
Additionally, it was also confirmed that such a high
selectivity could not be achieved when the catalyst was used
in an organic monophase, i.e. either 1,2-dichloroethane as a
solvent for adamantanone Baeyer–Villiger oxidation (yield:
7
1%; selectivity: 81%) or 1,4-dioxane as a solvent for
cyclobutanone Baeyer–Villiger oxidation (yield: 38%; selec-
tivity: 65%), whose respective selectivities were considerably
lower than those in FBS (selectivity > 97%). Another
exceptional advantage in FBS is that the catalyst can be
recovered and reused as described above, which is an
impossible task in the organic monophase system. It is worth
emphasing that such excellent yields and selectivity benefit
greatly from both the efficient Lewis acidity of
Sn[N(SO C F ) ] and the unique solution property of FBS.
4.3. A typical procedure of Hf[N(SO C F ) ] -catalyzed
2 8 17 2 4
2
8 17 2 4
fluorous biphase direct esterification
3
. Conclusions
As the described above transesterification of methyl
butyrate/n-octanol, acetic acid (60.0 mg, 1.0 mmol), cyclohex-
anol (100.2 mg, 1.0 mmol), Hf[N(SO C F ) ] (205.0 mg,
The fluorous biphase organic reactions using perfluorinated
2
8 17 2 4
Lewis acid as immobilized and effective catalysts was
performed. This fluorous biphase system approach offers
distinct advantages over the existing methods: (1) easy work-up
procedure, (2) recoverable and recyclable catalyst, (3) higher
yield and selectivity for the desired product at lower catalytic
loadings and (4) a broad application, suitable for a variety of
organic reactions, i.e. transesterification, direct esterification,
Friedel–Crafts acylation and Baeyer–Villiger oxidation.
0.05 mmol) and a mixture of perfluoro(methylcyclohexane)
(3 ml) and 1,2-dichloroethane (3 ml) were added to a 20 ml test
tube equipped with a Teflon-coated magnetic stirring. The
reactant mixture was stirred continuously at 50 8C for 8 h and
settled down for 10 s. Then this reacted mixture was turned into
an upper 1,2-dichloroethane phase for pure cyclohexyl acetate
(115.2 mg, 0.8 mmol) by silica gel chromatography and a lower
fluorous phase for the subsequent reaction. To the lower
fluorous phase, 1,2-dichloroethane (3 ml), acetic acid (60.0 mg,
1.0 mmol) and n-cyclohexanol (100.2 mg, 1.0 mmol) were
added. The other operations and procedure (e.g. stirring at
50 8C for 8 h, product separation) were the same as described
above for the first cycle. Such a procedure was repeated further
four times. Substantially, the yields of cyclohexyl acetate were
83, 81, 83 and 82% in the succeeding four times, respectively.
4
. Experimental
4
.1. General
1
13
19
H, C and F NMR spectra were recorded on a JEOL
JNM-ECA600 (600 MHz) instrument using tetramethylsilane
d 0.00), chloroform-d (d 77.0) and a,a,a-trifluorotoluene (d
63.20) as internal standards, respectively. GC analysis was
(
ꢀ
4.4. A typical procedure of Hf[N(SO C F ) ] -catalyzed
2
8 17 2 4
carried out on a SHIMADZU GC-1700AF. GC–MS measure-
ment was performed on a Hewlett-Packard G1800A GLS.
Atomic emission spectra were taken on IRIS/AP (Nippon
Jarrell Ash Co.). Products after isolation were qualitatively
fluorous biphase Friedel–Crafts acylation
1
To a mixture of GALDEN
SV 135 (1.5 ml) and
chlorobenzene (1.5 ml), were added Hf[N(SO C F ) ]
8 17 2 4
2
1
13
identified by GC–MS, H and C NMR, and quantitatively
analyzed by GC. All the products listed in Tables 1–4 are
known compounds and were identified by comparison of their
spectra data and retention time in GLC with those of authentic
samples.
(41.0 mg, 0.01 mmol), anisole (108.1 mg, 1.0 mmol) and acetic
anhydride (204.2 mg, 2.0 mmol). The reaction mixture was
stirred continuously at 100 8C for 1 h. Once the stirring was
stopped, the reaction mixture settled down at room tempera-
ture and turned into two liquid phases within 5 min, i.e. an
upper toluene and a lower SV 135 phase. Pure p-methoxyace-
tophenone product was obtained from the upper phase after silica
gel chromatography and reduced pressure evaporation
4.2. A typical procedure of Sn[N(SO C F ) ] -catalyzed
2 8 17 2 4
fluorous biphase transesterification
(120.1 mg, 80% isolated yield). The lower fluorous phase
A 10 ml test tube equipped with a Teflon-coated magnetic
stirring bar was charged with methyl butyrate (102.1 mg,
containing the catalyst was reused in the subsequent recycling
reactions, to which chlorobenzene (1.5 ml), anisole (108.1 mg,
1.0 mmol) and acetic anhydride (204.2 mg, 2.0 mmol) were
added, respectively. The other operations and procedure (e.g.
stirring at 100 8C for 1 h, product separation) were the same as
described above for the first cycle. Such a procedure was
repeated further three times. Substantially, the yields of p-
1
.0 mmol), n-octanol(130.2 mg, 1.0 mmol), Sn[N(SO C F ) ]
2 8 17 2 4
(
(
121.2 mg, 0.03 mmol), toluene (0.4 ml) and perfluorodecalin
1.0 ml). The tubewas placed in an organic synthesizer equipped
with a magnetic stirrer and heated at 80 8C for 15 h. The reaction
mixture was cooled to room temperature and then toluene

X. Hao et al. / Journal of Fluorine Chemistry 127 (2006) 193–199
199
[
[
2] D.-W. Zhu, Synthesis (1993) 953–954.
methoxyacetophenone were 79, 81 and 78% in the succeeding
three times, respectively.
3] The First International Conference on Green & Sustainable Chemistry,
Tokyo, Japan, March 2003.
[
[
[
4] I.T. Horv a´ th, J. R a´ bai, Science 266 (1994) 72–75.
5] I.T. Horv a´ th, J. R a´ bai, US Patent, 5,463,082 (1995).
6] H. Yamamoto (Ed.), Lewis Acids in Organic Synthesis, Wiley–VCH, New
York, 2000.
[
[
7] K. Ishihara, S. Kondo, H. Yamamoto, Synlett (2001) 1371–1374.
8] J. Xiang, S. Toyoshima, A. Orita, J. Otera, Angew. Chem. Int. Ed. Engl. 40
(
2001) 3670–3672.
4
fluorous biphase Baeyer–Villiger oxidation
.5. A typical procedure of Hf[N(SO C F ) ] -catalyzed
2 8 17 2 4
[
9] J. Otera, J. Acc. Chem. Res. 37 (2004) 288–296.
[
[
[
[
[
10] J. Xiang, A. Orita, J. Otera, Angew. Chem. Int. Ed. Engl. 41 (2002) 4117–
119.
4
To a mixture of perfluoro(methylcyclohexane) (3 ml) and
,2-dichloroethane (3 ml), were added Sn[N(SO C F ) ]
2 8 17 2 4
11] J. Nishikido, H. Nakajima, T. Saeki, A. Ishii, K. Mikami, Synlett (1998)
1347–1348.
1
12] J. Nishikido, F. Yamamoto, H. Nakajima, Y. Mikami, Y. Matsumoto, K.
Mikami, Synlett (1999) 1990–1992.
(
and 35% H O (194.3 mg, 2.0 mmol). The reaction mixture
80.8 mg, 0.02 mmol), 2-adamantanone (300.4 mg, 2.0 mmol)
2
2
13] K. Mikami, Y. Mikami, Y. Matsumoto, J. Nishikido, F. Yamamoto, H.
Nakajima, Tetrahedron Lett. 42 (2001) 289–292.
was stirred continuously at 25 8C for 2 h. Once the stirring was
stopped, the reaction mixture settled down and turned into two
liquid phases within 10 s, i.e. an upper 1,2-dichloroethane and a
lower perfluoro(methylcyclohexane) phase. Pure lactone was
obtained from the upper phase after silica gel chromatography
and reduced pressure evaporation (302.5 mg, 91% isolated
yield). The lower fluorous phase containing the catalyst was
reused in the subsequent recycling reactions, to which 1,2-
dichloroethane (3 ml), 2-adamantanone (300.4 mg, 2.0 mmol)
and 35% H O (194.3 mg, 2.0 mmol) were added. The other
14] K. Mikami, Y. Mikami, H. Matsuzawa, Y. Matsumoto, J. Nishikido, F.
Yamamoto, H. Nakajima, Tetrahedron 58 (2002) 4015–4021.
15] X. Hao, A. Yoshida, J. Nishikido, Tetrahedron Lett. 46 (2005) 2697–2700.
16] X. Hao, A. Yoshida, J. Nishikido, Green Chem. 6 (2004) 566–569.
17] X. Hao, A. Yoshida, J. Nishikido, Tetrahedron Lett. 45 (2004) 781–
[
[
[
7
85.
[
[
[
[
18] X. Hao, A. Yoshida, O. Yamazaki, J. Nishikido, Tetrahedron Lett. 44
(2003) 4977–4980.
19] O. Yamazaki, X. Hao, A. Yoshida, J. Nishikido, Tetrahedron Lett. 44
(
2003) 8791–8795.
20] X. Hao, A. Yoshida, O. Yamazaki, J. Nishikido, Green Chem. 5 (2003)
24–528.
21] A. Yoshida, X. Hao, J. Nishikido, Green Chem. 5 (2003) 554–557.
2
2
operations and procedure (e.g. stirring at 25 8C for 2 h, product
separation) were the same as described above for the first cycle.
Such a procedure was repeated further three times. Substan-
tially, the yields of lactone were 92, 90 and 93% in the
succeeded three times, respectively.
5
[22] I.A. Koppel, R.W. Taft, F. Anvia, S.-Z. Zhu, L.-Q. Hu, K.-S. Sung, D.D.
DesMarteau, L.M. Yagupolskii, Y.L. Yagupolskii, N.V. Ignat’ev, N.V.
Kondratenko, A.Y. Volkonskii, V.M. Vlasov, R. Notario, P.-C. Maria, J.
Am. Chem. Soc. 116 (1994) 3047–3057.
[
23] The catalyst was recovered from the fluorous phase without apparent
weight loss, i.e. 119 mg modified catalyst was recovered after the original
Acknowledgements
1
21 mg was recycled for five times. The recovered Sn[N(SO
catalyst was characterized by elemental analysis. Anal. Calcd for
Sn[N(SO : C, 19.03; Sn, 2.94. Found: C, 19.50; Sn, 2.90.
24] K. Ishihara, M. Nakayama, S. Ohara, H. Yamamoto, Tetrahedron 58
2002) 8179–8188.
2 8 17 2 4
C F ) ]
This work was supported by New Energy and Industrial
Technology Development Organization (NEDO) and Japan
Chemical Innovation Institute (JCII) through the R&D program
for Process Utilizing Multi-Phase Catalytic Systems.
2 8 17 2 4
C F ) ]
[
[
(
25] The catalyst was recovered from the fluorous phase without apparent
weight loss, i.e. 203 mg modified catalyst was recovered after the original
References
205 mg was recycled five times. The recovered Hf[N(SO
catalyst was characterized by elemental analysis. Anal. Calcd for
Hf[N(SO : C, 18.75; Hf, 4.35. Found: C, 18.72; Hf, 4.33.
26] J.A. Gladysz, Pure Appl. Chem. 73 (2001) 1319–1324.
2 8 17 2 4
C F ) ]
2 8 17 2 4
C F ) ]
[1] M. Vogt, Ph.D. Thesis, The application of perfluorinated polyethers for the
[
immobilization of homogeneous catalysts, Archen, Germany, 1991.