Transamidation catalyzed by a recoverable and reusable polyDMAP-based hafnium chloride and montmorillonite KSF

Article abstract of DOI:10.1080/00397910500297180

In this article, we described the use of an easily available polymer-based hafnium chloride and montmorillonite KSF catalyst (HfCl₄/KSF- polyDMAP) in transamidation under relatively mild conditions. This metal catalyst can be easily recovered and reused in this reaction to give the corresponding amides in good yields. Copyright Taylor & Francis, Inc.

Full text of DOI:10.1080/00397910500297180

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Transamidation Catalyzed by
a Recoverable and Reusable
PolyDMAP‐Based Hafnium
Chloride and Montmorillonite
KSF
a
a
Min Shi & Shi‐Cong Cui
a
State Key Laboratory of Organometallic
Chemistry , Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences , Shanghai, China
Published online: 22 Aug 2006.
To cite this article: Min Shi & Shi‐Cong Cui (2005) Transamidation Catalyzed by a
Recoverable and Reusable PolyDMAP‐Based Hafnium Chloride and Montmorillonite
KSF, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 35:22, 2847-2858
To link to this article: http://dx.doi.org/10.1080/00397910500297180
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Synthetic Communications , 35: 2847–2858, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500297180
Transamidation Catalyzed by a Recoverable
and Reusable PolyDMAP-Based Hafnium
Chloride and Montmorillonite KSF
Min Shi and Shi-Cong Cui
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of
Organic Chemistry, Chinese Academy of Sciences, Shanghai, China
Abstract: In this article, we described the use of an easily available polymer-based
hafnium chloride and montmorillonite KSF catalyst (HfCl /KSF-polyDMAP) in trans-
4
amidation under relatively mild conditions. This metal catalyst can be easily recovered
and reused in this reaction to give the corresponding amides in good yields.
Keywords: Hafnium chloride, montmorillonite KSF, polyDMAP, polymer-based
catalyst, recoverable and reusable, transamidation
INTRODUCTION
Amide exchange (transamidation) reaction is a useful transformation in
synthetic organic chemistry. The carboxamide group is chemically robust
and generally requires harsh conditions or highly evolved enzymes to
[1]
react. This attractive feature of these compounds underlies the prominence
of amide-based molecules in living systems and the versatility of synthetic
w
polyamides such as nylons and Kevlar . High temperatures (.2508C) can
promote chemical exchange in amide polymers or polymer/amine
[2]
mixtures. Enzyme-mediated transamidation has been achieved, although
[3]
the reaction has limited substrate scope and requires long reaction times.
Received in Japan April 28, 2005
Address correspondence to Min Shi, State Key Laboratory of Organometallic
Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
354 Fenglin Lu, Shanghai 200032, China. Fax: 86-21-64166128; E-mail: mshi@pub.
sioc.ac.cn
2
847

2848
M. Shi and S.-C. Cui
Recently, metal-based catalysis of transamidation received much attention.
For example, stoichiometric quantities of AlCl can mediate transamidation
3
[4]
between amine/carboxamide pairs at 908C in high yields. In addition,
Stahl and coworkers reported catalytic transamidation under moderate
[5]
conditions in the presence of lanthanide(III) triflates such as Sc(OTf)3.
Nowadays, serious environmental problems necessitate our rethinking of
strategies toward organic synthesis. The design or synthesis of recyclable
catalyst has become the key factor for a chemical reaction to be an economi-
cal, safe, environmentally benign, and resource- and energy-saving process.
For this transamidation, it is very clear that if we can design and synthesize
a recyclable polymer-based metal Lewis acid catalyst as a promoter, this
reaction would be accomplished in a more atom-economic way. In this
article, we report a polymer-based HfCl /montmorillonite KSF–catalyzed
4
transamidation between amine/carboxamide pairs in which the metal Lewis
acid catalyst can be recovered and reused for many times.
RESULTS AND DISCUSSION
It has been disclosed that montmorillonite (KSF)–wrapped scandium as a
[6]
heterogeneous catalyst is highly active for Michael addition. Therefore,
in an initial investigation, Sc(OTf)3 (13 mg, 0.025 mmol, 5 mol%) and
Sc(OTf) (13 mg, 0.025 mmol, 5 mol%)/KSF (100 mg) were employed as
3
the catalysts in the transamidation of acetamide 1a (30 mg, 0.5 mmol)
with benzylamine 2a (160 mg, 1.5 mL, 1.5 mmol) in toluene at 1008C. The
results are summarized in Table 1 (Entries 1 and 2). We found that the corre-
sponding amide 3a was formed in 22% and 57% yields, respectively.
Table 1. Transamidation by several Lewis acid catalysts
Time
(h)
Yield
a
(%) , 3a
Entry
Catalyst
1
2
3
4
5
6
7
Sc(OTf) (13 mg, 0.025 mmol)
Sc(OTf) (0.025 mmol)/KSF (100 mg)
KSF (100 mg)
3
20
20
20
20
20
20
20
22
57
15
20
54
67
87
3
4 5 24
Hf Cl O H24 (15 mg)
Hf Cl O H (15 mg)/KSF (100 mg)
4
5 24 24
HfCl
HfCl
4
4
(14 mg)
(14 mg)/KSF (100 mg)
a
Isolated yields.

Transamidation Using HfCl /KSF-polyDMAP
4
2849
The control experiment showed that montmorillonite (KSF) itself is less
effective in this reaction under identical conditions (Table 1, entry 3). Next,
we examined the hydrolytically more stable hafnium (Hf) oxychloride
complex (Hf Cl O H ) (15 mg) and hafnium(IV) chloride (14 mg,
4
5 24 24
0
.05 mmol, 10 mol%) themselves or in the combination with KSF (100 mg)
in this reaction. We selected hafnium(IV) chloride as a catalyst because it
has been proven that hafnium(IV) chloride is a highly active catalyst in the
[7]
direct condensation of carboxylic acids with alcohols. In addition, Hf(IV)
salts are quite practical because of their simplicity and applicability to
[7]
large-scale operations. After examination of these catalysts as shown in
Table 1 (entries 4–7), we found that the employment of HfCl (14 mg,
4
0.05 mmol, 10 mol%)/KSF (100 mg) as a catalyst in the reaction of
acetamide (0.5 mmol) with benzylamine (1.5 mmol) gave the best result,
and 3a was obtained in 87% yield (Table 1, entry 7). Hf Cl O H and
4
5 24 24
Hf Cl O H /KSF are less effective in this transamidation under identical
4
5 24 24
conditions (Table 1, entries 4 and 5).
Next, we screened several other solvents for this transamidation
with HfCl /KSF under the same reaction conditions. The results are summar-
4
ized in Table 2. In acetonitrile (CH CN), 1,2-dichloromethane (DCE)
3
under reflux, similar results as those in toluene were obtained (Table 2,
entries 1–3). In DMSO and water (H O), no reaction occurred (Table 2,
2
entries 4 and 5). Interestingly, we found that in acetonitrile (MeCN) with
the addition of water (H O, 1.0 equiv.) or ammonium (NH , 1.0 equiv.), the
2
3
corresponding amide can be obtained in 92% and 90% yield, respectively
Table 2, entries 6 and 7). This finding gives us an inspiration for preparation
of polymer-based HfCl /KSF catalyst. We thought that if the polymer-bound
(
4
[8]
4
-(N-benzyl-N-methylamino)pyridine (polyDMAP) (Scheme 1) was used
Table 2. Transamidation in a variety of solvents with HfCl /KSF
4
a
Yield (%) , 3a
Entry
Solvent
b
1
2
3
4
5
6
7
Toluene
CH CN
87
86
85
3
CH
DMSO
2 2
ClCH Cl
no reaction
no reaction
92
2
H O
CH CN þ H O (1.0 equiv.)
3
2
CH
3
CN þ NH
3
(1.0 equiv.)
90
a
Isolated yields.
The reaction was carried out at 1008C.
b

2850
M. Shi and S.-C. Cui
Scheme 1. PolyDMAP: dimethylaminopyridine, polymer-bound Lewis base.
instead of NH , a polymer-based HfCl /KSF catalyst could be easily
3
4
produced, and this catalyst should be easily recovered from the reaction
mixture. Therefore, we prepared HfCl /KSF and polyDMAP-based catalyst
4
by mixing HfCl /KSF and polyDMAP in a simple process. [The preparation
4
of this HfCl /KSF-polyDMAP is simple (See the Experimental section)]. A
4
white solid complex was formed, which is air and moisture stable. When
this polymer-based catalyst HfCl4 (14 mg, 0.05 mmol, 10 mol%)/KSF
(100 mg)-polyDMAP (100 mg) was used in this reaction, we found that the
corresponding amide 3a was formed in 90% yield. At the present stage, we
did not clearly understand why the addition of polyDMAP and NH can
3
promote the transamidation of acetamide with benzylamine to some extent.
Presumably, the coordination of polyDMAP and NH to the Hf metal center
3
can adjust its Lewis acidity and subsequently accelerate the reaction rate.
More important, this catalyst can be easily recovered by filtration and can
be reused five times with similar catalytic efficiency in this reaction. The
results are summarized in Table 3. The control experiment has been carried
out to exclude the contribution of the homogeneous catalysis. In the
Table 3. Recovered HfCl
a
this transamidation
4
/KSF-polyDMAPcatalyst in
b
Run
Yield (%)
1
2
3
4
5
90
88
90
85
84
a
HfCl
polyDMAP (100 mg).
4
(14 mg, 0.05 mmol), KSF (100 mg), and
b
Isolated yields.

Transamidation Using HfCl /KSF-polyDMAP
4
2851
transamidation, HfCl /KSF-polyDMAP catalyst is separated at about 50%
4
conversion. The treatment of the filtrate was carried out under the similar con-
ditions. We found that no reaction occurred. The examination of the filtrate by
microanalysis confirmed that no metal is contained in the filtrate. All these
results suggest that this is indeed a heterogeneous catalytic system.
Based on these investigations, we extended the scope and limitations of
this transamidation by use of other acylamides and amines. The results are
summarized in Table 4. Using para-chlorobenzylamine 2b or para-methoxy-
benzylamine 2c as the substrates in the transamidation of acetamide, both the
corresponding amide 3b and 3c were obtained in 70% yields (Table 4, entries
1
and 2). This result suggests that the substituents on the benzene ring did not
significantly affect the efficiency of this transamidation. For 2-phenylaceta-
mide 1b, this transamidation proceeded smoothly under identical conditions
to give the amides 3d–f in 80–83% yields (Table 4, entries 3–5). For
propionamide 1c and pentanoic acid amide 1d, the corresponding amides
were obtained in 73–90% yields under identical conditions (Table 4, entries
6
–9). It should be noted that for benzamide 1e and N-methylacetamide 1f,
the corresponding amides were formed in moderate yields (Table 4, entries
2 and 13). In all these cases, the HfCl /KSF-polyDMAP catalyst can be
1
4
recovered by filtration as well.
Using other aliphatic amines such as butylamine, allylic amine, and
cyclohexylamine as substrates, we found that this transamidation gave the
amides in low yields along with the formation of several by-products. In
Table 4. Transamidation of other acylamides and amines
a
Yield (%) , 3
Entry
Acylamide
CONH (1a)
CH CONH (1a)
Amine
CH NH
p-MeOC H CH NH (2c)
1
2
3
4
5
6
7
8
9
CH
3
2
p-ClC
6
H
4
2
2
(2b)
3b, 90
3c, 90
3d, 83
3e, 80
3f, 80
3g, 89
3h, 83
3i, 82
3j, 84
3k, 82
3l, 80
3m, 73
3n, 75
3
2
6
4
2
2
C
C
6
H
5
5
CH
CH
2
CONH
2
2
(1b)
(1b)
C
6
H
5
CH
2
NH
CH
2
(2a)
NH
6
H
2
CONH
p-ClC
6
H
4
2
2
(2b)
C H CH CONH (1b)
2
p-MeOC H CH NH (2c)
2
6
5
2
6
4
2
CH
3
CH
CH
2
2
CONH
CONH
2
2
(1c)
(1c)
C
6
H
5
CH
2
NH
CH
2
(2a)
NH
CH
3
p-ClC
6
H
4
2
2
(2b)
CH CH CONH (1c)
p-MeOC H CH NH (2c)
6
3
3
3
2
2
4
2
2
CH
CH
(CH
(CH
2
)
)
4
CONH
2
2
(1d)
(1d)
C
6
H
5
CH
2
NH
CH
2
(2a)
NH
10
11
12
13
2
4
CONH
p-ClC
6
H
4
2
2
(2b)
CH (CH ) CONH (1d)
2
p-MeOC H CH NH (2c)
6 4 2 2
3
2 4
C H CONH (1e)
6
C H CH NH (2a)
6
5
2
5
2
2
CH
3
CONHCH
3
(1f)
6
C H
5
CH
2
NH
2
(2a)
a
Isolated yields.

2852
M. Shi and S.-C. Cui
Scheme 2, we showed that utilizing allylic amine as the substrate in the
transamidation with 1a, the corresponding amide 3o was formed in 15%
yield along with the formation of imine 4 in 35% yield and some other uniden-
tified products in the presence of Sc(OTf) /KSF or HfCl /KSF-polyDMAP
3
4
based catalyst.
In summary, we reported in this paper a novel polymer-based HfCl /KSF
4
catalytic process of transamidation with acylamide and benzylamines in
acetonitrile. In this catalytic system, the catalyst HfCl /KSF-polyDMAP
4
can be easily recovered and reused in the same reaction for at least five
times, although this catalytic process still has some limitations for other
aliphatic amines. At any rate, this finding can open a new way to design
and prepare polymer-based metal catalysts. Further investigation to improve
this catalytic process of transamidation is undergoing.
EXPERIMENTAL
General Remarks
MPs were obtained with a Yanagimoto micro-melting-point apparatus and are
1
uncorrected. H NMR spectra were recorded on a Bruker AM-300 spec-
trometer for solution in CDCl with tetramethylsilane (TMS) as internal
3
standard; J values are in Hertz. Commercially obtained reagents were used
without further purification. Montmorillonite KSF (C.A.S.: 1318-93-0) was
purchased from Acros and the polymer-bound 4-(N-benzyl-N-methylamino)-
pyridine (polyDMAP) (2% cross-linked, typical loading: 5.5–6.0 mmol N/g)
was purchased from Aldrich Co. All reactions were monitored by TLC with
Huanghai GF254 silica-gel-coated plates. Flash column chromatography
was carried out using 300–400 mesh silica gel.
Preparation of Hafnium Oxychloride Complex
HfCl (500 mg) was hydrolyzed with distilled water (2.0 mL) in a glass vessel.
4
The excessive water was removed under reduced pressure upon heating at
8
08C. Then, the product was dried at 1208C for 24 h in an oven to give the
Scheme 2.

Transamidation Using HfCl /KSF-polyDMAP
4
2853
corresponding hafnium oxychloride complex as a white solid. Mp .3008C,
487 mg, yield: 96%. Anal. calcd. for Hf Cl O H requires Cl, 13.64%;
4 5 24 24
found: Cl, 14.99%. See Fig. 1.
The single crystal of this complex was obtained by recrystallization from
water. Therefore, this complex contains water in its crystal structure. The
crystal data of hafnium oxychloride complex has been deposited in FIZ
Karlsruhe with number CSD 414059. Empirical formula: H Cl O Hf ;
7
2
5
48
4
formula weight: 1731.79; crystal color, habit: colorless, prismatic; crystal
dimensions: 0.366 ꢀ 0.273 ꢀ 0.186 mm; crystal system: tetragonal; lattice
˚
˚
type: primitive; lattice parameters: a ¼ 17.0031(11) A, b ¼ 17.0031(11) A,
3
˚
˚
c ¼ 7.6897(7) A, a ¼ 908, b ¼ 908, g ¼ 908, V ¼ 2223.1(3) A ; space
3
group: P4/mnc; Z ¼ 2; D ¼ 1.909 g/cm ; F ¼ 1152; diffractometer:
calc
000
Rigaku AFC7R; residuals: R, Rw: 0.0808, 0.2076.
For hafnium oxychloride complex: Mp .3008C, 487 mg, yield: 96%.
Anal. calcd. for Hf Cl O H requires Cl, 13.64%; found: Cl, 14.99%. See
Fig 2.
4
5 24 24
Typical Reaction Procedure for the Transamidation Catalyzed by
HfCl /KSF-polyDMAP Catalyst
4
The mixture of HfCl (14 mg, 0.05 mmol), montmorillonite KSF (100 mg)
4
and polymer-bound 4-(N-benzyl-N-methylamino)pyridine (polyDMAP)
Figure 1. ORTEP draw of the hafnium oxychloride complex.

2854
M. Shi and S.-C. Cui
Figure 2. Crystal packing of hafnium oxychloride complex.
(
100 mg, ꢀ0.05 mmol) in CH CN was stirred for 5 min at room temperature,
3
and then acetamide (30 mg, 0.5 mmol) and benzylamine (0.15 mL, 160 mg,
.5 mmol) were added to the reaction mixture. The resulting heterogeneous
1
mixture was stirred at 808C for 20h. Afterward, the catalysts were recovered
by filtration, and the solvent was removed under reduced pressure. The residue
was purified by a column chromatography on silica gel (MeOH:CHCl ¼
3
1
:50) to give the product as a white solid (67.5 mg, yield: 90%).
N-Benzylacetamide (3a): A white solid, 67.5 mg, yield 90%; this is a known
1
compound. Its H NMR spectroscopic data are consistent with those reported
[
9]
1
in literature. Mp: 58–608C; H NMR (CDCl , TMS, 300 MHz): d 2.02
3
(
3H, s, CH ), 4.43 (2H, d, J ¼ 5.5 Hz, CH ), 5.78 (1H, s, NH), 7.25–7.35
3
2
(5H, m, ArH).
N-(4-Chlorobenzyl)acetamide (3b): A white solid, 82.5 mg, yield 90%; this is
1
a known compound. Its H NMR spectroscopic data are consistent with those
[
10]
1
reported in literature. Mp: 106–1088C; H NMR (CDCl , TMS, 300 MHz):
3
d 2.03 (3H, s, CH ), 4.40 (2H, d, J ¼ 5.6 Hz, CH ), 5.78 (1H, s, NH), 7.23–
3
2
7
.31 (4H, m, ArH).
N-(4-Methoxybenzyl)acetamide (3c): A white solid, 81 mg, yield 90%; this is
1
a known compound. Its H NMR spectroscopic data are consistent with those

Transamidation Using HfCl /KSF-polyDMAP
4
2855
[
11]
1
reported in literature. Mp: 94–968C; H NMR (CDCl , TMS, 300 MHz): d
3
2
.05 (3H, s, CH ), 3.74 (3H, s, OCH ), 4.25 (2H, d, J ¼ 6.0 Hz, CH ), 6.30
3
3
2
(
1H, s, NH), 6.86 (2H, d, J ¼ 8.3 Hz, ArH), 7.20 (2H, d, J ¼ 8.3 Hz, ArH).
N-Benzyl-2-phenylacetamide (3d): A white solid, 93.5 mg, yield 83%; this is a
1
known compound. Its H NMR spectroscopic data are consistent with those
[
12]
1
reported in literature.
Mp: 118–1208C; H NMR (CDCl , TMS,
3
3
NH), 7.10–7.35 (10H, m, ArH).
00 MHz): d 3.63 (2H, s, CH ), 4.25 (2H, d, J ¼ 5.7 Hz, CH ), 6.24 (1H, s,
2
2
N-(4-Chlorobenzyl)-2-phenylacetamide (3e): A white solid, 104 mg, yield
8
1
0%; this is a known compound. Its H NMR spectroscopic data are consistent
[
13]
1
with those reported in literature. Mp: 131–1478C; H NMR (CDCl , TMS,
3
3
NH), 7.23–7.40 (9H, m, ArH).
00 MHz): d 3.62 (2H, s, CH ), 4.43 (2H, d, J ¼ 5.6 Hz, CH ), 5.58 (1H, s,
2
2
N-(4-Methoxybenzyl)-2-phenylacetamide (3f): A white solid, 102.7 mg, yield
8
1
0%; this is a known compound. Its H NMR spectroscopic data are consistent
[
14]
1
with those reported in literature. Mp: 142–1448C; H NMR (CDCl , TMS,
3
3
00 MHz): d 3.64 (2H, s, CH ), 3.79 (3H, s, OCH ), 4.34 (2H, d, J ¼ 5.7 Hz,
2
3
CH ), 5.68 (1H, s, NH), 6.86 (2H, d, J ¼ 8.7 Hz, ArH), 7.20 (2H, d,
2
J ¼ 8.7 Hz, ArH), 7.25–7.35 (5H, m, ArH).
N-Benzylpropionamide (3g): A white solid, 73.5 mg, yield 89%; this is a
1
known compound. Its H NMR spectroscopic data are consistent with those
[
15]
1
reported in literature.
Mp: 45–478C; H NMR (CDCl , TMS, 300 MHz):
3
d 1.19 (3H, t, J ¼ 7.8 Hz, CH ), 2.26 (2H, q, J ¼ 7.5 Hz, CH ), 4.45 (2H, d,
3
2
J ¼ 5.7 Hz, CH ), 5.71 (1H, s, NH), 7.24–7.39 (5H, m, ArH).
2
N-4-Chlorobenzylpropionamide (3h): A white solid, 80.7 mg, yield 83%; this
1
is a known compound. Its H NMR spectroscopic data are consistent with
[
16]
1
those reported in literature.
Mp: 97–998C. H NMR (CDCl , TMS,
3
3
4
00 MHz) d 1.19 (3H, t, J ¼ 7.5 Hz, CH ), 2.26 (2H, q, J ¼ 7.5 Hz, CH ),
3
2
.44 (2H, d, J ¼ 5.7 Hz, CH ), 5.71 (1H, s, NH), 7.22–7.42 (4H, m, ArH).
2
N-(4-Methoxybenzyl)propionamide (3i): A white solid, 79.4 mg, yield 82%;
1
this is a known compound. Its H NMR spectroscopic data are consistent
[
15]
1
with those reported in literature.
Mp: 88–908C; H NMR (CDCl , TMS,
3
3
3
00 MHz): d 1.17 (3H, t, J ¼ 7.5 Hz, CH ), 2.23 (2H, q, J ¼ 7.5 Hz, CH ),
3
2
.80 (3H, s, OCH ), 4.38 (2H, d, J ¼ 4.8 Hz, CH ), 5.73 (1H, s, NH), 6.86
3 2
(
2H, d, J ¼ 7.5 Hz, ArH), 7.20 (2H, d, J ¼ 7.5 Hz, ArH).
N-Benzylhexanamide (3j): A white solid, 86.6 mg, yield 84%; this is a known
1
compound. Its H NMR spectroscopic data are consistent with those reported
[17]
1
in literature.
Mp: 46–488C; H NMR (CDCl , TMS, 300 MHz): d 0.89
3

2856
M. Shi and S.-C. Cui
(
3H, t, J ¼ 6.6 Hz, CH ), 1.25–1.36 (4H, m, CH ), 1.58–1.70 (2H, m, CH ),
3
2
2
2
.20 (2H, t, J ¼ 7.5 Hz, CH ), 4.42 (2H, d, J ¼ 5.4 Hz, CH ), 5.87 (1H, s, NH),
2
2
7
.23–7.38 (5H, m, ArH).
N-4-Chlorobenzylhexanamide (3k): A white solid, 82 mg, yield 82%; this is a
1
known compound. Its H NMR spectroscopic data are consistent with those
[
16]
1
reported in literature.
Mp: 99–1028C; H NMR (CDCl , TMS,
3
3
1
00 MHz) d 0.88 (3H, t, J ¼ 6.6 Hz, CH ), 1.24–1.35 (4H, m, CH ), 1.60–
3
2
.70 (2H, m, CH ), 2.26 (2H, t, J ¼ 7.5 Hz, CH ), 4.42 (2H, d, J ¼ 5.4 Hz,
2 2
CH ), 5.87 (1H, s, NH), 7.21–7.44 (4H, m, ArH).
2
N-(4-Methoxybenzyl)hexanamide (3l): A white solid, 94.9 mg, yield 80%; this
1
is a known compound. Its H NMR spectroscopic data are consistent with
[
17]
1
those reported in literature.
Mp: 90–938C; H NMR (CDCl , TMS,
3
3
1
00 MHz): d 0.89 (3H, t, J ¼ 6.6 Hz, CH ), 1.27–1.33 (4H, m, CH ), 1.60–
3
2
.71 (2H, m, CH ), 2.19 (2H, t, J ¼ 7.5 Hz, CH ), 3.80 (3H, s, OCH ), 4.37
2 2 3
(2H, d, J ¼ 4.8 Hz, CH ), 5.64 (1H, s, NH), 6.86 (2H, d, J ¼ 7.5 Hz, ArH),
2
7
.20 (2H, d, J ¼ 7.5 Hz, ArH).
N-Benzylbenzamide (3m): A liquid, 77.1 mg, yield 73%; this is a known
1
compound. Its H NMR spectroscopic data are consistent with those
[
18]
1
reported in literature.
3
Mp: 117–1198C; H NMR (CDCl , TMS,
3
00 MHz): d 4.64 (2H, d, J ¼ 5.4 Hz, CH ), 6.52 (1H, s, NH), 7.05–7.20
2
(
5H, m, ArH), 7.42 (2H, t, J ¼ 7.2 Hz, ArH), 7.47 (1H, t, J ¼ 7.2 Hz, ArH),
7
.85 (2H, t, J ¼ 7.2 Hz, ArH).
N-Benzyl-N-methylacetamide (3n): A white solid, 61.7 mg, yield 75%; this is
1
a known compound. Its H NMR spectroscopic data are consistent with those
[
19]
1
reported in literature.
1
Mp: 76–798C. H NMR (CDCl , TMS, 300 MHz): d
3
.96 (3H, s, CH ), 4.12 (3H, s, NCH ), 4.39 (2H, d, J ¼ 5.5 Hz, CH ), 5.79
3
3
2
(
1H, s, NH), 7.23–7.36 (5H, m, ArH).
N-Allylacetamide (3o): A colorless liquid, 7 mg, yield 15%; this is a known
1
compound. Its H NMR spectroscopic data are consistent with those
[
20] 1
reported in literature.
H NMR (CDCl , TMS, 300 MHz): d 2.67 (3H, s,
3
CH ), 3.19 (2H, d, J ¼ 5.4 Hz, CH ), 5.02 (1H, d, J ¼ 5.4 Hz, CH ), 5.11
3
2
2
(
1H, dd, J ¼ 7.2, 1.3 Hz, CH ), 5.77–5.88 (1H, m, CH), 5.83 (1H, s, NH).
2
0
N,N -Diallylacetamidine (4): A colorless liquid, 24 mg, yield 35%; this is
1
a known compound. Its H NMR spectroscopic data are consistent with
[
21] 1
those reported in literature.
H NMR (CDCl , TMS, 300 MHz): d 3.12
3
(
4H, d, J ¼ 6.5 Hz, CH ), 3.43 (3H, s, CH ), 5.18 (2H, d, J ¼ 5.7 Hz, CH ),
2
3
2
5
NH).
.21 (2H, dd, J ¼ 7.4, 1.5 Hz, CH ), 5.78–5.94 (2H, m, CH), 5.84 (1H, s,
2
[13]
C NMR (CDCl , TMS, 75 MHz): d 22.6, 51.2, 60.6, 121.2, 131.4,
3
1
73.0.

Transamidation Using HfCl /KSF-polyDMAP
4
2857
Recovery and Reuse of HfCl /KSF-polyDMAP Catalyst
4
This polymer-based metal catalyst can be easily recovered by simply filtration.
After filtration, 200 mg of the catalyst were recovered from the first reaction.
The recovered catalyst were added into the solution of acetamide (30 mg,
0
.5 mmol) and benzylamine (0.15 mL, 160 mg, 1.5 mmol) in CH CN
3
(2 mL). The reaction mixture was stirred at 808C for 20 h. Then, catalyst
was again recovered by filtration and the solvent was removed under
reduced pressure. The residue was purified by a column chromatography on
silica gel (MeOH:CHCl ¼ 1 : 50) to give the product as a white solid
3
(66.9 mg, yield: 90%). This catalyst can be reused at least five times and the
results have been summarized in Table 2.
ACKNOWLEDGMENTS
We thank the State Key Project of Basic Research (Project 973) (No.
G2000048007), Shanghai Municipal Committee of Science and Technology,
and the National Natural Science Foundation of China for financial support
(
20025206, 203900502, and 20272069).
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