Formylation of amines and alcohols using aminopropylated mesoporous SBA-15 silica (APMS) as an efficient and recyclable catalyst

Article abstract of DOI:10.1135/cccc2011131

Aminopropylated mesoporous SBA-15 silica (APMS) is introduced as a new, recyclable and efficient catalyst for the formylation of a variety of amines and alcohols by using readily available formic acid under solvent-free conditions.

Full text of DOI:10.1135/cccc2011131

Aminopropylated SBA-15 in Formylation Reactions
1979
FORMYLATION OF AMINES AND ALCOHOLS USING
AMINOPROPYLATED MESOPOROUS SBA-15 SILICA (APMS)
AS AN EFFICIENT AND RECYCLABLE CATALYST
Reihaneh MALAKOOTIa1,*, Sara SOBHANIb1,*, Nasrin RAZAVI , Soheila SHAFIEI and
b2
a2
a3
Rezvan MOKHTARI
a
Nanochemistry Research Laboratory, Department of Chemistry, University of Birjand,
Birjand 414, Iran; e-mail: reihaneh.malakooti@gmail.com, sohyla_shafiei@yahoo.com,
1
2
3
rzmkh@yahoo.com
b
Department of Chemistry, College of Sciences, Birjand University,
1
2
Birjand 414, Iran; e-mail: ssobhani@birjand.ac.ir, nasrin_razavi2009@yahoo.com
Received June 28, 2011
Accepted September 2, 2011
Published online January 31, 2012
Aminopropylated mesoporous SBA-15 silica (APMS) is introduced as a new, recyclable and
efficient catalyst for the formylation of a variety of amines and alcohols by using readily
available formic acid under solvent-free conditions.
Keywords: SBA-15; Solid bases; Formylation; Amines; Alcohols.
Formylation of amines to produce formamides is an important reaction in
synthetic organic chemistry. Formamides have wide applications as inter-
1
mediates in the preparation of pharmaceuticals such as fluoroquinolines ,
2
3
substituted aryl imidazoles , 1,2-dihydroquinolines , nitrogen-bridged
4
5
6
heterocycles , oxazolidinones and cancer chemotherapeutic agents .
They constitute important precursors in the synthesis of fungicides and
herbicides . Formamides are also Lewis base catalysts, which are known to
catalyze reactions such as allylation and hydrosilylation of carbonyl com-
pounds. In addition, formamides are very useful reagents in Vilsmeier
formylation reactions as well as in the synthesis of formamidines and iso-
2
7
8
9
1
0
cyanides . Formamide has been also undergone reactions to create nucleic
1
1
acid bases and simple base derivatives on a powdered TiO2 surface .
Alkynyl formamides have been subjected to the hydroamidation reaction in
the presence of Rhodium catalyst in order to construct the synthetic inter-
mediates of a proteasome inhibitor and salinosporamide A 12. Chemo-
selective activation of formamide by a transition metal catalyst has been
shown as an effective and attractive synthetic strategy in this synthesis.
Collect. Czech. Chem. Commun. 2011, Vol. 76, No. 12, pp. 1979–1990
©
2011 Institute of Organic Chemistry and Biochemistry
doi:10.1135/cccc2011131

1
980
Malakooti, Sobhani, Razavi, Shafiei, Mokhtari:
Moreover, the formyl group is a useful amino-protecting group in peptide
1
3
14
synthesis . Acetic formic anhydride is a common formylating reagent for
formylating the amines. This reagent is sensitive to atmospheric moisture
and cannot be stored due to decomposing to acetic acid and carbon mon-
1
5
16
oxide. Formylating reagents such as chloral , activated formic acid , acti-
1
7
18
19
20
vated formic acid esters , KF/Al O , ammonium formats , CDMT and
2
3
solid supported reagents21 are the other reported formylating reagents.
However, many of these reagents suffer from various drawbacks such as use
of sluggish, thermally unstable or toxic formylating agents/catalysts, dif-
ficult accessibility to reagents or applicability only for the formylation of
aromatic amines. Use of organic solvents, high temperature, long reaction
time and formation of by-products are the other limitation of the reported
methods.
Modified mesoporous silica by alkali metals or organic basic groups are
2
2
important solid base catalysts in organic chemistry . In recent years,
aminopropylated mesoporous SBA-15 silica (APMS) which is easily prepared
by the reaction of 3-aminopropyl(triethoxy)silane with SBA-15 has been at-
tracted much attention by organic chemists, as a solid base catalyst for the
promotion of organic transformations2
2a–22d
. These compounds were also
2
3
applied as useful intermediates for further functionalization .
In conjunction of our interest in the development of new applications of
2
4
recyclable solid catalysts , in this paper, we wish to introduce a simple,
new and efficient protocol for the formylation of amines by formic acid in
the presence of a catalytic amount of recyclable aminopropylated meso-
porous SBA-15 silica as a solid base catalyst under solvent-free conditions.
EXPERIMENTAL
Chemicals were purchased from Merck and Fluka Chemical Companies. All of the products
are known and were identified by their spectral data. IR spectra were run on a Perkin–Elmer 780
instrument. NMR spectra was recorded on a Bruker Avance DPX-400. Mass spectra was re-
corded on a Shimadzu GCMS-QP5050A. Elemental analysis for C, H and N was obtained by
using a Elementar, Vario EL III. The purity of the products and the progress of the reactions
were accomplished by TLC on silica-gel polygram SILG/UV254 plates. X-ray diffraction (XRD;
Bruker D8ADVACE) with Ni-filtered CuKα radiation (1.5406 Å) was investigated. Data was
–
1
recorded with a speed of 2° min and a step of 0.05°. N2 adsorption/desorption isotherms
were determined at 77.40 K with a Quantachrome NOVA apparatus. Before measurements,
SBA-15 sample was outgassed under vacuum at 150 °C for 12 h and APMS sample was
outgassed under nitrogen at 90 °C for 12 h. Using the Brunauer–Emmett–Teller (BET)
method and Barrett–Joyner–Halenda (BJH) analyses, the specific surface area and the pore
size distributions were obtained from the desorption branch of the isotherms, respectively.
Collect. Czech. Chem. Commun. 2011, Vol. 76, No. 12, pp. 1979–1990

Aminopropylated SBA-15 in Formylation Reactions
1981
Synthesis of SBA-15
SBA-15 was prepared according to the work of Zhao25. Pluronic P123 triblock copolymer
2 g) dissolved in H O (15 ml). HCl (2 M, 60 ml) was added to the solution, followed by add-
(
2
ing TEOS (4.25 g) at 313 K in 24 h. The molar composition of the mixture, TEOS/
P123/HCl/H O, was 1:0.017:6:192. The resulting mixture was heated at 373 K under static
2
conditions for another 24 h. The resulting solid product was filtered and washed with
deionized water. The P123 template was reduced by calcining the material at 823 K in air for
6
h.
Synthesis of APMS by Grafting
APMS was prepared according to the procedure described previously with minor modifica-
2
6
tion . SBA-15 (1 g) was carefully vacuum-dried at a temperature of 393 K and stored under
nitrogen atmosphere prior to the addition of dry toluene (30 ml). Then 3-aminopropyl-
trimethoxysilane (2.5 ml) was added to the solution. The mixture was refluxed under stir-
ring for 18 h. The sample was filtered and then cleaned by shoxhlet extraction in toluene
for 12 h and dried at 80 °C for 24 h.
Formyaltion of Amines and Alcohols. General Procedure
APMS (0.08 g, 0.02 mmol) was added to the stirred mixture of amino alcohol (1 mmol) and
formic acid 98% w/w (2–10 mmol) in an oil bath at 40 °C and stirred for an appropriate
time (Tables II and III). CH Cl (10 ml) was added to the cooled reaction mixture. The cata-
2
2
lyst was filtered off, washed with CH Cl (2 × 10 ml), dried at 100 °C for 1 h and reused for
2
2
the similar reaction. Filtrate was washed by water (2 × 10 ml) and dried over anhydrous
Na SO . The organic solvent was removed under reduced pressure and the resulting crude
2
4
product was purified by column chromatography eluted with n-hexane–EtOAc (1:1).
N,N′-1,3-Phenylenebisformamide: Light yellow solid, m.p. 157–159 °C. 1H NMR (400 MHz,
DMSO): 10.22 bs, 2 H (NH); 8.26 s, 2 H (CHO); 7.93 s, 1 H (Ar); 7.30 d, 2 H, J(4,5) = 9.6
1
3
(
H-4); 7.25 t, 1 H, J(5,6) = 8.4 (H-5). C NMR (100 MHz, DMSO): 160.0, 139.0, 129.7, 114.9,
1
10.4.
-Morpholine carbaldehyde: Colorless oil. 1H NMR (400 MHz, CDCl ): 7.98 s, 1 H (CHO);
4
3
3
3
.62 t, 2 H, J(2,3) = 4.4 (H-3); 3.58 t, 2 H, J(5,6) = 5.8 (H-5); 3.49 t, 2 H, J(2,3) = 4.8 (H-2);
.33 t, 2 H, J(5,6) = 4.8 (H-6). 13C NMR (100 MHz, CDCl ): 160.8, 67.1, 66.3, 45.7, 40.5.
3
RESULTS AND DISCUSSION
At first, aminopropylated mesoporous SBA-15 silica was synthesized by
known methods26 modified slightly. The percentage of the supported ami-
no groups on SBA-15 (3.34%) was obtained by CHN analysis.
The XRD patterns of calcined SBA-15 and APMS were also studied (Fig. 1).
The X-ray diffraction pattern of SBA-15 showed three well resolved peaks
corresponding to the reflections (1 0 0), (1 1 0) and (2 0 0), associated with
p6mm space group and hexagonal symmetry of SBA-15 (Fig. 1a). A similar
XRD pattern was observed for APMS, which revealed that SBA-15 still had
Collect. Czech. Chem. Commun. 2011, Vol. 76, No. 12, pp. 1979–1990

1
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Malakooti, Sobhani, Razavi, Shafiei, Mokhtari:
a high degree of hexagonal mesoporous organization in APMS structure
Fig. 1b). A decrease in the peak intensities with a slightly forward shift
(
in XRD pattern of APMS showed that amine groups placed inside of the
SBA-15 channels.
N adsorption/desorption isotherms and the pore-size distribution of cal-
2
cined SBA-15 and APMS are shown in Fig. 2. The specific surface areas were
estimated from the adsorption branch of isotherms using the Barrett–
FIG. 1
The powder XRD patterns of calcined SBA-15 (a) and APMS (b)
FIG. 2
Nitrogen adsorption/desorption isotherms incorporated with pore size distribution profiles at
the inset for calcined SBA-15 (a) and APMS (b)
Collect. Czech. Chem. Commun. 2011, Vol. 76, No. 12, pp. 1979–1990

Aminopropylated SBA-15 in Formylation Reactions
1983
Emmett–Teller (BET) technique. Pore size distributions were calculated from
the desorption branch of isotherms via the Barrett–Joyner–Halenda (BJH)
model. The results in Fig. 2 presented typical IV isotherm with H1-type hys-
teresis loop at high relative pressure according to the IUPAC classification
for mesoporous materials27 with uniform pore size distributions. Corre-
sponded textural parameters are also listed in Table I. As shown in Table I,
only the wall thickness of APMS is increased in comparison with SBA-15.
Other parameters such as specific surface area, pore volume and pore diam-
eter are decreased. These observations are contributed to incorporation of
aminopropyl groups onto SBA-15. In a comparison with Zeleňák’s proce-
dure26 for APMS synthesis, an increasing in surface area and a slight de-
creasing in amine groups loading are clearly observed in the present
method for the synthesis of APMS (Table I).
TABLE I
Physicochemical properties of catalysts: S , specific surface area (m2 g–1); VBJH, pore vol-
BET
3
–1
ume (cm
(
g ); DBJH, pore diameter (nm); A , cell parameters (nm); D , interplanar spacing
o 100
3
–1
–1
nm); W, wall thickness (nm): VMI , micropore volume (cm
g
), amine loading (mmol g )
Amine
loading
Material
SBET
VBJH
DBJH
Ao
D100
W
VMI
SBA-15
APMS
890.4
1.27
6.063
4.606
10.4164
12.083
8.854
4.3534
7.477
0.06968
–
2
6
(
(
687)
242.4
0.4573
10.2706
0.003197
2.38
(2.72)
2
6
26
134)
a
Calculated from the desorption branch. b W = Ao – DBJH (Ao = 2D100/√3).
Figure 3 shows the α plot for the SBA-15 and APMS samples. The α plot
s
s
is obtained based on the standard nitrogen adsorbtion isotherm
Fig. 2).Micropore volume (VMI) is determined by intercept of adsorption
(
axis (Table I).
In the next step, N-formylation of different types of amines with formic
acid was studied in the presence of APMS in order to find a new application
of APMS as a catalyst in organic synthesis. Finding the best reaction condi-
tions, a series of reactions of aniline with formic acid catalyzed by different
molar ratios of APMS under solvent-free conditions were investigated. The
best yield of N-phenylformamide was obtained with 2 equivalents of formic
acid in the presence of 20 mole % of APMS at 40 °C. Then, the optimized
reaction conditions were used for the formylation of various amines with
formic acid catalyzed by APMS (Scheme 1, Table II).
Collect. Czech. Chem. Commun. 2011, Vol. 76, No. 12, pp. 1979–1990

1
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Malakooti, Sobhani, Razavi, Shafiei, Mokhtari:
R
HCO H
R
2
HN
N
CHO
R'
APMS (20 mole%) R'
solvent-free
SCHEME 1
Formylation of amines with formic acid catalyzed by APMS
TABLE II
APMS catalyzed formylation of amines with formic acid under solvent-free conditions
Entryref.
Substrate
HCO H, mmol
Time, min
Yield , %
a
2
116a
216a
316b
416a
516b
616b
716a
828
aniline
2
2
2
2
2
2
3
6
4
2
2
2
2
2
2
10
2
2
2
2
2
15
120
60
60
5
95
95
95
80
95
95
70
95
95
90
95
80
95
95
95
95
95
80
80
95
90
p-anisidine
3-aminophenol
4-methylaniline
3-bromoaniline
4-aminobenzoic acid
4-nitroaniline
p-phenylenediamine
m-phenylenediamine
ethanolamine
cyclooctylamine
benzylamine
180
600
420
30
10
5
929
1
016b
1
1
130
231
30
5
1
316b
432
butylamine
1
iso-propylamine
tert-butylamine
diphenylamine
dibutylamine
imidazole
5
1
1
516a
616a
5
30b
1
733
5
1
1
816a
916a
30b
30
15
15
morpholine
2
2
031
132
piperidine
isoleucine
a
Yields refer to those of pure isolated products characterized by comparison of their spectro-
scopic data with those of authentic samples. Reaction temperature 40 °C. b Reaction temper-
ature 70 °C.
Collect. Czech. Chem. Commun. 2011, Vol. 76, No. 12, pp. 1979–1990

Aminopropylated SBA-15 in Formylation Reactions
1985
As indicated in Table II, formylation of anilines substituted with different
electron-donating and electron-withdrawing groups proceeded well and
the corresponding N-phenylformamides were obtained in 70–95% yields
(
entries 1–7). Under the similar reaction conditions, both amino groups in
diamines underwent formylation reaction (entries 8 and 9). Aliphatic
amines and benzyl amine which normally show poor yields1
6f,34
, were
formylated in 80–95% yields by employing a catalytic amount of APMS
entries 10–17). It is worth to mention that excellent chemoselectivity was
(
observed for substrates with hydroxyl functionalities providing N-formyl
derivatives as the sole product without side reactions (entries 3 and 10).
Furthermore, formylation reaction of heterocyclic amines and isoleucine as
an α-aminoacid gave the corresponding products in good to high yields
(
entries 18–21).
After performing formylation reaction of aniline, under the conditions
described in Table II, CH Cl was added to the reaction mixture and the
2
2
catalyst was filtered off and reused for the similar reaction. This process was
carried out for five runs without noticeable reduction in the catalytic activ-
ity of the catalyst. The average isolated yield for five consecutive runs was
9
3.8%, which clearly demonstrates the practical reusability of the catalyst
(
Fig. 4). This reusability demonstrates the high stability and turnover of
APMS under the employed conditions. It is worth noting that the recycl-
ability test was stopped after five runs.
FIG. 3
The αs plot for samples of SBA-15 (a) and APMS (b)
Collect. Czech. Chem. Commun. 2011, Vol. 76, No. 12, pp. 1979–1990

1
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Malakooti, Sobhani, Razavi, Shafiei, Mokhtari:
Formylation of the hydroxyl groups is considered as one of the most
3
5
widely used transformations in organic chemistry , because deformylation
can be affected selectively in the presence of acetate or other ester protect-
TABLE III
APMS catalyzed formylation of alcohols with formic acid under solvent-free conditions
Entryref.
Substrate
Time, min
Yield , %
a
116d
216d
316d
438
538
639
716c
816c
938
benzyl alcohol
4-metoxybenzyl alcohol
4-chlorobenzyl alcohol
1-phenyl ethanol
2-phenyl ethanol
n-butyl alcohol
2-octanol
30
5
95
95
90
90
90
95
90
90
90
80
30
15
15
5
30
30
5
menthol
cyclohexanol
1
040
tert-butyl alcohol
30
a
Yields refer to those of pure isolated products characterized by comparison of their spectro-
scopic data with those of authentic samples. Reaction conditions: HCO H (10 equivalents),
2
reaction temperature 40 °C.
FIG. 4
Reusability of APMS as a catalyst for the formylation of aniline. Time, min (white), Yield, %
(
black)
Collect. Czech. Chem. Commun. 2011, Vol. 76, No. 12, pp. 1979–1990

Aminopropylated SBA-15 in Formylation Reactions
1987
ing groups. Furthermore, if the alcoholic group is planned to be oxidized
later in the synthetic processes, the formylated alcoholic group does not
need to be deprotected and direct oxidation, under Oppenauer conditions,
3
6
can be realised . Moreover, formate esters serve as useful synthetic reagents
3
7
and intermediates . In order to show the general applicability of this
method, we have also tried formylation reaction of hydroxyl functional
groups in alcohols with formic acid. The results showed that the reactions
involving benzylic and primary/secondary/tertiary aliphatic alcohols
worked well and the expected O-formylated products smoothly achieved
in 80–95% yields (Table III). Comparison of formylation of alcohols with
N-formylation reaction reveals that more amount of formic acid is required
for the O-formylation reaction.
Showing the catalytic effect of APMS in the formylation of alcohols, reac-
tion of 4-methoxybenzyl alcohol with formic acid in the absence of any
catalyst was examined. However, this reaction remained incomplete and
SCHEME 2
Selective formylation of amines in the presence of benzyl alcohol
Collect. Czech. Chem. Commun. 2011, Vol. 76, No. 12, pp. 1979–1990

1
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Malakooti, Sobhani, Razavi, Shafiei, Mokhtari:
only 40% of the desired product was obtained after 24 h. A similar reaction
in the presence of SBA-15 led to the formation of the desired product in
9
0% yield after 2 h. The results of this study showed that APMS, which is
one of the organic-inorganic hybrid materials not only acted as a solid base
catalyst, but also had an interaction with formic acid. This kind of interac-
tion is known in the literature41 and fascinates the formylation reaction. To
determine the selectivity of the method, formylation of benzyl alcohol in
the presence of different amines was studied (Scheme 2). It was observed
that the method was highly selective for the formylation of different types
of amines such as aniline and primary/secondary amines versus alcohols.
Both amino groups in 1,3-diaminobenzene underwent formylation reaction
in the presence of benzyl alcohol with good selectivity and produced the
desired product in 85% yield.
CONCLUSION
In conclusion, APMS was prepared according to the procedure described
previously with minor modification from SBA-15. The incorporation of
aminopropyl groups onto SBA-15 was shown by XRD and BET methods.
The synthesized APMS was used as a new, re-usable and efficient solid base
catalyst for formylating a wide variety of aliphatic and aromatic amines and
alcohols by using readily available formic acid under solvent-free condi-
tions. Ease of recovery and catalyst reusability makes this method an eco-
nomic, benign and waste-free chemical process for the formylation of
amines and alcohols. Use of water tolerant and thermally stable catalyst,
simple reaction setup, not requiring specialized equipment, high product
yields and short reaction times are the other advantages of the presented
protocol.
We are thankful to Birjand University Research Council for their support on this work.
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