One-pot synthesis of aniline derivatives from nitroarenes under mild conditions promoted by a recyclable polymer-supported palladium catalyst

Article abstract of DOI:10.1016/j.apcata.2011.05.010

This work describes the one-pot direct reductive amination of carbonyl compounds with nitroarenes promoted by a polymer supported palladium catalyst, in the presence of molecular hydrogen as the reductant. This methodology is applicable, with slight differences, to both aliphatic and aromatic aldehydes. The operational simplicity, the mild reaction conditions, the high yields and the good recyclability of the supported catalyst are major advantages of this method. TEM observations of the catalyst showed that the active species are palladium nanoparticles having a size distribution centered at 5 nm within the polymeric support.

Full text of DOI:10.1016/j.apcata.2011.05.010

Applied Catalysis A: General 401 (2011) 134–140
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
One-pot synthesis of aniline derivatives from nitroarenes under mild conditions
promoted by a recyclable polymer-supported palladium catalyst
Maria Michela Dell’Annaa,∗, Piero Mastrorillia, Antonino Rizzutia, Cristina Leonellib
a Dipartimento d’Ingegneria delle Acque e di Chimica del Politecnico di Bari, via Orabona, 4 70125, Bari Italy
b Dipartimento d’Ingegneria dei Materiali e dell’Ambiente, Università di Modena e Reggio Emilia, via Vignolese, 905 41125 Modena Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
This work describes the one-pot direct reductive amination of carbonyl compounds with nitroarenes
promoted by a polymer supported palladium catalyst, in the presence of molecular hydrogen as the
reductant. This methodology is applicable, with slight differences, to both aliphatic and aromatic aldehy-
des. The operational simplicity, the mild reaction conditions, the high yields and the good recyclability
of the supported catalyst are major advantages of this method. TEM observations of the catalyst showed
that the active species are palladium nanoparticles having a size distribution centered at 5 nm within the
polymeric support.
Received 22 February 2011
Received in revised form 5 May 2011
Accepted 8 May 2011
Available online 13 May 2011
Keywords:
One-pot reductive amination
Palladium nanoparticles
Supported catalysis
TEM
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
gen donor at room temperature (only for aliphatic aldehydes)
[24]; (iii) molecular hydrogen with aromatic [25] and aliphatic
Amines and their derivates act as important synthones in
organic chemistry [1]. They are highly versatile building blocks for
various organic target molecules and are essential precursors to a
variety of biologically active compounds [2], such as pharmaceuti-
cals and agrochemicals. Due to their importance, several methods
have been developed for the preparation of amines [3–5]. Direct
reductive amination of aldehydes and ketones, in which a mixture
of an aldehyde or ketone and an amine is treated with a reductant
is one of the most useful methods for the preparation of sec-
ondary or tertiary amines [6–9]. The commonest reducing agents
are hydrides [10–15], such as, for example, sodium cyanoboro-
hydride and sodium triacetoxyborohydride [16,17] or molecular
hydrogen in the presence of a platinum-triad catalyst [9,18,19].
The use of sodium cyanoborohydride and sodium triacetoxy-
borohydride has as drawback the formation of toxic byproducts
(HCN, NaCN) or the use of corrosive acetic acid. A variant of this
method consists in the use of organosilanes as reducing reagent
[20].
[26] aldehydes as reagents. In the case of aromatic aldehydes,
the reaction was carried out stepwise and the imine formation
was achieved in more than 24 h. Moreover, for some substrates
the use of triethylamine was necessary to poison the catalyst and
improve selectivity. With aliphatic aldehydes, high yields were
achieved when all the reagents were mixed from the beginning.
More recently, Sreedhar et al. reported on gum acacia supported
palladium nanoparticles which promoted reductive N-alkylation of
nitroarenes using molecular hydrogen as reductant and methanol
as solvent [27]. The catalyst was recovered at the end of reaction
and recycled up to five runs without loss of activity and selectivity.
Following our studies on the palladium catalyzed hydrogenation
reaction [28] of alkenes, alkynes, carbonyl compounds, nitroarenes
and nitriles, herein we report the catalytic activity of polymer
supported Pd nanoparticles in the direct reductive amination of
aldehydes with nitroarenes under atmospheric pressure of hydro-
gen for the synthesis of mono N-alkyl amines.
Recently, efforts have been made to carry out the reductive ami-
nation of carbonyl compounds directly with nitrobenzene [21,22].
The most commonly used catalytic systems are based on Pd/C with:
(i) decaborane at high temperature in the presence of acetic acid
to prevent reductive etherification [23]; (ii) HCOONH4 as hydro-
2. Experimental
2.1. General considerations
Methanol and nitrobenzene were distilled under inert atmo-
sphere before use. All other chemicals were purchased from
commercial sources and used as received. Palladium content in Pd-
pol was assessed after sample mineralization by atomic absorption
spectrometry using a PerkinElmer 3110 instrument. GC–MS data
∗
Corresponding author. Tel.: +39 0805963695; fax: +39 0805963611.
E-mail address: mm.dellanna@poliba.it (M.M. Dell’Anna).
0926-860X/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.apcata.2011.05.010

M.M. Dell’Anna et al. / Applied Catalysis A: General 401 (2011) 134–140
135
(EI, 70 eV) were acquired on a HP 7890 instrument using a HP-
2.3. Typical experimental procedure for the reductive amination
of aromatic aldehydes with nitroarenes (one-pot, two step
method)
5MS cross-linked 5% PH ME siloxane (30.0 m × 0.25 mm × 0.25 ␮m)
capillary column coupled with a mass spectrometer HP 5973. The
products were identified by comparison of their GC–MS features
with those of authentic samples or by their NMR 1H and 13C spec-
tra. Reactions were monitored by TLC carried out on 0.25 mm silica
gel coated glass plates using UV light as visualizing agent or by
GC–MS. Products were purified by flash column chromatography
with silica gel and petroleum ether bp 40–60 ◦C/dichloromethane
as eluant. The microstructure of the polymeric matrix embedded
Pd nanoparticles was determined by TEM observations at accel-
eration voltage of 200 kV (Model JEM 2010, Jeol, Akishima Tokyo,
Japan), equipped with X-ray energy dispersive spectroscopy (EDS).
The samples were prepared by dispersing the powders in distilled
water using an ultrasonic stirrer and then placing a drop of sus-
pension on a copper grid covered with a transparent polymer film,
followed by drying and carbon coating. The particle size distri-
butions were obtained by TEM image analysis using the ImageJ
software (freeware software: http://rsb.info.nih.gov/ij/).
The catalyst Pd-pol (80 mg, 0.9 mol%) was added to a stirred
solution of nitroarene (2.0 mmol) in methanol (2.0 mL). The result-
ing suspension was stirred under an atmosphere of hydrogen
(rubber balloon) at room temperature for the specified period of
time (step 1). During this time the catalyst turned black. Alde-
hyde (2.0 mmol) was then added, and the reaction mixture was
stirred under air for a couple of minutes, before being stirred
under an atmosphere of hydrogen for the specified period (step
2). The progress of the reaction was monitored by TLC or/and
GC–MS. At the end of reaction, the reaction mixture was filtered
and the solvent was removed under reduced pressure to give the
crude product, which was purified by flash chromatography using
petroleum ether-dichloromethane as eluant.
2.4. Typical experimental procedure for the reductive amination
of aliphatic aldehydes with nitroarenes (one-pot, one step
method)
2.2. Catalyst preparation
The catalyst Pd-pol (80 mg, 0.9 mol%), the nitroarene (2.0 mmol)
and the aldehyde (2.0 mmol) were put into a 100 mL Schlenk tube
and methanol (2.0 mL) was added. The resulting suspension was
stirred under an atmosphere of hydrogen (rubber balloon) at room
temperature for the specified period of time. During this time the
catalyst turned black. The progress of the reaction was monitored
by TLC or/and GC–MS. At the end of reaction, the reaction mixture
was filtered and the solvent was removed under reduced pressure
to give the crude product, which was purified by flash chromatog-
raphy using petroleum ether-dichloromethane as eluant.
The supported catalyst (Pd-pol) was prepared as described
below with slight differences respect to the procedure reported in
our previous article [29]. This new procedure used a lower polymer-
ization temperature, in order to prevent the thermal reduction of
Pd, which could decrease the catalytic performance of the insoluble
material.
221.6 mg (1.25 mmol) of PdCl2 and 175.4 mg (3.0 mmol) of NaCl
were placed into a reaction flask and 10 mL of deionized water was
added. The resulting brown suspension was stirred for 30 min at
50 ◦C and during this time, it was converted into a brick red solution
(solution A), which was cooled to room temperature.
2.5. Recycling of catalyst
To a solution of NaOH (200 mg, 5.0 mmol) in water (10 mL), 2-
(acetoacetoxy)ethyl methacrylate (HAAEMA) (1.071 g, 5.0 mmol)
was added and left under stirring at room temperature for 5 min.
The resulting solution was added to the Na2PdCl4 solution A at
room temperature, causing the sudden precipitation of a red oil.
After40 min stirring, the supernatantsolutionwasremovedandthe
red oil was washed with water (3 × 5 mL), extracted with methy-
lene chloride (15 mL) and dried over Na2SO4. After filtration, the
methylene chloride was removed under vacuum and the result-
ing oil was dissolved in cold THF (3 mL). This solution was treated
under stirring with cold pentane (25 mL) affording Pd(AAEMA)2 as
an orange powder, which was washed (2 × 5 mL) with cold pen-
After completion of the reaction the catalyst was recovered by
filtration and washed with methanol (3 × 5 mL) and diethyl ether
(3 × 5 mL) and dried under vacuum for further reuse.
3. Results and discussion
The catalyst used in this work is the polymer supported Pd
complex (Pd-pol) obtained by co-polymerization of Pd(AAEMA)2
(AAEMA− = deprotonated form of 2-(acetoacetoxy)ethyl methacry-
late) with ethyl methacrylate and ethylene glycol dimethacrylate
[29–32].
An initial evaluation of the catalyst performance was carried
for the system benzaldehyde/nitrobenzene under an atmospheric
pressure of hydrogen at room temperature in methanol using a
PhCHO/PhNO2/Pd molar ratio of 1/1/0.009.
The use of an aromatic aldehyde as substrate is a tough task
as: (a) the hydrogenation to the corresponding alcohol is compet-
itive with the desired reduction of nitrobenzene precluding the
formation of the imine intermediate; (b) since the correspond-
ing imine intermediate is quite stable, it can undergo backward
reaction to aldehyde and amine, with possible subsequent alde-
hyde hydrogenation; (c) the target secondary benzyl amine may
be decomposed by the Pd catalyst under hydrogen via cleavage of
the benzyl group [33].
Optimization of the experimental conditions led to one-pot
reaction with 95% yield (Scheme 1). These conditions (two step
method) involve the following procedure: the initial quantitative
reduction of nitrobenzene with hydrogen (1 atm) in the presence
of Pd-pol (step 1); the addition of benzaldehyde and the subse-
quent hydrogenation of the resulting imine under one atmosphere
tane and dried under vacuum for 2 h. Anal. Calc. for PdC20H26O10
:
C, 45.00; H, 4.92; Pd, 19.97. Found: C, 44.50; H, 4.99; Pd, 19.76. Yield:
90%.
Ethyl methacrylate (2.84 g, 25 mmol) was added to a solution
containing Pd(AAEMA)2 (532.8 mg, 1.0 mmol) in THF (3 mL) and the
resulting orange solution was warmed up to 50 ◦C. Then, ethylene
glycol dimethacrylate (0.8 mL, 4.24 mmol) and azaisobutyronitrile
(5 mg) were added to the solution followed by stirring at 50 ◦C
exposing it to the light of a table lamp. After 1 h, it was noticed
that the stirring was stopped by the formation of the polymer. The
mixture was then cooled at room temperature, and 20 mL of ace-
tone was added to the solid obtained. After removal of the solvent,
the solid was ground with a mortar and pestle, and left under vig-
orous stirring in acetone (20 mL) overnight in order to obtain a
fine powder. The solid was then washed with acetone (3 × 5 mL)
and n-hexane (3 × 5 mL) and dried under vacuum to afford military
green powder of Pd-pol. Yield: 3.50 g of polymer. Anal.: C, 52.42%;
H, 7.06%; Pd, 2.50%. IR (KBr): (cm−1) ꢀ = 2960 vs, 1724 vs, 1605 w,
1506 w, 1481 m, 1266 s, 1145 s, 1025 m.

136
M.M. Dell’Anna et al. / Applied Catalysis A: General 401 (2011) 134–140
NO2
70% yield (entry 5), the main by-products being an isomeric mixture
of N1-benzyl-N3-benzylidene-4-methylbenzene-1,3-diamine and
N3-benzyl-N1-benzylidene-4-methylbenzene-1,3-diamine. While
in all other cases the time required to complete step 1 was 5.5 h
and that to complete step 2 was 2.5–7 h, the reaction involving
2,4-dinitrotoluene and benzaldehyde required 15 h for step 1 and
26 h for step 2. When p-chloronitrobenzene and benzaldehyde were
used, extensive dehalogenation of the nitro compound during step 1
occurred resulting in a yield of phenylbenzylamine as high as 82%
(entry 6). In the reaction of p-nitroacetophenone with benzalde-
hyde, high yields in the desired secondary amine containing the
carbonyl group were achieved both in the first cycle (entry 7) and in
the re-cycle (entry 8). In this case care must be taken in controlling
the time of the first step (nitro group hydrogenation) since, once
all p-nitroacetophenone is transformed into p-aminoacetophenone
the catalyst is able to reduce the carbonyl group to alcohol (and
eventually to alkane).
1) H2 (p = 1 atm), 5.5 h
2) benzaldehyde, 2 min under air
3) H2 (p = 1 atm), 2.5 h
H
N
Pd-pol , CH3OH, r.t.
95 %
Scheme 1. Synthesis of benzyl phenyl amine.
The substrates 5-methyl-2-nitro-phenol and benzaldehyde
gave quantitatively the corresponding secondary amine both in the
first cycle (entry 9) and in the re-cycle (entry 10).
Aliphatic aldehydes were also used for the one-pot reductive
amination with Pd-Pol. In some cases it was not necessary to sepa-
rate the nitrobenzene reduction step from the imine hydrogenation
step. In fact, the aliphatic imine intermediates are readily hydro-
genated to the product, and the hydrogenation of the carbonyl
group is not competitive with the reduction of the nitro or imine
groups. Thus, the reaction of nitrobenzene and iso-butyraldehyde
gave 83% isolated yield of the desired product after 7.5 h (Scheme 2
and entry 1 of Table 2). The catalyst did not lose activity when
recycled (entry 2 of Table 2).
Fig. 1. Reductive amination of benzaldehyde with nitrobenzene over eight cycles.
Table 2 also shows results obtained using nitrobenzene with
several aliphatic aldehydes. Pivalaldehyde and iso-valeraldehyde
gave acceptable (72–77%) yields of the desired secondary amines,
both in the first run and in the recycle (entries 3–6 of Table 2).
2-Phenylpropanal and phenylacetaldehyde, both having a phenyl
group in ␣ position gave lower yields (48–65%, entries 7, 8, 10,
11 of Table 2) due to partial reduction of the aldehyde to alco-
hol. However, carrying out the reactions with 2-phenylpropanal or
phenylacetaldehyde by two step method the yield increased to 87%
(entry 9 of Table 2) and 90% (entry 12 of Table 2), respectively. The
linear aldehyde n-heptanal gave poor yield in heptyl phenyl amine
when the experiment was carried out by mixing nitrobenzene and
n-heptanal under H2 at the beginning of the reaction. By carrying
out the same reaction under two step method, a satisfactory 80%
yield was obtained (entry 13 of Table 2).
We investigated the nature of the catalysis (homogeneous or
heterogeneous) by measuring the Pd leaching in solution and by
testing the catalytic activity of the mother liquors. In all reported
cases, the elemental analyses carried out on the catalyst before and
after two catalytic cycles (eight runs for the reaction described in
Fig. 1) revealed that the metal content in the catalyst was equal
to that of the pristine material. Moreover, the Pd analysis of the
reaction solutions after Pd-pol filtration revealed the absence of
metal. Finally, to confirm the heterogeneous nature of the catal-
ysis, we isolated the mother liquors of the reaction carried out
of hydrogen (step 2). Blank tests revealed that no product formed
when the reaction was carried out in the absence of the Pd catalyst.
As reported by Sreedhar et al., when the reductive amination of
benzaldehyde with nitrobenzene was performed in the presence of
traditional heterogeneous catalysts, such as Pd–SiO2 and Pd–TiO2,
the nitrobenzene was reduced to the corresponding amine mod-
erately, but the hydrogenation of in situ generated imine did not
proceed even after 24 h [27]. On the other hand, using 10% Pd/C as
catalyst, the same reaction gave, after 6 h, only 20% yield of product
[27].
Fig. 1 shows the recyclability of the catalyst for the one-pot,
two step synthesis of benzyl phenyl amine. In fact Pd-pol could be
recovered after reaction (the overall one-pot transformation took
8 h for each cycle) by simple filtration in air and reused several
times without loss of activity.
Table 1 shows the results obtained for reactions carried using
benzaldehyde or 2-methyl-benzaldehyde and different nitroben-
zenes. Very good yields were achieved for the nitrobenzene/2-
methylbenzaldehyde system, both in the first run and in the
recycle (entries 1–2). Similar results were obtained using p-
ethyl-nitrobenzene (having an electron donor substituent) as
nitro-substrate (entries 3–4). When the dinitro substrate 2,4-
dinitrotoluene was used with two equivalents of benzaldehyde,
N1,N3-dibenzyl-4-methylbenzene-1,3-diamine was obtained in
NO2
H
N
Pd-pol (0.9 mol%)
CH3OH, r.t.
O
+
H2 (p = 1 atm)
7.5 h
83%
Scheme 2. Synthesis of phenyl i-butyl amine.

M.M. Dell’Anna et al. / Applied Catalysis A: General 401 (2011) 134–140
137
Table 1
One-pot, two step synthesis of aryl-benzyl aminesa.
Entry
Nitroarene
Aldehyde
Product
Time of step 2
Yieldb (%)
O
O
H
H
1
PhNO2
5 h
5 h
95
93
N
H
2c
”
”
”
NO2
3
2.5 h
2.5 h
93
95
N
H
4c
”
”
”
H
N
O
NO
2
26 hd
70e
H
5
HN
NO
2
NO2
O
O
H
H
6
2.5 h
82
N
H
Cl
NO2
O
C
7f
2.5 h
96
N
C
H
O
8c,f
”
”
”
2.5 h
2 h
95
NO2
HO
O
HO
9f
99e
H
N
H
10c,f
”
”
”
2 h
99e
a
Reaction conditions: nitroarene (2.0 mmol), aldehyde (2.0 mmol), methanol (2.0 mL), Pd-pol (0.9 mol%) at room temperature under H2 (p = 1 atm); the time for step 1 was
5.5 h.
b
c
d
e
f
isolated yield.
recycle of the previous run.
the time required to complete step 1 was 15 h.
chromatographic yield.
solvent: a mixture of methanol (2.0 mL) and dichloromethane (2.0 mL).
using nitrobenzene and benzaldehyde, stopped at ca. 30% and ca.
60% conversion of the benzylidenephenylimine, by filtration of the
supported catalyst after 0.5 h and 1 h from the addition of benzalde-
hyde, respectively. Then the mixture deprived of Pd-pol was stirred
at RT under H2 (p = 1 atm) for 18 h. GLC analysis of the resulting
solution revealed that the imine conversion remained unchanged.
In addition, the amount of Pd detected in mother liquors at 30%
and 60% imine conversion was negligible (ca. 3 ppm), while the
palladium content in the corresponding recovered catalyst was
practically that of the fresh catalyst, within the experimental error.
All these data indicate that Pd leaching during reaction is negli-
gible and that the reaction presumably occurs on the solid surface
of the catalyst.
In order to gain insights into the morphology of the polymeric
catalyst, TEM analyses were carried out on Pd-pol (i) as pristine
(Pd-pol0); (ii) after two cycles of reaction with nitrobenzene and

138
M.M. Dell’Anna et al. / Applied Catalysis A: General 401 (2011) 134–140
Table 2
One-pot, one step synthesis of phenyl-alkylaminesa.
Entry
Aldehyde
Product
Time
Yieldb (%)
O
1
7.5 h
7.5 h
9 h
83
85
77
75
H
H
N
H
2c
3
”
”
O
N
H
4c
”
”
”
9.5 h
O
5
5 h
75
72
60
N
H
H
6c
7
”
5.5 h
9 h
O
H
N
H
8c
9
”
”
”
”
9 h
65
87
13 hd
O
10
12 h
48
N
H
H
11c
12
”
”
”
”
12 h
50
90
10 he
H
N
O
13
8.5 hf
80
H
a
Reaction conditions: nitrobenzene (2.0 mmol), aldehyde (2.0 mmol), methanol (2.0 mL), Pd-pol (0.9 mol%) at room temperature under H2 (p = 1 atm).
b
c
d
e
f
isolated yield.
recycle of the previous run.
carried out using two step method: 6 h for step 1 and 7 h for step 2.
carried out using two step method: 6 h for step 1 and 4 h for step 2.
carried out using two step method: 6 h for step 1 and 2.5 h for step 2.
benzaldehyde (Pd-pol2); (iii) after eight cycles of the same reaction
(Pd-pol8). The corresponding TEM nanostructures are reported in
Fig. 2.
rial, respectively. In the case of Pd-pol2 the formation of new Pd
nanoparticles is generated by the hydrogen atmosphere [35] under
which the two reaction cycles are carried out. In addition, in Pd-pol2
(Fig. 2b) a rougher surface microstructure of the polymeric matrix
is noticed when compared to Pd-pol0.
TEM image of Pd-pol8 (Fig. 2c) shows an even higher number
of Pd nanoparticles per unit area with respect to the previous two
specimens, but the overall amount of Pd agglomerates remains still
small. This explains why the catalytic activity of the supported cat-
alyst recovered after eight cycles was comparable to that of the
catalyst employed in two runs.
In conclusion, in all of the three samples the Pd nanoparticle
distribution tends to homogeneously distribute within the poly-
mer matrix. For Pd-pol0 the Pd nanoparticle formation is limited
and ascribable only to thermal polymerization of metal containing
acrylate-type monomers leading to an average particle size of ca.
9 nm [34]. On the contrary, for Pd-pol2 and Pd-pol8 the extensive Pd
nanoparticle formation is ascribable to the hydrogen reduction of
Pd(II) supported polymer in which spherical Pd nanoparticles with
size of ca. 5 nm are obtained [35].
TEM image of Pd-pol0 (Fig. 2a) shows that Pd nanoparticles are
round irregular polyhedra with a mean diameter of roughly 9 nm
embedded in a smooth microstructure of the polymeric matrix.
TEM selected area electron diffraction (SAED) pattern apparently
consists of a ring pattern due to the diffraction of the thin metallic
Pd-crystallites (inset of Fig. 2a). Pd-pol0 is found to be constituted
by atomic Pd(II) polymeric network. However, the formation in
the pristine catalyst of metallic Pd nanoparticles with a low num-
ber density and a mean diameter of 9 nm could occur during the
thermal polymerization step of the catalyst synthetic procedure.
In fact, the formation of primary Pd nanoparticles is caused by
thermal decomposition of metal- containing precursors in accor-
dance with the simulated process proposed by Rozenberg et al.
[34].
TEM image of Pd-pol2 (Fig. 2b) shows a higher number of Pd
nanoparticles per unit area with respect to the pristine catalyst. The
Pd nanoparticles have a bimodal size distribution: the first one cen-
tered around 5 nm and the second one describing the small amount
of agglomerates. The SAED pattern (inset of Fig. 2b) shows spots
and rings typical for agglomerated and nano-crystalline mate-
As it was observed for Pd-pol2, TEM microstructure of
the Pd supported catalyst recovered after two cycles in
the reaction between iso-butyraldehyde and nitrobenzene

M.M. Dell’Anna et al. / Applied Catalysis A: General 401 (2011) 134–140
139
Fig. 2. Transmission electron micrograph and associated SAED pattern and size distribution (insets) of matrix polymer embedded Pd nanoparticles: (a) Pd-pol before use in
catalysis (Pd-pol0), (b) Pd-pol recovered after two cycles of the reaction described in Fig. 1 (Pd-pol2), (c) Pd-pol recovered after eight cycles of the reaction described in Fig. 1
(Pd-pol8).
showed Pd nanoparticles with
at 5 nm.
a
size distribution centered
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4. Conclusion
Pd-pol was shown to be an active and reusable catalyst for
the one-pot synthesis of secondary amines via reductive amina-
tion at room temperature under an atmospheric pressure of H2.
This protocol, applied with slight differences when reacting aro-
matic aldehydes instead of aliphatic ones, permits the preparation
of a diverse range of N-alkyl amines in good yields. Chemical and
TEM analyses showed that the catalytically active species are sup-
ported Pd nanoparticles with a primary particles’ size distribution
centered around 5 nm formed under reaction conditions.
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