Direct Synthesis of Lactams from Keto Acids, Nitriles, and H2 by Heterogeneous Pt Catalysts

Article abstract of DOI:10.1002/cctc.201701355

We report herein the first general catalytic system for the direct synthesis of N-substituted γ- and δ-lactams by reductive amination/cyclization of keto acids (including levulinic acid) with nitriles and H₂ under mild conditions (7 bar H₂, 110 °C, solvent free). The most effective catalyst, Pt and MoO_x co-loaded TiO₂ (Pt-MoO_x/TiO₂), shows a wide substrate scope, high turnover number (TON), and good reusability.

Full text of DOI:10.1002/cctc.201701355

Accepted Article
Title: Direct synthesis of lactams from keto acids, nitriles, and H2 by
heterogeneous Pt catalysts
Authors: Ken-ichi Shimizu, Abeda S. Touchy, S. M. A. H. Siddiki,
Ashvini Bhosale, Takashi Toyao, Yuji Mahara, Junya
Ohyama, and Atsush Satsuma
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10.1002/cctc.201701355
ChemCatChem
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Direct synthesis of lactams from keto acids, nitriles, and H2 by
heterogeneous Pt catalysts
S. M. A. H. Siddiki,[a] Abeda S. Touchy,[a] Ashvini Bhosale,[a] Takashi Toyao,[a,b] Yuji Mahara,[b] Junya
Ohyama,[b,c] Atsush Satsuma,[b,c] Ken-ichi Shimizu*[a,b]
Abstract: We report herein the first general catalytic system for
direct synthesis of N-substituted γ- and δ-lactams by reductive
amination/cyclization of keto acids (including levulinic acid) with
nitriles and H2 under mild conditions (7 bar H2, 110 °C, solvent-free).
The most effective catalyst, Pt and MoOx co-loaded TiO2 (Pt-
MoOx/TiO2), shows a wide substrate scope, high turnover number
(TON), and good reusability.
LA and H2 can provide a sustainable and practical route to the γ-
lactams. Very recently, Corma, Iborra and co-workers[18] have
reported the first general method for one-pot synthesis of the N-
substituted γ-lactams via reductive amination of ethyl levulinate with
nitro compounds under 10 bar H2 using a heterogeneous Pt catalyst,
though the method requires large amount of ethyl levulinate (3 equiv.
with respect to the nitro compounds).[18] As for the use of nitriles
alternative to primary amines, to our knowledge, only one patent by
Manzer[19] reported the synthesis of the N-substituted γ-lactams from
LA and nitriles (3-penteneitrile and benzonitrile) under H2 using Pd,
Rh, Ru, or Pt loaded on carbon or Al2O3 catalysts. However, the
method has several disadvantages such as low yields (< 43.4%),
limited scope, no example of catalyst reuse, low turnover number
(TON), and necessities of high H2 pressure (55-69 bar), high
temperature (150 °C), and dioxane as solvent.
Introduction
Sustainable use of biomass is a major challenge in chemistry.
Selective reductive transformation of biomass to chemicals via
platform compounds plays a key role in this research area.[1]
Levulinic acid (LA) is a key platform compound, because it can be
obtained by acid-catalyzed dehydration of lignocellulosic biomass
and can be converted to various chemicals.[1] Among the chemicals,
N-alkyl-5-methyl-2-pyrrolidones (in other word, N-substituted γ-
lactams), which can be produced by reductive amination of LA, are
industrially used as solvents, surfactants, complexing agents, and
intermediates for fine chemicals.[2,3] Previous non-catalytic4 and
catalytic[5-10] methods for this reaction used formic acid[4-11] or a
During our efforts on catalytic hydrogenation reactions by Pt-
MoOX/TiO2,[12,20,21] inspired by previous efforts on the utilization of
nitriles as primary amine surrogate,[19,22] we have found that Pt-
MoOX/TiO2 selectively catalyzes the synthesis of N-substituted γ-
and δ-lactams from 1:1 mixture of keto acids (including LA) and
nitriles under 7 bar H2 at 110 °C in the absence of solvent. To our
knowledge, this is the first example of general catalytic system for
direct synthesis of N-substituted lactams from keto acids, nitriles,
and H2. It should be noted that the selective reaction of nitriles with
equimolar amount of keto acids under H2 is a challenging reaction,
because hydrogenation of nitriles to primary amines (intermediates
of the lactam synthesis) is accompanied by the formation of
secondary and tertiary amines.[15-17]
hydrosilane[9] as
a reductant. Most of the methods used
homogeneous catalysis which suffer from difficulties in
catalyst/product separation and catalyst reuse and needs of
additives,
expensive
reductants,
or
a
toxic
solvent
(dichloromethane).[4] Uses of a reusable heterogeneous catalyst and
molecular H2 as a reductant[11] can make this reaction more practical.
Recently, we have reported a reusable heterogeneous catalyst, Pt
and MoOx co-loaded TiO2 (Pt-MoOX/TiO2), for the synthesis of N-
substituted γ-lactams from LA, primary amines and H2.[12] Later,
several heterogeneous catalytic systems (Pt/TiO2,[13] FeNi
nanoparticles[14]) were reported to be effective for this type of
transformation.
Results and Discussion
Table 1 summarizes the results for catalyst screening using
5 wt% metal-loaded metal oxides containing 0.01 mmol (1
mol%) of the active metals with respect to LA. Reaction of neat
LA (1a, 1 mmol) with n-octanenitrile (2a, 1 mmol) under 7 bar
H2 at 110 oC for 24 h was used as a model reaction. No reaction
occurred in the catalyst-free conditions (entry 1). The metal-free
MoOX/TiO2 support showed only 2% yield of the desired product,
5-methyl-1-octyl-pyrrolidin-2-one (3a). Among the MoOx/TiO2-
supported metal catalysts (entries 3-10), Pt-MoOX/TiO2 (entry
3) showed the highest yield (85%) of 3a. For Pt-MoOX/TiO2,
increasing the Mo content from 7 wt% (entry 3) to 15 wt% (entry
11) resulted in higher yield (92%) of 3a. The most effective
catalyst, Pt-MoOX/TiO2 with 15 wt% loading of Mo (entry 11), is
hereafter used as the standard catalyst. Note that the yields of
Considering that some of the nitriles[15-17] and nitro compounds are
the intermediates of primary amines, one-pot reactions of them with
[a]
Dr. S. M. A. H. Siddiki, Dr. A. S. Touchy, Dr. K. Kon, Dr. T. Toyao,
Prof. Dr. K. Shimizu
Institute for Catalysis, Hokkaido University, N-21, W-10, Sapporo,
Japan
E-mail: kshimizu@cat.hokudai.ac.jp
[b]
[c]
Y. Mahara, Dr. Ohyama, Prof. Dr. Satsuma
Graduate School of Engineering, Nagoya University, Nagoya 464-
8603, Japan
Dr. T. Toyao, Dr. Ohyama, Prof. Dr. Satsuma, Prof. Dr. K. Shimizu
Elements Strategy Initiative for Catalysis and Batteries, Kyoto
University, Katsura, Kyoto 615-8520, Japan
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10.1002/cctc.201701355
ChemCatChem
FULL PAPER
byproducts, di-n-octylamine (4a) and tri-n-octylamine (5a), for
this catalyst are relatively low compared to the other catalysts.
Figure 1 shows the time course of the reaction by the standard
catalyst. The profile shows selective conversion of 2a to the
desired product 3a while the yields of byproducts (4a and 5a
)
leveled-off at the initial period of the reaction.
Pt/TiO2 (entry 12) showed lower yield of 3a than Pt-
MoOX/TiO2 (entry 11). In our previous report, this tendency was
observed for the 3a synthesis from LA (1a), n-octylamine
(instead of n-octanenitrile) under H2.[12] Based on the fact that
3a yield increased with increase in the negative shift of the C=O
stretching band in the IR spectra of adsorbed acetone on these
catalysts, we proposed that activation of C=O group of 1a by
Lewis acid sites of MoOX/TiO2 is responsible for the high activity
of Pt-MoOX/TiO2.[12] As described later, the reaction of 1a with
amine is a key step of the present system. Hence, the high
activity of Pt-MoOX/TiO2 in Table 1 can be due to cooperation
of Mon+ (Lewis acid) sites with Pt sites (H2 dissociation sites).
Next, we studied the effect of various reaction conditions on
the catalytic properties of Pt-MoOX/TiO2 for the reaction of LA
Then, we studied the scope of nitriles for the catalytic reaction.
Table 3 shows the yields of N-substituted γ-lactams (N-
substituted-5-methyl-2-pyrrolidones) from LA and various
nitriles under 7 bar H2 by 1 mol% Pt-MoOX/TiO2. Aliphatic
nitriles (entries 1,2), dimethylaminopropionitrile (entry 3), ethyl
cyanoacetate (entry 4), methoxypropionitrile (entry 5),
benzonitrile (entry 6), benzonitrile derivatives with electron-
donating (entries 7,8) and electron-withdrawing (entry 9)
substituents, 2-naphthonitrile (entry 10), 3-cyanopyridine (entry
11), 3-cyanothiophene (entry 12), 3-cyanofurane (entry 13),
phenylacetonitrile (entry 14), phenylacetonitrile derivatives with
electron-donating (entries 15,16) and electron-withdrawing
(entry 17) substituents, and 2-naphthylacetonitrile (entry 18)
were selectively converted to the corresponding γ-lactams in
good to high yields (upto 92%). The results show that nitriles
with a wide range of functional groups were well-tolerated under
our reaction conditions. The catalytic properties of our method
are superior to those in an earlier patent,[19] where low yields
(<43.4%) of lactams have been obtained only for two nitriles
under high H2 pressure (55-69 bar) at high temperature
(150 °C).
(
1a) with n-octanenitrile (2a) for 24 h (Table 2). The reactions of
1 mmol 2a with various amount of 1a at 100 oC under the
solvent-free conditions (entries 1-3) showed that the 2a
conversion and the 3a yield (based on 2a) did not increase with
increase in the amount of 1a. The reactions of 1 mmol 1a with
various amount (1-1.5 mmol) of 2a showed that the excess
amount of 2a gave lower amount of 3a and higher amount of
byproducts (4a, 5a) than the stoichiometric condition (results
not shown). Thus, we adopted the reaction of 1 mmol 1a with 1
mmol 2a as the standard conditions. With increase in the H2
pressure from 3 bar (entry 1) to 5 and 7 bar (entries 4,5), the
conversion of 2a and the yield of 3a increased. Under 7 bar H2,
As shown in equations (2) and (3), the method was applicable
to direct synthesis of N-substituted γ-lactams from keto acid or
2-carboxybenzaldehyde and n-octanenitrile (2a) under H2.
o
the yield of 3a increased with the temperature upto 110 C
(entry 6), but further increase in the temperature (entries 7,8)
decreased the yield of 3a and increased in the yields of
byproducts (4a,
5a). At the optimal temperature (110 oC) and H2
pressure (7 bar), the reaction in various solvent showed that the
solvent-free conditions (entry 6) gave higher yield of 3a than the
reactions in the solvent, such as toluene, o-xylene, n-decane,
and dioxane (entries 9-12). Summarizing these results, we
determined the standard conditions: 1a
/
2a = 1/1, 110 oC, 7 bar
The same method was applicable to the synthesis of N-
substituted δ-lactams from 4-acetylbutyric acid with various
nitriles (Table 4). The reactions of aliphatic nitrile (entry 1),
benzonitrile (entry 2), its derivatives with electron-donating
(entry 3,4) and electron-withdrawing (entry 5) substituents, 3-
cyanopyridine (entry 6), 3-cyanofurane (entry 7), and
phenylacetonitrile (entry 8) afforded the N-aryl δ-lactams in 76-
92% yields. To our knowledge, this method is the first general
catalytic system for direct synthesis of N-substituted γ- and δ-
lactams from keto acids and nitriles with H2.
H2, without solvent.
ICP-AES analysis of the filtrate showed that the Pt content in
the solution was below the detection limit. These results confirm
that the reaction is attributed to the heterogeneous catalysis of
Pt-MoOX/TiO2. Figure 2 shows the result of catalyst recycle test.
After the standard reaction, followed by adding 3 mL 2-propanol
to the mixture, the catalyst separation from the mixture by
filtration, washing the catalyst with 6 mL acetone, drying the
catalyst at 90 °C (12 h), and by reduction of it at 300 °C (0.5 h),
the recovered catalyst showed high yields of 3a (90-84%)
during the following 4 cycles. As shown eqn. (1), the standard
reaction with 0.09 mol% of Pt-MoOX/TiO2 (5.3 mg) gave 85%
yield of 3a. This value corresponds to TON of 980.
Next, we discuss a reaction pathway (Scheme 1) which is
supported by the results of the control reactions in equations
(4)-(8) at 110 °C for 1 h. First, we studied the side reaction
pathways from nitriles (2) to secondary amine (4). Under 7 bar
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10.1002/cctc.201701355
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H2, n-octanenitrile 2a was hydrogenated to give di-n-octylamine
4a in 30% yield. Self-coupling of n-octylamine under 7 bar H2,
eqn. (5), resulted in lower yield of 4a (3%) than the
hydrogenation of n-octanenitrile in eqn. (4). Considering the
literature,[17] the most probable route from nitriles to secondary
amines is shown in Scheme 1. The nitrile
give imine 2’ and primary amine 2’’. The imine 2’ reacts with
the primary amine 2’’ to give the secondary imine which is
hydrogenated to secondary amine 4 [17]
Our results in eqn. (4)
and (5) are consistent with this scheme; the secondary amine
4a) is not produced by self-coupling of the primary amine but
by the hydrogenation of the nitrile via the imine intermediate 2’
2 is hydrogenated to
3
.
Scheme 1. A possible reaction pathway of Pt-MoOX/TiO2-
(
catalyzed reductive amination of LA with amines under H2.
.
If the reaction of the primary amine 2’’ with 1a under H2 (target
reaction) is faster than the reaction of the primary amine 2’’ with
Finally, we discuss the structure of the standard Pt-
MoOx/TiO2 catalyst. Previously,[12,20] we reported detailed
characterization of Pt-MoOx/TiO2 (with Mo loading of 7 wt%) by
temperature programmed reduction in H2, X-ray absorption
spectroscopy, CO adsorption, and TEM and the structural
model was proposed as follows. Thin layer (or small clusters)
of MoOx species covers the surface of TiO2, and Pt metal
nanoparticles with mean diameter of 4.7 nm are supported on
the Mo oxides-covered TiO2. Exposed Mon+ cations on the
surface MoOx species act as Lewis acid sites, while Pt sites act
as H2 dissociation sites. The MoOx-covering model was based
on the indirect evidences. Hence, we carried out the
microscope studies to obtain the direct evidence on the model.
Figure 3 shows TEM images of Pt-MoOx/TiO2 (Pt = 5 wt%, Mo
= 15 wt%). Pt metal particles with size in a range of 3-5 nm are
observed on the support surface, while MoOx particles are not
observed.
the imine intermediate 2’ (side reaction), the lactam
8 could be
selectively obtained. This assumption is verified by the higher
yield of the lactam (76%) by the reaction of 1a and n-octylamine
under H2, eqn. (6), than the yield of secondary amine 4a (30%)
in eqn. (4). Thermal condensation of the primary amine with 1a
under N2, eqn. (7), was also fast; it gave the imine intermediate
6
in 17% yield (by 1H-NMR) even under the catalyst-free
conditions. The C=N bond in the intermediate can be
hydrogenated to give the final intermediate , which undergoes
intramolecular amidation to give the lactam and H2O. We
observed the intermediate as a byproduct of the reaction of
6
7
7
LA, n-octylamine and H2 in eqn. (6). The yield of the lactam from
n-octanenitrile 2a (39%) in eqn. (8) is lower than that from n-
octylamine (76%) in eqn. (6), which is consistent with the
pathway in Scheme 1. From the above mechanistic discussion,
the reason of the selective conversion of nitriles to the lactams
(with low formation of secondary and tertiary amines) is due to
the faster reaction of the primary amine 2’’ with keto acid than
To achieve elemental mapping over a catalyst particle, we
carried out high-angle annular dark-field scanning transmission
electron microscopy (HAADF-STEM),[23] in conjunction with
EDX analysis in Figure 4. Yellow pixels (Pt) are observed on
the 2-5 nm sized white particles. Cyan pixels (Mo) are not
aggregated but highly dispersed over the TiO2 particle (red
pixels) and on the Pt particles. The absence of aggregated Mo
species are consistent with the structural model of Pt-
MoOx/TiO2 proposed in our previous study;[20] thin layer (or
small clusters) of MoOx species covers the surface of TiO2, and
Pt metal nanoparticles are supported on the MoOx-covered
TiO2. Additionally, the presence of Mo on the Pt particles shown
in Figure 4 suggests that some of the MoOx species are present
on the Pt particles. The interface between Pt particle and MoOx
thin layer and perimeter between Pt particle and MoOx on it can
act as Pt/ Mon+ (Lewis acid) cooperative sites which effectively
catalyze the present catalytic reaction.
with the imine intermediate 2’
.
1 mol% Pt-MoOx/TiO2
no solvent
H
+ H2
n-octyl
N
n-octyl
n-heptyl-CN
(4)
(5)
2a
1 mmol
4a
7 bar
30% yield
H
110 °C, 1 h
1 mol% Pt-MoOx/TiO2
n-octyl-NH2
H
2
n-octyl
4a
N n-octyl
+
no solvent
1 mmol
3% yield
110 °C, 1 h
O
1 mol% Pt-MoOx/TiO2
no solvent
OH
+ H2
+ n-octyl-NH2
N
O
n-octyl
(6)
O
7 bar
3a
1 mmol
1 mmol
110 °C, 1 h
76% yield
O
HO
HN
n-octyl
6a
8% yield
O
O
no catalyst
+ n-octyl-NH2
HO
(7)
(8)
HO
1 mL toluene
110 °C,1 h
O
1 mmol
Conclusions
1 mmol
N
n-octyl
17% yield (1H-NMR)
We have found the first general and reusable catalytic system
for one-pot synthesis of N-substituted lactams by reductive
conversion of keto acids (including levulinic acid) with nitriles
and H2 under mild conditions (7 bar H2, 110 °C, solvent-free)
O
1 mol% Pt-MoOx/TiO2
no solvent
OH
+ H2
+ n-heptyl-CN
N
O
n-octyl
2a
O
1 mmol
1 mmol
7 bar
3a
39% yield
110 °C, 1 h
H
n-octyl
N
n-octyl
4a
6% yield
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10.1002/cctc.201701355
ChemCatChem
FULL PAPER
using the Pt-MoOx/TiO2 catalyst. This method may be a
dark-field scanning transmission electron microscopy (HAADF-
STEM), in conjunction with energy dispersive X-ray spectroscopy
(EDS) mapping images were taken on a JEM-2100F (JEOL)
operated at 200 kV accelerating voltage. The samples for
TEM, STEM and EDS analyses were prepared by putting drops of a
methanol solution onto a carbon-coated copper grid.
sustainable route to N-substituted lactams from biomass.
Experimental Section
General
Commercially available organic compounds (from Tokyo Chemical
Industry, Sigma-Aldrich, or Kanto Chemical Co. Ltd.) were used
without further purification. The GC (Shimadzu GC-2014) and GCMS
(Shimadzu GCMS-QP2010) analyses were carried out with Ultra
ALLOY capillary column UA+-1 (Frontier Laboratories Ltd.) using
nitrogen and He as the carrier gas.
Acknowledgements
This work was supported by the ENEOS Hydrogen Trust Fund,
KAKENHI grants JP16H06595 and JP17H01341 from JSPS, and a
MEXT program "Elements Strategy Initiative to Form Core Research
Center". The authors are indebted to the technical division of the
Institute for Catalysis (Hokkaido University) for the manufacturing of
experimental equipment.
Catalyst preparation
TiO2 (JRC-TIO-4, 50 m2 g-1) was supplied from Catalysis Society of
Japan. The M-MoOX/TiO2 catalysts (M = 5 wt% Pt, Ir, Ru, Rh, Pd, Re,
Ni, Co, Cu; 7 or 15 wt% Mo) were prepared by a sequential
impregnation method as follows. Metal sources were aqueous HNO3
solutions of Pt(NH3)2(NO3)2, Rh(NO3)3, and Pd(NH3)2(NO3)2 and
aqueous solution of RuCl3, NH4ReO4, nitrates (Ni, Co, Cu), and
(NH4)6Mo7O24·4H2O. MoO3-loaded TiO2 (MoO3/TiO2) was prepared
by mixing TiO2 powder with aqueous solution of (NH4)6Mo7O244H2O
(50 mL), followed by evaporation of the mixture at 50 °C, drying the
solid at 90 °C for 12 h, and by calcination in air at 500 °C for 3 h.
Then, MoO3/TiO2 and aqueous HNO3 solution of Pt(NH3)2(NO3)2
were mixed, evaporated, dried at 90 °C to yield a Pt(II)-loaded
precursor. Before the catalytic experiment, the catalysts were
prepared by reduction of the precursor in a Pyrex tube under flowing
H2 (20 cm3 min-1) at 300 °C for 0.5 h.
Keywords: amination • hydrogenation • keto acids • nitriles
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Catalytic reactions
The catalytic reactions were carried out as follows. After the
reduction, the as-prepared catalyst in the closed Pyrex tube sealed
with a septum inlet was cooled to room temperature under H2,
followed injection of mixture of 1 mmol levulinic acid (LA), 1 mmol
nitriles, and 0.2 mmol n-dodecane. Then, the septum was removed
under air, a magnetic stirrer bar was put in the tube, followed by
inserting the tube inside stainless autoclave (28 cm3). After being
sealed, the reactor was charged with 7 bar H2 and heated at 110 ˚C
under stirring (500 rpm). After 24 h, the reactor was cooled followed
by adding 2-propanol (6 cm3) to the mixture, followed by removal of
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Table 1. Catalytic synthesis of 3a from 1a
,
2a and H2.[a]
Table 3. Synthesis of γ-lactams from 1a and nitriles under H2.
Entry
1
Nitriles
Products
Yield (%)[a]
92
Conv.
(%)
Yield (%)
Entry Catalysts
2a
3a
4a
5a
1
2
blank
MoOX/TiO2
0
4
0
2
0
0
0
0
2
3
n-decanenitrile
90
3
Pt-MoOx/TiO2
Ir-MoOx/TiO2
Ru-MoOx/TiO2
Rh-MoOx/TiO2
Pd-MoOx/TiO2
Re-MoOx/TiO2
Ni-MoOx/TiO2
Co-MoOx/TiO2
Cu-MoOx/TiO2
Pt-MoOx/TiO2
Pt/TiO2
100
10
6
85
6
6
9
4
1
1
5
3
0
0
(88)
6
68
85
9
28
51
7
17
9
21
23
0
7
4
5
6
(85)
(73)
82
7
0
8
8
6
0
0
9
6
2
0
0
10
11b
12
5
2
0
0
100
61
92
34
3
5
11
15
[a]
Conversion of 2a and yields were determined by GC. Mo
loading is 7 wt% for entries 2-10. [b] Mo =15 wt%
7
8
88
87
Table 2. Reaction of 1a with 2a and H2 by Pt-MoOX/TiO2 under
various conditions.[a]
9
72
10
11
12
13
91
(76)
83
nLA
Entr
y
PH2
[bar] [oC]
T
Conv.
[%]
Yield [%]
Solvent
[mmol
3a 4a 5a
1
2
1
3
3
3
5
7
7
7
7
7
7
7
7
100
100
100
100
100
110
120
140
110
110
110
110
no
no
78
78
69
70
67
80
86
92
85
78
45
38
16
8
3
3
3
3
4
3
5
7
9
6
4
4
6
5
1.2
1.5
1
81
3
no
76
5
4
no
88
5
14
15
16
17
18
84
76
75
72
88
5
1
no
96
6
6
1
no
100
100
100
65
5
7
1
no
10
15
11
9
8
1
no
9
1
toluene
o-xylene
n-decane
dioxane
10
11
12
1
53
1
26
6
1
17
5
[a] Conversion of 2a and yields were determined by GC.
[a] Isolated yields. GC yields are in parentheses.
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10.1002/cctc.201701355
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Table 4. Synthesis of δ-lactams from 4-acetylbutyric acid (1b
)
100
80
60
40
20
0
and nitriles under H2.
Entry
1
Nitriles
Products
Yield (%)[a]
96
1
2
3
4
5
2a
Cycle number
Figure 2. Reuse of Pt-MoOX/TiO2 for 3a synthesis under
conditions in entry 6 of Table 2.
2
3
4
5
6
7
8
94
92
95
78
86
88
92
O
N
Cl
O
N
Figure 3. Representative TEM images of Pt-MoOx/TiO2.
N
Pt
HAADF
[a] Isolated yields.
100
3a
2a
80
60
40
Mo
Ti
20
4a
5a
0
10
20
30
t [h]
Figure 1. Time-yields profile; conditions are in Table 1 (entry 11).
Figure 4. HAADF-STEM images superimposed with EDX elements
mapping of Pt-MoOx/TiO2. The yellow, cyan, and red pixels in the
mapping correspond to Pt, Mo, and Ti, respectively.
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Entry for the Table of Contents (Please choose one layout)
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S. M. A. H. Siddiki, A. S. Touchy, A.
Bhosale, T. Toyao, Y. Mahara, J.
Ohyama, A. Satsuma, K. Shimizu
Page No. – Page No.
Direct synthesis of lactams from keto
acids, nitriles, and H2 by
We report the first general and reusable catalytic system for one-pot
synthesis of N-substituted lactams by reductive conversion of keto acids
(including levulinic acid) with nitriles and H2 under mild conditions.
heterogeneous Pt catalysts
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