Recyclable covalent triazine framework-supported iridium catalyst for the N-methylation of amines with methanol in the presence of carbonate

Article abstract of DOI:10.1016/j.jcat.2021.02.030

An iridium complex Cp*Ir@CTF, which is synthesized by the coordinative immobilization of [Cp*IrCl₂]₂ on a functionalized covalent triazine framework (CTF), was found to be a general and highly efficient catalyst for the N-methylation of amines with methanol in the presence of carbonate. Under environmentally benign conditions, a variety of desirable products were obtained in high yields with complete selectivities and functional group friendliness. Furthermore, the synthesized catalyst could be recycled by simple filtration without obvious loss of catalytic activity after sixth cycle. Notably, this research exhibited the potential of covalent triazine framework-supported transition metal catalysts for hydrogen autotransfer process.

Full text of DOI:10.1016/j.jcat.2021.02.030

Journal of Catalysis 396 (2021) 281–290
Contents lists available at ScienceDirect
Journal of Catalysis
journal homepage: www.elsevier.com/locate/jcat
Recyclable covalent triazine framework-supported iridium catalyst for
the N-methylation of amines with methanol in the presence of carbonate
1
1
⇑
Peng Liu , Jiazhi Yang , Yao Ai, Shushu Hao, Xiaozhong Chen, Feng Li
School of Chemical Engineering, Nanjing University of Science & Technology, Nanjing 210094, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
An iridium complex Cp*Ir@CTF, which is synthesized by the coordinative immobilization of [Cp*IrCl2]2 on
a functionalized covalent triazine framework (CTF), was found to be a general and highly efficient catalyst
for the N-methylation of amines with methanol in the presence of carbonate. Under environmentally
benign conditions, a variety of desirable products were obtained in high yields with complete selectivities
and functional group friendliness. Furthermore, the synthesized catalyst could be recycled by simple fil-
tration without obvious loss of catalytic activity after sixth cycle. Notably, this research exhibited the
potential of covalent triazine framework-supported transition metal catalysts for hydrogen autotransfer
process.
Received 7 January 2021
Revised 22 February 2021
Accepted 26 February 2021
Available online 10 March 2021
Keywords:
Covalent triazine framework
Iridium
Ó 2021 Published by Elsevier Inc.
Recyclable
N-Methylation
Methanol
1. Introduction
and Shimizu’s groups have developed independently recyclable
solid molecular NHC-Ir catalysts [28] and carbon-supported Pt
The N-methylation of amines represents one of the most impor-
tant C-N bond-forming reactions in organic synthesis and it was
widely utilized for the preparation of natural products, pharma-
ceuticals, agrochemicals, fine chemicals, polymers and materials
[1,2]. Conventionally, such transformations were performed with
highly toxic and/or hazardous methylating agents, such as methyl
iodide, dimethyl sulfate or diazomethane, in the presence of a sto-
ichiometric or excess amount of base [3,4]. In addition, these pro-
cedures still suffer from the low selectivity (the formation of
overmethylated products). In recent years, much attention has
been directed to the N-methylation of amines with methanol as
an alternative methylating agent based on transiton metal-
catalyzed hydrogen autotransfer processes (or hydrogen-
borrowing strategy) [5-9]. This strategy is highly attractive due
to the use of an abundant, renewable and biodegradable C1 source,
and high atom economy and environmental friendliness. Although
a series of homogeneous transition metal catalysts, such as Ir [10-
15], Ru [16-19], Mn [20-22], Fe [23,24], Co [25], Re [26] and Pd [27]
complexes, have been utilized for the N-methylation of amines
with methanol, the practical application is highly limited due to
the difficult in the separation and recyclability of catalysts. Tu
nanoparticles (Pt/C) [29] as heterogeneous catalysts for this trans-
formations. However, these two procedures required the presence
of a stoichiometric amount of inorganic strong base (NaOH,
KOtBu). From the standpoint of sustainable chemistry, the devel-
opment of a new type of recyclable heterogeneous catalyst for
the N-methylation of amines with methanol under more environ-
mentally benign conditions is highly desirable.
Recently, covalent triazine frameworks (CTFs) have attracted
much attention because they have high stabilities in both acidic
and basic media, large pore volumes and high surface areas [30-
33]. In particular, functionalized CTFs with a large number of coor-
dination sites in their pore walls were considered to be excellent
supporting materials to metal ions [34-40]. More recently, CTF
supported-Ir, Rh, Ru, Ni complexes been applied to catalytic trans-
formations, such as hydrogenation of CO2 to formate, dehydro-
genation of formic acid, C-H borylation reactions and transfer
hydrogenation of carbonyl compounds [41-50]. We have devel-
oped a series of homogeneous iridium-catalyzed transformations
with the activation of alcohols as electrophiles based on hydrogen
autotransfer process [51-62] and acceptorless hydrogenation
[54,63-65]. As a continuing effort in this field, we turned our atten-
tion from homogeneous catalysis to heterogenous one. Herein, we
wish to describe the synthesis and characterization of a heteroge-
neous iridium catalyst Cp*Ir@CTF, and developed it as the first
recyclable catalyst for the N-methylation of amines with methanol
under in the presence of carbonate.
⇑
Corresponding author.
E-mail address: fengli@njust.edu.cn (F. Li).
1
These authors contributed equally to this work.
https://doi.org/10.1016/j.jcat.2021.02.030
0021-9517/Ó 2021 Published by Elsevier Inc.

P. Liu, J. Yang, Y. Ai et al.
Journal of Catalysis 396 (2021) 281–290
BET surface and pore volume were reduced to 395 m2/g and
0.13 cm3/g from 693 m2/g and 0.23 cm3/g, respectively, which is
still porous enough for the facile diffusion of amines and methanol
into catalytic sites (Table S2). To understand the coordination envi-
ronment of the Ir ion in CTF, XPS measurements were conducted
and these results are referenced to the C-1s value of 284.6 eV.
The Ir-4f7/2 electron-binding energy (EBE) was found to be
62.1 eV, which is 0.6 eV lower than that of IrCl3 (62.7 eV) [67]. It
indicates that N^N and Cp* ligands donate electron density to the
Ir cation. For comparison, the Ir-4f7/2 EBE value of homogeneous
catalyst [Cp*Ir(bpy)Cl]Cl is also proven to be 62.1 eV, which indi-
cate that both Cp*Ir@CTF and [Cp*Ir(bpy)Cl]Cl have similar coordi-
nation environments around the Ir cation (Fig. 3, Fig. S6, Fig. S7).
With the synthesized Cp*Ir@CTF in hand, we examined its cat-
alytic activity for the N-methylation of aniline (1a) with methanol
(2) (Table 1). In the presence of Cp*Ir@CTF (0.5 mol % Ir) and Cs2-
CO3 (1 equiv), the model reaction was carried out in methanol
(1 mL) at 125 °C for 12 h to afford the product 3a in 95% yield
(Table 1, entry 1). Attempts to use of K2CO3 or Na2CO3 as an alter-
native base, decrease reaction temperature or reduce the amount
of Cs2CO3 resulted in relatively low yields (Table 1, entries 2–6).
2. Result and discussion
The porous CTF was prepared according to the previous proce-
dure [66]. 2,6-Pyridinedicarbonitrile and ZnCl2 were heated in a
sealed ampule at 400 °C for 48 h. The formation of the triazine
group and absence of cyanide group were identified by the FTIR
spectrum (Fig. S1). Then, the metalation of CTF with [Cp*IrCl2]2
proceeded for 12 h in 70 °C to give Cp*Ir@CTF (Scheme 1, Fig. 1
(a)). The scanning electron microscopy (SEM) analysis showed that
CTF and Cp*Ir@CTF are irregular block-shaped morphologies
(Fig. S2, Fig. 1(b) and Fig. S3). In addition, the homogeneous distri-
bution of Ir and Cl atoms throughout the CTF support were con-
firmed by the energy dispersive spectroscopy (SEM-EDS)
mapping (Fig. 1(c) and Fig. 1(d)). The actual loading amount of Ir
on CTF was determined to be 3.22 wt% by the inductively coupled
plasma mass spectrometry (ICP-MS) analysis (Table S2). Further-
more, the surface properties of CTF and Cp*Ir@CTF were investi-
gated by the N2 adsorption–desorption isotherm and Barrett-
Joyner-Halenda (BJH) method (Fig. 2). The N2 sorption isotherm
of CTF and Cp*Ir@ CTF exhibited type 1 isotherm with both micro
and meso-pores. After the incorporation of [Cp*IrCl2]2 to CTF, the
N
N
N
N
Cl-
Cl-
N
N
N
N
N
N
Cl Ir
N
[Cp*IrCl2]2
N
N
N
N
N
N
DCM, 70 oC
N
N
N
N
N
N
N
N
N
N
N
N
N
Cp*Ir@bpy-CTF
bpy-CTF
Scheme 1. The synthetic route for Cp*Ir@CTF.
bpy-CTF
250
200
150
100
50
Cp*Ir@bpy-CTF
0
0.0
0.2
0.4
0.6
0.8
1.0
Relative pressure (p/p0)
Fig. 2. N2 sorption measurements of CTF (black) and Cp*Ir@CTF (red). (For
interpretation of the references to colour in this figure legend, the reader is
referred to the web version of this article.)
Fig. 1. (a) Photograph and (b) SEM image of Cp*Ir@CTF; EDS mapping of (c) Ir, (d)
Cl.
282

P. Liu, J. Yang, Y. Ai et al.
Journal of Catalysis 396 (2021) 281–290
Table 2
The N-Methylation of Various Aromatic Amines and Aliphatic Amines with Methanol
Catalyzed by Cp*Ir@CTFa,b.
(a)
C1s: 284.7 eV
290
288
286
284
282
280
Binding energy (eV)
Ir4f7/2: 62.1 eV
(b)
Ir4f5/2: 65.1 eV
70
68
66
64
62
60
58
Binding energy (eV)
Fig. 3. Deconvoluted X-ray photoelectron spectra of (a) C-1 s and (b) Ir-4f of
Cp*Ir@CTF (black) and [Cp*Ir(bpy)Cl]Cl (red). (For interpretation of the references to
colour in this figure legend, the reader is referred to the web version of this article.)
Table 1
The N-Methylation of Aniline with Methanol under Various Conditionsa,b.
and ester, were also tolerated, and N-methylated products 3k
and 3l were obtained in 81% and 83% yields, respectively. Transfor-
mations of 2-aminopyridines and 2-aminonaphthalene proceeded
smoothly to give corresponding products 3m and 3n in 85% and
87% yields, respectively. Furthermore, this catalytic system was
also applied to amino-azoles, affording N-exo-substituted products
3o-3s in 89–94% yields with complete regioselectivity. When ali-
phatic primary amines, such as amantadine and 1-octylamine,
were served as substrates, N,N-dimethylated products 3t and 3u
were obtained in 89% and 92% yields, respectively. It may con-
tributed that aliphatic amines are more nucleophilic than aromatic
ones.[68] In the case of aliphatic secondary amines, such as 1,2,3,4-
tetrahydroisoquinoline and 4-(3-(piperidin-4-yl)propyl)piperidine,
reactions gave desired products 3v and 3w in 82% and 83% yields,
respectively.
To further expand the scope of reaction, the N-methylation of a
series of sulfonamides with methanol were examined (Table 3).
The transformation of benzenesulfonamides afforded the corre-
sponding product 5a in 90% yield. Bezenesulfomaindes bearing
both an electron-donating or electron-withdrawing substituent
were successfully converted to desired products 5b-5i in 88–93%
yields. Furthermore, thienyl- and naphthyl-sulfonamides were
It was also found that no reaction occurred in the presence of
Cp*Ir@CTF and Cs2CO3 alone (Table 1, entries 7–8).
Encouraged by the promising result (Table 1, entry 1), the N-
methylation of a variety of aromatic and aliphatic amines with
methanol was investigated (Table 2). Reactions of anilines bearing
an electron-donating group afforded corresponding products 3b
and 3c in 83% and 80% yields, respectively. Substrates bearing
one or two halogen atoms and more electron-withdrawing sub-
stituents, such as trifluoromethyl, trifluoromethoxy were also con-
verted to desired products 3d-3j in 83–93% yields. It was found
that readily reducible or labile functional groups, such as cyano
283

P. Liu, J. Yang, Y. Ai et al.
Journal of Catalysis 396 (2021) 281–290
Table 3
To facilitate understand the reaction mechanism, a series of
control experiments were conducted. When parallel N-
methylation of 1a with CH3OH and CD3OD proceeded under stan-
dard reaction conditions, a significant kinetic isotope effect (KIE)
(KH/KD = 3.63) was found (Scheme 4, Eq. (1)). Furthermore, com-
petitive N-methyaltion of 1a with a mixture of CH3OH and CD3OD
(v/v = 1/1) was also undertaken (Scheme 4, Eq. (2)). It could be
speculated that PhN = CH2 (72%) and PhN = CD2 (28%) were gener-
ated in the step of condensation. These results indicated that the C-
H bond cleavage of methanol may be involved in the rate-
determining step [70].
The N-Methylation of
a Variety of Sulfonamides with Methanol Catalyzed by
Cp*Ir@CTFa,b.
As outlined in Fig. 4, the recyclability of catalyst for the model
reaction was investigated. After each recycling, the catalyst was
recovered by filtration, washed thoroughly with methanol, and
applied to the next cycle. The activities of catalyst are well main-
tained during recycling experiments and the NMR yield of 3a
was still up to 90% in sixth cycle. The recovered catalyst after sixth
cycle was further investigated. FT-IR spectrum of the recovered
catalyst was similar to the fresh catalyst, indicating functional
groups in the original catalyst were maintained (Fig. S1). Similarly,
the SEM image and EDS mapping had shown that the original mor-
phology and the homogeneous distribution of Ir atom in CTF were
maintained (Fig. S3 and Fig. S5). The recovered catalyst possessed a
slightly lower amount of incorporated Ir than the fresh catalyst
(Table S1). However, the chlorine concentration was reduced to
below the detection limit of EDS, supporting that chlorido ligands
may not be involved in the catalytic cycle.
3. Conclusions
proven to be suitable substrates and corresponding products 5j and
5k were obtained in 91% and 92% yields, respectively. This catalytic
system was also compatible with aliphatic sulfonamides, giving
corresponding products 5l-5o in 82–92% yields.
Furthermore, the gram-scale synthesis of biologically active
molecular butenafine (a drug used for treating tinea) was under-
taken (Scheme 2). Under standard conditions (Table 1, entry 1),
the N-methylation of (4-tert-butyl-benzyl)-naphthalen-1-ylme
thyl-amine (6, 20 mmol) with methanol was performed to give
the corresponding product 7 in 85% yield.
Based on experimental results, a possible mechanism was pro-
posed for the present N-methylation of amines with methanol cat-
alyzed by Cp*Ir@CTF (Scheme 3). The initial step of the reaction
involved the formation of methoxo iridium species A@ CTF by
the reaction of Cp*Ir@CTF with methanol under the acceleration
of Cs2CO3.[69] Accompanied by the b-hydrogen elimination of
methoxo iridium species A@CTF, an iridium hydride species
B@CTF and formaldehyde were generated. The condensation
between the resulting formaldehyde and amines occurred to afford
iridium imines. Then, the addition of iridium hydride into the C@N
bond of imines afforded amido-iridium species C@CTF. Finally, a
catalytically active methoxo iridium species A@CTF was regener-
ated and N-methylated amines were released via the amido-
methoxo exchange reaction between species C@CTF and methanol.
In summary, we have demonstrated that an iridium complex
Cp*Ir@CTF, which is synthesized by the coordinative immobiliza-
tion of [Cp*IrCl2]2 on a functionalized covalent triazine framework
(CTF), could be utilized as the first heterogeneous catalyst for the
N-methylation of amines with methanol in the presence of carbon-
ate. Under environmentally benign conditions, a variety of desir-
able products were obtained in high yields with complete
selectivities and functional group friendliness. Furthermore, the
synthesized could be recycled by simple filtration without obvious
loss of catalytic activity after sixth cycle. Notably, this research
exhibited the potential of covalent triazine framework-supported
transition metal catalysts for hydrogen autotransfer process.
4. Experimental section
4.1. General experimental details
All reagents and materials used in this study were obtained
from commercial sources and used as received unless mentioned
otherwise. Quant 250 FEG operated at an accelerating voltage of
20.0 kV was used for the Scanning Electron Microscopy (SEM)
and Energy-Dispersive X-ray Spectroscopy (EDS) measurements.
X-ray Photoelectron Spectroscopy (XPS) analysis was performed
Cp*Ir@CTF (0.5 mol % Ir)
Cs2CO3 (1 equiv)
MeOH (40 mL)
N
H
N
Me
125 oC, 12 h
6 (20 mmol)
7, 85% yield
Scheme 2. Synthesis of a Biologically Active Molecular.
284

P. Liu, J. Yang, Y. Ai et al.
Journal of Catalysis 396 (2021) 281–290
N
N
Cl-
N
N
N
Cl Ir
N
N
N
N
N
N
N
N
N
N
Cp*Ir@CTF
MeOH, Cs2CO3
N
N
+
N
N
N
MeO Ir
N
N
N
N
Me
NH
R
N
N
N
N
N
N
CH3OH
A
N
N
N
N
+
H
N
+
H
H
N
N
N
N
N
N
H
Ir
R
H
Ir
+
N
N
N
O
H
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
C
B
N
N
+
R-NH2
N
H
N
N
H
Ir
+
N
H
N
N
N
R
H20
N
N
N
N
N
N
N
B
Scheme 3. The Proposed Reaction Mechanism.
285

P. Liu, J. Yang, Y. Ai et al.
Journal of Catalysis 396 (2021) 281–290
H
N
D
N
Cp*Ir@CTF (0.5 mol % Ir)
Cs2CO3 (1 equiv)
NH2
NH2
CH3
CD3
+ CH3OH/CD3OD
(1)
125 oC, 12 h
3a
8
1a
KH/KD = 3.63
H/D
N
H/D
N
CH3
CH2D
+
Cp*Ir@CTF (0.5 mol % Ir)
Cs2CO3 (1 equiv)
1a
47%
25%
(2)
+
125 oC, 12 h
H/D
N
H/D
N
CH3OH
+
CHD2
CD3
+
CD3OD
25%
3%
Scheme 4. Control Experiments.
4.2. Procedure for the synthesis of CTF
100
80
60
40
20
0
CTF was synthesized according to a reported procedure [73].
2,6-Pyridinedicarbonitrile (0.30 g, 2.32 mmol) and zinc chloride
(1.61 g, 11.80 mmol) were charged to a 20 mL ampoule under Ar
atmosphere and closed with septum. The ampoule was then sealed
under vacuum by flame and the contents were heated to 400 °C in
a furnace for a period of 48 h. The heating rate was maintained to
be 60 °C/h. The furnace was cooled to 20 °C after 48 h. The crude
product was collected, ground well and stirred with 500 mL of
water for 3 h. The black solid was filtered and washed with water
and acetone. The resulting solid was refluxed with 1 M HCl solu-
tion (500 mL) for 16 h, filtered and washed with 1 M HCl
(3 ꢀ 100 mL), H2O (3 ꢀ 100 mL), THF (3 ꢀ 100 mL), and acetone
(3 ꢀ 100 mL). The black solid was dried under vacuum at 200 °C
for 6 h.
1
2
3
4
5
6
Number of cycle
4.3. Procedure for the synthesis of Cp*Ir@CTF
Fig. 4. Recyclability of Cp*Ir@CTF for the N-methylation of 1a with methanol.
To a suspension of CTF (0.5 g) in 50 mL of dichloromethane was
added [Cp*IrCl2]2 (0.3 g) under N2 atm. The resulting suspension
was refluxed under N2 atm for 12 h. After 12 h, the black solid
was filtered and washed with an excess of dichloromethane
(10 ꢀ 25 mL) to remove the unreacted metal precursor. The as-
synthesized catalyst was dried under vacuum at 25 °C for 36 h.
on a PHI QUANTERA II using Mg K
a as the excitation source. All
binding energy values were calibrated using the adventitious car-
bon C1s peak at 284.6 eV. Metal contents in the Cp*Ir@CTF was
determined by inductively coupled plasma optical emission spec-
trometry (ICP-MS) (iCAP-Q, Thermo Fisher Scientific) using micro-
wave assisted acid digestion system (MARS6, CEM/U.S.A). BET
surface area and N2 adsorption–desorption measurements were
conducted at 77 K using an automated gas sorption system (ASAP
2020). ATR-IR measurements were recorded on a Thermo Fisher
Scientific Nicolet iS 10 instrument. Melting points were measured
on a X-6 micro-melting apparatus. Proton nuclear magnetic reso-
nance (1H NMR) spectra were recorded at 500 MHz using a 500
spectrometer. Chemical shifts are reported in delta (d) units, parts
per million (ppm) downfield from tetramethylsilane or ppm rela-
tive to the center of the singlet at 7.26 ppm for CDCl3. Coupling
constants J values are reported in Hertz (Hz), and the splitting pat-
terns were designated as follows: s, singlet; d, doublet; t, triplet; m,
4.4. General procedure for the N-methylation of amines with methanol
catalyzed by Cp*Ir@CTF
To an oven-dried, 25 mL Schlenk tube were added amines
(0.5 mmol), methanol (1.5 mL), Cp*Ir@CTF (15.0 mg, 0.0025 mmol,
0.5 mol %), Cs2CO3 (163 mg, 0.5 mmol). The mixture of reaction
was heated at 125 °C in an oil bath for 12 h. The reaction mixture
was cooled to ambient temperature, concentrated in vacuo and
purified by flash column chromatography with hexanes/ethyl acet-
ate to afford the corresponding product.
N-Methylaniline (3a) [74]: Yellow oil; 89% yield (48 mg); 1H
NMR (500 MHz, CDCl3) d 7.18 (t, J = 7.9 Hz, 2H), 6.70 (t,
J = 7.3 Hz, 1H), 6.60 (d, J = 8.1 Hz, 2H), 3.66 (br s, 1H), 2.80 (s,
3H); 13C {1H} NMR (125 MHz, CDCl3) d 149.3, 129.1, 117.2,
112.3, 30.6.
N,4-Dimethylbenzenamine (3b) [75]: Brown oil; 83% yield
(50 mg); 1H NMR (500 MHz, CDCl3) d 7.03 (d, J = 8.2 Hz, 2H),
6.57 (d, J = 8.3 Hz, 2H), 2.83 (s, 3H), 2.27 (s, 3H); 13C {1H} NMR
(125 MHz, CDCl3) d 147.0, 129.6, 126.4, 112.5, 31.0, 20.2.
multiplet; b, broad. Carbon-13 nuclear magnetic resonance (13
C
NMR) spectra were recorded at 125 MHz using a 500 spectrometer.
Chemical shifts are reported in delta (d) units, ppm relative to the
center of the triplet at 77.0 ppm for CDCl3. 13C NMR spectra were
routinely run with broadband decoupling. Analytical thin-layer
chromatography (TLC) was carried out using 0.2 mm commercial
silica gel plates. [Cp*IrCl2]2 [71] and [Cp*Ir(bpy)Cl]Cl [72] were
synthesized according to the previously reported methods.
286

P. Liu, J. Yang, Y. Ai et al.
Journal of Catalysis 396 (2021) 281–290
4-Methoxy-N-methylbenzenamine (3c) [76]: Yellow oil; 80%
yield (55 mg); 1H NMR (500 MHz, CDCl3) d 6.82 (d, J = 8.8 Hz,
2H), 6.60 (d, J = 8.9 Hz, 2H), 3.77 (s, 3H), 2.81 (s, 3H); 13C {1H}
NMR (125 MHz, CDCl3) d 152.0, 143.6, 114.8, 113.5, 55.7, 31.5.
4-Fluoro-N-methylbenzenamine (3d) [77]: Yellow oil; 83%
yield (52 mg); 1H NMR (500 MHz, CDCl3) d 6.91 (t, J = 8.8 Hz,
2H), 6.57–6.52 (m, 2H), 3.60 (br s, 1H), 2.81 (s, 3H); 13C {1H}
NMR (125 MHz, CDCl3) d 155.7 (d, JC-F = 234.7 Hz), 145.6, 115.4
(d, JC-F = 22.3 Hz), 113.0 (d, JC-F = 7.4 Hz), 31.2.
3,5-Difluoro-N-methylbenzenamine (3e) [78]: Colorless oil;
93% yield (67 mg); 1H NMR (500 MHz, CDCl3) d 6.15–6.05 (m,
3H), 3.95 (br s, 1H), 2.80 (s, 3H); 13C {1H} NMR (125 MHz, CDCl3)
d 164.0 (dd, JC-F = 243.7 Hz and 16.1 Hz), 151.3 (t, JC-F = 13.4 Hz),
94.8 (dd, JC-F = 21.7 Hz and 7.0 Hz), 92.0, (t, JC-F = 26.4 Hz), 30.3.
4-Chloro-N-methylbenzenamine (3f) [79]: Yellow oil; 91%
yield (64 mg); 1H NMR (500 MHz, CDCl3) d 7.18 (d, J = 8.8 Hz,
2H), 6.54 (d, J = 8.8 Hz, 2H), 3.74 (br s, 1H), 2.80 (s, 3H); 13C {1H}
NMR (125 MHz, CDCl3) d 147.9, 128.9, 121.5, 113.4, 30.7.
N-Methyl-2,4-dichloroaniline (3g) [76]: Yellow oil; 88% yield
(77 mg); 1H NMR (500 MHz, CDCl3) d 7.22 (d, J = 2.3 Hz, 1H),
7.10 (dd, J = 8.7 Hz and 2.4 Hz, 1H), 6.51 (d, J = 8.7 Hz, 1H), 4.30
(br s, 1H), 2.85 (d, J = 4.8 Hz, 3H); 13C {1H} NMR (125 MHz, CDCl3)
d 143.6, 128.4, 127.6, 120.7, 119.1, 111.0, 30.3.
4-Bromo-N-methylbenzenamine (3h) [62]: Yellow oil; 86%
yield (80 mg); 1H NMR (500 MHz, CDCl3) d 7.23 (d, J = 8.9 Hz,
2H), 6.44 (d, J = 8.8 Hz, 2H), 3.71 (br s, 1H), 2.76 (s, 3H); 13C {1H}
NMR (125 MHz, CDCl3) d 148.2, 131.7, 113.8, 108.6, 30.6.
3,5-Bis(trifluoromethyl)-N-methylaniline (3i) [79]: Yellow
oil; 87% yield (106 mg); 1H NMR (500 MHz, CDCl3) d 7.15 (s, 1H),
6.92 (s, 2H), 4.18 (br s, 1H), 2.90 (d, J = 5.2 Hz, 3H); 13C {1H}
NMR (125 MHz, CDCl3) d 149.6, 132.2 (q, JC-F = 32.6 Hz), 123.5 (q,
JC-F = 273.3 Hz), 111.2 (d, JC-F = 3.2 Hz), 109.9–109.7 (m), 30.1.
N-Methyl-4-(trifluoromethoxy)benzenamine (3j) [62]: Pale
yellow oil, 90% yield (86 mg); 1HNMR (500 MHz, CDCl3) d 7.06
(d, J = 8.6 Hz, 2H), 6.56 (d, J = 8.9 Hz, 2H), 3.79 (br s, 1H), 2.83 (s,
3H); 13C {1H} NMR (125 MHz, CDCl3) d 148.0, 140.2, 122.2, 120.6
(q, JC-F = 254.3 Hz), 112.4, 30.7.
4-(Methylamino)benzonitrile (3k) [16]: White solid; 81% yield
(54 mg); 1H NMR (500 MHz, CDCl3) d 7.40 (d, J = 8.7 Hz, 2H), 6.54
(d, J = 8.7 Hz, 2H), 4.42 (br s, 1H), 2.85 (d, J = 4.6 Hz, 3H); 13C {1H}
NMR (125 MHz, CDCl3) d 152.2, 133.5, 120.6, 111.7, 98.0, 29.8.
Methyl 4-(methylamino)benzoate (3l) [13]: White solid; 83%
yield (69 mg); mp 94–95 °C; 1H NMR (500 MHz, CDCl3) d 7.87 (d,
J = 8.7 Hz, 2H), 6.55 (d, J = 8.7 Hz, 2H), 3.85 (s, 3H), 2.88 (s, 3H);
13C {1H} NMR (125 MHz, CDCl3) d 167.3, 152.8, 131.4, 118.1,
110.9, 51.4, 30.0.
7.01 (t, J = 7.7 Hz, 1H), 5.80 (br s, 1H), 3.10 (s, 3H); 13C {1H}
NMR (125 MHz, CDCl3) d 162.8, 148.4, 142.8, 123.8, 120.6, 116.0,
108.6, 29.2.
N-Methylbenzothiazol-2-amine (3q) [81]: White solid; 93%
yield (76 mg); mp 137–138 °C; 1H NMR (500 MHz, CDCl3) d 7.57
(d, J = 7.9 Hz, 1H), 7.49 (d, J = 8.0 Hz, 1H), 7.28 (t, J = 7.6 Hz, 1H),
7.05 (t, J = 7.6 Hz, 1H), 3.04 (s, 3H); 13C {1H} NMR (125 MHz, CDCl3)
d 169.2, 152.3, 130.1, 125.8, 121.1, 120.8, 118.2, 31.5.
N,6-Dimethylbenzo[d]thiazol-2-amine (3r) [82]: White solid;
89% yield (79 mg); mp 151–152 °C; 1H NMR (500 MHz, CDCl3) d
7.41 (d, J = 8.2 Hz, 1H), 7.39 (s, 1H), 7.10 (d, J = 8.2 Hz, 1H), 6.46
(br s, 1H), 3.07 (s, 3H), 2.39 (s, 3H); 13C {1H} NMR (125 MHz, CDCl3)
d 168.2, 150.2, 130.9, 130.2, 127.0, 120.8, 118.0, 31.5, 21.1.
6-Fluoro-N-methylbenzo[d]thiazol-2-amine (3s) [83]: White
solid; 94% yield (86 mg); mp 158–160 °C; 1H NMR (500 MHz,
CDCl3) d 7.45 (dd, J = 8.8 Hz and 4.8 Hz, 1H), 7.30 (dd, J = 8.2 Hz
and 2.6 Hz, 1H), 7.04–6.99 (m, 1H), 5.47 (br s, 1H), 3.10 (s, 3H);
13C {1H} NMR (125 MHz, CDCl3)
d 167.9, 158.0 (d, JC-
= 240.0 Hz), 148.8, 131.0 (d, JC-F = 10.7 Hz), 119.0 (d, JC-
= 8.5 Hz), 113.4 (d, JC-F = 23.9 Hz), 107.5 (d, JC-F = 27.0 Hz), 31.5.
N,N-Dimethyl-1-adamantylamine (3t) [84]: Yellow oil; 89%
F
F
yield (80 mg); 1H NMR (500 MHz, CDCl3) d 2.23 (s, 6H), 2.04 (s,
3H), 1.66–1.59 (m, 9H), 1.58–1.53 (m, 3H); 13C {1H} NMR
(125 MHz, CDCl3) d 53.4, 37.8, 36.9, 36.7, 29.4.
N,N-Dimethyloctan-1-amine (3u) [13]: Yellow oil, 92% yield
(72 mg); 1H NMR (500 MHz, CDCl3) d 2.26–2.20 (m, 8H), 1.49–
1.42 (m, 2H), 1.29 (s, 10H), 0.88 (t, J = 6.8 Hz, 3H); 13C NMR
(125 MHz, CDCl3) d 59.8, 45.3, 31.7, 29.4, 29.1, 27.6, 27.4, 22.5,
13.9.
2-Methyl-1,2,3,4-tetrahydroisoquinoline (3v) [62]: White
solid; 82% yield (60 mg); mp 122–123 °C; 1H NMR (500 MHz,
CDCl3) d 7.15–7.09 (m, 3H), 7.02 (d, J = 6.8 Hz, 1H), 3.58 (s, 3H),
2.93 (t, J = 6.0 Hz, 2H), 2.69 (t, J = 6.0 Hz, 2H), 2.45 (s, 3H); 13C
{1H} NMR (125 MHz, CDCl3) d 134.5, 133.6, 128.5, 126.3, 126.0,
125.5, 57.8, 52.8, 46.0, 29.0.
1-Methyl-4-(3-(1-methylpiperidin-4-yl)propyl)piperidine
(3w) [85]: Yellow oil; 83% yield (99 mg); 1H NMR (500 MHz, CDCl3)
d 2.63 (d, J = 11.1 Hz, 4H), 2.07–2.03 (m, 6H), 1.68 (t, J = 11.0 Hz,
4H), 1.46 (d, J = 11.1 Hz, 4H), 1.14–0.97 (m, 12H); 13C {1H} NMR
(125 MHz, CDCl3) d 55.9, 46.3, 36.6, 34.9, 32.3, 23.7.
N-Methylbenzenesulfonamide (5a) [86]: Yellow oil; 90% yield
(77 mg); 1H NMR (500 MHz, CDCl3) d 7.84 (t, J = 7.5 Hz, 2H), 7.55 (t,
J = 7.4 Hz, 1H), 7.49 (d, J = 7.4 Hz, 2H), 5.17 (br s, 1H), 2.59 (s, 3H);
13C {1H} NMR (125 MHz, CDCl3) d 138.5, 132.6, 129.0, 127.0, 29.1.
N,4-Dimethylbenzenesulfonamide (5b) [87]: White solid; 93%
yield (86 mg); mp 73–74 °C; 1H NMR (500 MHz, CDCl3) d 7.73 (d,
J = 8.2 Hz, 2H), 7.28 (d, J = 8.1 Hz, 2H), 4.43 (br s, 1H), 2.58 (s,
3H), 2.39 (s, 3H); 13C {1H} NMR (125 MHz, CDCl3) d 143.4, 135.5,
129.6, 127.1, 29.1, 21.4.
4-Methoxy-N-methylbenzenesulfonamide (5c) [86]: White
solid; 91% yield (92 mg); mp 94–95 °C; 1H NMR (500 MHz, CDCl3)
d 7.76 (d, J = 8.8 Hz, 2H), 6.94 (d, J = 8.7 Hz, 2H), 5.08 (br s, 1H), 3.82
(s, 3H), 2.56 (s, 3H); 13C {1H} NMR (125 MHz, CDCl3) d 162.8, 130.0,
129.2, 114.1, 55.5, 29.1.
4-Fluoro-N-methylbenzenesulphonamide (5d) [88]: White
solid; 90% yield (85 mg); mp 68–69 °C; 1H NMR (500 MHz, CDCl3)
d 7.88 (dd, J = 8.8 Hz and 5.0 Hz, 2H), 7.20 (t, J = 8.6 Hz, 2H), 4.78 (br
s, 1H), 2.65 (d, J = 5.4 Hz, 3H); 13C {1H} NMR (125 MHz, CDCl3) d
165.0 (d, JC-F = 254.4 Hz), 134.7, 129.8 (d, JC-F = 9.2 Hz), 116.2 (d,
JC-F = 22.6 Hz), 29.1.
2-Chloro-N-methylbenzenesulfonamide (5e) [89]: White
solid; 88% yield (90 mg); mp 59–60 °C; 1H NMR (500 MHz, CDCl3)
d 8.05 (d, J = 7.7 Hz, 1H), 7.50 (d, J = 3.8 Hz, 2H), 7.43–7.38 (m, 1H),
2.59 (s, 3H); 13C {1H} NMR (125 MHz, CDCl3) d 135.7, 133.8, 131.6,
131.5, 127.2, 29.1.
N-Methylpyridin-2-amine (3m) [13]: Yellow oil; 85% yield
(46 mg); 1H NMR (500 MHz, CDCl3) d 8.06 (d, J = 4.3 Hz, 1H),
7.44 (t, J = 7.8 Hz, 1H), 6.57 (t, J = 6.0 Hz, 1H), 6.39 (d, J = 8.4 Hz,
1H), 2.91 (s, 3H); 13C {1H} NMR (125 MHz, CDCl3) d 159.4, 147.7,
137.5, 112.5, 106.0, 28.9.
N-Methylnaphthalen-2-amine (3n) [79]: Brown solid; 87%
yield (68 mg); mp 128–129 °C; 1H NMR (500 MHz, CDCl3) d
7.77–7.67 (m, 3H), 7.45 (t, J = 7.5 Hz, 1H), 7.28 (t, J = 7.4 Hz, 1H),
6.92–6.88 (m, 1H), 6.85 (d, J = 2.0 Hz, 1H), 3.86 (br s, 1H, NH),
2.95 (s, 3H); 13C {1H} NMR (125 MHz, CDCl3) d 147.0, 135.3,
128.7, 127.6, 127.4, 126.3, 125.9, 121.8, 117.9, 103.7, 30.7.
1-Benzyl-N-methyl-1H-benzo[d]imidazole-2-amine
(3o)
[13]: White solid; 90% yield (107 mg); mp 174–175 °C; 1H NMR
(500 MHz, CDCl3) d 7.53 (d, J = 7.8 Hz, 1H), 7.34–7.28 (m, 3H),
7.16–7.10 (m, 3H), 7.07–7.03 (m, 2H), 5.06 (s, 2H), 3.06 (s, 3H);
13C {1H} NMR (125 MHz, CDCl3) d 155.0, 142.1, 135.3, 134.8,
129.0, 127.9, 126.2, 121.3, 119.7, 116.4, 107.1, 45.4, 29.9.
N-Methyl-1,3-benzoxazol-2-amine (3p) [80]: White solid; 92%
yield (68 mg); mp 97–98 °C; 1H NMR (500 MHz, CDCl3) d 7.35 (d,
J = 7.7 Hz, 1H), 7.23 (d, J = 7.9 Hz, 1H), 7.15 (t, J = 7.6 Hz, 1H),
287

P. Liu, J. Yang, Y. Ai et al.
Journal of Catalysis 396 (2021) 281–290
4-Chloro-N-methylbenzenesulfonamide (5f) [88]: White
solid; 90% yield (93 mg); mp 59–60 °C; 1H NMR (500 MHz, CDCl3)
d 7.78 (d, J = 8.6 Hz, 2H), 7.46 (d, J = 8.6 Hz, 2H), 2.60 (s, 3H); 13C
{1H} NMR (125 MHz, CDCl3) d 139.1, 137.1, 129.3, 128.6, 29.1.
4-Bromo-N-methylbenzenesulfonamide (5g) [87]: Yellow
solid; 93% yield (116 mg); mp 74–76 °C; 1H NMR (500 MHz, CDCl3)
d 7.70 (d, J = 8.6 Hz, 2H), 7.62 (d, J = 8.6 Hz, 2H), 5,26 (br s, 1H), 2.60
(s, 3H); 13C {1H} NMR (125 MHz, CDCl3) d 137.6, 132.3, 128.7,
127.6, 29.1.
N-Methyl-4-(trifluoromethyl)benzenesulfonamide (5h) [13]:
White solid; 91% yield (109 mg); mp 77–78 °C; 1H NMR
(500 MHz, CDCl3) d 8.00 (d, J = 8.2 Hz, 2H), 7.79 (d, J = 8.2 Hz,
2H), 4.98 (br s, 1H), 2.68 (d, J = 5.4 Hz, 3H); 13C {1H} NMR
(125 MHz, CDCl3) d 142.3, 134.3 (q, JC-F = 33.1 Hz), 127.6, 126.2
(q, JC-F = 3.6 Hz), 123.1 (q, JC-F = 273.1 Hz), 29.1.
132.7, 128.6, 127.8, 127.6, 127.5, 127.3, 127.2, 125.8, 125.4,
125.1, 61.9, 61.6, 42.3, 34.4, 31.4.
4.6. Kinetic isotope effect (KIE) studies
Parallel reactions for the N-methylation were carried out using
CH3OH and CD3OD under identical conditions following the gen-
eral procedure. And the progress of the reaction was analysed by
1H NMR. All the reactions were repeated twice and the average
data were plotted as yield (%) vs time (h).
PhNDCD3 (8) [94]: Yellow oil; 1H NMR (500 MHz, CDCl3) d 7.20
(t, J = 7.6 Hz, 2H), 6.72 (t, J = 7.3 Hz, 1H), 6.62 (d, J = 7.8 Hz, 2H); 13
C
{1H} NMR (125 MHz, CDCl3) d 149.2, 129.1, 117.1, 112.3, 29.6 (m).
4.7. Competitive for the N-methylation of 1a
N-Methyl-4-(trifluoromethoxy)benzenesulfonamide
(5i)
[13]: Yellow oil; 89% yield (114 mg); 1H NMR (500 MHz, CDCl3) d
7.92 (d, J = 8.8 Hz, 2H), 7.35 (d, J = 8.4 Hz, 2H), 4.84 (br s, 1H),
2.67 (d, J = 5.3 Hz, 3H); 13C {1H} NMR (125 MHz, CDCl3) d 152.0,
137.1, 129.2, 120.9, 120.1 (q, JC-F = 259.5 Hz), 29.1.
Reaction were carried out using CH3OH/CD3OD (v/v = 1/1, total
volume: 1.5 mL) under identical conditions following the general
procedure. And the progress of the reaction was analysed by 1H
NMR. The incorporation of zero, one, two or three deuterium on
the methyl of the product was determined by 1H NMR spectrum
of crude mixture according to the previous report.
N-Methylthiophene-2-sulfonamide (5j) [90]: Brown solid;
91% yield (81 mg); mp 78–81 °C; 1H NMR (500 MHz, CDCl3) d
7.63–7.58 (m, 2H), 7.10 (t, J = 4.3 Hz, 1H), 4.79 (br s, 1H), 2.73 (d,
J = 5.4 Hz, 3H); 13C {1H} NMR (125 MHz, CDCl3) d 139.5, 132.1,
131.8, 127.3, 29.4.
Declaration of Competing Interest
N-Methylnaphthalene-2-sulfonamide (5k) [91]: Purple solid;
92% yield (102 mg); mp 105–107 °C; 1H NMR (500 MHz, CDCl3) d
8.45 (s, 1H), 7.88 (dd, J = 26.3 Hz and 9.1 Hz, 4H), 7.63–7.53
(m,2H), 5.39 (br s, 1H), 2.64 (s, 3H); 13C {1H} NMR (125 MHz,
CDCl3) d 135.4, 134.7, 132.0, 129.4, 129.1, 128.7, 128.6, 127.8,
127.4, 122.2, 29.2.
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
Acknowledgements
N-Methyl(phenyl)methanesulfonamide (5l) [92]: White solid;
88% yield (82 mg); mp 110–111 °C; 1H NMR (500 MHz, CDCl3) d
7.36 (s, 5H), 4.66 (br s, 1H), 4.20 (s, 2H), 2.61 (s, 3H); 13C {1H}
NMR (125 MHz, CDCl3) d 130.5, 129.2, 128.7, 128.6, 57.4, 29.6.
N-Methylcyclopropanesulfonamide (5m) [62]: Yellow oil; 91%
yield (62 mg); 1H NMR (500 MHz, CDCl3) d 4.72 (br s, 1H), 2.79 (d,
J = 5.2 Hz, 3H), 2.42–2.36 (m, 1H), 1.15–1.09 (m, 2H), 1.00–0.95 (m,
2H); 13C {1H} NMR (125 MHz, CDCl3) d 29.4, 28.4, 4.8.
N,2-Dimethyl-2-propanesulfonamide (5n) [62]: Yellow oil;
82% yield (62 mg); 1H NMR (500 MHz, CDCl3) d 3.14 (br s, 1H),
2.78 (d, J = 5.6 Hz, 3H), 1.15 (s, 9H); 13C {1H} NMR (125 MHz,
CDCl3) d 55.4, 31.4, 22.4.
Financial support by National Natural Science Foundation of
China Jiangsu Province (BE20180051) and Postgraduate Research
& Practice Innovation Program of Jiangsu Province (KYCX20_0379)
is greatly appreciated.
Appendix A. Supplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.jcat.2021.02.030.
References
[1] S.A. Lawrence, Amines: Synthesis, Properties, and Applications, Cambridge
University, Cambridge, 2006.
[2] A. Ricci, Amino Group Chemistry: From Synthesis to the Life Sciences, Wiley-
VCH, Weinheim, 2008.
[3] F.A. Carey, R. Sundberg, J. Advanced Organic Chemistry, 4th ed. Kluwer
Academic: New York (2001) Part B, Chapter 3.2.5.
N-Methylmethanesulfonamide (5o) [13]: Yellow oil; 87% yield
(47 mg); 1H NMR (500 MHz, CDCl3) d 4.74 (br s, 1H), 2.93 (s, 3H),
2.79 (d, J = 5.1 Hz, 3H); 13C {1H} NMR (125 MHz, CDCl3) d 38.4,
29.2.
[4] R.N. Salvatore, C.H. Yoon, K.W. Jung, Synthesis of Secondary Amines,
Tetrahedron 57 (2001) 7785–7811.
4.5. Procedure for the synthesis of biologically active molecular
butenafine (Scheme 2)
[5] G.E. Dobereiner, R.H. Crabtree, Dehydrogenation as a Substrate-Activating
Strategy in Homogeneous Transition-Metal Catalysis, Chem. Rev. 110 (2010)
681–703.
[6] G. Guillena, D. Ramon, M. Yus, Hydrogen Autotransfer in the N-Alkylation of
Amines and Related Compounds using Alcohols and Amines as Electrophiles,
Chem. Rev. 110 (2010) 1611–1641.
[7] S. Bahn, S. Imm, L. Neubert, M. Zhang, H. Neumann, M. Beller, The Catalytic
Amination of Alcohols, ChemCatChem 3 (2011) 1853–1864.
[8] A. Corma, J. Navas, M.J. Sabater, Advances in One-Pot Synthesis through
Borrowing Hydrogen Catalysis, Chem. Rev. 118 (2018) 1410–1459.
[9] T. Irrgang, R. Kempe, 3d-Metal Catalyzed N- and C-Alkylation Reactions via
Borrowing Hydrogen or Hydrogen Autotransfer, Chem. Rev. 119 (2019) 2524–
2549.
[10] F. Li, J. Xie, H. Shan, C. Sun, L. Chen, General and Efficient Method for Direct N-
monomethylation of Aromatic Primary Amines with Methanol, RSC Adv. 2
(2012) 8645–8652.
[11] S. Michlik, T. Hille, R. Kempe, The Iridium-Catalyzed Synthesis of
Symmetrically and Unsymmetrically Alkylated Diamines under Mild
Reaction Conditions, Adv. Synth. Catal. 354 (2012) 847–862.
[12] J. Campos, L.S. Sharninghausen, G.M. Manas, R.H. Crabtree, Methanol
Dehydrogenation by Iridium N-Heterocyclic Carbene Complexes, Inorg.
Chem. 54 (2015) 5079–5084.
To an oven-dried, 250 mL Schlenk tube were added (4-tert-Bu
tyl-benzyl)-naphthalen-1-ylmethyl-amine (6, 20 mmol), methanol
(40 mL), Cp*Ir@CTF (600 mg, 0.1 mmol, 0.5 mol %), Cs2CO3 (6.52 g,
20 mmol). The mixture of reaction was heated at 125 °C in an oil
bath for 12 h. The reaction mixture was cooled to ambient temper-
ature, concentrated in vacuo and purified by flash column chro-
matography with hexanes/ethyl acetate to afford the
corresponding product.
N-[[4-(1,1-dimethylethyl)phenyl]methyl]-1-naphthaleneme
thanamine (7) [93]: Yellow solid; 85% yield (5.40 g); mp 200–
201 °C; 1H NMR (500 MHz, CDCl3) d 7.88–7.84 (m, 3H), 7.82 (s,
1H), 7.60 (d, J = 8.4 Hz, 1H), 7.52–7.46 (m, 2H), 7.39 (dd, J = 19.5
and 8.3 Hz, 4H), 3.72 (s, 2H), 3.60 (s, 2H), 2.28 (s, 3H), 1.37 (s,
9H); 13C {1H} NMR (125 MHz, CDCl3) d 149.7, 137.0, 136.0, 133.3,
288

P. Liu, J. Yang, Y. Ai et al.
Journal of Catalysis 396 (2021) 281–290
[13] R. Liang, S. Li, R. Wang, L. Lu, F. Li, N-Methylation of Amines with Methanol
[40] H.S. Jena, C. Krishnaraj, G.B. Wang, K. Leus, J. Schmidt, N. Chaoui, P. Van der
Voort, Acetylacetone Covalent Triazine Framework: An Efficient Carbon
Capture and Storage Material and a Highly Stable Heterogeneous Catalyst,
Chem. Mater. 30 (2018) 4102–4111.
[41] S. Padmanaban, G.H. Gunasekar, M. Lee, S. Yoon, Recyclable Covalent Triazine
Framework-based Ru Catalyst for Transfer Hydrogenation of Carbonyl
Compounds in Water, ACS Sustain. Chem. Eng. 7 (2019) 8893–8899.
[42] G.H. Gunasekar, K. Jung, S. Yoon, Hydrogenation of CO2 to Formate using a
Simple, Recyclable, and Efficient Heterogeneous Catalyst, Inorg. Chem. 58
(2019) 3717–3723.
[43] G.H. Gunasekar, J. Shin, K. Jung, K. Park, S. Yoon, Design Strategy toward
Recyclable and Highly Efficient Heterogeneous Catalysts for the
Hydrogenation of CO2 to Formate, ACS Catal. 8 (2018) 4346–4353.
[44] G.H. Gunasekar, K. Park, V. Ganesan, K. Lee, N. Kim, K. Jung, S. Yoon, A Covalent
Triazine Framework, Functionalized with Ir/N-Heterocyclic Carbene Sites, for
the Efficient Hydrogenation of CO2 to Formate, Chem. Mater. 29 (2017) 6740–
6748.
Catalyzed by
Ligand, Org. Lett. 19 (2017) 5790–5793.
[14] D. Deng, B. Hu, M. Yang, D. Chen, Methylation of Amines and Ketones with
Methanol Catalyzed by an Iridium Complex Bearing 2-
a Cp*Ir Complex Bearing a Functional 2,2’-Bibenzimidazole
a
Hydroxypyridylmethylene Fragment, Organometallics 37 (2018) 3353–3359.
[15] G. Toyooka, A. Tuji, K. Fujita, Efficient and Versatile Catalytic Systems for the
N-Methylation of Primary Amines with Methanol Catalyzed by N-Heterocyclic
Carbene Complexes of Iridium, Synthesis 50 (2018) 4617–4626.
[16] T.T. Dang, B. Ramalingam, A.M. Seayad, Efficient Ruthenium-Catalyzed N-
Methylation of Amines Using Methanol, ACS Catal. 5 (2015) 4082–4088.
[17] O. Ogata, H. Nara, M. Fujiwhara, K. Matsumura, Y. Kayaki, N-Monomethylation
of Aromatic Amines with Methanol via PNHP-Pincer Ru Catalysts, Org. Lett. 20
(2018) 3866–3870.
[18] B. Paul, S. Shee, K. Chakrabarti, S. Kundu, Tandem Transformation of Nitro
Compounds into N-Methylated Amines: Greener Strategy for the Utilization of
Methanol as a Methylating Agent, ChemSusChem 10 (2017) 2370–2374.
[19] G. Choi, S.H. Hong, Selective N-Formylation and N-Methylation of Amines
Using Methanol as a Sustainable C1 Source, ACS Sustain. Chem. Eng. 7 (2019)
716–723.
[45] K. Park, G.H. Gunasekar, N. Prakash, K. Jung, S. Yoon,
A Highly Efficient
Heterogenized Iridium Complex for the Catalytic Hydrogenation of Carbon
Dioxide to Formate, ChemSusChem 8 (2015) 3410–3413.
[20] S. Elangovan, J. Neumann, J.B. Sortais, K. Junge, C. Darcel, M. Beller, Efficient
and Selective N-alkylation of Amines with Alcohols Catalysed by Manganese
Pincer Complexes, Nat. Commun. 7 (2016) 12641.
[21] J. Neumann, S. Elangovan, A. Spannenberg, K. Junge, M. Beller, Improved and
General Manganese-Catalyzed N-Methylation of Aromatic Amines Using
Methanol, Chem. Eur. J. 23 (2017) 5410–5413.
[22] M. Huang, Y. Li, Y. Li, J. Liu, S. Shu, Y. Liu, Z. Ke, Room Temperature N-
Heterocyclic Carbene Manganese Catalyzed Selective N-Alkylation of Anilines
with Alcohols, Chem. Commun. 55 (2019) 6213–6216.
[23] A. Lator, S. Gaillard, A. Poater, J. Renaud, Well-Defined Phosphine-Free Iron-
Catalyzed N-Ethylation and N-Methylation of Amines with Ethanol and
Methanol, Org. Lett. 20 (2018) 5985–5990.
[46] P. Sudakar, G.H. Gunasekar, I. Baek, S. Yoon, Recyclable and Efficient
Heterogenized Rh and Ir Catalysts for the Transfer Hydrogenation of
Carbonyl Compounds in Aqueous Medium, Green Chem. 18 (2016) 6456–
6461.
[47] A.V. Bavykina, A.I. Olivos-Suarez, D. Osadchii, R. Valecha, R. Franz, M. Makkee,
F. Kapteijn, J. Gascon, Facile Method for the Preparation of Covalent Triazine
Framework coated Monoliths as Catalyst Support: Applications in C1 Catalysis,
ACS Appl. Mater. Interfaces 9 (2017) 26060–26065.
[48] A.V. Bavykina, E. Rozhko, M.G. Goesten, T. Wezendonk, B. Seoane, F. Kapteijn,
M. Makkee, J. Gascon, Shaping Covalent Triazine Frameworks for the
Hydrogenation of Carbon Dioxide to Formic Acid, ChemCatChem 8 (2016)
2217–2221.
[24] K. Polidano, B.D.W. Allen, J.M.J. Williams, L.C. Morrill, Iron-Catalyzed
Methylation Using the Borrowing Hydrogen Approach, ACS Catal. 8 (2018)
6440–6445.
[25] Z. Liu, Z. Yang, X. Yu, H. Zhang, B. Yu, Y. Zhao, Z. Liu, Efficient Cobalt-Catalyzed
Methylation of Amines Using Methanol, Adv. Synth. Catal. 359 (2017) 4278–
4283.
[26] D. Wei, O. Sadek, V. Dorcet, T. Roisnel, C. Darcel, E. Gras, E. Clot, J. Sortais,
Selective Mono N-methylation of Anilines with Methanol Catalyzed by
Rhenium Complexes: An Experimental and Theoretical Study, J. Catal. 366
(2018) 300–309.
[49] E. Rozhko, A.V. Bavykina, D. Osadchii, M. Makkee, J. Gascon, Covalent Organic
Frameworks as Supports for a Molecular Ni Based Ethylene Oligomerization
Catalyst for the Synthesis of Long Chain Olefins, J. Catal. 345 (2017) 270–280.
[50] A.V. Bavykina, M.G. Goesten, F. Kapteijn, M. Makkee, J. Gascon, Efficient
Production of Hydrogen from Formic Acid Using
a Covalent Triazine
Framework Supported Molecular Catalyst, ChemSusChem 8 (2015) 809–812.
[51] F. Li, C. Sun, H. Shan, X. Zou, J. Xie, From Regioselective Condensation to
Regioselective N-Alkylation: A Novel and Environmentally Benign Strategy for
the Synthesis of N, N0-Alkyl Aryl Ureas and N, N0-Dialkyl Ureas, ChemCatChem
5 (2013) 1543–1552.
[27] R. Mamidala, P. Biswal, M.S. Subramani, S. Samser, K. Venkatasubbaiah,
Palladacycle-Phosphine Catalyzed Methylation of Amines and Ketones Using
Methanol, J. Org. Chem. 84 (2019) 10472–10480.
[52] F. Li, P. Qu, J. Ma, X. Zou, C. Sun, Tandem Synthesis of N-Alkylated Amides from
Aldoximes and Alcohols by Using a Ru/Ir Dual-Catalyst System, ChemCatChem
5 (2013) 2178–2182.
[28] J. Chen, J. Wu, T. Tu, Sustainable and Selective Monomethylation of Anilines by
Methanol with Solid Molecular NHC-Ir Catalysts, ACS Sustain. Chem. Eng. 5
(2017) 11744–11751.
[53] P. Qu, C. Sun, J. Ma, F. Li, The N-Alkylation of Sulfonamides with Alcohols in
Water Catalyzed by the Water-Soluble Iridium Complex {Cp*Ir[6,60-(OH)2bpy]
(H2O)}[OTf]2, Adv. Synth. Catal. 356 (2014) 447–459.
[29] M.A.R. Jamil, A.S. Touchy, M.N. Rashed, K.W. Ting, S.M. Siddiki, T. Toyao, Z.
Maeno, K. Shimizu, N-Methylation of Amines and Nitroarenes with Methanol
Using Heterogeneous Platinum Catalysts, J. Catal. 371 (2019) 47–56.
[30] P. Kuhn, M. Antonietti, A. Thomas, Porous, Covalent Triazine-Based
Frameworks Prepared by Ionothermal Synthesis, Angew. Chem. Int. Ed. 47
(2008) 3450–3453.
[54] F. Li, C. Sun, N. Wang, Catalytic Acceptorless Dehydrogenative Coupling of
Arylhydrazines and Alcohols for the Synthesis of Arylhydrazones, J. Org. Chem.
79 (2014) 8031–8039.
[55] F. Li, J. Ma, N. Wang, a-Alkylation of Ketones with Primary Alcohols Catalyzed
by a Cp*Ir Complex Bearing a Functional Bipyridonate Ligand, J. Org. Chem. 79
(2014) 10447–10455.
[31] M.J. Bojdys, J. Jeromenok, A. Thomas, M. Antonietti, Rational Extension of the
Family of Layered, Covalent, Triazine-Based Frameworks with Regular
Porosity, Adv. Mater. 22 (2010) 2202–2205.
[32] K. Schwinghammer, S. Hug, M.B. Mesch, J. Senker, B.V. Lotsch, Phenyl-Triazine
Oligomers for Light-Driven Hydrogen Evolution, Energy Environ. Sci. 8 (2015)
3345–3353.
[56] R. Wang, J. Ma, F. Li, Synthesis of a-Alkylated Ketones via Tandem Acceptorless
Dehydrogenation/a-Alkylation from Secondary and Primary Alcohols
Catalyzed by Metal-Ligand Bifunctional Iridium Complex [Cp*Ir(2,20-bpyO)
(H2O)], J. Org. Chem. 80 (2015) 10769–10776.
[57] L. Lu, J. Ma, P. Qu, F. Li, Effective Recognition of Different Types of Amino
Groups:
From
Aminobenzenesulfonamides
to
Amino-(N-alkyl)
[33] P. Kuhn, A. Forget, D.S. Su, A. Thomas, A. Antonietti, From Microporous Regular
Frameworks to Mesoporous Materials with Ultrahigh Surface Area: Dynamic
Reorganization of Porous Polymer Networks, J. Am. Chem. Soc. 130 (2008)
13333–13337.
[34] C.E. Chan-Thaw, A. Villa, P. Katekomol, D.S. Su, A. Thomas, L. Prati, Covalent
Triazine Framework as Catalytic Support for Liquid Phase Reaction, Nano Lett.
10 (2010) 537–541.
[35] K. Kamiya, R. Kamai, K. Hashimoto, S. Nakanishi, Platinum-modified Covalent
Triazine Frameworks Hybridized with Carbon Nanoparticles as Methanol-
tolerant Oxygen Reduction Electrocatalysts, Nat. Commun. 5 (2014) 5040.
[36] F. Chang, J.P. Guo, G.T. Wu, L. Liu, M. Zhang, T. He, P.K. Wang, P. Yu, P. Chen,
Covalent Triazine-based Framework as an Efficient Catalyst Support for
Ammonia Decomposition, Rsc Adv. 5 (2015) 3605–3610.
benzenesulfonamides via Iridium-Catalyzed N-Alkylation with Alcohols, Org.
Lett. 17 (2015) 2350–2353.
[58] R. Wang, H. Fan, W. Zhao, F. Li, Acceptorless Dehydrogenative Cyclization of o-
Aminobenzyl Alcohols with Ketones to Quinolines in Water Catalyzed by
Water-Soluble Metal-Ligand Bifunctional Catalyst [Cp*(6,60-(OH)2bpy)(H2O)]
[OTf]2, Org. Lett. 18 (2016) 3558–3561.
[59] W. Zhao, P. Liu, F. Li, Quinazolinones from o-Aminobenzonitriles by One-Pot
Sequential Selective Hydration/Condensation/Acceptorless Dehydrogenation
Catalyzed by an Iridium Complex, ChemCatChem 8 (2016) 1523–1530.
[60] P. Liu, R. Liang, L. Lu, Z. Yu, F. Li, Use of a Cyclometalated Iridium(III) Complex
Containing a N^C^N-Coordinating Terdentate Ligand as a Catalyst for the
a-
Alkylation of Ketones and N-Alkylation of Amines with Alcohols, J. Org. Chem.
82 (2017) 1943–1950.
[37] Z.F. Wang, C.B. Liu, Y. Huang, Y.C. Hu, B. Zhang, Covalent Triazine Framework-
[61] R. Wang, Y. Tang, M. Xu, C. Meng, F. Li, Transfer Hydrogenation of Aldehydes
and Ketones with Isopropanol under Neutral Conditions Catalyzed by a Metal-
Ligand Bifunctional Catalyst [Cp*Ir(2,20-bpyO)(H2O)], J. Org. Chem. 83 (2018)
2274–2281.
Supported Palladium as
a Ligand-free Catalyst for the Selective Double
Carbonylation of Aryl Iodides under Ambient Pressure of CO, Chem.
Commun. 52 (2016) 2960–2963.
[38] Z. Li, T. He, L. Liu, W.D. Chen, M. Zhang, G.T. Wu, P. Chen, Covalent Triazine
Framework Supported Non-Noble Metal Nanoparticles with Superior Activity
for Catalytic Hydrolysis of Ammonia Borane: From Mechanistic Study to
Catalyst Design, Chem. Sci. 8 (2017) 781–788.
[39] R. Xu, X.S. Wang, H. Zhao, H. Lin, Y.B. Huang, R. Cao, Rhenium-modified Porous
Covalent Triazine Framework for Highly Efficient Photocatalytic Carbon
Dioxide Reduction in a Solid-gas System, Catal. Sci. Technol. 8 (2018) 2224–
2230.
[62] C. Meng, P. Liu, N.T. Tung, X. Han, F. Li, N-Methylation of Amines with
Methanol in Aqueous Solution Catalyzed by a Water-Soluble Metal-Ligand
Bifunctional Dinuclear Iridium Catalyst, J. Org. Chem. 85 (2020) 5815–5824.
[63] C. Sun, X. Zou, F. Li, Direct Use of Methanol as an Alternative to Formaldehyde
for the Synthesis of 3,30-Bisindolylmethanes (3,30-BIMs), Chem. Eur. J. 19
(2013) 14030–14033.
[64] F. Li, L. Lu, J. Ma, Acceptorless Dehydrogenative Condensation of o-
Aminobenzamides with Aldehydes to Quinazolinones in Water Catalyzed by
289

P. Liu, J. Yang, Y. Ai et al.
Journal of Catalysis 396 (2021) 281–290
a Water-Soluble Iridium Complex [Cp*Ir(H2O)3][OTf]2, Org. Chem. Front. 2
(2015) 1589–1597.
[78] S.B. Herzon, J.F. Hartwig, Direct, Catalytic Hydroaminoalkylation of
Unactivated Olefins with N-Alkyl Arylamines, J. Am. Chem. Soc. 129 (2007)
6690–6691.
[79] J. Jiao, R.X. Zhang, H.N. Chang, J. Wang, J. Wei, Y.X. Shi, Z.G. Chen, A Facile and
Practical Copper Powder-Catalyzed, Organic Solvent- and Ligand-Free Ullmann
Amination of Aryl Halides, J. Org. Chem. 76 (2011) 1180–1183.
[80] J. Wang, J.T. Hou, J. Wen, J. Zhang, X.Q. Yu, Iron-catalyzed Direct Amination of
Azoles Using Formamides or Amines as Nitrogen Sources in Air, Chem.
Commun. 47 (2011) 3652–3654.
[65] F. Li, L. Lu, P. Liu, Acceptorless Dehydrogenative Coupling of o-
Aminobenzamides with the Activation of Methanol as a C1 Source for the
Construction of Quinazolinones, Org. Lett. 18 (2016) 2580–2583.
[66] M. Soorholtz, L.C. Jones, D. Samuelis, C. Weidenthaler, R.J. White, M. Titirici, D.
A. Cullen, T. Zimmermann, M. Antonietti, J. Maier, R. Palkovits, B.F. Chmelka, F.
Schüth, Local Platinum Environments in a Solid Analogue of the Molecular
Periana Catalyst, ACS Catal. 6 (2016) 2332–2340.
[67] B. Folkesson, ESCA Studies on the Charge Distribution in Some Dinitrogen
Complexes of Rhenium, Iridium, Ruhenium, and Osmium, Acta. Chem. Scand.
27 (1973) 287–302.
[81] D. Fajkusova, P. Pazdera, Unexpected Formation of Benzothiazoles in the
Synthesis of New Heterocycles: Benzo-1,2,4-dithiazines, Synthesis 8 (2008)
1297–1305.
[68] Similar cases also occurred in other transition metal-catalyzed the N-
methylation of aliphatic amines with methanol, see: Ref. 13, 16,18,19.
[69] Fujita, Yamaguichi and co-workers have proposed that base would stimulate
the formation of iridium alkoxide species by trapping hydrogen chloride, see:
(a) K. Fujita, S. Furukawa, R. Yamaguchi, Oxidation of Primary and Secondary
[82] A.D. Jordan, C. Luo, A.B. Reitz, Efficient Conversion of Substituted Aryl
Thioureas to 2-Aminobenzothiazoles Using Benzyltrimethylammonium
Tribromide, J. Org. Chem. 68 (2003) 8693–8696.
[83] S. Toulot, T. Heinrich, F.R. Leroux, Convenient and Reliable Routes Towards 2-
Aminothiazoles: Palladium-Catalyzed versus Copper-Catalyzed Aminations of
Halothiazoles, Adv. Synth. Catal. 355 (2013) 3263–3272.
Alcohols Catalyzed by
a Pentamethylcyclopentadienyliridium Complex, J.
Organomet. Chem. 649 (2002), 289–292. (b) K. Fujita, K. Yamamoto, R.
Yamaguchi, Oxidative Cyclization of Amino Alcohols Catalyzed by a Cp*Ir
Complex. Synthesis of Indoles, 1,2,3,4-Tetrahydroquinolines, and 2,3,4,5-
Tetrahydro-1-benzazepine, Org. Lett. 4 (2002), 2691–2694. (c) K. Fujita, T.
Fujii, R. Yamaguchi, Cp*Ir Complex-Catalyzed N-Heterocyclization of Primary
[84] H. Niu, L. Lu, R. Shi, C. Chiang, A. Lei, Catalyst-free N-Methylation of Amines
Using CO2, Chem. Commun. 53 (2017) 1148–1151.
[85] X.J. Cui, X.C. Dai, Y. Zhang, Y.Q. Deng, F. Shi, Methylation of Amines,
Nitrobenzenes and Aromatic Nitriles with Carbon Dioxide and Molecular
Hydrogen, Chem. Sci. 5 (2014) 649–655.
Amines with Diols:
Synthesis of Cyclic Amines, Org. Lett. 6 (2004), 3525–3528.
[70] E.M. Simmons, J.F. Hartwig, On the Interpretation of Deuterium Kinetic Isotope
Effects in C-H Bond Functionalizations by Transition-Metal Complexes, Angew.
Chem. Int. Ed. 51 (2012) 3066–3072.
A
New Catalytic System for Environmentally Benign
[86] D. Maclean, R. Hale, M. Chen, The Reversed Kenner Linker: A New Safety-Catch
Linker for the Preparation of N-Alkyl Sulfonamides, Org. Lett. 3 (2001) 2977–
2980.
[87] F.C. Xu, M. Xu, X.Y. Jia, Y.C. Li, Gold-Catalyzed Synthesis of Benzil Derivatives
and a-Keto Imides via Oxidation of Alkynes, Org. Lett. 13 (2011) 1556–1559.
[71] R.G. Ball, W.A.G. Graham, D.M. Heinekey, J.K. Hoyano, A.D. McMaster, B.M.
Mattson, S.T. Michel, Synthesis and Structure of Dicarbonylbis(.eta.-
pentamethylcyclopentadienyl)diiridium, Inorg. Chem. 29 (1990) 2023–2025.
[72] R. Ziessel, Efficient Homogeneous Photochemical Water Gas Shift Reaction
Catalysed under Extremely Mild Conditions by Novel Iridium(III) Complexes:
[88] H. Wang, S. Sun, J. Cheng, Copper-Catalyzed Arylsulfonylation and Cyclizative
Carbonation of N-(Arylsulfonyl)acrylamides Involving Desulfonative
Arrangement toward Sulfonated Oxindoles, Org. Lett. 19 (2017) 5844–5847.
[89] R.R. Singhaus, R.C. Bernotas, R. Steffan, E. Matelan, E. Quinet, P. Nambi, I.
Feingold, C. Huselton, A. Wilhelmsson, A. Goos-Nilsson, J. Wrobel, 3-(3-
Aryloxyaryl)imidazo[1,2-a]pyridine Sulfones as Liver X Receptor Agonists,
Bioorg. Med. Chem. Lett. 20 (2010) 521–525.
[90] M. Chen, X.X. Zhao, C. Yang, W.J. Xia, Further Insight into the Photochemical
Behavior of 3-Aryl-N-(arylsulfonyl)propiolamides: Tunable Synthetic Route to
Phenanthrenes, RSC Adv. 7 (2017) 12022–12026.
[(g
5-Me5C5)Ir(bpy)Cl]+, [(
g
5-Me5C5)Ir(bpy)H]+, and [(
g
5-Me5C5)Ir(phen)
Cl]+(bpy = 2,20-bipyridine; phen = 1,10-phenanthroline), J. Chem. Soc. Chem.
Commun. 16–17 (1988).
[73] S. Hug, M.E. Tauchert, S. Li, U.E. Pachmayr, B.V. Lotsch, A Functional Triazine
Framework Based on N-Heterocyclic Building Blocks, J. Mater. Chem. 22 (2012)
13956–13964.
[91] M. Chen, C. Yang, Y. Wang, D. Li, W. Xia, UV Light Induced Direct Synthesis of
[74] W.S. Youn, Y.H. Kim, Pd(II)/Ag(I)-Promoted One-Pot Synthesis of Cyclic Ureas
from (Hetero) Aromatic Amines and Isocyanates, Org. Lett. 18 (2016) 6140–
6143.
Phenanthrene
Propiolamides, Org. Lett. 18 (2016) 2280–2283.
[92] B. Hill, Y. Liu, S.D. Taylor, Synthesis of -Fluorosulfonamides by Electrophilic
Derivatives
from
a
Linear
3-Aryl-N-(arylsulfonyl)
a
[75] N. Sakai, M. Sasaki, Y. Ogiwara, Copper(II)-Catalyzed Oxidative N-Nitrosation
of Secondary and Tertiary Amines with Nitromethane under an Oxygen
Atmosphere, Chem. Commun. 51 (2015) 11638–11641.
[76] I. González, J. Mosquera, C. Guerrero, R. Rodríguez, J. Cruces, Selective
Monomethylation of Anilines by Cu(OAc)2-Promoted Cross-Coupling with
MeB(OH)2, Org. Lett. 11 (2009) 1677–1680.
[77] M. Rueping, C. Vila, A. Szadkowska, R.M. Koenigs, J. Fronert, Photoredox
Catalysis as an Efficient Tool for the Aerobic Oxidation of Amines and Alcohols:
Bioinspired Demethylations and Condensations, ACS Catal. 2 (2012) 2810–
2815.
Fluorination, Org. Lett. 6 (2004) 4285–4288.
[93] L. Wang, K. Jenkinson, A.E.H. Wheatley, K. Kuwata, S. Saito, H. Naka,
Photocatalytic N-Methylation of Amines over Pd/TiO2 for the
Functionalization of Heterocycles and Pharmaceutical Intermediates, ACS
Sustain. Chem. Eng. 6 (2018) 15419–15424.
[94] H. Yang, L. Zhang, L. Jiao, N-Methylanilines as Simple and Efficient Promoters
for Radical-Type Cross-Coupling Reactions of Aryl Iodides, Chem. Eur. J. 23
(2017) 65–69.
290