A polymer supported Cu(II) catalyst for oxidative amidation of benzyl alcohol and substituted amines in TBHP/H2O

Article abstract of DOI:10.1016/j.catcom.2017.10.023

A new polymer supported copper complex of 2,6-bis(benzimidazolyl)pyridine Cu(PS-BBP)Cl₂ was prepared and characterized by elemental analyses, AAS, ESR, IR and UV–Vis spectral studies, magnetic moment measurement and thermogravimetric analyses. A facile oxidative coupling of alcohols and amines to synthesize amides was developed using Cu(PS-BBP)Cl₂ as a catalyst and tert-butyl hydroperoxide (TBHP) as an oxidant using water as a solvent in a one-pot process. The optimum conditions were determined for the reaction of benzyl alcohol and benzylamine by varying solvents, temperature, substrate to TBHP ratio and catalyst concentration and the yield resulted was found to be 95%. The catalyst showed excellent catalytic activity and reusability. A tentative reaction mechanism has been proposed.

Full text of DOI:10.1016/j.catcom.2017.10.023

Accepted Manuscript
A polymer supported Cu(II) catalyst for oxidative amidation of
benzyl alcohol and substituted amines in TBHP/H2O
M.K. Renuka, V. Gayathri
PII:
S1566-7367(17)30442-9
doi:10.1016/j.catcom.2017.10.023
CATCOM 5234
DOI:
Reference:
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
5 August 2017
23 October 2017
25 October 2017
Please cite this article as: M.K. Renuka, V. Gayathri , A polymer supported Cu(II) catalyst
for oxidative amidation of benzyl alcohol and substituted amines in TBHP/H2O. The
address for the corresponding author was captured as affiliation for all authors. Please
check if appropriate. Catcom(2017), doi:10.1016/j.catcom.2017.10.023
This is a PDF file of an unedited manuscript that has been accepted for publication. As
a service to our customers we are providing this early version of the manuscript. The
manuscript will undergo copyediting, typesetting, and review of the resulting proof before
it is published in its final form. Please note that during the production process errors may
be discovered which could affect the content, and all legal disclaimers that apply to the
journal pertain.

ACCEPTED MANUSCRIPT
A Polymer supported Cu(II) catalyst for oxidative amidation of benzyl alcohol and
substituted amines in TBHP/H2O
Renuka M K and Gayathri V*
Department of Chemistry, Central College Campus, Bangalore University, Bangalore-
5
60001, Karnataka, India.
*
Corresponding author e-mail: gayathritvr@yahoo.co.in, Phone: 080-22961348
1

ACCEPTED MANUSCRIPT
Abstract: A new polymer supported copper complex of 2,6-bis(benzimidazolyl)pyridine
Cu(PS-BBP)Cl2 was prepared and characterized by elemental analyses, AAS, ESR, IR and
UV-Vis spectral studies, magnetic moment measurement and thermogravimetric analyses. A
facile oxidative coupling of alcohols and amines to synthesize amides was developed using
Cu(PS-BBP)Cl2 as a catalyst and tert-butyl hydroperoxide (TBHP) as an oxidant using water
as a solvent in a one-pot process. The optimum conditions were determined for the reaction
of benzyl alcohol and benzylamine by varying solvents, temperature, substrate to TBHP ratio
and catalyst concentration and the yield resulted was found to be 95%. The catalyst showed
excellent catalytic activity and reusability. A tentative reaction mechanism has been
proposed.
Keywords: Oxidative amidation; Benzyl alcohol; Hemiaminal; Polymer supported Cu(II)
complex; Substituted amines.
2

ACCEPTED MANUSCRIPT
1
. Introduction
The amide bond is an important linkage in natural products, synthetic polymers and
pharmaceutical compounds, and amides are important class of compounds that are used as
starting materials for engineering plastics, detergents and lubricants. In organic synthesis,
primary amides are potent substrates for primary amines, nitriles, amino acid derivatives and
heterocycle preparation. In nature, primary amides are present in numerous biologically
active molecules [1-11]. The synthetic methods for amides can be achieved through the
amidation of activated carboxylic acids, such as acid chlorides, esters and anhydrides [12-17].
Zinc salts catalyzed oxidative amidation of benzyl alcohols with aliphatic/aromatic amines
using TBHP as oxidant under solvent free conditions have also been investigated [18]. ZnBr2
catalyzed the oxidation of N-methylbenzylamine to benzamides in the presence of pyridine
and TBHP, wherein pyridine stabilized the active species [19]. Ruthenium(II)diamine
II
6
complex catalyzed the intramolecular cyclization of amino alcohols [20]. Ru (η -arene)
complex with 1,2,3-triazolylidene ligands catalysed the reactions of primary alcohols and
amines to imines and amides [21]. Ru and Pt metal complexes catalyzed amidation of nitriles
[22,23], [Rh(1,5-cyclooctadiene)2]BF4 catalyzed oxidative amination of aldehydes to give
various aliphatic and aromatic amides [24]. RhCl(PPh3)3, [Ir(Cp*)Cl2)]2, tributyltin hydride,
Pd/C, [PdCl2(PMePh2)2] and [Pd2(dibenzylideneacetone)3] catalyzed conversion of
aldoximes, alkynes and haloarenes to amides by utilising amines [26-30].
Several methods have been reported for the oxidative amidation using alcohols and
amines as the starting materials [31-35]. Ruthenium complex based on 2-(di-tert-
butylphosphinomethyl)-6-(diethylaminomethyl)pyridine
without acid or base promoters [36]. In situ generated complex from [Ru(p-cymene)Cl2]2 or
Ru(benzene)Cl2]2 with N-heterocyclic carbene and acetonitrile catalysed amide synthesis
ligand
catalysed
these
reactions
[
from alcohols and amines in high yields [37]. Ru complex with 1,3-diisopropylimidazol-2-
ylidene in the presence of potassium tert-butoxide and tricycloalkylphosphine catalysed
amidation from alcohols and amines [38]. These homogeneous catalytic systems have some
disadvantages, such as they can be easily destroyed during the course of the reaction and
cannot be recycled. Some heterogeneously metal catalyzed primary amide syntheses from
primary alcohol have also been reported [39-42]. Polymer-supported palladium-N-
heterocyclic carbene complex has been used as an efficient heterogeneous recyclable catalyst
for coupling between aryl halides with alkyl/aryl isocyanides to give corresponding amides
3

ACCEPTED MANUSCRIPT
[43].
A
polymer-supported terpyridine-palladium(II) complex has been used for
azidocarbonylation of aryl iodides with NaN3 to yield primary aryl amides [44].
Heterogeneous Au and Au/Fe, Au/Ni or Au/Co catalysed oxidative amidation using
molecular oxygen [45].
Since there are very few reports available for the oxidative amidation using polymer
supported copper complex, an intriguing method of oxidative amidation was developed in the
present work for promoting coupling of amines and benzyl alcohol in TBHP and water. This
reaction proceeds in a clean economical manner without any acid, base or additives, and
generates water and t-butanol as by-products. The use of water as solvent features many
benefits such as improving reactivities and selectivities, simplifies the workup procedure and
also environmental concerns. With increasing regulatory pressure focusing on organic
solvents, the developments of nonhazardous alternatives are of great importance.
2
. Experimental
2
.1. Materials and methods
Chloromethylated polystyrene divinyl benzene (PS) was obtained as a gift from
THERMAX Ltd. India. The CuCl2.2H2O, o-phenylenediamine, 2,6-pyridinedicarboxylic
acid, TBHP (70%), benzene, ethylbenzene and cyclohexane were purchased from Merck and
used without further purification. Solvents were used after purification by standard methods.
Elemental analyses were carried out with an Elementar Vario Micro Cube CHNS analyser.
Diffuse reflectance UV-vis spectra were recorded as BaSO4 disks on a Shimadzu UV-Vis-
NIR model-3101P spectrophotometer. FT-IR spectra of solid compounds were taken using a
−1
Shimadzu 8,400 s FTIR spectrometer in the range of 4000-400 cm using KBr disks.
Thermogravimetric analyses was carried out with a TA instrument, SDT analyser model
Q600. ESR measurements were carried out in the solid state at room temperature in a
standard X band JES - FA200 spectrometer. The percentage of Cu in the supported complex
was determined by using AAS, Avanta Pm, GF 3000. NMR spectra were recorded in CDCl3
1
13
by using Bruker Avance spectrometer ( H NMR at 500 MHz; C NMR at 125 MHz).
Tetramethysilane was used as reference, and the chemical shifts were reported in ppm. Spin
multiplicities are described as s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet), dd
(doublet of doublet) and br s (broad singlet).
4

ACCEPTED MANUSCRIPT
2
.2. Preparation of polymer supported complex Cu(PS-BBP)Cl2 (Scheme 1)
2
,6-bis(benzimidazolyl)pyridine (BBP) and functionalized polymer were prepared
according to the literature methods [46, 47]. To the 1.0 g of functionalized polymer (PS-
BBP), 10 mL of ethanol was added and kept for 1 h. To it, CuCl .2H O (1 mmol; 0.17 g) in
2
2
1
0 mL of ethanol was added and stirred at 70 ºC for 48 h. The resulting green colored
polymer supported complex was filtered, Soxhlet extracted with ethanol and dried for 24 h at
1
00 ºC.
Scheme 1. Preparation of the polymer anchored Cu(II) complex, Cu(PS-BBP)Cl2.
3
3
3
. Results and discussion
.1. Characterization of Cu(PS-BBP)Cl2
.1.1. CHN analyses and AAS
Polymer supported complex Cu(PS-BBP)Cl2 was synthesized by reacting PS-BBP
with CuCl2.2H2O. The C, H and N% in Cu(PS-BBP)Cl2 were found to be 86.8, 9.1 and
4
3
.1%, respectively. The Cu in Cu(PS-BBP)Cl2 was determined by AAS and was found to be
.3%.
3
.1.2. FT-IR and Electronic spectral studies
5

ACCEPTED MANUSCRIPT
-
1
-1
PS-BBP exhibited peaks due to ν(N-H) around 3190 cm and the peak at 1623 cm is
assigned to ν(C=N) of benzimidazole/pyridine moieties in addition to polymer peaks. The IR
spectrum of Cu(PS-BBP)Cl2 displayed peaks due to ν(C=N) and ν(N-H) at 1612 and 3190
-
1
cm , respectively. The shift of ν(C=N) peak in the supported complex as compared to PS-
BBP indicated the coordination of copper through N of C=N moieties of pyridine and
benzimidazole.
Electronic spectra of PS, BBP, PS-BBP and Cu(PS-BBP)Cl2 complex are depicted in
Fig. S1. The peaks in the range 200-334 nm are observed in free ligand as well as in the
complex, and PS-BBP have been assigned to intraligand n → π* and π → π* transitions of
benzimidazole groups. The electronic spectrum of the Cu(PS-BBP)Cl2 complex showed two
2
2
2
2
characteristic bands at 412 and 765 nm assigned to the dxz, dyz → dx -y ( B1g → Eg) and
2
2
2
2
2
dxy → dx -y ( B1g → B2g) transitions, respectively. Because of the low intensity of dz →
2
2
2
2
dx -y ( B1g → A1g) transition, this band is usually not observed as a separate band in the
distorted square pyramidal complex.
3
.1.3. TGA studies
º
Thermograms of Cu(PS-BBP)Cl2 and PS were obtained at the heating rate of 10 C
-
1
º
min under nitrogen atmosphere up to 550 C. PS showed decomposition of 34% due to loss
º
º
of chloride in the range of 279-410 C and loss of polymer occurred above 410 C. The
thermal decomposition of Cu(PS-BBP)Cl2 occured in three steps; first step involved the
º
removal of two chlorides with weight loss of ~ 3.7% in the temperature range of 180-195 C,
º
while the second decomposition step occurred in the range 195-386 C accompanied with a
weight loss of ~ 20.1%, and which could be ascribed to the decomposition of BBP ligand.
º
The polymer decomposed above 386 C (Fig. 1).
6

ACCEPTED MANUSCRIPT
o
1
80 C
o
a)
b)
2
79 C
~
3.7% weight loss
o
9
8
7
6
5
4
3
0
0
0
0
0
0
0
1
95 C
~
34.0% weight loss
~ 20.1% weight loss
o
4
10 C
o
3
86 C
~
41.0% weight loss
o
4
95 C
1
00
200
300
400
500
o
Temperature ( C)
Fig. 1. Thermograms of a) PS and b) Cu(PS-BBP)Cl2.
.1.4. EPR and magnetic moment measurements
The EPR spectrum of Cu(PS-BBP)Cl2 recorded in polycrystalline state at room
3
temperature revealed the coordination environment around copper(II). The EPR spectrum of
Cu(PS-BBP)Cl2 displayed three g values at 2.49, 2.30 and 2.07 due to g1, g2 and g3,
respectively (Fig. 2). The value of g1 > g2 > g3 > 2.0023 and the ratio of g2-g1/g3-g2 = R was
found to be 0.82. The values of R < 1 for the complex suggest a distorted square pyramidal
2
2
geometry around Cu with dx -y as the ground state. Room temperature magnetic moment of
Cu(PS-BBP)Cl2 was measured using a vibrating sample magnetometer (VSM). It exhibited a
value of 1.74 BM, which is very consistent with the expected spin-only magnetic moment S =
9
½
, d copper (II) system.
7

ACCEPTED MANUSCRIPT
5
00
0
2.30
2
.49
-500
2
.07
-
1000
1500
-
3
00
400
Magnetic field (mT)
Fig. 2. X band EPR spectrum of Cu(PS-BBP)Cl2 at room temperature.
Based on the above results, square pyramidal geometry was suggested for polymer anchored
Cu(II) complex.
3
3
.2. Catalytic activity measurements
.2.1 General procedure for the preparation of amides
The reaction was carried out using 1 mmol benzyl alcohol, 1.2 mmol benzyl amine
and 40 mg Cu(PS-BBP)Cl2 (0.0210 mmol of Cu) in the presence of TBHP (2 mmol) in 2 mL
of water at 80 ºC for 10 h (Scheme 2). The reaction was monitored by TLC. The product was
extracted with ethyl acetate and purified by column chromatography. The oxidative
amidation of benzyl alcohol with benzyl amine was chosen as a model reaction to optimize
the reaction conditions (Scheme 2).
Scheme 2. Oxidative amidation of benzyl alcohol and benzylamine.
8

ACCEPTED MANUSCRIPT
To find out the optimum reaction conditions, the reaction was carried out by varying the
temperature, solvents, substrate to oxidant ratio and the catalyst concentration (Table 1). The
amidation reaction was carried out by varying the reaction temperature from 60 to 90 ºC with
4
0 mg (0.0210 mmol) of Cu(PS-BBP)Cl2 catalyst in 2 mL water for 10 h. The product yield
increased with rise in temperature up to 80 ºC (78% at 60 ºC, 82% at 70 ºC and at 80 ºC,
5%) but after a further increase to 90 ºC the yield of amide decreased to 79%. This might be
9
due to the enhanced decomposition of TBHP at higher temperature. In acetonitrile (85%),
tetrahydrofuran (60%), ethyl alcohol (89%) and 1:1 mixture of water and ethyl alcohol
(92%), the conversion was lower than that in water (95%). Water being a highly polar
molecule renders benzyl alcohol, amine and oxidant (70 % TBHP in water) soluble to give
homogeneous clear solution, except polymer supported catalyst. This facilitates the insertion
of TBHP into polymer supported Cu(II) complex.
The effect of oxidant concentration on reaction was monitored using three different
amounts of aqueous 70% TBHP viz. 1, 2 and 3 mmol for a fixed amount of reactants (1 mmol
of benzyl alcohol and 1.2 mmol of benzyl amine) and Cu(PS-BBP)Cl2 (0.0210 mmol) in 10
mL H2O at 80 ºC. When the molar ratio of reactant to oxidant was 1:1, product yield was
4
8%. Reactions at 1:2 and 1:3 molar ratio gave same % of product (95%). These results
suggest that 1:2 molar ratio of reactants to TBHP is ideal for the maximum yield. The
reaction was carried out by varying four different amounts viz. 0.0104, 0.5157, 0.0210 and
0
0
.0262 mmol of Cu(PS-BBP)Cl2 at 80 °C using 1:2 molar ratio of substrate to TBHP. As
.0210 mmol of catalyst gave maximum yield, this concentration was considered sufficient to
carry out the reaction.
Table 1. Optimization of the reaction conditions.
Entry
Temperature
ºC)
Solvent
Substate:TBHP
Catalyst
concentration
mmol X 10 )
Yield
(%)
(
-
2
(
1
2
3
4
5
6
7
8
9
60
70
80
90
80
80
80
80
80
H2O
H2O
H2O
H2O
CH3CN
THF
1:2
1:2
1:2
1:2
1:2
1:2
1:2
1:2
1:2
2.10
2.10
2.10
2.10
2.10
2.10
2.10
2.10
1.04
78
82
95
89
75
80
92
89
43
H2O + C2H5OH(1:1)
C2H5OH
H2O
9

ACCEPTED MANUSCRIPT
1
1
1
1
0
1
2
3
80
80
80
80
H2O
H2O
H2O
H2O
1:2
1:2
1:1
1:3
1.57
2.62
2.10
2.10
73
90
48
95
Thus, it was observed that with 1:2 molar ratio of substrate to TBHP, 0.0210 mmol Cu(PS-
BBP)Cl2, 2 mL water at 80 ºC in 10 h was the optimal reaction condition to afford the desired
amide in good yield. When the blank reaction was carried out in the presence of reactants and
TBHP without catalyst, even after 10 h, the yield was 10%. No amide formation was found in
the absence of TBHP. Thus, it was concluded that Cu(PS-BBP)Cl2 and TBHP were essential
to obtain the desired amide product. By using this optimum reaction conditions, the reaction
was carried out for different amines. It was found that the electron donating groups (Table 2,
entries 1 and 10) on the aromatic ring substituted amines reacted more efficiently with benzyl
alcohol than those with electron withdrawing groups (Table 2, entries 5-7 and 12). Secondary
amines are poor substrates in this reaction, showing lower yield (Table 2, entry 2). The
oxidative amidation was also conducted using aliphatic alcohols, such as pentanol, and
cyclohexylmethanol, with the yield of benzylamineto be 68 and 72 %, respectively (Table 2,
entry 13 and 14). Progress of the reactions was monitored by thin layer chromatography
(TLC). Products were isolated by extracting the reaction mixture in ethyl acetate and purified
1
13
by column chromatography and subjected to H and C NMR spectral analyses.
Table 2. Oxidative amidation of benzyl alcohol (1-12) with primary and secondary amines.
a
No.
1
Amines
Products
% Yield
86
1
0

ACCEPTED MANUSCRIPT
2
87
3
4
80
95
5
6
73
70
7
76
8
9
92
82
1
1

ACCEPTED MANUSCRIPT
1
0
87
92
1
1
1
2
78
68
b
1
3
4
c
1
72
Reaction conditions: Benzyl alcohol (1 mmol), amine (1.2 mmol), Cu(PS-BBP)Cl2 (0.0210
a
mmol), TBHP (2 mmol) in Water (2 mL) at 80 ºC in 10 h . Isolated yield.
b: Pentanol (1 mmol), benzylamine (1.2 mmol).
c: Cyclohexylmethanol (1 mmol), benzylamine (1.2 mmol).
3
.3. Reaction mechanism
The non-free radical nature of this reaction was confirmed by the addition of a free
radical inhibitor 2,6-di-t-butyl-4-methylphenol (BHT, 1 equiv) to the reaction mixture
wherein amide formation was not inhibited. A tentative mechanism for the oxidative
amidation by the coupling of an alcohol with an aromatic amine is expected to proceed via
oxidation of the alcohol to an aldehyde and formation of an intermediate hemiaminal. Further
oxidation of the hemiaminal would lead to the amide, with elimination of water and t-butanol
(Scheme 3).
1
2

ACCEPTED MANUSCRIPT
Scheme 3. A tentative mechanism for oxidative amidation.
1
13
3
.4. H and C-NMR spectral data of amides
1
. N-p-Tolylbenzamide
1
H NMR (500 MHz, CDCl3): δ 2.39 (s, 3H), 6.39 (br s, 1H), 7.21-7.29 (d, 2H), 7.30-7.36 (m,
1
3
5
1
H), 7.69 (d, 2H). C NMR (125 MHz): δ 21.49, 127.10, 127.50, 127.88, 128.74, 129.23,
31.58, 138.50, 141.93, 167.47.
2
. Phenyl(piperidin-1-yl)methanone
1
3

ACCEPTED MANUSCRIPT
1
H NMR (500 MHz, CDCl3): δ 1.48-1.63 (br s, 6H), 3.30 (br s, 2H), ), 3.67 (br s, 2H), 7.35
1
3
(
s, 5H). C NMR (125 MHz): δ 24.55, 25.59, 26.50, 43.06, 48.70, 126.73, 128.35, 129.29,
1
36.49, 170.24.
3
. N-Phenylbenzamide
1
13
H NMR (500 MHz, CDCl3): δ 6.50 (br s, 1H), 7.42-7.52 (m, 5H), 7.79-7.85 (m, 5H).
C
NMR (125 MHz): δ 127.10, 127.50, 127.88, 128.74, 129.23, 131.58, 138.50, 141.93, 167.47.
4
. N-Benzylbenzamide
1
H NMR (500 MHz, CDCl ): δ 4.64-4.65 (d, 2H), 6.44 (br s, 1H), 7.26-7.32 (m, 5H), 7.35-
3
1
3
7
1
.36 (t, 2H), 7.41-7.51 (t, 1H), 7.79 (d, 2H). C NMR (125 MHz): δ 44.24, 114.57, 125.02,
25.22, 135.50, 135.76, 147.13, 147.15, 149.21, 165.06.
5
. N-(4-Nitrophenyl)benzamide
1
H NMR (500 MHz, CDCl3): δ 6.45 (br s, 1H), 7.34 (m, 5H), 7.54-7.56 (m, 2H), 7.64-7.66
1
3
(
m, 2H). C NMR (125 MHz): δ 126.77, 126.91, 127.97, 128.49, 131.42, 134.38, 135.46,
1
48.31, 167.26.
6
. N-(2,4-Dichlorobenzyl)benzamide
1
H NMR (500 MHz, CDCl3): δ 4.68 (d, 2H), 6.64 (br s 1H), 7.23 (dd, 1H), 7.45-7.40 (m, 4H),
1
3
7
1
.51 (t, 1H), 7.77 (d, 2H). C NMR (125 MHz): δ 41.32, 126.94, 127.24, 128.52, 129.23,
30.76, 131.64, 133.86, 133.91, 134.06, 134.23, 167.51.
7
. N-(4-chlorobenzyl)benzamide
1
H NMR (500 MHz, CDCl3): δ 4.60-4.62 (dd, 2H), 6.50 (br s, 1H), 7.26-7.32 (m, 4H), 7.41-
1
3
7
1
.45 (t, 2H), 7.49-7.52 (t, 1H), 7.78-7.79 (d, 2H). C NMR (125 MHz): δ 44.24, 125.02,
25.23, 135.50, 135.76, 147.14, 149.21, 149.50, 151.18, 169.06.
8
. N-(Cyclohexylmethyl)benzamide
1
H NMR (500 MHz, CDCl3): δ 0.97-1.04 (q, 2H), 1.14-1.29 (m, 3H), 1.55-1.63 (m, 1H),
.65-14.69 (m, 2H), 1.73-1.80 (m, 4H), 3.31 (t, 2H), 6.19 (br s, 1H), 7.43 (t, 2H), 7.49 (t, 1H),
1
1
4

ACCEPTED MANUSCRIPT
1
3
7
1
.75-7.77 (d, 2H). C NMR (125 MHz): δ 28.93, 29.81, 31.32, 32.15, 47.00, 125.75, 128.23,
29.55, 135.62, 175.31.
9
. N-(Pyridin-2-yl)benzamide
1
H NMR (500 MHz, CDCl3): δ 6.45 (br s, 1H), 7.34-7.56 (m, 5H), 7.64 (m, 2H), 7.66 (m,
1
3
2
1
H). C NMR (125 MHz): δ 114.53, 114.57, 125.02, 125.22, 135.50, 135.76, 147.13,
49.21, 149.50, 167.06.
1
0. N-(5-methylpyridin-2-yl)benzamide
1
H NMR (CDCl , 500 MHz): δ 2.33 (s, 3H), 7.12-7.17 (m, 3H), 7.52 (br s, 1H), 7.59-7.61 (d,
3
1
3
1
1
H), 7.67-7.69 (m, 2H), 8.38-8.43 (m, 1H). C NMR (125 MHz): δ 19.36, 117.92, 120.08,
21.00, 123.90, 124.86, 125.75, 125.91, 131.28, 131.90, 165.86.
1
1. N-Butylbenzamide
1
H NMR (500 MHz, CDCl3): δ 0.94-0.97 (t, 3H), 1.37-1.45 (m, 2H), 1.57-1.63 (m, 2H), 3.43-
1
3
3
.47 (m, 2H), 6.23 (br s, 1H), 7.27-7.43 (m, 2H), 7.47-7.50 (m, 1H), 7.75-7.77 (m, 2H).
C
NMR (125 MHz): δ 13.67, 20.06, 31.63, 39.72, 126.80, 128.36, 131.11, 134.80, 167.53.
1
2. N-(5-Chloropyridin-2-yl)benzamide
1
H NMR (500 MHz, CDCl3): δ 6.50-6.51 (m, 1H), 6.64 (br s, 1H), 7.15 (m, 1H), 7.16 (d,
1
3
1
1
H), 7.26-7.36 (m, 4H), 7.42 (d, 1H). C NMR (125 MHz): δ 126.94, 128.43, 128.79,
29.40, 129.93, 131.45, 133.44, 134.11, 135.53, 167.43.
1
3. N-benzylpentanamide
1
H NMR (500 MHz, CDCl3): δ 0.91 (t, 3H), 1.62 (m, 2H), 1.34 (m, 2H), 2.20 (t, 2H), δ 4.41
1
3
(
d, 2H), 5.97 (br s, 1H), 7.22-7.36 (m, 5H). C NMR (125 MHz): δ 13.73, 19.11, 35.50,
3
8.57, 43.45, 127.38, 127.72, 128.60, 138.35, 172.90.
4. N-benzylcyclohexanecarboxamide
1
1
5

ACCEPTED MANUSCRIPT
1
H NMR (500 MHz, CDCl
m, 6H), 3.29-3.31 (m, 2H), 6.19 (br s, 1H), 7.41-7.50 (m, 3H), 7.76 (m, 2H). C NMR (125
MHz): δ 25.76, 26.33, 30.85, 37.97, 46.16, 126.80, 128.43, 131.19, 134.86, 167.55.
3
): δ 0.96-1.03 (m, 2H), 1.13-1.29 (m, 2H), 1.54 (m, 1H), 1.59-1.80
1
3
(
3
.5. Recycling ability
The recycling ability of the catalyst was also examined for the probe reaction under
optimized reaction conditions. After the reaction, catalyst was filtered and dried in vacuum
and reused for the oxidative amidation reaction. The %-yield remained almost constant up to
three runs and slightly decreased for the fourth cycle. The recycled catalyst was subjected to
AAS and the results indicated that metal complex was not leached out from the support (Fig.
S2).
4
. Conclusions
A Cu(PS-BBP)Cl2 catalyst was synthesized and characterized and its activity was
investigated towards oxidative amidation of benzyl alcohols with aromatic amine surrogates
using TBHP in water. Both secondary and tertiary benzamides can be prepared without using
any noxious reagents. The electronic effects of the substituent can also perturb the amidation
reaction. The tolerance of the reaction to water creates the potential for the conversion of
biomolecules. A plausible reaction mechanism for the oxidative amidation reaction was
suggested. The catalyst showed excellent activity and recycled up to three runs.
Acknowledgments
Authors are thankful to Bangalore University for providing research facilities. Renuka M K
thank UGC for awarding junior research fellowship. Thermax Ltd., India is gratefully
acknowledged for providing polymer beads.
References
[1] J.M. Humphrey, A.R. Chamberlin, Chem. Rev. 97 (1997) 2243-2266.
[2] C.E. Mabermann, in Encyclopedia of Chemical Technology, ed. J.I. Kroschwitz, Wiley,
New York, 1 (1991) 251–266.
1
6

ACCEPTED MANUSCRIPT
[3] R. Opsahl, in Encyclopedia of Chemical Technology, ed. J.I. Kroschwitz, Wiley, New
York, 2 (1991) 346–356.
[
4] N. Ibrahim, M. Legraverend, J. Org. Chem. 74 (2009) 463-465.
5] C.M.R. Volla, P. Vogel, Org. Lett. 11 (2009) 1701-1704.
6] Y. Pan, F. Zheng, H. Lin, Z. Zhan, J. Org. Chem. 74 (2009) 3148-3151.
7] C. Yang, C.U. Pittman, Synth. Commun., 28 (1998) 2027-2041.
8] J.J. Eisch, J.N. Gitua, Organometallics. 22 (2003) 24-26.
[
[
[
[
[9] J.A. Campbell, G. McDougald, H. McNab, L.V C. Rees, R.G. Tyas, Synthesis. 20
(2007) 3179-3184.
[
10] K. Manjula, M.A. Pasha, Synth. Commun., 37 (2007) 1545-1550.
11] S. Budavari, The Merck Index, Merck, Rahway, USA, 11th edn, 1989.
12] J.K. Park, W.K. Shin, D.K. An, Bull. Korean Chem. Soc. 34 (2013) 1592-1594.
13] B. Gnanaprakasam, D. Milstein, J. Am. Chem. Soc. 133 (2011) 1682-1685.
14] R. Arora, S. Paul, R. Gupta, Can. J. Chem. 83 (2005) 1137-1140.
[
[
[
[
[15] C. Han, J.P. Lee, E. Lobkovsky, J.A. Porco, J. Am. Chem. Soc. 127 (2005) 10039-
1
0044.
[16] H. Morimoto, R. Fujiwara, Y. Shimizu, K. Morisaki, T. Ohshima, Org. Lett. 16 (2014)
2
018-2021.
[17] Y. Li, L. Ma, F. Jia, Z. Li, J. Org. Chem. 78 (2013) 5638-5646.
[18] X.F. Wu, M. Sharif, A.P. Davtyan, P. Langer, K. Ayub, M. Beller, Eur. J. Org. Chem.
(2013) 2783-2787.
[19] X.F. Wu, C.B. Bheeter, H. Neumann, P.H. Dixneuf, M. Beller, Chem. Commun. 48
(2012) 12237-12239.
[20] A. Nova, D. Balcells, N.D. Schley, G.E. Dobereiner, R.H. Crabtree, O. Eisenstein,
Organometallics. 29 (2010) 6548-6558.
1
7

ACCEPTED MANUSCRIPT
[21] A. Prades, E. Peris, M. Albrecht, Organometallics. 30 (2011) 1162-1167.
[22] S.I. Murahashi, T. Naota, E. Saito, J. Am. Chem. Soc. 108 (1986) 7846-9847.
[23] C.J. Cobley, M. van den Heuvel, A. Abbadi, J.G. de Vries, Tetrahedron Lett. 41 (2000)
2
467-2470.
[
24] A. Tillack, I. Rudloff, M. Beller, Eur. J. Org. Chem. (2001) 523-528.
25] S. Park, Y. Choi, H. Han, S.H. Yang, S. Chang, Chem. Commun. (2003) 1936-1937.
26] N.A. Owston, A.J. Parker, J.M.J. Williams, Org. Lett. 9 (2007) 73-75.
[
[
[27] Y. Uenoyama, T. Fukuyama, O. Nobuta, H. Matsubara, I. Ryu, Angew. Chem. Int. Ed.
4
4 (2005) 1075-1078.
[
28] Y.S. Lin, H. Alper, Angew. Chem. Int. Ed. 40 (2001) 779-781.
29] Y. Uozumi, T. Arii, T. Watanabe, J. Org. Chem. 66 (2001) 5272-5274.
30] P. Nanayakkara, H. Alper, Chem. Commun. (2003) 2384-2385.
31] L.U. Nordstrom, H. Vogt, R. Madsen, J. Am. Chem. Soc. 130 (2008) 17672-17673.
32] X. Liu, K.F. Jensen, Green Chem. 15 (2013) 1538-1541.
33] C. Chen, Y. Zhang, S. H. Hong, J. Org. Chem. 76 (2011) 10005-10010.
[
[
[
[
[
[34] A.J.A. Watson, R.J. Wakeham, A.C. Maxwell, J.M.J. Williams, Tetrahedron. 70, (2014)
3
683-3690.
[35] A.J.A. Watson, A.C. Maxwell, J.M.J. Williams, Org. Lett. 11 (2009) 2667-2670.
[36] C. Gunanathan, Y. Ben-David, D. Milstein, Science. 317 (2007) 790-792.
[37] S.C. Ghosh, S. Muthaiah, Y. Zhang, X. Xu, S.H. Hong, Adv. Synth. Catal. 351,
(2009) 2643-2649.
[38] J.H. Dam, G. Osztrovszky, L.U. Nordstrøm, R. Madsen, Chem. Eur. J. 16 (2010) 6820-
1
627.
[39] J. Zhu, Y. Zhang, F. Shi, Y. Deng, Tetrahedron Lett. 53 (2012) 3178-3180.
1
8

ACCEPTED MANUSCRIPT
[40] R. Nie, J. Shi, S. Xia, L. Shen, P. Chen, Z. Hou, F. Xiao, J. Mater. Chem. 22 (2012)
1
8115-18118.
[41] K. Yamaguchi, H. Kobayashi, Y. Wang, T. Oishi, Y. Ogasawara, N. Mizuno, Catal. Sci.
Technol. 3 (2013) 318-327.
[42] T. Ishida, H. Watanabe, T. Takei, A. Hamasaki, M. Tokunaga, M. Haruta, Appl. Catal.
A. 425-426 (2012) 85-90.
[
43] J.B. Khairnar, B.M. Bhanage, Synthesis. 2014, 46 (2014) 1236-1242.
44] T. Suzuka, H. Sueyoshi, K. Ogihara, Catalysts. 7 (2017) 107-115.
45] J.F. Soule, H. Miyamura, S. Kobayashi, J. Am. Chem. Soc. 133 (2011) 18550-18553.
46] A.W. Addison, P.J. Burke, Heterocyclic Chem. 18 (1981) 803-805.
47] M.K. Renuka, V. Gayathri, Transition. Met. Chem. 42 (2017) 25-34.
[
[
[
[
1
9

ACCEPTED MANUSCRIPT
Highlights

A novel polymer supported Cu(II) complex was prepared and characterized physico-
chemical methods.



Elegant method for the preparation of amides using TBHP as oxidant in water
Non free radical mechanism was studied
Catalyst was reused for three times
2
0