Application of nanoparticle mediated N-arylation of amines for the synthesis of pharmaceutical entities using vit-E analogues as amphiphiles in water

Article abstract of DOI:10.1039/c4ra15267k

The first CuI-nanoparticle catalyzed inter and intramolecular N-arylation of amines using vitamin E analogues (TPGS) as amphipiles has been developed in water. Application of this transition metal-amphiphile C-N bond formation methodology is further extended for the synthesis of substituted indoles, bioactive natural product tryptanthrin and intermediates of pharmaceutical entities such as imatinib, nilotinib, selective D3 agonist/antagonist ligands, and oxacarbazepine. This journal is

Full text of DOI:10.1039/c4ra15267k

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: A. Kumar and A.
Bishnoi, RSC Adv., 2015, DOI: 10.1039/C4RA15267K.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

RSC Advances
Page 1 of 5Journal Name
Dynamic Article Links ►
View Article Online
DOI: 10.1039/C4RA15267K
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/xxxxxx
ARTICLE TYPE
Application of Nanoparticle Mediated N-Aryaltion of Amines for the Synthesis of
Pharmaceutical Entities using Vit-E analogues as Amphiphile in Water
Atul Kumar,* and Ajay Kumar Bishnoi
5
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
First CuI-nanoparticle catalyzed inter and intramolecular N-arylation of amines using vitamin E
analogues (TPGS) as amphipile have been developed in water. Application of this transition metal-
amphiphile C-N bond formation methodology is further extended for the synthesis substituted
10 indole, bioactive natural product tryptanthrin and intermediates of pharmaceutical entities such as
Imatinib, Nilotinib, selective D3 agonist/antagonist ligand, and Oxacarbazpine.
Introduction
In twenty first century the chemical transformations are not only
evaluated by yield of synthesis /process, but a complete art of
15 synthesis is required for the evaluation of synthesis /process. The
formula for evaluation of synthesis becomes YES (Yield,
Economics ꢀ eco friendliness and Stereochemistry).1 To address
economics and environmental sustainability emphasis is direct
towards development of green medium, and recyclable reagents.2
20 Development of green medium is fascinating area since the ionic
liquid has been introduced but later on IL biodegradability and
greenness in under question mark.3 Therefore water is consider as
the best available choice in nature. Water a solvent of life, as
almost all the biochemical reaction under goes in water.4
25 However, poor aqueous solubility of organic compounds or
reactivity of many transitionꢀmetal/organo catalysts are the main
limitation, which can be overcome by the introducing organic
microenvironment in aqueous phase.5
Previous report:
cat [(allyl)PdCl]2
ligand 2, KOH
R2
N
Br
R2
Ar
R1
R1
2 % PTS/H2O, rt
H
Ar
Ph
Ph
Me
R2 = H, Ph, Me
P(t-Bu)2
Takasago's cBRIDP (2)
50 This work:
N
Br
CuI-NP, NaOH
CuI-NP, NaOH
N
N
TPGS-750-M/water
N
TPGS-750-M/water
HN
R1
R1
R1
N
H
A smart strategy to solve these issues is micellar catalysis.6
30 Recently developed the transition metal coupling reaction
catalyzed in water with TPGSꢀ750ꢀM / PTS.7 TPGSꢀ750ꢀM is a
biodegradable and waterꢀsoluble derivative of natural vitamin E,
which is formed by esterification of vitamin E succinate with
polyethylene glycol (PEG) 1000.8 It is consisting of a tocopherol
35 (vitamin E) hydrophobic group and a PEG hydrophilic group.
Micellar catalysis greenness methodology which allows the E
factor approach to zero.9 Micelles are mainly simple spherical
supramolecules, which are formed by amphiphiles in water and
have ability to solubilization of both nonpolar and polar
40 substrates, reagents, and catalysts.10
55
Figure 1. Nꢀaryaltion of amines reaction using VitꢀE Amphiphile
in Water and their position on HLB Scale
aMedicinal and Process Chemistry Division, CSIR-Central Drug
Research Institute, Lucknow, 226031, India,
E-mail: dratulsax@gmail.com,
Fax: +91 522-26234051; Tel +91 522-2612411
Lipshutz et al. reported Nꢀaryaltion of amines reaction using PTS
45
†
Electronic supplementary information (ESI) available:
60 as nonionic amphiphile with [(pꢀallyl)PdCl]2 as catalyst,
Takasago’s as ligand and base in presence of water.11 Inspired by
Experimental details and NMR spectra. See supporting
This journal is © The Royal Society of Chemistry [year]
[journal], [year], [vol], 00–00 | 1

RSC Advances
Page 2 of 5
View Article Online
DOI: 10.1039/C4RA15267K
this report we wish to report here first CuIꢀnanoparticle catalyzed
inter and intramolecular Nꢀarylation of amines using vitamin E
analogues (TPGS) as amphipile in water. To the best of our
Triton Xꢀ100 and PTS. Therefore, TPGS was found to be the best
amphiphile with Nano CuI for the synthesis of Nꢀarylation of
amines in water.
knowledge this is first report on Cu nano and Vitamin E 45 The copper(I) salts such as CuBr, CuCl, Cu2O, and CuI were
5
analogues as amphiphile used for catalyzing CꢀN bond formation.
We utilised this methodology for the synthesis of medicinally
important indoles12, anticancer and antitubercular natural product
tryptanthrin.13 We further extended the protocol for the synthesis
found to be inferior to CuI nanoparticles (Table 1, entries 11ꢀ15).
Among the bases studied, Et3N, K2CO3, KOtBu, K3PO4, provided
lower yields than NaOH (Table 1, entries 1–5). Of the copper
catalysts investigated, CuI nanoparticles were significantly
of intermediates of pharmaceutical entities such as clinically used 50 superior to other catalyst (Table 1, entries 1). In order to evaluate
10 anticancer drugs14 Imatinib, Nilotinib, selective D3
agonist/antagonist ligand15 for the treatment of alzimeres and,
drug addiction therapy and anticonvulsant Oxacarbazpine.16
Our initial efforts were focused on the actual effectiveness of an
the catalyst loading, the reaction was carried out using 1.5, 3.5,
and 5.0 % mole nano CuI at room temperature in water. It was
found that 3.5 % mole NPꢀCuI is sufficient to give the desired
product in excellent yield with an enhanced rate (Table 1, entries
efficient nano catalyst for the Nꢀarylation of amines reaction in 55 8–10).
15 nanomicelles in water. For this investigation the reaction of
bromobenzene and morpholine, taken as a model reaction, control
experiment carried out “on water” (i.e., without amphiphile) led
to no product formation after 10 h at room temperature as well as
refluxing.
A control reaction carried out “on water” (i.e., in the absence of
amphiphile) confirmed the importance of micellar catalysis in
facilitating Nꢀarylation of amines coupling reaction in aqueous
media (Table 2).
60 Table 2: Optimisation of Amphiphiles Concentration
20
Entry
Conc.(wt %)
Amphiphile
Yield(%)
Table 1. Optimization of reaction conditions for synthesis of Nꢀ
Aryl amines
1
2
3
4
2 %
1 %
5 %
0
TPGS
TPGS
TPGS
TPGS
92
70
82
10
CuI-NP, NaOH
Br
O
HN
N
O
2 % surfactant/water, rt
25
A lower concentration of amphiphile was therefore deemed
favorable, although too low a concentration or its complete
65 absence was detrimental. Consequently, TPGS (2 wt %) was
selected for further studies. A wide array of aromatic amines,
azoles, secondary amines were under goes Nꢀarylation with aryl
halides in excellent yields ( Scheme 1).
Entry
[Cu] (mol %)
Base
Solvent
Yield
(%)[b]
1
2
3
4
5
6
7
8
CuI (np (3.5))
CuI (np (3.5))
CuI (np (3.5))
CuI (np (3.5))
CuI (np (3.5))
CuI (np (3.5))
CuI (np (3.5))
CuI (np (3.5))
CuI (np (1.5))
CuI (np (5.0))
CuI (15)
NaOH
KOtBu
K2CO3
Et3N
TPGS
TPGS
TPGS
TPGS
TPGS
Brij 30
Triton Xꢀ100
PTS
TPGS
TPGS
TPGS
TPGS
TPGS
TPGS
TPGS
92
80
72
65
52
65
72
80
78
90
70
48
52
48
35
K3PO4
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
70 Scheme 1: Nꢀarylation of amines via intermolecular amination
N
Br
9
CuI-NP, NaOH
CuI-NP, NaOH
N
10
11
12
13
14
15
N
TPGS-750-M/water
N
TPGS-750-M/water
Cu2O
Cu(OAc)2
CuBr
CuCl
R1
R1
R1
HN
N
H
N-arylation of amines
aReaction conditions: aReaction conditions: bromobenzene(1.0 mmol),
morpholine (1.5 mmol), CuIꢀNP (3.5 % mole), NaOH as base (3 equ.),
O
N
O
75
80
85
aqueous TPGS (2 wt %) amphiphile solution (5 ml) as solvent for 4.5 hr
N
b
NH
N
30 at rt.
Isolated yield. np = nanoparticles, TPGS (DLꢀαꢀTocopherol
MeO
methoxypolyethylene glycol succinate), PTS (Polyoxyethanylꢀαꢀ
tocopheryl sebacate.
4
(90 %)
(90 %)
(91 %)
(92 %)
2
3
1
We further carried out the reaction with nano CuI catalyst at
35 room temperature in water for 10 h but found very less yield.
After that we was explore nonionic amphiphile such as oil/water
emulsifier and detergent. However, the use of amphiphile (Brij
30) and nano CuI resulted in the formation of the desired product
in 65% yield at room temperature. In search of an efficient
40 amphiphile, we further screened various amphiphiles in the
model Nꢀarylation of amines reaction in water such as Brij 30,
O
Cl
N
NH
NH
NH
MeO
6
OMe
(90 %)
5
(88 %)
7
85 %
8
(85 %)
2
| Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 3 of 5
RSC Advances
View Article Online
DOI: 10.1039/C4RA15267K
35
R
N-arylation of azoles
N
N
HN
NH
Br
N
N
N
N
N
N
N
CuI-NP, NaOH
N
linker
N
N
H
2 % TPGS/H2O
rt, 1.5 hr
Selective D3
receptor ligand
18
(yield 82%)
Intermediate
NC
40
O
11
12
9
(86 %)
10
(88 %)
(85 %)
(90 %)
N
Scheme 5: Synthesis of Tryptanthrin
N
N
N
NH2
O
O
N
N
45
N
CuI-NP, NaOH
N
NH2
NH2
Cl
CF3
2 % TPGS/H2O
rt, 1 hr
N
Cl
15
O
O
13
19 (85 %)
NC
(80 %)
14
(84 %)
(82 %)
Tryptanthrin
To explore this methodology, we have economically synthesized
the intermediate of high profile anticancer drugs such as Imatinib,
Nilotinib. The process exhibits a broad scope for the synthesis of
intermediates of imatinib, nilotinib, selective D3 receptor ligand,
bioactive natural product tryptanthrin, substituted indoles, and
oxacarbazepine respectively (Schemes 2ꢀ 7). After completion of
reaction, the catalyst was recovered from the reaction mixture by
10 centrifugation and reused for the next fresh reaction. It is
noteworthy that the catalyst could be reused at least five times
without any significantly loss of efficiency. Therefore, we
Application of intramolecular N-aryl amination reaction:
50
5
Scheme 6: Synthesis of intermediate of Oxacarbazepine:
O
O
O
CuI-NP, NaOH
N
N
Br 2 % TPGS/H2O
80 0C, 6 hr
H
O
NH2
20
NH2
21 (82 %)
Oxcarbazepine
(anticonvulsant)
Intermediate
suspected that because of large surface area, nanoparticles have 55 Scheme 7: One pot synthesis of substituted Indole via
very high catalytic properties as compare to other catalyst.
Application of intermolecular N-aryl amination:
Scheme 2: Synthesis of Intermediate of Imatinib:
Intramolecular amination
15
Br
CuI-NP, NaOH
R1
Br
R1
Br
NH2
N
2 % TPGS/H2O
90 0C, 15 Hr
H
60
Br
H
20
Br
N
N
Br
N
N
N
N
H
NO2
H
MeO2C
Imatinib
(Anticancer)
N
N
22
(74 %)
23
(72 %)
NO2
65
CuI-NP, NaOH
2 % TPGS/H2O
60 0C, 9 hr
Br
NH2
N
Br
Br
N
(Yield= 90 %)
16
N
H
Ph
Intermediate
(70 %)
(70 %)
25
Scheme 3: Synthesis of N1ꢀSelective Intermediate of Nilotinib
24
25
70 The surface property and the composition of the catalyst were
characterized from Scanning electron microscope (SEM),
Transmission electron microscope (TEM) and energy dispersive
Xꢀray analysis (EDX). The EDX spectrum (shown in Figure 3)
further authenticates the presence of Cu in the nanocomposite. In
75 addition, in the SEM, TEM analysis of CuI nanoparticles,
interestingly, the shape and size of the nanoparticles remained
unchanged before and after the reaction.
N
N
Br
HN
N
Nilotinib
(Anticancer)
CuI-NP, NaOH
2 % TPGS/H2O
rt, 6 hr
F3C
NH2
F3C
NH2
85 % single regioisomer
Intermediate (17)
30
Scheme 4: Synthesis of Intermediate of Selective D3 Receptor
ligand
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 3

RSC Advances
Page 4 of 5
View Article Online
DOI: 10.1039/C4RA15267K
tryptanthrin, intermediates of pharmaceutical entity such as life
saving anticancer drugs Imitinib, Nilotinib and anticonvulsant
35 drug Oxacarbazepine. The amphiphile used is biodegradable and
catalyst have have good recyclability. The nano CuI mediated
organic synthesis (NAMOꢀSynthesis) in aqueous media via
micellar catalysis has immense future in application in the area
of medicinal chemistry and material science.
40
Experimental Section
General procedure for preparation of CuI nanoparticles
45 0.464 g (4 mmol) of dimethylglyoxime (dmgH) and 0.400 g (2
mmol) of Cu(OAc)2.H2O were added into 50 ml of absolute
ethanol in sequence, which was stirred at 0°C for 30 min to get
brown precipitates Cu(dmg)2. Then the collected precipitates
dispersed in 50 ml of absolute ethanol again, 0.664 g (4 mmol) KI
50 was added and stirred vigorously for 2 h. After that, the mixture
was transferred into 60 mL Teflonꢀlined stainless steel autoclave.
The autoclave was sealed and heated at 180°C for 6 h, and then
the reactor bomb is allowed to cool to room temperature. Black
precipitates were obtained, then centrifugalized and washed with
55 ethanol and deionized water for three times to ensure the removal
of the impurities. The final product was then dried in a vacuum
oven at room temperature for 12 h.17
5
10
General procedure for the N-Arylation of Amine / Azoles:
60 The Nꢀarylation of amines was carried out in a round bottomed
flask. In a typical experiment, a mixture of chlorobenzene (1
mmol), morpholine (1.5 mmol), CuI NPs (3.5 mol%) and NaOH
(3 equ.) were dissolved in aqueous TPGS (2 wt %) amphiphile
solution (5 ml) as solvent and stirred for the 4.5 hours at room
65 temperature. The reaction was monitored to completion using
TLC. At the end of reaction, the mixture was then cooled to room
temperature and poured into distilled water. The products were
extracted using EtOAc and the organic layer was dried over
anhydrous sodium sulphate (Na2SO4). The solvent was
70 evaporated in vacuo, the crude products were purified by column
chromatography using EtOAc / hexane solvent system.
Figure 2. (a) SEM images of catalyst before the reaction (b) After the 5th
run (c) TEM images before the reaction (d) After the 5th run, (e) EDX
15 image of fresh catalyst, and (f) EDX image of catalyst after 5th run
.
Table 3. Recyclability of CuI Nanoparticles
CuI-NP, NaOH
Br
O
HN
N
O
2 % surfactant/water, rt
20
Run
1a
2b
3b
4b
Catalyst recovery (%)
Product Yield (%)
General procedure for the 2-BromoIndole derivatives in one-
pot.
85
81
74
72
70
92
86
82
80
75
75 The intramolecular amination reaction was carried out in a round
bottomed flask. In a typical experiment, a mixture of 2ꢀ(2,2ꢀ
dibromovinyl)aniline (1 mmol), CuI NPs (3.5 mol%) and NaOH
(3.0 equ.) were dissolved in aqueous TPGS (2 wt %) amphiphile
5b
0
solution (5 ml) as solvent and stirred for the 15 hours at 90 C
aCuI nanoparticles (3.5 mol %), bromobenzene (1.0 mmol), morpholine
(1.5 mmol) base (1.5 equ.), aqueous TPGS (2 wt %) amphiphile solution
(5 ml) as solvent for 4.5 hr at rt (room temperature). bThe recovered
catalyst was used under identical reaction conditions to those for the first
80 temperature. The reaction was monitored to completion using
TLC. At the end of reaction, the mixture was then cooled to room
temperature and poured into distilled water. The products were
extracted using EtOAc and the organic layer was dried over
anhydrous sodium sulphate (Na2SO4). The solvent was
85 evaporated in vacuo, the crude products were purified by silica
column chromatography using EtOAc / hexane solvent system.
25 run.
Conclusions
In summary, We have developed first CuIꢀnanoparticle catalyzed
30 inter and intramolecular Nꢀarylation of amines using vitamin E
analogues (TPGS) as amphiphile in aqueous environment. This
methodology is further extended to bioactive natural product
Note and References:
90
4
| Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 5 of 5
RSC Advances
View Article Online
DOI: 10.1039/C4RA15267K
1.
2.
(a) S. Kobayashi, Adv. Synth. Catal. 2002, 344, 219 b) S.
Kobayashi, K. Manabe, Acc. Chem. Res. 2002, 35, 209 – 217. (b)
R. Ciriminna, M. Pagliaro, Org. Process Res. Dev. 2013, 17,
1479-1484. (c) U. M. Lindstrom, Chem. Rev. 2002, 102, 2751; c)
C. J. Li, Chem. Rev. 2005, 105, 3095. (d) D. J. C. Constable, A.
D. Curzons, V. L. Cunningham, Green Chem. 2002, 4, 521-527.
(a) M.E. Zakrzewska, E. B. Łukasik, R.B. Łukasik, Chem. Rev.
2011, 111, 397-417. (b) N. Azizi, E. Batebi, S. Bagherpour and H.
Ghafuri, RSC Adv., 2012, 2, 2289-2293. (c) D. G. Blackmond, A.
Armstrong, V. Coombe, A. Wells, Angew. Chem. Int. Ed., 2007,
46, 3798-3800; Angew. Chem. Int. Ed. 2007, 46, 3798 – 3800. (d)
A. Kumar, A. K. Bishnoi, RSC Adv., 2014, 4, 31973-31976.
(a) A. Romero, A. Santos, J. Tojo, and A. Rodri ´ guez, J. Hazard.
Mater., 2008, 151, 268–273; (b) N. V. Plechkova, and K. R.
Seddon, Chem. Soc. Rev., 2008, 37, 123–150. (c) A. Kumar, A. K.
Bishnoi, RSC Adv., 2014, 4, 41631-41635.
(a) P. A. Grieco, Organic Synthesis in Water, Blacky Academic
and Professional: London, 1998. (b) C. J. Li, T. H. Chan, Organic
Reactions in Aqueous Media, John Wiley & Sons: New York,
1997. (c) B. Cornils, W. A. Herrmann, Aqueous- Phase
Organometallic Chemistry: Concepts and Applications; Wiley-
VCH: Weinheim, 1998.
(a) T. Tang, T. Metanawin, A. Hebden, P. McGowan, X. S.
Wang, Chem. Commun., 2010, 46, 6663-6665. (b) N. S.Ieong, K.
Brebis, L. E. Daniel, R.K. O’Reilly, M. I. Gibson, Chem. Commun.,
2011, 47, 11627-11629. (c) A. Xie, M. Cao, Y. Liu, L. Feng, X. Hu,
W.Dong, Eur. J. Org. Chem. 2014, 436-441.
(a) T. Dwars, E. Paetzold, and G. Oehme, Angew. Chem. 2005,
117, 7338 – 7364; Angew. Chem. Int. Ed. 2005, 44, 7174 – 7199;
(b) B. H. Lipshutz, D. W. Chung, B. Rich, Org. Lett. 2008, 10,
3793–3796. (c) B. H. Lipshutz, and A. R. Abela, Org. Lett. 2008,
10, 5329–5332.
(a) B. H. Lipshutz, S. Ghorai, Aldrichimica Acta 2008, 41, 59–72.;
Aldrichimica Acta 2012, 45, 3-16. (b) H. Borowy-Borowski, M.
Sikorska-Walker, P. R. Walker, U.S. Patent 6,045,826, Apr 4,
2000.; U.S. Patent 6,191,172, Feb 20, 2001.; U.S. Patent
6,632,443, Oct 14, 2003. (c) B. H. Lipshutz, N. A. Isley, J. C.
Fennewald, and E. D. Slack, Angew. Chem., Int. Ed. 2013, 52,
10952-10958.
75
80
85
90
5
10
15
20
25
30
35
40
45
50
55
60
65
3.
4.
5.
6.
7.
8.
9.
B. H. Lipshutz, S. Ghorai, A. R. Abela, R. Moser, T. Nishikata, C.
Duplais, and A. Krasovskiy, J. Org. Chem. 2011, 76, 4379–4391.
(a) N. Miyaura, and A. Suzuki, Chem. Rev. 1995, 95, 2457. (b) B.
H. Lipshutz, N. A. Isley, J. C. Fennewald, and E. D. Slack, Angew.
Chem., Int. Ed. 2013, 52, 10592.
10. (a) T. Dwars, E. Paetzold, G. Oehme, Angew. Chem. 2005, 117,
7338 – 7364; Angew. Chem. Int. Ed. 2005, 44, 7174 – 7199. (b)
N.Giri, S. L. James, Chem. Commun., 2011, 47, 245-247. (c) S. R.
K. Minkler, B. H. Lipshutz, N. Krause, Angew. Chem. Int. Ed.,
2011, 50, 7820-7823.
11. B. H. Lipshutz, D. W. Chung, and B. Rich, Adv. Synth. Catal.
2009, 351, 1717 – 1721.
12. (a) N. K. Kaushik, N. Kaushik, P. Attri, N. Kumar, C. H. Kim, A. K.
Verma, and E. H. Choi, Molecules, 2013, 18, 6620. (b) H.
Shirinzadeh, B. Eren, H. G. Orhan, S. Suzen, and S. Ozden,
Molecules, 2010, 15, 2187.
13. S. Yang, X. Li, F. Hu, Y. Li, Y. Yang, J. Yan, C. Kuang, and
Q.Yang, J. Med. Chem. 2013, 56, 8321-8331.
14. (a) F. Stegmeier, M. Warmuth, W. R. Sellers, and M. Dorsch,
Clinical Pharmacology & Therapeutics, 2010, 87, 543-552. (b)
H. Kantarjian, et al.; N Engl J Med., 2006, 354, 2542–2551.
15. C. Fischer, and B. Koenig, Beilstein J. Org. Chem. 2011, 7, 59–74
16. M. Mazza, G. D. Marca, M. D. Nicola, G. Martinotti, G. Pozzi, L.
Janiri, P. Bria, and S. Mazza, Epilepsy & Behavior, 2007, 10, 397-
401.
17. (a) X. L. Li, X. Y. Zhu, T. L. Duan, and Y. T. Qian, Solid State
Communications, 2006, 138, 526-529. (b) H. J. Xu, Y. F. Liang, X.
F. Zhou, and Y. S. Feng, Org. Biomol. Chem., 2012, 10, 2562–
2568.
70
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 5