Graphene oxide nanosheets: A highly efficient and reusable carbocatalyst catalyzes the Michael-cyclization reactions of 4-hydroxycoumarins, 4-hydroxypyrone and 4-hydroxy-1-methylquinolinone with chalcone derivatives in aqueous media

Article abstract of DOI:10.1039/c5ra08776g

Graphene oxide nanosheets were found to be a highly efficient, reusable and cost-effective carbocatalyst for the facile synthesis of highly diversified 4H-pyrans via a one-pot, two-component condensation reaction between freshly prepared chalcones and 4-hydroxycoumarin in aqueous media offering excellent yields. The new, green and metal free synthetic method also enables the condensation reaction for the formation of a library of pyranoquinolines and pyranopyrans.

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Graphene Oxide Nanosheets: A Highly Efficient and Reusable Organocatalyst Significantly
Improvises The Tandem Michael-Cyclization Reactions of 4-Hydroxycoumarins, 4-Hydroxypyrone
and 4-Hydroxy-1-methylquinolinone With Chalcones Derivatives Leading to 4H-pyran Scaffold in
Aqueous Media
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ARTICLE TYPE
Graphene Oxide Nanosheets: A Highly Efficient and Reusable Carbocatalyst Catalyzes the Michael-
Cyclization Reactions of 4-Hydroxycoumarins, 4-Hydroxypyrone and 4-Hydroxy-1-methylquinolinone
With Chalcone Derivatives in Aqueous Media
5
Nazia Kausar, Partha Pratim Ghosh, Gargi Pal, Asish R. Das*
Department of Chemistry, University of Calcutta, Kolkata-700009, India
§
*Corresponding author. Tel.: +913323501014, +919433120265; fax: +913323519754;
Eꢀmail address: ardchem@caluniv.ac.in, ardas66@rediffmail.com (A R Das)
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
10 DOI: 10.1039/b000000x
Graphene Oxide nanosheets were found to be a highly efficient, reusable and costꢀeffective carbocatalyst for the facile synthesis of
highly diversified 4Hꢀpyrans via oneꢀpot, twoꢀcomponent condensation reaction between freshly prepared chalcones and 4ꢀ
hydroxycoumarin in aqueous media offering excellent yields. The new, green and metal free synthetic method also enables the
condensation reaction for the formation of a library of pyranoquinolines and pyranopyrans
15
active pyranoquinolinones, dimeric quinolinone alkaloids and
other polycyclic heterocycles. Modification of this class of
Introduction
compound has been of great interest to researchers as their unique
Development of innovative synthetic methodologies involving
50 structures led to several applications in different areas. In
the use of chemicals that reduce the hazards to humans and the
particular, simulenoline, huajiaosimuline, and zanthodioline are
20 environment have engorged key interest in recent decades.1 In
potent inhibitors of platelet aggregation,14 while Nꢀ
this regard, utilization of catalysts that combine the toxicological
methylflindersine, isolated from Orixa japonica, acts as an
assistances of a metalꢀfree synthesis with the facile recovery and
insecticide for livestock.15 Recently it was reported that
recycling of a heterogeneous system is of tremendous importance
55 pyranoquinolinones zanthosimuline and huajiaosimuline isolated
and the avoidance of hazardous organic solvents follows the
from Zanthoxylum simulans exhibit cytotoxic activity against
25 fundamental strategy to achieve the usefulness.2 Use of water
human cancer cells.7
reduces the use of harmful organic solvents and is regarded as an
essential research topic in green chemistry.3 In addition, water
has unique physical and chemical properties, and by utilizing
these it would be possible to tune the reactivity or selectivity that
30 cannot be attained in organic solvents.4
2Hꢀpyran heterocyclic core is embedded as a fundamental
substructure in several subclasses of natural products such as
pyranocoumarins,5 pyranonaphthoquinones,6 pyranochalcones,7
pyranoquinolinones,8 and chromenes.9 Pyranocoumarins which
35 have wide occurrence in natural products as well as synthetic
molecules and exhibit a broad spectrum of biological activities
such as antifungal, insecticidal, anticancer, antiꢀHIV,
antiinflammatory, and antibacterial activities.10 In
particular
the 2ꢀhydroxyꢀ3,4ꢀdihydroꢀpyrano[3,2ꢀc]chromenꢀ5ꢀone motif is
40 the core of important natural products and a versatile template for
the preparation of a variety of biologically active molecules. The
antiprotozoan ethuliacoumarins11 as well as the uterotonic
pterophyllins12,13 (Figure 1) show a wide range of activities may
be expected from this family of compounds. Furthermore,
45 quinolinone quinone methides constitute such a class of versatile
synthones for the synthesis of naturally occurring biologically
Figure 1: Biologically active 2Hꢀpyran derivatives
60 The diversity of the structures encountered, as well as their
biological and pharmaceutical relevance, have motivated research
aimed at the development of new economical, efficient, and
selective synthetic strategies to access these compounds.
variety of methods have been developed to achieve the synthesis
A
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of this 4Hꢀpyran nucleus. Most of the methods16 reported
previously have focused on the modification and the optimization
of the process parameters of the asymmetric Michael addition of
1,3ꢀcyclic dicarbonyl compounds to α,βꢀunsaturated carbonyl
systems to minimize reaction time and maximize reaction
conversion to achieve the desired 4Hꢀpyrans in high purity. These
methodologies suffer from long reaction times, harsh reaction
conditions, the use of high thermal energy, involvement of metal
triflate as catalyst along with excess reagents or toxic solvents
5
10 which give poor yields of products, or have tedious workup
procedures.16 Moreover; the striking disadvantage of almost all
reported methods is that the catalysts are consumed in the
reaction. This scenario strongly suggests a new approach that
meets the requirements of sustainable chemistry and is still worth
15 demanding. Recently, graphene oxide nano sheets have attracted
enormous interest in the development of composite materials and
catalysts, due to their remarkable physical, chemical and
electrical characteristics, including a very high specific surface
area. In organic synthesis polycarbon acids and polyacids on
20 carbon nanostructures are considered more vigorous in aqueous
media than other solid acids such as ion exchange resins,
heteropolyacids and layer transition metal oxides; which
facilitates us to report the use of graphene oxide nano sheets, a
readily available, inexpensive and efficient carbocatalyst17, for
25 the synthesis of various 4Hꢀpyran compounds in excellent and
efficient yields in aqueous media (Scheme 1). The present work
materializes as a part of our ongoing research program involving
water as the solvent and nanoparticles as the significant catalyst
in the synthesis of various biologically active molecules.18
30
50
Figure 2: Preparation of graphene oxide nanosheets
Further, the nature of the chemical functionalities was
characterized by FTIR. An intense and broad peak appeared at
55 3424cmꢀ1, attributed to the stretching mode of a O–H bond,
reveals the abundance of hydroxyl groups in graphene oxide.
The strong band at 1722 cmꢀ1 (νC=O) represents carboxylic
acid and carbonyl groups. Furthermore, the bands at 1224 cmꢀ
1 and 1053 cmꢀ1 are attributed to the presence of C–OH and C–
60 O(epoxy) groups, respectively, in graphene oxide nano sheets.
Furthermore, the presence of very fine morphological features
on the HRTEM and FESEM images of the graphene oxide
nanosheets exposes that graphene oxide is composed of a few
number of layers, resulting in a high surface area for an
65 efficient catalytic reaction(Figure 3).
Figure 3 :(a)TEM and (b)FESEM images of GO nano sheets
70
Scheme 1: Synthesis of 4Hꢀpyran scaffolds from reaction between
chalcones and 4ꢀhydroxycoumarins/ 4ꢀhydroxypyrone or 4ꢀhydroxyꢀ1ꢀ
methylquinolinone
In order to confirm graphene oxide nanosheets to be the key
for interpreting the reactions possible in aqueous media, we
have studied a screening test employing a series of catalysts
and solvents as well as under solvent free conditions with the
75 optimism to maximize the product yield in short reaction time
(Table 1). Initially, 3ꢀ(4ꢀnitrophenyl)ꢀ1ꢀphenylpropenone (1.0
mmol) and 4ꢀhydroxycoumarin (1.0 mmol) were refluxed in
the presence of H2O and ethanol as the solvent without any
catalyst source but the reaction even after 24 h failed to
80 afford any product (Table 1, entries 1 and 2). Then the
reaction was carried out in water in the presence of pꢀ
toluenesulphonic acid (PTSA) under reflux condition and the
product was isolated in 33% yield (Table 1, entry 3). The
reactions were also restrained by using trifluoroacetic acid
85 (TFA), trifluoro methanesulphonic acid (TfOH) acid as the
catalyst (Table 1, entries 4 & 5). Lewis acid catalysts, such as
Cu(OAc)2, FeCl3 were tested but did not promote the reaction
forward(Table 1, entries 6 and 7) while use of ionic liquid,
[Bmim][BF4] as a catalyst in aqueous media provided trace
35 Result and discussion
Graphene oxide nano sheets were prepared by the oxidation of
19
graphite powder via minor modification of known methods
under severe oxidizing conditions. The presence of various
chemical functionalities on graphene oxide nanosheets and their
40 dispersion in water were examined by XRD and FTIR. Figure 2
shows the XRD patterns obtained for graphene oxide powder.
Graphene oxide nano sheet shows a little broad peak (002)
centered at 11.61, corresponding to an interlayer spacing of 0.74
nm. The oxidation of graphite powder leads to the introduction of
45 various functional groups. These functional groups are bonded on
edges and basal planes of graphitic layers, as well as the presence
of trapped water molecules between these layers, expanding the
interlayer spacing in graphene oxide nano sheets.
90 amount of the
desired product(Table 1, entries 8).
2
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bYield of isolated product.
Interestingly, we observed that GO nano sheets were most
effective for the selective formation of desired product due to
its high surface area. Again GO nanosheets showed
outstanding activity in the formation of desired product than
commercially available GO (Table 1, entry 17) in terms of
reaction time and yield. Eventually we got satisfaction
because the reaction proceeded well affording the desired
product in 90% yield within 3 h (Table 1, entry 10).
c Reaction failed to provide any product.
We then focused our attention by taking graphene oxide nano
15 sheets as the right catalyst for experiment to design and also
generalize the favorable condition for the reaction. So, we
attempted some screening test with graphene oxide nano sheets.
The quantity of the catalyst plays a vital role for the formation of
the desired product. The use of 5 mol% GO nano sheets
20 diminished the quantity of yield whereas the yield of the product
also decreased when we used 15 mol% GO nano sheets (Table 1,
entry 11 and 12).While water was used as a solvent because it
showed superiority than other solvents tested which include
ethanol (Table 1, entry 13), acetonitrile (Table 1, entry 14) and
25 chloroform (Table 1, entry 15). Under solvent free condition
(Table 1, entry 15) at 110oC, GO nano sheets failed to provide
satisfactory output and the yield was maximum (90%) in aqueous
condition. Hence, this optimized condition was applied for all
experiments taking equimolar amounts of substituted chalcone
30 (1) and 4ꢀhydroxy coumarin (2) in the presence of 10 mol % GO
nano sheets in aqueous media at 80oC (Scheme 1). Typically, a
mixture of substituted chalcone (1.0 mmol) and 4ꢀ
5
Table 1: Screening of catalyst and solvents and reaction conditions:
Entry
Catalysts
Solvent
condition
Time(h) Yielda,b
(%)
1
2
3
4
5
6
7
8
9
ꢀ
H2O
EtOH
H2O
H2O
H2O
H2O
H2O
H2O
H2O
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
24
24
24
24
24
24
24
24
10
ꢀc
ꢀc
ꢀ
PTSA (10 mol%)
TFA (10 mol%)
TfOH (10 mol%)
Cu(OAc)2(10 mol%)
FeCl3 (10 mol%)
[Bmim][BF4]
33
16
28
ꢀc
ꢀc
trace
55
Bulk GO (10 mol%)
hydroxycoumarin/
4ꢀhydroxyꢀ1ꢀmethylquinolinone/
4ꢀ
10 GO nano sheet (10
mol%)
H2O
80
3
90
67
78
81
19
26
11
71
hydroxypyrane (1.0 mmol) and 10 mol % GO nano sheets in 3ml
35 water was refluxed for 2ꢀ4 hrs, which afforded a library of 4Hꢀ
pyran derivatives in good to excellent yields (80ꢀ90%) (Table 2).
11
GO nano sheet (5
mol%)
H2O
reflux
reflux
reflux
reflux
reflux
110 oC
80
3
12 GO nano sheet (15
mol%)
H2O
3
13 GO nano sheet (10
mol%)
EtOH
3
14 GO nano sheet (10 CH3CN
mol%)
3
15 GO nano sheet (10
mol%)
CHCl3
3
16 GO nano sheet (10 Solvent
3
mol%)
Commercial GO
nano sheet (10
mol%)
free
17
H2O
10
10 aAll reactions were carried out with 3ꢀ(4ꢀnitrophenyl)ꢀ1ꢀphenylpropenone
(1.0 mmol) and 4ꢀhydroxycoumarin (1.0 mmol)
Table 2: Substrates Scope for the synthesis of 4Hꢀpyran derivatives.
40
Time (h) Yieldb(%)
3.5 88
Sl. no.
substrate
Chalcones
Product
1
3a
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2
3
3.5
3.5
92
OH
O
O
O
CN
3b
90
3c
4
5
3
4
86
85
3d
3e
6
7
3
4
92
84
3f
3g
3h
8
3.5
89
4
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9
3
3
88
3i
10
87
3j
3k
3l
11
12
13
4
3
3
85
84
90
O
N
O
3m
14
2.5
94
3n
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15
16
2.5
2.5
95
3o
93
3p
17
2
91
3q
18
19
3
3
88
89
3r
3s
20
2
95
3t
6
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21
3
88
3u
During the formation of pyranocoumarins and pyranopyrans, the
reaction proceeds via the similar Michael addition and
intramolecular cyclization pathway but the dehydration step was
25 not observed under the imposed reaction condition after
prolonged heating. No side products were isolated on both of the
cases which further proved the operational simplicity with
excellent yields. It is seen that when methylquinolinone was used
as substrate, the dehydration products were obtained owing to the
30 presence of high electron rich nitrogen centre which may abstract
the βꢀhydrogen of the OHꢀgroup and facilitated the dehydration
product.
bYield of isolated product.
A wide range of activated as well as unactivated chalcones with
electronꢀdeficient and electronꢀrich aryl groups were highly
compatible under the developed protocol and provided good to
excellent yields of the corresponding products. The structures of
the desired products were characterized by H and 13C NMR, IR
and HRMS spectral data. The Xꢀray crystal structure of 6ꢀmethylꢀ
10 4ꢀ(4ꢀnitrophenyl)ꢀ2ꢀphenylꢀ4,6ꢀdihydroꢀ5Hꢀpyrano[3,2ꢀ
c]quinolinꢀ5ꢀone (3q) (Figure 4) further confirmed the product
identity.
5
1
It is important to emphasize on the catalyst recyclability that is a
crucial feature of the green chemistry. The reusability of the
35 catalyst was studied through the condensation of 3ꢀ(4ꢀ
nitrophenyl)ꢀ1ꢀphenylpropenone
(1.0
mmol)
and
4ꢀ
hydroxycoumarin (1.0 mmol). The separated catalyst was
collected, followed by washing with acetone several times to
remove all the organic substances. It was then dried at room
40 temperature and was recycled five consecutive times with almost
unaltered catalytic activity (recovery amount 92% and yield, 86%
after 5th run)(Figure 5). Furthermore, to take advantage of the
highly efficient green protocol, the reaction was scaled up to 10
mmol scale, excellent results were obtained in the stipulated time
45 as mentioned in Table 2.
Figure 4: Single crystal structure of compound 3q (CCDC 1025207)
15 Presumably, this transformation occurs via Michael addition of
chalcone and 4ꢀhydroxyꢀ1ꢀmethylquinolinone. The intermediate I
then undergoes sequential intramolecular cyclization followed by
dehydration in order to fabricate the targeted molecule (Scheme
2).
Figure 5: Reusability study of GO nano sheets
Experimental Section:
General Procedure for the synthesis of Chalcones:
50 Acetophenone (5mol%) was added to NaOH (0.05%) in 2 ml
EtOH solution in a round bottom flask immersed in an ice bath.
Aldehyde (5mol%) was then added dropwise from a dropping
funnel with constant stirring. Reaction mixture was stirred
vigorously for 2 h, then kept in refrigerator overnight and finally
55 filtered. The product thus appeared, was washed with cold water
followed by iceꢀcold ethanol to get pure chalcones.
Preparation of GO nano sheets:
20
The graphene oxide nanosheets were synthesized from natural
graphite powder .Graphite powder (1gm) and NaNO3 (1gm) were
Scheme 2: Plausible reaction pathway for 4Hꢀpyrans
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2. (a) K. Ding, Y. Uozomi, Handbook of Asymmetric Heterogeneous
Catalysis, WileyꢀVCH, Verlag, Weinheim, 2008; (b) M. Benaglia,
Recoverable and Recyclable Catalysts, WileyꢀVCH, Weinheim, 2009.
3. P. Tundo, P. Anastas, D. StC. Black, Breen J, T. Collins, S. Memoli,
60 Miyamoto J, M. Polyakoff, W. Tumas, Pure Appl. Chem., 2000, 72, 1207.
4. (a) D. C Rideout, R. J Breslow, Am. Chem. Soc., 1980, 102, 7816; (b)
R. Breslow, Acc. Chem. Res., 1991, 24, 159; (c) J. B. F. N Engberts, M. J.
Blandamer, Chem. Commun., 2001, 1701.
added into 50 ml 98% concentrated H2SO4 under vigorous stirring
condition in a 250 ml conical flask placed in an ice bath. After a
few minutes the whole mass was converted to black slurry. Then
KMnO4 (6 gm) was added slowly into the slurry maintaining the
reaction temperature 15oC to 20°C. After 3 h, the whole system
was taken out from the ice bath and diluted with 100 ml water
and then stirred for 3 h at ambient temperature. To control the pH
of the reaction medium and also to terminate the reaction, 200 ml
hot water followed by 30% H2O2 were added to the above
10 reaction mixture until excess permanganate and manganese
dioxide were reduced to colourless soluble manganese sulfate.
The resultant yellow precipitate was washed with distilled water
several times and the residue was subjected to centrifuge to get
the pure graphene oxide powder. After repeated centrifugation,
15 salts and ions from the oxidation process can be removed from
GO suspensions. The GO nano sheets sample was collected and
dried at 60°C for 24 h. GO nano particles were characterized
using its FESEM and TEM images (Figure 3).
5
5. G. Desimoni, G. Tacconi, Chem. Rev., 1975, 75, 651.
65 6. M. J. McLaughlin, R. P Hsung, J. Org. Chem., 2001, 66, 1049.
7. I. S. Chen, S. J. Wu, I. L. Tsai, J. Nat. Prod., 1994, 57, 1206.
8. M. F. Grundon, V. N. Ramchandran, B. M. Sloan, Tetrahedron Lett.,
1981, 22, 3105.
9. J. L. Asherson, D. W. Young, J. Chem. Soc., Perkin Trans. 1.,1980,
70 512.
10. (a) R. S. Mali, P. P. Joshi, P. K. Sandhu, A. ManekarꢀTilve, J. Chem.
Soc., Perkin Trans. 1., 2002, 371; (b) Y. C. Shen, L. T Wang, C. Y. Chen,
Tetrahedron Lett., 2004, 45, 187; (c) W. F. Fong, X. L. Shen, C.
Globisch, M. Wiese, G. Y. Chen, G. Y. Zhu, Z. L. Yu, A. K. W. Tse, Y. J.
75 Hu, Bioorg. Med. Chem., 2008, 16, 3694; (d) L. Xie, Y. Takeuchi, L. M.
Cosentino, A. T. McPhail, K. H. Lee, J. Med. Chem., 2001, 44, 664; (e)
C. R. Su, S. F. Yeh, C. M. Liu, A. G. Damu, T. H. Kuo, P. C. Chiang, K.
F. Bastow, K. H. Lee, T. S. Wu, Bioorg. Med. Chem., 2009, 17, 6137; (f)
D. L. Galinis, R. W. Fuller, T. C. McKee, J. H. Cardellina II, R. J,
80 Gulakowski, J. B. McMahon, M. R. Boyd, J. Med. Chem., 1996, 39,
4507; (g) D. N. Nicolaides, D. R. Gautam, K. E. Litinas, L. D. J.
Hadjipavlou, K. C. Fylaktakidou., Eur. J. Med. Chem., 2004, 39, 323; (h)
E. Melliou, P. Magiatis, S. Mitaku, A. L. Skaltsounis, E. Chinou, I.
Chinou, J. Nat. Prod., 2005, 68, 78.
General Procedure for the synthesis of 4H-pyran derivatives:
20
A
mixture of freshly prepared chalcone (1 mmol) and
hydroxyquinolinone/hydroxyꢀchromene/pyrone derivative
(1mmol) were added to a well stirred solution of GO nanosheets
(8mg, 10 mol%) in 3ml H2O at room temperature. The mixture
o
was then stirred at 80 C for the required period of time (TLC).
25 After completion of each reaction, the crude product mixture was
extracted with ethyl acetate (3x10ml). Removal of ethyl acetate
under reduced pressure and purification of the crude product by
column chromatography (silica gel 100ꢀ200 mesh) provided pure
products. All compounds were well characterized by 1H, 13C
30 NMR, FTꢀIR and HRMS analysis.
85 11. H. A. OketchꢀRabah, E. Lemmich, S. F. Dossaji, T. G. Theander, C.
E. Olsen, C. Cornett, A Kharazmi, S. B. Christensen. J. Nat. Prod., 1997,
60, 458.
12. D. A. Mulholland, Orlando USA; (Oral Communication, Abstr. Oꢀ20)
39th ASP Meeting; July 19ꢀ24, 1998.
Conclusion
90 13. (a) G. Appendino, G Cravotto, G. M. Nano, G. Palmisano, 8th
Belgian Organic Syntheses Symposium; Gent, Belgium, Abstr. Aꢀ27, July
10ꢀ14, 2000; (b) G. Appendino, G. Cravotto, G. B. Giovenzana, G.
Palmisano, J. Nat. Prod., 1999, 62, 1627.
14. I. S. Chen, S. J. Wu, I. J. Tsai, T. S. Wu, J. M. Pezzuto, M. C. Lu, H.
95 Chai, N. Suh, C. M. Teng, J. Nat. Prod., 1994, 57, 1206.
In conclusion, an extremely efficient method has been developed
for the synthesis of pyranoquinolinones pyranocoumarins and
pyranopyrans via a oneꢀpot twoꢀcomponent condensation reaction
35 in aqueous media using GO nano sheets as an ecoꢀfriendly
degradable organocatalyst for the first time. This method is
bestowed with several green chemistry principles, such as high
conversions, simplicity in operation, and use of cost efficient eco
friendly reaction medium, simple workup procedure, high yields
40 of products and only water as the byproduct. Application of nano
reusable catalyst in synthesis of complex molecules extends the
scope and may contribute to progress further in chemical
research.
15. (a) S. Funayama, K. Murata, S. Nozoe, Phytochemistry., 1994, 36,
525; (b) J. W. Huffman, M. T Hsu, Tetrahedron Lett., 1972, 13, 141.
16. (a) J. Jayashankaran, R. Durga, R. S. Manian, R. Raghunathan,
Tetrahedron Lett., 2006, 47, 2265; (b) M. Ghandi, M. T. Nazeri, M
100 .Kubicki, Tetrahedron, 2013, 69, 4979; (c) G. M. Coppola, Syn.
Commun., 2004, 34, 3381; (d) S. Manikandan, M. Shanmugasundaram,
R. Raghunathan, Tetrahedron, 2002, 58, 8957; (e) A. K. Bagdi, A. Maji,
A.Hajra, Tetrahedron Lett., 2013, 54, 3892.; (f) M. Gohain, J. H. van
Tonder, B. C. B. Bezuidenhoudt, Tetrahedron Lett., 2013, 54, 3773; (g)
105 N. Halland, T Velgaard, K.A. Jorgensen, J. Org. Chem., 2013, 68, 5067.
17. (a) R. Daniel, W. Dreyer, W. Christopher, Bielawsk, Chem Sci., 2011,
2, 1233; (b) S. Navalon, A. Dhakshinamoorthy, M. Alvaro, H. Garcia,
Chem. Rev., 2014, 114, 6179.
18. (a) P. P. Ghosh, A. R. Das, J. Org. Chem., 2013, 78, 6170: (b) P. P.
110 Ghosh, G. Pal, S. Paul, A. R. Das, Green Chem., 2012, 14, 2691; (c) S.
Paul, P. Bhattacharya, A. R. Das, Tetrahedron Lett., 2011, 52, 4636; (d)
K. Pradhan, S, Paul, A. R. Das, RSC. Adv., 2015, 5, 12062; (e) S. Paul, K.
Pradhan, S. Ghosh, S. K. De, A. R. Das, Adv. Synth. & Catal., 2014, 356,
1301; (f) P. Bhattacharyya, S. Paul, A. R. Das, RSC Adv., 2013,3, 3203;
115 (g) G. Pal, S .Paul, A. R. Das, Synthesis, 2013, 45, 191; (h) G .Pal, S,
Paul, A. R. Das, New J. Chem., 2014, 38, 2787; (i) G. Pal, S. Paul, P. P.
Ghosh. A. R. Das, RSC. Adv., 2014, 4, 8300; (j) P. P. Ghosh, S. Paul, A.
R. Das, Tetrahedron Lett., 2013, 54, 138.
Acknowledgement
45 We acknowledge the financial support from University of
Calcutta. N.K. thanks DST, New Delhi, India for DSTꢀInspire
fellowship. Crystallography was performed at the DSTꢀFIST,
Indiaꢀfunded Single Crystal Diffractometer Facility at the
Department of Chemistry, University of Calcutta. We also
50 acknowledge IISER Kolkata and IACS for HRMS facility. We
are thankful to Mr. Indranil Roy for his cooperation.
References:
1. (a) P. T. Anastas , J. C. Warner, Green Chem., Theory and Practice,
Oxford University Press, New York, 1998; (b) I. T. Horva´th, P. T.
55 Anastas, Chem. Rev., 2007, 107, 2169.
8
| Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

RSC Advances
Page 10 of 10
View Article Online
DOI: 10.1039/C5RA08776G
19. (a) W. S. Hummersand, R. E. Offeman, J. Am. Chem. Soc., 1958, 80,
1339; (b) B. Y. Zhu, W. C. X. Li, J. W. Suk, J. R. Potts, R. S. Ruoff, Adv.
Mater., 2010, 22, 3906; (c) L. Shahriary, A. A. Athawale, International
Journal of Renewable Energy and Environmental Engineering, 2014, 2,
58.
5
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