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Acknowledgements
This work was supported by; (a) the Global Frontier Program
through the Global Frontier Hybrid Interface Materials
(GFHIM) of the National Research Foundation of Korea (NRF)
funded by the Ministry of Science, ICT & Future Planning 10
(2013M3A6B1078874), (b) Science Foundation Ireland under
grant no. 14/IA/2581 and by the Irish Research Council under
award GOIPD/2016/575, and (c) SFS would like to thank
University Grants Commission, New Delhi for awarding D. S.
Kothari Post-Doctoral Fellowship scheme (F.4-2/2006(BSR)/CH/
16-17/0015).
Fig. 2 Reproducibility test of GONPs for BCDs synthesis.
Notes and references
with 4-hydroxycoumarin to afford product (5) (see Scheme 2). It
was revealed that intermediates (II) and (IV) were very reactive
towards the subsequent reaction with pyrazolone and 4-
hydroxycoumarin respectively.27
1 A. T. Bell, Science, 2003, 299, 1688–1691.
´
2 D. Pla and M. Gomez, ACS Catal., 2016, 6, 3537–3552.
3 L. Chng, N. Erathodiyil and J. Y. Ying, Acc. Chem. Res., 2013,
20, 1825–1837.
4 H. Song, Acc. Chem. Res., 2015, 48, 491–499.
5 J. A. Torres, F. G. E. Nogueira, M. C. Silva, J. H. Lopes,
T. S. Tavares, T. C. Ramalho and A. D. Correa, RSC Adv.,
2017, 7, 16460–16466.
6 Y. Yong, R. Su, X. Liu, W. Xu, Y. Zhang, R. Wang, P. Ouyang,
J. Wu, J. Ge and Z. Liu, Biochem. Eng. J., 2018, 129, 26–32.
7 Q. Husain, J. Nanosci. Nanotechnol., 2018, 18, 486–499.
8 J. B. Bharate, S. B. Bharate and R. A. Vishwakarma, ACS
Comb. Sci., 2014, 16, 624–630.
9 D. R. Dreyer, H. P. Jia and C. W. Bielawski, Angew. Chem., Int.
Ed., 2010, 49, 6813–6816.
10 C. Su, M. Acik, K. Takai, J. Lu, S. Hao, Y. Zheng, P. Wu,
Q. Bao, T. Enoki, Y. J. Chabal and K. P. Loh, Nat.
Commun., 2012, 3, 1298–1307.
In the multicomponent reactions proceeded through interme-
diate (II) or (IV) could not be measurably detected in current study.
Aer completion of the reaction, tautomerisation occurred in the
pyrazolone ring of product (5). This may exist in three tautomeric
forms viz. the CH, OH and NH.27–30,40,41 The GONPs catalyst has
both non-toxic and reusable features. Thus, the present protocol
fullls the criteria for green-synthesis and reusability. The
robustness of GONPs for the synthesis of BCDs was tested by
scrutinizing the effect of the phase and its reusability.17–19 When
the synthesis of BCDs was carried out using the phases and active
sites, the GONPs play signicant role in catalytic activity. Finally,
the GONPs, being a heterogeneous catalyst, can be easily separated
from the reaction mixture and reused ve times successfully
(Fig. 2), by reuse of GONPs for the model reaction.
ˆ
11 P. T. Anastas and M. M. Kirchhoff, Acc. Chem. Res., 2002, 35,
686–694.
Conclusion
In conclusion, the present protocol has several features such as;
(i) the prepared GONPs are nanocrystalline and mesoporous
with acidic functional groups, (ii) the GONPs demonstrate
a superior catalytic performance with as high as 93–82% iso-
lated product yields, (iii) unveiling report of the biologically
important highly functionalized BCDs using a solid, metal-free,
nontoxic and reusable heterogeneous green/eco-friendly acid
catalyst. A facile one-pot multi-component protocol has been
demonstrated for the synthesis of biologically important, highly
functionalized BCDs. The reaction was performed in ethanol
solvent at 50 ꢀC using GONPs as a heterogeneous acid catalyst.
The products were puried by recrystallization from ethanol
and chromatography-free separation methods, where the use of
volatile and hazardous solvents, generally preferred, is avoided.
These GONPs should nd several applications in MCRs leading
to biologically potent molecules in the near future, which is
a topic of ongoing work.
12 D. L. Trimm, Appl. Catal., A, 2001, 212, 153–160.
13 Y. Li and W. Shen, Chem. Soc. Rev., 2014, 43, 1543–1574.
14 I. Fechete, Y. Wang and J. C. Vedrine, Catal. Today, 2012,
189, 2–27.
15 G. V. Smith and F. Notheisz, Heterogenous Catalysis in
Organic Chemistry, Academic Press, New York, 1999.
16 F. Hu, M. Patel, F. Luo, C. Flach, R. Mendelsohn,
E. Garfunkel, H. He and M. Szostak, J. Am. Chem. Soc.,
2015, 137, 14473–14480.
17 S. Navalon, A. Dhakshinamoorthy, M. Alvaro and H. Garcia,
Chem. Rev., 2014, 114, 6179–6212.
18 D. Deng, L. Xiao, I. Chung, I. S. Kim and M. Gopiraman, ACS
Sustainable Chem. Eng., 2017, 5, 1253–1259.
19 C. L. Su and K. P. Loh, Acc. Chem. Res., 2013, 46, 2275–2285.
20 D. S. Su, J. Zhang, B. Frank, A. Thomas, X. Wang,
J. Paraknowitsch and R. Schlogl, ChemSusChem, 2010, 3,
169–180.
21 M. J. Allen, V. C. Tung and R. B. Kaner, Chem. Rev., 2010, 110,
132–145.
22 W. S. Hummers and R. E. Offeman, J. Am. Chem. Soc., 1958,
80, 1339.
Conflicts of interest
There are no conicts to declare.
17378 | RSC Adv., 2018, 8, 17373–17379
This journal is © The Royal Society of Chemistry 2018