4
Tetrahedron Letters
0816), E-enstatite (JCPDS ref. file-00-002-0546), SO- Strontium aluminum
To confirm the heterogeneous nature of catalyst and catalytic
activity bound to the solid phase, a hot-filtration test was
performed. 4-Methoxybenzaldehyde, 4-bromothiophenol,
oxide(JCPDS ref. file-00-024-1187)].
malononitrile, and the glass ceramic material catalyst mixed
together in water on an oil bath under reflux. The catalyst was
filtered off (from the hot reaction mixture) after 15 min. The
filtered reaction mixture was then refluxed without the catalyst
for the next 2 h; no further formation of the corresponding
product was observed, indicating that no homogeneous catalyst
was involved.
2.1.3. Differential thermal analysis (DTA)
Two well defined exothermic peaks were visible for DTA
thermo-grams when the glass sample was analyzed at a heating
rate of 5/min, first peak appeared (Tp1) at 786°C and second
crystal peak (Tp2) appeared at 856°C. By X-Ray analysis, it was
confirmed that 1st crystal peak was for potassium
fluorophlogopite and second crystal peak for strontium
fluorophlogopite. From DTA analysis we also obtained glass
transition temperature (Tg) at around 675°C and nucleation
temperature (Tn) at around 720°C.
90
Tp1
1st run
2nd run
3rd run
4th run
60
30
0
Tp2
Exo
Tg
Endo
5°C/min
200
400
600
800
1000
15 30 45 60 75 90 105 120
Time (min)
Temperature (°C)
Figure 4. Differential thermal analysis plots of glass samples of heating
rate 5°C /min.
Figure 6. Kinetics plot demonstrating the recycling efficiency of the glass
ceramic material catalyst or the reaction forming 4a.
2.2. Optimization of catalyst loading
3. Conclusion
The reactions were carried out using different amounts of the
catalyst and the optimum amount (20 mg) has been determined.
Figure 5 shows a remarkable increase in output according to the
increase in the quantity of the catalyst upto 20 mg (Figure 5).
With higher amount of catalyst no significance increase in the
yield was observed. In order to use the minimum amount of the
catalyst, we have been limited to 20 mg for the continuation of
the study. The reaction forming 4a was chosen as a model for
this purpose.
In conclusion, a glass ceramic material has been synthesized
and successfully used for the first time for one pot
multicomponent synthesis in water. The present method shows
very high atom economic with very high yields of the products.
The catalyst is highly stable, environmentally benign and
renewable. Because of simplicity of the procedure associated
with environmentally benign features, it is hoped that this
methodology will be embraced by the synthetic organic
community at large.
90
Acknowledgements
% Yields at
60
different amount of catalyst
We acknowledge TEQIP for fellowship.
Reference and notes
30
1. 1. (a) Bannwarth, W.; Hinzen, B.; Eds. Combinatorial Chemistry:
From Theory to Application; Wiley-VCH: Weinheim, Germany,
2006; (b) Illgen, K.; Nerdinger, S.; Behnke, D.; Friedrich, C. Org.
Lett. 2005, 7, 39; (c) Posner, G. H. Chem. Rev. 1986, 86, 831; (d)
Ray, S.; Das, P.; Banerjee, B.; Bhaumik, A.; Mukhopadhyay, C.
ChemPlusChem 2015, DOI: 10.1002/cplu.201402405.
0
0
5
10
15
20
25
30
Amount of catalyst (mg)
Figure 5. Amount effect of the catalyst in the synthesis of pyridines.
2.3. Recycling experiment
2. Thimmaiah, M.; Li, P.; Regati, S.; Chen, B.; Zhao, J. C. G.;
Tetrahedron Lett. 2012, 53, 4870.
The reusability of the catalyst in the 6-arylthio-pyridine
formation reaction was examined taking the reaction forming 4a
as model reaction. Nearly quantitative catalyst (up to 95 %) could
be recovered from each run. In a test of four cycles, the catalyst
could be reused without significant loss of catalytic activity. The
kinetics of the fresh catalyst was evaluated as shown in Figure 6.
The yield did not increase substantially after 2 h. Also we had
performed the kinetic study with the recycled catalyst for the next
consecutive three runs. The results of kinetic plots suggested that
the catalyst retained good efficiency after recycling.
3. (a) Perrier, V.; Wallace, A. C.; Kaneko, K.; Safar, J.; Prusiner, S.
B.; Cohen, F. E. Proc. Natl. Acad. Sci. U.S.A. 2000, 97, 6073; (b)
Nirschl, A. A.; Hamann, L.G. US Pat. Appl. Publ. 2,005,182,105
A1 20,050,818 (2005); (c) Harada, H.; Watanuki, S.; Takuwa, T.;
Kawaguchi, K.; Okazaki, T.; Hirano, Y.; Saitoh, C. PCT Int. Appl.
WO 2002006237 A1 20020124 (2002); (d) Reddy, T. R. K.;
Mutter, R.; Heal, W.; Guo, K.; Gillet, V. J.; Pratt, S.; Chen, B. J.
Med. Chem. 2006, 49, 607; (e) May, B. C. H.; Zorn, J. A.; Witkop,
J.; Sherrill, J.; Wallace, A. C.; Legname, G.; Prusiner, S. B.;
Cohen, F. E.; J. Med. Chem. 2007, 50, 65; (f) Levy, S. B.;
Alekshun, M. N.; Podlogar, B. L.; Ohemeng, K.; Verma, A. K.;
Warchol, T.; Bhatia, B.; Bowser, T.; Grier, M. US Pat. Appl.
2,005,124,678 A1 20,050,609 (2005); (g) Anderson, D. R.; Stehle,