Paper
RSC Advances
in the synthesis of 3,4-dihydro-5-etoxycarbonyl-4-(4-phenyl)-6-
methylpyrimidine-2(1H)-one (4a) with those of other method-
ologies which have employed other earlier homogeneous and
heterogeneous catalysts. It is crystal clear that a suitable
methodology in terms of product yield, reaction time, and
especially catalyst amount has been developed.
7 D. Zhang, C. H. Zhou, C. X. Lin, D. S. Tong and W. H. Yu,
Appl. Clay Sci., 2010, 50, 1.
8 Crystal Structures of clay and their X-ray identication,
Monograph, ed. G. W. Brindly and G. Brown, Mineralogical
Society, London, 1980, pp. 125–195.
9 E. P. Giannelis, R. Krishnamoorti and E. Manias, Adv. Polym.
Sci., 1999, 118, 108.
In the next phase of the survey, to check the recovery and
reuse cycle of the catalyst, the reaction of 4-nitrobenzaldehyde, 10 M. Okamoto, S. Mallapragada and B. Narasimhan,
ethyl acetoacetate and urea under the optimized reaction
conditions was selected as a model reaction. Aer separating
and washing the retained catalyst with ethanol, the above-
mentioned solvent was evaporated, and the catalyst was dried
Biodegradable Polymer/Layered Silicate Nanocomposites:
a review, Handbook of Biodegradable Polymeric Materials
and Their Applications, American Scientic Publishers,
Valencia, California, 2005, pp. 1–45.
and reused for the same reactions. This process was performed 11 H. Shi, T. Lan and T. Pinnavaia, Chem. Mater., 1996, 8,
over ve periods, and all reactions led to the desired products 1584.
with negligible change in terms of the reaction time and yield, 12 S. Yariv and H. Cross, in Clays and Clay Minerals, ed. M.
obviously showing the practical recyclability of this catalyst Dekker, New York, 2002, pp. 463–566.
(Fig. 7). However, the yield of product was reduced from 96% to 13 O. Ozdemir, B. Armagan, M. Turan and M. S. Celik, Dyes
94% aer the 5th run. Pigm., 2004, 62, 49.
A reasonable pathway for the reaction of ethyl acetoacetate, 14 F. Shirini, M. Seddighi, M. Mazloumi, M. Makhsous and
aldehyde, and urea or thiourea conducted in the presence of M. Abedini, J. Mol. Liq., 2015, 208, 291.
Co@imine-Na+-MMT is presented in Scheme 2. Due to the 3d 15 S. Sarvi-Beigbaghlou, K. Marjani, A. Habibi and S. V. Atghia,
empty orbital in the cobalt ion, the activated aldehyde (2), and RSC Adv., 2016, 6, 20306.
ethyl acetoacetate (1) can be created through a coordinative 16 C. O. Kappe, Eur. J. Med. Chem., 2000, 35, 1043.
bond and stabilized by cobalt. The dihydropyrimidin-2(1H)-one 17 S. S. Kim, B. S. Choi, J. H. Lee, K. K. Lee, T. H. Lee, Y. H. Kim
synthesis probably begins via initial formation of the acylimine
and S. Hyunik, Synlett, 2009, 599.
intermediate (5) by nucleophilic addition of urea (3) to the 18 K. S. Atwal, B. N. S. Wanson, S. E. Unger, D. M. Floyd,
activated aldehyde (2). The resulting adduct (5) undergoes
dehydration to give the complex (6). In this stage, activated ethyl
S. Mereland, A. Hedberg and B. C. J. O'Reilly, Med. Chem.,
1991, 34, 806.
acetoacetate (1) attacks the complex (6). Furthermore, an open- 19 P. G. Biginelli, Gazz. Chim. Ital., 1893, 23, 360.
chain ureide (7) is created which undergoes intramolecular 20 Y. Huang, F. Yang and C. Zhu, J. Am. Chem. Soc., 2005, 127,
cyclization to afford the nal product (4) (Scheme 3).
16386.
21 U. B. More, Asian J. Chem., 2012, 24, 1906.
22 J. T. Starcevich, T. J. Laughlin and R. S. Mohan, Tetrahedron
Lett., 2013, 54, 983.
23 M. M. Khodaei, A. R. Khosropour and M. Beygzadeh, Synth.
Commun., 2004, 34, 1551.
24 C. O. Kappe, D. Kumar and R. S. Varma, Synthesis, 1999, 10,
1799.
25 M. N. Esfahani, S. J. Hoseini and F. Mohammadi, Chin. J.
Catal., 2011, 32, 1484.
4. Conclusions
In conclusion, we have introduced a simple, facile, and efficient
protocol for the synthesis of a wide range of biologically and
pharmacologically 3,4-dihydropyrimidin-2(1H)-ones in the
presence of Co@imine-Na+-MMT as a new, environmentally
friendly and reusable heterogeneous catalyst via a one-pot
Knoevenagel condensation of aldehyde, ethyl acetoacetate and
urea under solvent-free conditions.
26 K. A. Kumar, M. Kasthuraiah, C. S. Reddy and C. D. Reddy,
Tetrahedron Lett., 2001, 42, 7873.
27 M. A. Bigdeli, G. Gholami and E. Sheikhhosseini, Chin.
Chem. Lett., 2011, 22, 903.
28 A. Kumar and R. A. Maurya, Tetrahedron Lett., 2007, 48, 4569.
References
1 K. Majdzadeh-Ardakani, A. H. Navarchian and F. Sadeghi, 29 F. Tamaddon, Z. Razmi and A. A. Jafari, Tetrahedron Lett.,
Carbohydr. Polym., 2010, 79, 547. 2010, 51, 1187.
2 S. Kantevari, S. V. N. Vuppalapati and L. Nagarapu, Catal. 30 P. Salehi, M. Dabiri, M. A. Zolgol and M. A. B. Fard,
Commun., 2007, 8, 1857. Tetrahedron Lett., 2003, 44, 2889.
3 J. S. Yadav, B. V. S. Reddy, B. Eeshwaraiah and M. Srinivas, 31 S. D. Salim and K. G. Akamanchi, Catal. Lett., 2011, 12, 1153.
Tetrahedron, 2004, 60, 1767.
4 B. S. Kumar, A. Dhakshinamoorthy and K. Pitchumani,
Catal. Sci. Technol., 2014, 4, 2378.
32 S. Asghari, M. Tajbakhsh, B. Jafarzadeh-Kenari and
S. Khaksar, Chin. Chem. Lett., 2011, 22, 127.
33 M. Zeinali-Dastmalbaf, A. Davoodnia, M. M. Heravi,
5 F. Shirini, M. Mamaghani and S. V. Atghia, Catal. Commun.,
2011, 12, 1088.
N.
Tavakoli-Hoseini,
A.
Khojastehnezhad
and
H. A. Zamani, Bull. Korean Chem. Soc., 2011, 32, 656.
6 D. S. Tong, C. H. Zhou, M. Y. Li, W. H. Yu, J. Beltramini, 34 S. Rostamnia and A. Morsali, RSC Adv., 2014, 4, 10514.
C. X. Lin and Z. P. Xu, Appl. Clay Sci., 2010, 48, 569.
35 J. Lu and H. Ma, Synlett, 2000, 63.
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 17732–17740 | 17739