期刊
JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL
卷 353, 期 -, 页码 122-131出版社
ELSEVIER
DOI: 10.1016/j.molcata.2011.11.015
关键词
Mg-Al-hydrotalcite; Aza-Michael addition; Green protocol; Acidic/basic sites; Pyrazolo[1,5-a]pyrimidine; Microwave irradiations
资金
- King Abdulaziz University
- Saudi Basic Industries Corporation (SABIC) [MS 3/11]
Mg-Al hydrotalcite was synthesized by a co-precipitation method. We have studied the effect of calcination temperature and hydration of the calcined phases on their catalytic activity for the synthesis of pyrazolo[1,5-a]pyrimidine derivatives (aza-Michael addition product). The structure of the as-synthesized sample and the presence of the anions in the interlayer galleries of hydrotalcites, have been determined by X-ray diffraction and FTIR spectroscopy. On calcining the material at 450 degrees C, it was amorphous periclase phase. Re-hydration of the calcined phase resulted in the formation of hydrotalcite-like phase. Such treatment to the as-synthesized hydrotalcite significantly changed the pore structure and the BET-surface area as determined from N-2 physisorption at 77 K. The as-synthesized Mg-Al-hydrotalcite catalyst was found to be the most efficient for the aza-Michael reaction relative to the activated solid catalysts tested. The high performance of this catalyst was attributed to the co-operative contribution of its acidic and basic sites. We have shown that this microwave assisted reaction provides an eco-friendly alternative to the conventional syntheses where soluble bases are used. Furthermore, the reaction was performed over a considerably shorter time scale and generated significantly higher yields than traditional methods. (C) 2011 Elsevier B.V. All rights reserved.
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