A. Zali, A. Shokrolahi / Chinese Chemical Letters 23 (2012) 269–272
271
2
. Results and discussion
In the beginning, we decided to investigate the role of nano-sulfated zirconia as a catalyst in the synthesis of
amidoalkyl naphthols (Scheme 1). In the absence of a catalyst no amidoalkyl naphthol was observed, even after a
prolonged reaction time. The effect of the catalyst was also studied under various conditions. In all cases the amount of
the catalyst was crucial to a good yield and reaction rate. It was determined that 0.2 g of the catalyst (nano-sulfated
zirconia) was optimal to this reaction. If less than 0.1 g of nano-sulfated zirconia was used the low yields resulted, even
after a long reaction time; the yield of the products did not increase when more than 0.2 g of nano-sulfated zirconia was
used.
In all cases, aromatic aldehydes with substituents carrying either electro-donating or electron-withdrawing groups
reacted successfully and gave the products in high yields. It was shown that the aromatic aldehydes with electron
withdrawing groups reacted faster than the aromatic aldehydes with electron releasing group as would be expected.
Aromatic aldehydes with steric hindrance such as 2-chloro benzaldehyde reacted at long reaction times. The high
catalytic activity of nano-sulfated zirconia is due to high acidity and the large pore dimensions which provide good
access to the acid sites on the surface of catalyst [41].
To study the regeneration and reusability of the catalyst, catalyst was recovered from the reaction mixture by
filtration and washed with acetone followed by drying at 110 8C for 2 h and thermal activation at 450 8C for 2 h. Thus
regenerated catalyst was used for the reaction synthesis of entry 1 under the similar reaction conditions for 5 cycles.
After every reaction cycle the catalyst was recovered, washed and activated as above. The same activity as fresh
catalyst without any loss of its activity for recovered catalyst was found.
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