An eco-friendly, simple, and effective protocol is developed
for
the synthesis of various multisubstituted 2-aminothiophenes. In the
presence of a catalytic amount of ZnO (5 mol %), ketones or
aldehydes, malononitrile and elemental sulfur were converted to the
corresponding 2-aminothiophene derivatives in moderate to high yields
(27%–70%) under solvent-free conditions at 100 °C. Zinc
oxide as an efficient, readily available, and reusable catalyst, showed
very good catalytic activity for the synthesis of 2-aminothiophene
derivatives. Thus far, little research has been reported on the Gewald
reaction under solvent-free conditions; to the best of our knowledge,
this is the first time that it has been proposed as an inexpensive
and readily available catalyst for use in the target synthetic route.
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