2-Hydroxyethylammonium acetate: an efficient and reusable homogeneous catalyst for the synthesis of Hantzsch 1,4-dihydropyridines

Abstract

2-Hydroxyethylammonium acetate ionic liquid was found to be an excellent catalyst for the one-pot synthesis of 1,4-dihydropyridine derivatives via Hantzsch reaction of ethyl acetoacetate or acetoacetanilide, ammonium acetate, and various aromatic aldehydes. The combinatorial syntheses were achieved for the first time using 2-hydroxyethylammonium acetate ionic liquid as a homogeneous catalyst. The catalyst was active for the Hantzsch reaction in alcohol at reflux. The products were isolated in good yields (78–93 %). The resulting substituted dihydropyridines were characterized and confirmed by1H NMR spectral data. The catalyst offers simple means for recovery and the isolated catalyst was reused for three rounds for the synthesis without significant loss of catalytic activity. For all the other reactions carried out with the recycled catalyst, results were similar to that with the fresh catalyst.