Nano silica-bonded aminoethylpiperazine: a highly efficient and reusable heterogeneous catalyst for the synthesis of 4H-chromene and 12H-chromeno[2,3-d]pyrimidine derivatives

Abstract

The reaction of nano silica with 3-chloropropyltrimethoxysilane followed by treatment with aminoethylpiperazine afforded nano silica-bonded aminoethylpiperazine (SB-APP). The structure of the synthesized SB-APP was characterized by FT-IR, TGA, BET, SEM and elemental analysis and identified as an efficient basic catalyst for the preparation of 2-amino-4H-chromenes and 12H-chromeno[2,3-d]pyrimidine derivatives. One-pot three-component reaction of phenols, aromatic aldehydes and malononitrile in the presence of the catalytic amounts of SB-APP afforded high yield of the corresponding 2-amino-4H-chromenes under mild reaction conditions. 12H-Chromeno[2,3-d]pyrimidines were successfully synthesized with reasonable yield by reacting the 2-amino-4H-chromenes with acetic anhydride in the same pot without purification of the corresponding chromene intermediates. All products were characterized by FT-IR, 1H NMR, 13C NMR and MS data. The catalyst was simply recovered from the reaction mixture and reused several times without significant loss of catalytic activity.