Investigation of N,N′‐Disulfopiperazinium Chlorometallates of Fe(III), Ni(II) and Co(II) as Hybrid Catalysts for the Synthesis of 1,2‐Dihydroquinazoline Derivatives

Three organic salts of N,N′‐disulfopiperazinium cation with complex metal chloride anions of Fe(III), Ni(II) and Co(II) cations were developed as Brønsted‐Lewis acidic hybrid materials in solid state. Their structural compositions were established by FT‐IR, UV‐Visible, SEM, EDX, Powder XRD and Raman techniques. Thermogravimetric analyses showed removal of physisorbed water around 100 °C for Fe(III) salt in contrast to 150–170 °C for Ni(II) & Co(II) organic salts for strongly bound water molecules in highly crystalline state. Their Brønsted acidities were determined from comparative UV‐visible spectra of 4‐nitroaniline in water in presence of the halometallates while Lewis acidity strength was observed via FT‐IR spectra of these salts in presence of pyridine as probe molecule. The catalytic activity of these acidic organic salts was investigated for three‐component synthesis of 1,2‐dihydroquinazolines as recyclable heterogeneous catalysts. Three‐component one‐pot synthesis of 1,2‐dihydroquinazolines were done using Brønsted‐Lewis acidic chlorometallate salts of Fe(III), Ni(II) and Co(II) as catalysts under optimized reaction conditions. The catalysts facilitated high product yields and were recyclable.