Rapid and easy access to Biginelli reaction for the synthesis of tetrahydropyrimidine-5-carboxamides in the presence of magnetized BPHCSF nanostructure under mild conditions

Abstract

This paper depicts a facile, rapid, and effective approach of a nanocatalyst named 4,4′-bipyridin-1-ium hydrogen sulfate grafted on chloropropyl functionalized silica gel-nano-Fe₃O₄ (BPHCSF) for the synthesis of two series of tetrahydropyrimidine-5-carboxamide derivatives. These derivatives were produced via the Biginelli reaction of 3-oxo-N-(4-phenylthiazol-2-yl)-butanamide or 3-oxo-N-(5-phenyl-1,3,4-thiadiazol-2-yl)butanamide with urea and diverse aldehydes in a green environment under optimized conditions (0.01 g of catalyst, 1 mL of EtOH, 60 °C). Compared to previous papers for the synthesis of Biginelli reaction derivatives, the current protocol shows significant improvements in terms of products yield, reaction time, catalyst recyclability, temperature, and comprehensiveness in producing a variety of products derived from aromatic, heteroaromatic, and aliphatic aldehydes. The high performance of the BPHCSF nanostructure in producing the above derivatives is probably due to its effective basic and acidic centers, which is justified through the proposed mechanism. Meanwhile, the magnetic nature of BPHCSF assisted its isolation from the reaction mixture and promoted its reproducibility up to seven times without significant reduction in its catalytic activity.

Graphical abstract