HClO₄‐Al₂O₃ as a Prominent Catalyst in the Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones/thiones under Environmentally Friendly Solvent Conditions

Abstract

An accessible, non‐toxic, easy to handle and stock catalyst with high efficiency was developed in this study for the synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones/thiones. Al2O3 was used as a support for HClO4, resulting in a heterogeneous and reusable catalyst for the Biginelli reaction. In the absence of the catalyst, the reaction provided a yield of 19%. However, in the presence of HClO4‐Al2O3 it was possible to synthesize 16 examples of DHPMs/thiones with improved yields (80‐98%), in reaction periods of 1 to 3 hours. The catalyst also stood out for its stability against temperature and the reagents used.

Biocatalytic Kinetic Resolution to Access Enantiomerically Enriched Dihydropyrimidinone/Thiones through Recognition of a Remote Stereocentre

“…The scope of catalysts is very broad, but the predominant classes are Bronsted and Lewis acids, either in homogeneous or heterogeneous form. [16,17] In addition, other advantages have been incorporated into synthetic methodologies, such as solvent-free reactions, the aid of microwave [18] or ultrasound irradiation [19] and continuous flow conditions. [20] In the field of biological applications, enantiomers could present better biological activity than its peer.…”

“…Due to the interest of research groups in the biological properties of DHPMs, several studies have been performed to improve the synthetic methodologies of this class of compounds. The scope of catalysts is very broad, but the predominant classes are Bronsted and Lewis acids, either in homogeneous or heterogeneous form [16,17] . In addition, other advantages have been incorporated into synthetic methodologies, such as solvent‐free reactions, the aid of microwave [18] or ultrasound irradiation [19] and continuous flow conditions [20] …”