Efficient synthesis of quinazolinones through base promoted dehydrocyclization using a copper(II) catalyst

Area of Science:

• Coordination Chemistry
• Catalysis
• Organic Synthesis

Background:

• Schiff base ligands derived from keto-pyrazoles are effective chelating agents.
• Copper(II) complexes can serve as catalysts in organic transformations.
• Quinazolin-4(3H)-one cores are important scaffolds in biologically active molecules.

Purpose of the Study:

• To synthesize and characterize novel copper(II) complexes with N^N^O chelating Schiff base ligands.
• To investigate the catalytic activity of these complexes in the dehydrogenation of primary alcohols.
• To elucidate the reaction mechanism and establish a sustainable synthetic route.

Main Methods:

• Synthesis of keto-pyrazole based ligands and their copper(II) complexes.
• Single-crystal X-ray diffraction for structural elucidation.
• Catalytic dehydrogenation reactions with mechanistic studies (mercury poisoning, HRMS).

Main Results:

• Characterization of two copper(II) complexes with square planar geometry.
• Successful catalysis of alcohol dehydrogenation with aminobenzamides, yielding quinazolin-4(3H)-one cores.
• High yields (up to 96%) and broad substrate scope achieved.
• Validation of a non-radical, two-electron hydride transfer mechanism.

Conclusions:

• Novel copper(II) complexes act as efficient, phosphine-free catalysts for alcohol dehydrogenation.
• The developed method provides a sustainable and practical route to biologically significant N-heterocycles.
• The catalytic system exhibits excellent functional group tolerance and substrate compatibility.