Mechanochemical synthesis of α,β-dibromoketones using pyridinium tribromide

Abstract α,β-Dibromo compounds are important intermediates in the synthesis of epoxides and 1,2-diols. They can α-functionalization ketones to form electrophilic atoms for subsequent substitution reactions. However, conventional bromination methods often involve hazardous solvents, prolonged reaction times and generate chemical waste. In this study, α,β-dibromoketones 2a and 2b were synthesized from aldol condensation products ( 1a and 1b ) using pyridinium tribromide via a green and solvent-free mechanochemical approach at room temperature. The reactions afford excellent yields of 75 % and 95 %, demonstrating high efficiency and a reduced environmental footprint. Characterisations of these compounds were carried out using 1 H and 13 C Nuclear Magnetic Resonance (NMR) and high-resolution mass spectrometry (HRMS). This work establishes a green and energy-efficient mechanochemical bromination method, demonstrating the potential of mechanochemistry as an environmentally friendly alternative to traditional halogenation and as an efficient route to construct complex molecular frameworks relevant to pharmaceutical and synthetic chemistry applications.