Microwave-assisted synthesis of 2'-hydroxychalcone derivatives in 1-decyl-3-methylimidazolium bromide ionic liquid...

Three 2'-hydroxychalcone derivatives were synthesized via microwave-assisted organic synthesis using the ionic liquid 1-decyl-3-methylimidazolium bromide ([DMIm]Br) as the medium. The reactions, conducted at 80°C under 300 W microwave power for 10 min, yielded products with yields of 65, 72 and 81%. A computational study using density functional theory with B3LYP and ωB97X functionals examined the reactivity of precursors via Fukui function analysis. Results showed that higher reactivity of benzaldehyde derivatives correlated with increased product yields: o-vanillin > anisaldehyde > salicylaldehyde. The cyclization of 2,2'-dihydroxy-3-methoxychalcone to its flavanone derivative was also simulated, revealing a two-step mechanism with the first step being rate-determining (activation energy: 63.8 kJ mol^-1). Additionally, the formation of [DMIm]Br was found to proceed through an S_N2 mechanism, with an activation energy of 197.3  kJ mol^-1. These experimental and computational findings underscore the predictive power of Fukui-based reactivity in optimizing chalcone synthesis in ionic liquid media.