Titanium superoxide – a stable recyclable heterogeneous catalyst for oxidative esterification of aldehydes with alkylarenes or alcohols using TBHP as an oxidant

Abstract

Titanium superoxide efficiently catalysed the oxidative esterification of aldehydes with alkylarenes or alcohols, under truly heterogeneous conditions, to afford the corresponding benzyl and alkyl esters in excellent yields. Mechanistic studies have established that this "one pot" direct oxidative esterification process proceeds through a radical pathway, proven by a FTIR spectral study of a titanium superoxide-aldehyde complex as well as spin trapping experiments with TEMPO. The intramolecular version of this protocol has been successfully demonstrated in the concise synthesis of 3-butylphthalide, an anti-convulsant drug.

Nickel exchanged supported 12-tungstophosphoric acid: synthesis, characterization and base free one-pot oxidative esterification of aldehyde and alcohol

“…Oxidative esterication of aldehydes with alcohols has received increasing attention during recent years because such raw materials are abundantly available in industry. 1 Various groups have reported one step conventional methods for oxidative esterication of aldehydes, based on TS-1, 2 V 2 O 5 -SPC/SPB (SPCsodium percarbonate, SPB sodium perborate), 3 supported gold nanoparticle Au/TiO 2 , 4 Pb and Mg doping in Al 2 O 3 -supported Pd, 5 palladium/NHC, 6 manganese phthalocyanine immobilized on silica gel, 7 supported gold-nickel oxide nanoparticles (AuNiO x ), 8 magnesia supported gold nanoparticles (Au/MgO), 9 titanium superoxide, 1 palladium complex immobilized on magnetite-graphene oxide nanocomposite, 10 graphite oxide and oxone, 11 iron oxalate capped iron-copper nanomaterial (Fe(ox)Fe-CuOx), 12 reduced graphene oxide supported Co 3 O 4 nanoparticles (Co 3 O 4 /rGO), 13 supported iron oxide nano particles (FeNP), 14 gold nanoparticles supported on Ce-Zr oxide, 15 polystyrene supported rhodium nanoparticles (Rh@PS), 16 PTFE supported gold nanoparticles 17 and sulfate radical redox systems. 18 Many methods suffer from disadvantages such as use of expensive and polluting reagents, an inert atmosphere and lengthy reaction times.…”

Magnetic Co3O4/reduced graphene oxide nanocomposite as a superior heterogeneous catalyst for one-pot oxidative esterification of aldehydes to methyl esters

“…We have shown the first successful oxidative esterification methodology using TBHP as oxidant in significantly shorter reaction times than those usually used. 23d, [29][30][31][32] The synergistic effect of rGO support was observed and the hybrid catalyst exhibited superior catalytic activity than the…”

Recent developments in oxidative esterification and amidation of aldehydes

“…9 They described a Ti-superoxide catalysed direct conversion of aldehydes, both aliphatic and aromatic, into carboxylic esters via C-H activation of alkylarenes or using alcohols. Notably, alkyl aromatics, which are seldom utilized in oxidative esterification due to the low reactivity of sp 3 C-H bonds, are effective in this procedure.…”