III International Conference

PP-I-58MECHANISTIC STUDY ON THE OXIDATION OF FUNCTIONALIZED PHENOLSAND NAPHTHOLS IN Ti-MMM-2/H 2 O 2 AND FePcS-SiO 2 / t BuOOH SYSTEMSZalomaeva O.V. 1, 2 , Kholdeeva O.A. 1 , Ivanchikova I.D. 1 , Sorokin A.B. 21 Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russia2 Institute de Recherche sur la Catalyse, CNRS, 2, avenue A. Einstein, 69626 VilleurbanneCedex, FranceE-mail: zalomaeva@catalysis.ruThe mechanisms of the selective oxidation of alkyl-substituted phenols and naphtholswith H 2 O 2 and t BuOOH in the presence of heterogeneous catalysts, mesoporous titaniumsilicateTi-MMM-2 and silica-supported iron tetrasulfophthalocyanine FePcS/SiO 2 ,respectively, have been suggested based on the analysis of the main processes’ regularities,by-product structures, and the results of the ESR study using spin traps.Quinones bearing different functional groups are important products and intermediates infine chemistry. For example, 2,3,5-trimethyl-1,4-benzoquinone (TMBQ) is a precursor in thesynthesis vitamin E and 2-methyl-1,4-naphthoquinone (‘menadione’, vitamin K 3 , MNQ) is asynthetic analog of vitamin K widely used as a blood-coagulating agent. The development ofenvironmentally benign methods for the production of functionalized quinones via oxidationof the corresponding phenols with clean oxidants over true heterogeneous catalysts is achallenging goal.Recently we have found that oxidation of 2,3,6-trimethylphenol (TMP) and 2-methyl-1-naphthol (MNL) with H 2 O 2 over hydrothermally stable mesoporous titanium-silicate catalystTi-MMM-2 [1-3] and with tert-butylhydroperoxide ( t BuOOH) over irontetrasulfophthalocyanine (FePcS) anchored on silica [3-5] afford TMBQ and MNQ with amoderate to high yield. The different effects of the substrate concentration and catalystamount on the selectivity to quinones observed in the two catalytic systems indicated differentoxidation mechanisms. The product study by 1 H NMR and mass-spectrometry revealed thatthe main by-products formed in the Ti-MMM-2/H 2 O 2 system are C-C-coupling dimers, whichis consistent with a homolytic oxidation mechanism. Indeed, intermediate aryloxyl andoxyaryloxyl radicals were identified by ESR using the spin trap DBNBS (3,5-dibromo-4-nitrosobenzene-sulfonic acid). On the contrary, no C-C-coupling by-products and radicalintermediates were found in the FePcS/SiO 2 / t BuOOH catalytic system. The main by-productsof MNL oxidation in this system were 2-methyl-2,3-epoxy-1,4-naphthoquinone and 1,2-dihydro-2-tert-butylperoxy-2-methyl-1-oxonaphthalene. All these facts collectively allowed109