Oxidation of aromatic aldehydes and ketones by H2O2/CH3ReO3 in ionic liquids: a catalytic efficient reaction to achieve dihydric phenols

Methyltrioxorhenium Catalysis in Nonconventional Solvents: A Great Catalyst in a Safe Reaction Medium

“…[27] All of the products were obtained in very good conversions (> 98 %) and 6 was published a few years ago (Scheme 7). [28] In this work, the formyl group of the benzaldehyde derivatives 67-74 and the acetyl moiety of the hydroxylated acetophenones 91-94 is either oxidized to a carboxyl group or converted into a hydroxy function. The oxidation of 4-methoxybenzaldehyde 67, chosen as model substrate for the initial investigation, showed to be faster, even if less selective, at 50 8C as compared to 25 8C, affording, besides 4-methoxyphenol 75, small amounts of hydroquinone 76 and 4-methoxybenzoic acid 83 (Scheme 7).…”

“…A series of organic substrates having different functional groups such as styrene 5 (Scheme 2), benzhydrol 39 (Scheme 5), 2-adamantanone 113 (Scheme 8), p-hydroxybenzaldehyde 68, 2,3-dimethylnaphthalene 190, diphenyl sulfide 192, and 3,5-dimethylphenol 195 (Scheme 25), along with different alkyl-substituted phenols 47-52 (Scheme 6), 1-naphthol 65, and methoxytoluene derivatives 59-61 (Scheme 6) were oxidized, under catalytic conditions, also comparing reactivities in DMC with those previously reported for molecular solvents and ILs. [27][28][29] Generally, oxidations afford high substrate conversions and yields. Products were obtained after shorter reaction times than in traditional solvents, and similar to those observed in ILs.…”

Ionic Liquids as Solvents for Catalyzed Oxidations of Organic Compounds

“…According to Bernini et al, the R-catalyst/IL system can be repeatedly recycled after extraction of the organic compounds with diethyl ether. [50,51] Saladino et al have disagreed about this assertion, [34] but the reuse of the Re catalyst/IL solution for at least five times with no loss of activity has been the subject of a recent addendum by Bernini et al [52,53] Instead of a rhenium catalyst, Kalkote et al used an Sn-b-molecular sieve for the oxidation of 1-phenylpropan-2-one and acetophenone or benzophenone derivatives [Eqs. (35) - (37)].…”

Sulfonated carbon catalyzed oxidation of aldehydes to carboxylic acids by hydrogen peroxide

“…However, the reactivity of aqueous H 2 O 2 is insufficient for the direct oxidation of aldehydes to carboxylic acids. Therefore, hydrogen peroxide was often used as oxidant for the oxidation of aldehydes to carboxylic acids in combination with other reagents as catalysts including base [15], acid [5], transition metals [4,6,16] and N-methylpyrrolidin-2-one hydrotribromide [7]. However, these systems are associated with the drawbacks such as the requirement of strong acidic/basic conditions, use of toxic and heavy metals, and difficult regeneration and reuse.…”