Catalytic oxidation of α-pinene with tert-butyl hydroperoxide in the presence of Fe-pillared montmorillonite

Abstract

The reaction of α pinene with tert butyl hydroperoxide can proceed via allylic oxidation or α pinene isomerization, depending on the structural features of the catalysts based on Fe pillared montmorillonite.In spite of diversity of available methods for allylic oxidation of olefins, only few oxidation systems give α,β unsaturated alcohols or carbonyl compounds in ap propriate yields. Oxidation systems based on the lead(IV), selenium(IV), and chromium(VI) compounds turned out to be good in laboratory practice. 1 The main disadvantage of these methods is the use of considerable excess of oxi dizing reagents and, as a consequence, a lot of hazardous Pb , Se , and Cr containing waste. This fact stimulated the development of catalytic methods for the allylic oxi dation of olefins, 2 among which a special role belongs to the methods of heterogeneous catalytic oxidation using aluminosilicates 3 or aluminophosphates 4 modified by transition metals as catalysts.Among a wide series of natural and synthetic alumi nosilicates, minerals of the smectite group, including montmorillonite, are of highest interest for researchers due to their accessibility, low cost, and a possibility of purposeful control of the chemical properties and porous structure of these minerals by the intercalation into the interlayer space of ions or polynuclear metal hydroxo complexes and other modifying agents.As a rule, the catalytic properties of aluminosilicates are based on the Lewis and Brönsted acidic sites. Natural Na montomorillonite is rarely used as a catalyst for trans formations of organic substrates because of its low ther mal stability and fairly low catalytic activity. The catalytic activity and sorption properties of montmorillonite can substantially be enhanced by its activation with mineral acids. Such a treatment removes octahedrally coordinated ions (Al, Fe) and isomorphously substituted tetrahedrally coordinated ions from the montmorillonite structure 5 and, as a consequence, increases the number of acidic sites. Another method for the modification of layered alumino silicates is the exchange of interlayer cations for cations of other metals, which increases the total number of acidic sites and also changes the ratio of the Lewis and Brönsted sites. Acid activated and M n+ modified montmorillonites have been used successfully as catalysts in olefin isomer ization 6 and dimerization, 7 addition of water, halogen chlorides, alcohols, and thiols at the double bond of ole fins, 8 acylation 9 and alkylation 10 of alcohols, hydrolysis of acetals and ketals, 11 rearrangements of alkylphenyl es ters, 12 Diels-Alder 13 and Friedel-Krafts 14 reactions, etc. As a rule, the conversion and selectivity of the processes are much lower in the presence of mineral or Lewis acids.One more method for the modification of layered alu minosilicates, in particular, montmorillonite, is the sub stitution of interlayer cations for metal polyhydroxo complexes. Intercalated polyhydroxocomplexes undergo complete or partial dehydroxylation upon the thermal trea...

Kinetic study of α-pinene allylic oxidation over FePcCl16-NH2-SiO2 catalyst

“…In summary, FePcCl16-NH2-SiO2 is a stable and active catalyst for the allylic oxidation of [21] h a YVE: verbenone yield. b TBHP/α-pinene mol ratio = 4, 9 g/L catalyst.…”

“…Verbenone has been obtained using homogeneous and heterogeneous catalysts with moderate yields (Table 1) [14,15]; however, the requirement of expensive and toxic solvents [16][17][18][19], difficulty in catalyst recovery and product purification [20], inert atmosphere or large amount of catalyst and time, limit the application in some of those systems. Furthermore, in some cases reports do not include catalytic stability [21]. Hexadecachlorinated iron phthalocyanine immobilized on commercial silica FePcCl16-NH2-SiO2 (Fig.…”

“…LFe III  LFe III -(-) OOR + H (+) Eq (21). This alkyl hydroperoxo complex (LFe III -OOR) can undergo both homolytic and/or heterolytic cleavage of the O-O bond to form LFe IV =O or LFe V =O adapting L +* Fe IV =O state according to Eq (22).…”

Pillared Clay Catalysts in Green Oxidation Reactions

“…Romanenko et al [76] found that the reaction of α-pyrene with tert-butyl hydroperoxide can proceed via allylic oxidation or α-pyrene isomerization, Scheme 11.6 Mechanism proposed for the cyclohexanone oxidation over synthetic Mg-saponite depending on the structural features of the catalysts based on Fe-PILC. After 50 h of reaction, Fe-PILC mainly gives isomerization products (limonene and camphene).…”

Novel access to verbenone via ruthenium nanoparticles-catalyzed oxidation of α-pinene in neat water

“…-Scheme 1 -Up to now, various catalytic systems, either molecular complexes [16][17][18][19][20] or heterogeneous catalysts [21][22][23][24][25][26][27][28][29][30][31][32], have been used to produce verbenone. Nevertheless, in the most cases, low to medium yields were obtained ( Figure 1) or most of these processes still suffer from various drawbacks, such as sophisticated catalytic systems, toxic organic solvents and high amounts of oxidants, long reaction times, and difficult catalyst's recovery.…”