Ketoisophorone Research Articles

Isophorone on Au/MgO/Ag(001): Physisorption with Electrostatic Site Selection

We report a computational study of isophorone C9H14O adsorption on a Ag(001)-supported ultrathin MgO film with Au adatoms and clusters employing density functional theory calculations. The calculations show that the keto form of isophorone is more stable than the enol tautomers both in gas phase and on the MgO/Ag(001) surface. The interaction between the keto isophorone and step and terrace sites of MgO/Ag(001) displays long interaction distances, relatively weakly exothermic adsorption energies, lack of charge transfer, and minor changes in the density of states, all of which indicate that the molecule merely physisorbs on the surface. The step sites are energetically preferred adsorption sites due to attractive electrostatic interaction between more exposed Mg2+ cations and the polar O=C bond in isophorone. The adsorption on the step sites is 0.6 to 0.8 eV more exothermic compared with terrace sites. The calculations suggest that isophorone can chemisorb on MgO/Ag(001) surface but requires the presence ...

Kinetics Study on Oxidation of β-Isophorone Using Molecular Oxygen

The oxidation kinetics of β-isophorone (β-IP) using molecular oxygen catalyzed by iron(III) acetylacetonate was investigated in a lab-scale agitator bubbling reactor. β-IP was found to give keto-isophorone (KIP) and 4-hydroxy-3,5,5-trimethyl-2-cyclohexen-1-one (HIP) along with little isomerization product α-isophorone (α-IP). The results show that the oxidation reaction took place in the pseudo–first-order fast reaction regime. The experiment was conducted under the mass transfer reaction regime as the mass transfer resistances could not be easily eliminated. The intrinsic kinetics was obtained through apparent kinetics. The activation energy of oxidation of β-IP to KIP is 70.5 ± 4.1 kJ mol–1, and the value of ln AKIP is 33.53 ± 1.22. Meanwhile, the activation energy of oxidation of β-IP to HIP is 86.4 ± 5.4 kJ mol–1 and the value of ln AHIP is 36.23 ± 1.52, which could provide theoretical basis for industrial design, amplification of reactor, and the optimization of reaction.

Novel catalytic system: N-hydroxyphthalimide/hydrotalcite-like compounds catalysing allylic carbonylation of cyclic olefins

Abstract-hydroxyphthalimide (NHPI) combined with stable and recoverable transition metal–aluminium binary hydrotalcite-like compounds (M-Al HTLcs, M = Cu, Ni, Co) as an unprecedented catalytic system was demonstrated for the allylic carbonylation, as the model reaction, of cyclic olefins with tert-butyl hydroperoxide (TBHP), using isophorone (IP) to ketoisophorone (KIP). The results showed NHPI combined with Cu-Al HTLcs to be an efficient catalytic system and the influences of various reaction conditions of the catalytic reaction were optimised. A maximum IP conversion of 68.0 % with 81.8 % selectivity to KIP was afforded under the optimal reaction conditions. Experiments of repeatability and restorability showed Cu-Al HTLcs to be stable for at least five cycles without noticeable loss of catalytic activity. Expanding substrates could also be efficiently converted to the corresponding ketones under the optimised reaction conditions with appreciable yields. A plausible catalytic reaction mechanism was proposed.

Aerobic oxidation of β-isophorone by tetraphenylporphyrin catalysts in pyridine solution

A kinetic study was conducted using five metallo-tetraphenylporphyrins (MTPPs) as catalysts for the aerobic oxidation reaction of β-isophorone (β-IP) to ketoisophorone (KIP). The oxidation reaction catalyzed by MTPPs (M=Cr, Mn, Fe, Co and Cu) was observed over a seven hour period under a range of experimental conditions. Changes in the specificity of conversion of reactant to the product, KIP, and the main side-product, α-isophorone (α-IP), were observed at temperatures ranging from 60°C to 75°C, in solvents with varying compositions of pyridine and β-IP, with different MTPP catalysts, oxygen gas flow rates, and solution agitation frequencies. Control experiments show that MTPP catalysts modestly increase the rate of KIP formation, but significantly improve specificity through the apparent suppression of α-IP formation. Analysis revealed that MnTPP (CH3COO−) produced the highest product specificity ratio [KIP]/[α-IP]. Given that all of the metals were in the 3+ oxidation state in this study and there was no observed binding by O2 to any of the MTPP catalysts, the catalytic mechanism is suggested to involve the binding of β-IP to the MTPP metal center. Binding of β-IP is most favorable when pyridine is the trans ligand, but β-IP is also observed to weakly bind when trans to acetate in the MnTPP adduct. This conclusion is supported by electronic absorption spectroscopy, resonance Raman spectroscopy and density functional theory (DFT) calculations. The role played by the catalyst appears to be the activation of hydrogen abstraction following the substrate's ligation to the metal, rather than the more traditional role of MTPPs as O2 activation catalysts by ligation of diatomic O2. β-IP oxidation is an example of a case where the catalyst appears to have a more important role for improving the specificity of the reaction (through decreasing side-product formation) rather than increasing the rate of product formation.

Metal-free direct oxidation of α-isophorone to ketoisophorone by I2 under photoirradiation

Molecular iodine was first utilized for direct oxidation of α-isophorone (α-IP) to ketoisophorone (KIP) with molecule oxygen at room temperature and the effects of amount of iodine, solvents and reaction time were investigated extensively. The optimized result shows that 70.2% conversion of α-isophorone and 82.6% selectivity of ketoisophorone are obtained with 15% iodine (molar fraction) in acetonitrile under photoirradiation for 5 h. Moreover, the possible mechanism is proposed.

An Efficient and Mild Oxidation of α-Isophorone to Ketoisophorone Catalyzed by N-Hydroxyphthalimide and Copper Chloride

N-hydroxyphthalimide (NHPI) and copper chloride (CuCl2) were first utilized for aerobic oxidation of αisophorone (α-IP) to ketoisophorone (KIP) and the effects of co-catalysts, temperature, reaction time, solvent, amount of CuCl2 and pressure of oxygen were investigated extensively. NHPI/CuCl2 turned out to be highly efficient to this oxidation with up to 91.3% conversion and 81.0% selectivity under mild conditions. And various hydrocarbons including benzylic compounds, cycloalkene and its derivatives were also oxidized smoothly under optimized conditions. Moreover, the possible reaction mechanism was proposed and verified by FT-IR spectra.

Aerobic oxidation of β-isophorone catalyzed by N-hydroxyphthalimide: the key features and mechanism elucidated

Due to the insufficient understanding of the selective oxidation mechanism of α/β-isophorones (α/β-IP) to ketoisophorone (KIP), the key features in the β-IP oxidation catalyzed by N-hydroxyphthalimide (NHPI) have been explored via theoretical calculations. β-IP is more favourable to being activated by phthalimide-N-oxyl radical (PINO˙) and peroxyl radical (ROO˙) than α-IP owing to the different C-H strengths at their reactive sites, thereby exhibiting selective product distributions. It was found that NHPI accelerates β-IP activation due to the higher reactivity of PINO˙ than ROO˙ and the equilibrium reaction between them, yielding considerable hydroperoxide (ROOH) and ROO˙. In addition, the ROOH decomposition is more favourable viaα-H abstraction by radicals than its self-dehydration and thermal dissociation. The strong exothermicity of this α-H abstraction, along with that from H-abstraction by co-yielded hot HO˙, is in favor of the straightforward formation of KIP, simultaneously leading to the isomerization of a few β-IP to α-IP and production of 4-hydroxyisophorone (HIP) and water. The proposed mechanisms, consistent with the experimental observations, allow for the deeper understanding and effective design of oxidation systems involving similar substrates or NHPI analogues that are of industrial importance.

Enoate reductases from non conventional yeasts: Bioconversion, cloning, and functional expression in Saccharomyces cerevisiae

Old yellow enzymes (OYEs, EC 1.6.99.1) are flavin-dependent oxidoreductases that catalyze the stereoselective trans-hydrogenation of the double bond, representing a promising alternative to metal-based catalysis. Bioconversion of ketoisophorone (KIP) by 28 non-conventional yeasts belonging to 16 different species was investigated. Growing cells of most of the strains reduced KIP via OYE and showed high stereoselectivity, producing R-levodione as major product. Competition by carbonyl reductase (CR) activity was observed in several strains. The best performing yeasts belong to Candida castellii, Kazachstania spencerorum and Kluyveromyces marxianus exhibited yields of levodione ≥77% up to 95% e.e., and. Candida freyschussii, the sole strain lacking the OYE gene, reduced KIP only to unsaturated alcohols via CR. Nine unedited OYE genes were cloned, sequenced, and heterologously expressed in Saccharomyces cerevisiae BY4741ΔOye2, a mutant that showed negligible OYE and CR activities. Compared with the corresponding wild-type yeasts, growing cells of the recombinant strains bioconverted KIP with improved yields of OYE products, minor competition by CR activity, and lower enantioselectivity. In particular, resting cells of recombinant S. cerevisae presented the best performance in KIP bioconversion. Based on the results herein reported, selected strains of non-conventional yeasts and novel OYE genes can be profitably used as innovative biocatalysts in asymmetric reductions.

Metal and solvent-free oxidation of α-isophorone to ketoisophorone by molecular oxygen

The metal and solvent-free oxidation of α-isophorone to ketoisophorone (KIP) using N -hydroxy phthalimide (NHPI) as the catalyst under atmospheric oxygen was studied, eliminating the isomerization process of α-isophorone to β-isophorone. The effect of co-catalyst, temperature, time, amount of NHPI, and recycling on the oxidation was investigated. The oxidation of α-isophorone proceed well without any co-catalyst under 60 °C for 10 h, which was different with the traditional oxidation of α-isophorone at high temperature. Furthermore, NHPI can be easily separated and reused with a slight loss on its activity. This aerobic oxidation process by NHPI provides a good alternative way for the industrial synthesis of KIP.

Liquid phase catalytic oxidation of isophorone with tert-butylhydroperoxide over Cu/Co/Fe–MgAl ternary hydrotalcites

Abstract Liquid phase catalytic oxidation of isophorone was carried out over M–MgAl ternary hydrotalcites, where M is Cu, Co or Fe, using tert -butylhydroperoxide (TBHP) as an oxidant. The influence of various reaction parameters, namely, substrate/catalyst mass ratio, substrate:oxidant mole ratio, nature of oxidant, solvent, reaction temperature and reaction time on the activity and selectivity for the desired reaction, were studied. The catalysts were synthesized by the coprecipitation technique using metal nitrates and a NaOH/Na 2 CO 3 mixture. Powder X-ray diffraction and thermal analysis of these samples confirmed the presence of hydrotalcite like layered network. Oxidation of isophorone over these catalysts resulted mainly in the formation of ketoisophorone (KIP). A maximum isophorone conversion of 74% with 100% selectivity to KIP was observed over CuMgAl-13 at 333 K up to 48 h using acetonitrile as a solvent, followed by CoMgAl-13 (36%) and FeMgAl-13 (25%). The redox properties of transition metal ions played an important role in driving the reaction and a reaction mechanism involving predominantly free radicals were proposed. An increase in the conversion of isophorone was observed with decreasing substrate/catalyst mass ratio down to 20. With respect to the influence of reaction temperature, the conversion increased up to 333 K and decreased when the temperature was further increased. Among the solvents studied acetonitrile showed maximum conversion and selectivity to KIP, where as methanol showed minimum conversion. An increase in the conversion of isophorone was observed with decreasing molar ratio of isophorone to TBHP. A gradual increase in the conversion of isophorone was observed with reaction time and the maximum conversion was observed at 48 h. Reusable studies showed that the catalysts were stable and reusable up to three cycles without substantial loss of activity.

Advances in homogeneous and heterogeneous catalytic aerobic oxidation of isophorone to ketoisophorone

Homogeneous and heterogeneous systems for the catalytic aerobic allylic oxidation of α- and β-isophorone (α- and β-IP) to ketoisophorone (KIP) have been investigated. A detailed study has been conducted on the influence of several parameters for the phosphomolybdic acid (PMA)/DMSO/potassium tert-butoxide combination which provides KIP in high yield (68% isolated) from α-IP. Metal(bis-salicylaldehyde)s (M(sal) 2) are new homogeneous catalysts for α- and β-IP oxidation. (M(sal) 2) immobilized on aminopropyl-modified silica gel and metal(salen) incorporated in silica aerogels, prepared in our laboratory, have also been investigated for isophorone oxidation. The combined study suggests that the base/solvent plays a pivotal role in directing selectivity in the allylic oxidation of highly substituted cyclic olefins in homogeneous catalysis. In addition, the solvent/additive combination can also dictate the stability of heterogeneous catalysts under conditions necessary for facile dioxygen activation for allylic oxidation. Differences in the activities of the homogeneous and immobilized systems may be associated with the phenomenon of site isolation leading to different reaction pathways.

Industrial application of Nafion-systems in rearrangement-aromatisation, transesterification, alkylation, and ring-closure reactions

Nafion, a perfluorinated sulphonic acid ion-exchange polymer, is known to be a very strong Brønsted acid. Thus, Nafion NR 50 and Nafion/SiO 2 with 15 wt.% Nafion-loading were selected, in order to elucidate the potential for rearrangement-aromatisation of ketoisophorone (KIP) to 2,3,5-trimethylhydroquinone diacetate (TMHQ-DA) in presence of acetic acid anhydride as acylating agent, transesterification of TMHQ-DA to 2,3,6-trimethylhydroquinone monoacetate (TMHQ-1-MA) and reaction of isophytol (IP) with trimethylhydroquinone (TMHQ) to (all- rac)-α-tocopherol. For the rearrangement-aromatisation of KIP to TMHQ-DA supported Nafion/SiO 2 was markedly more active than the unsupported Nafion NR 50. Both Nafion-systems generally revealed remarkably high selectivity, which ranged up to 94 GC-a% TMHQ-DA at high conversion. The major side-product was 3,4,5-trimethylcatechol diacetate. In case of Nafion/SiO 2, pre-treatment under vacuum and especially grinding of the extrudates seemed to increase activity at comparably high selectivity. Recycling Nafion/SiO 2 after filtering and rinsing with acetic acid anhydride led to gradually decreasing activity. Without intermediate isolation of TMHQ-DA, Nafion/SiO 2 was active and selective for the formation of TMHQ-1-MA. Using the Nafion systems in the reaction of IP and TMHQ revealed that remarkably high conversion of IP (>95%) and compared with zinc chloride/Brønsted acid or BF 3-catalysed reaction good yields (≈92%) and selectivities were obtained. We found a strong dependency on the solvent polarity. In further experiments, the recovery of the catalyst was tested.

Oxidation by molecular oxygen using zeolite encapsulated Co(II)saloph complexes

Co(II) Schiff base complexes encapsulated in zeolite-Y having the general formula Co(II)L-Y (where L=salicylaldehyde- o-phenylenediimine (saloph), chloro-salicylaldehyde- o-phenylenediimine (Cl-saloph), bromo-salicylaldehyde- o-phenylenediimine, (Br-saloph) and nitro-salicylaldehyde- o-phenylenediimine, (nitro-saloph) and Y=zeolite Na-Y) have been synthesized and characterized for their physicochemical and spectroscopic properties. The neat and encapsulated catalysts were tested for their catalytic activities in the oxidation of β-isophorone (BIP) to keto-isophorone (KIP) using air as an oxidant at ambient conditions of pressure and temperature. It was found that the catalytic activities of encapsulated catalysts were higher than their homogeneous analogues in the oxidation reaction. Among the catalysts, however, Co(II)Cl-saloph neat and its encapsulated forms were comparatively more active than other catalysts tested in the oxidation reaction. The catalytic activities of neat and their encapsulated forms followed the same trend and the order of reactivities were: Co(II)Cl-saloph>Co(II)Br-saloph>Co(II)nitro-saloph>Co(II)saloph. Kinetics of Co(II)Cl-saloph-Y catalyzed aerial oxidation of BIP was investigated and the rates of oxidation have been obtained for variations made in catalyst, substrate and oxidant concentrations. Mechanism of oxidation involving Co(III)OO superoxo intermediate species in the oxidation of BIP has been established by UV–VIS using Co(II)saloph neat complex. Effect of temperature on the rates of oxidation of BIP was also studied and from Arrhenius plot, thermodynamic activation parameters estimated have been reported.

Kinetics of oxidation of β-isophorone to keto-isophorone catalyzed by manganese Schiff base complex using molecular oxygen

Kinetic investigations were carried out on the oxidation of β-isophorone (β-IP) to keto-isophorone (KIP) catalyzed by [LMn(III)(Cl)], (where, L=bis-salicylaldehydeethylenedi-imine, salen) at temperature in the range 10–27°C and partial pressure 0.2–3 atm of molecular oxygen. β-IP gave mainly KIP as the oxidation product under the reaction conditions studied. Initial rate approach was adopted to evaluate kinetic parameters of the reaction. From the kinetic investigations, it was found that the rate of oxidation of β-IP showed a first-order dependence with respect to catalyst and substrate concentrations, and half-order dependence on the partial pressure of oxygen. The effect of temperature on the rates of oxidation was also investigated and from the Arrhenius plot of −ln rate vs. 1/ T, the activation energy estimated is 16.12 kcal mol −1. Thermodynamic activation parameters such as enthalpy, entropy and free energy of the reaction were calculated from the known thermodynamic equations. Based on the kinetic investigations, a plausible mechanism for manganese salen complex catalyzed oxidation of β-IP to KIP has been proposed.