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Rh(PPh 3 ) 3 Cl was immobilized on a (OEt) 3 Si(CH 2 ) 3 PPh 2 modified MCM-41 to form a stable hydrogenation catalyst. The morphology of the catalyst was characterized by X-ray absorption spectroscopy. The EXAFS results indicates that the immobilized Rh catalyst has an average Rh–O s (O s is a surface oxygen) and Rh–Si bond distances of 2.01 A and 3.15 A, respectively, suggesting that monomeric Rh complex bonds to the MCM-41 surface. However, the structure of the immobilized Rh complex is not retained after hydrogenation of cyclohexene at 75 °C under 150 psi of H 2 . After the reaction, the presence of Rh–Rh contribution with average bond distance of 2.68 A and coordination number of 1.3 and the missing contribution with bond distance of 3.85 A suggest that the reaction induces the coalescence of Rh complex to form dimeric Rh species. However, formation of trace amount of Rh metal clusters cannot be ruled out because rather small characteristic peak for the missing Rh–Rh shell may be covered by noise.

Unsubstituted and tertiary-butyl substituted salicylaldimine complexes of Cu(II) and Co(II) immobilized on silica supports (MCM-41, SBA-15 and Davisil 710) were tested as catalysts for cyclohexene oxidation using hydrogen peroxide as an oxidant under an oxygen atmosphere. The effect of the nature of the salicylaldimine ligand and the type of support were investigated. Allylic species were isolated as the major products with cyclohexene–epoxide produced as a by-product in only some instances. Product selectivity was found to be greatly influenced by the nature of the support material.

Tridentate Schiff base ligands derived from aromatic aldehydes and benzhydrazide, and their iron complexes [Fe(L1)(HL1)] 1, [Fe(HL1)Cl2(CH3OH)]·(CH3OH) 2 and [Fe(HL2)Cl2(H2O)] 3 have been prepared and characterized (H2L1 = (E)-N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide, H2L2 = (E)-N′-(5-bromo-2-hydroxybenzylidene)benzohydrazide). The crystal structure of 2 has been determined. The electrochemical properties of these complexes have been investigated by cyclic voltammetric technique in acetonitrile solutions. Electrochemical studies have revealed quasi-reversibility for these compounds. The catalytic potential of these complexes has been tested for the oxidation of cyclooctene using tert-butylhydroperoxide (TBHP) as oxidant. The effects of the molar ratio of oxidant to substrate, the temperature, the co-catalyst concentration and the solvent have been studied. Excellent selectivities have been obtained for the epoxidation of cyclohexene, cyclooctene, norbornene, cis- and trans-stilbene.

Selective cis -dihydroxylation of various olefins has been carried out using molybdenum acetylide complex CpMo(CO) 3 (C CPh) ( 1 ) as catalyst and hydrogen peroxide as an efficient and environmentally benign oxidant. In case of cyclohexene, very high conversion (95%) and selectivity (86%) for cis -dihydroxylated product has been achieved using H 2 O 2 as an oxidant and t -butanol as a solvent. cis -Dihydroxylation of other substrates like styrene, α-methyl styrene, limonene and cyclopentene has also been carried out with very high selectivity for diol. The catalyst and intermediate species have been characterized using FT-IR, UV–vis spectral analysis and XPS studies as well as cyclic voltametric studies. These studies suggest that molybdenum oxo–peroxo complex is the catalytically active species. The intermediate blue complex when characterized by ESI MS suggested the formation of dimeric molybdenum complex and XPS and cyclic voltametric studies confirm the presence of mixed valence Mo(V) and Mo(VI) in the reaction intermediate. Based on the characterization results possible mechanism for dihydroxylation is proposed. Interestingly, even though the catalyst is homogeneous; it could be recovered quantitatively by extraction in aqueous phase and recycled five times without any appreciable loss in cyclohexene conversion and selectivity for cis -1,2-cyclohexanediol.

The synthesis and characterisation of three dimeric cis-dioxomolybdenum(VI) complexes involving Schiff-base ligands is described. Ligands were obtained by condensation of salicylaldehyde with aromatic nitrogen–nitrogen linkers (4,4′-diaminodiphenylmethane; 4,4′-diaminodiphenylether; 4,4′-diaminodiphenylsulfone). [MoO2(acac)2] reacted with the prepared ligands; bis[(N,O-salicylidene)-4,4′-diaminodiphenyl]methane, H2L1; bis[(N,O-salicylidene)-4,4-diaminodiphenyl]ether, H2L2; bis[(N,O-salicylidene)-4,4′-diaminodiphenyl]sulfone, H2L3; forming six-coordinated cis-dioxoMo(VI) complexes; [MoO2L1–3]2. The yellow colored, non-electrolytic and diamagnetic compounds were characterized by elemental analyses and spectroscopic techniques (IR, 1H NMR and UV–vis). These complexes show good catalytic activity and selectivity in the epoxidation of cyclohexene with t-butylhydroperoxide (TBHP), especially for complex [MoO2L3]2, which could give a nearly 88% of epoxidation conversion and 94% of selectivity. Introduction of the electron-withdrawing group to the aromatic nitrogen–nitrogen linkers of complex strongly increases the effectiveness of a catalyst. The addition of single-wall carbon nanotubes (SWNT) can enhance the activity of the Mo complexes and the selectivity toward epoxide. It is also better for the recycling of the Mo complex, the catalytic activity and the selectivity toward which still held at a high level after four times using.

Catalytic epoxidation of cycloalkenes to corresponding epoxides using molecular oxygen was carried out in presence of cobalt(II) exchanged zeolite X based catalysts. Effect of temperature (353–418 K) and pressure (30–150 psi) was studied to obtain the optimum conditions for the reaction. The best results were obtained at 60 psi pressure and 373 K using NaCoX96 catalyst with cycloalkene conversion and epoxide selectivity for cyclohexene, cycloheptene and cis-cyclooctene were obtained in the range 26–47 and 48–100% respectively. Alkali and alkaline earth cationic promoters were introduced into the zeolite catalyst in order to study the effect of basicity of the catalyst on the cycloalkene conversion and epoxide selectivity. Cobalt(II) exchanged zeolites X, NaCoX96, seems to be efficient heterogeneous catalysts for the epoxidation reactions using molecular oxygen. The catalyst was observed to be recyclable as conversion and selectivity were retained even after four catalytic reaction cycles.

Mn(III) and Mo(IV)-Salen complexes homogeneous and immobilized on a silica surface have been tested in the catalytic epoxidation of cyclooctene and cyclohexene with tert-butylhydroperoxide (TBHP) and hydrogen peroxide (HP) as an oxidant. The effects of reaction conditions on the epoxide yield as well as the epoxidation rate with different catalysts have been established. The catalytic decomposition of TBHP by manganese and molybdenum-Salen complexes has been studied. The peptide immobilized Salen complexes were compared in catalytic activity with ester bound ones. The immobilized catalysts show stable catalytic activity in manifold reuses. The Mo-Salen complexes homogeneous as well as immobilized exhibited high catalytic activity for the epoxidation of cyclooctene, whereas Mn-Salen complex systems cause additionally non-productive decomposition of hydroperoxide.

Commercially available zinc perchlorate hexahydrate [Zn(ClO 4 ) 2 ·6H 2 O] was found to be highly effective catalyst for opening of epoxide ring by thiols under solvent-free condition at room temperature for efficient synthesis of 2-hydroxysulfides. The catalytic activity of various group I/II metal perchlorates followed the order Zn(ClO 4 ) 2 ·6H 2 O ≫ Mg(ClO 4 ) 2 ·6H 2 O > Ba(ClO 4 ) 2 ·6H 2 O ⋙ LiClO 4 . The Zn(ClO 4 ) 2 ·6H 2 O-catalysed reaction of epoxides derived from cyclic and acyclic olefines with thiols afforded β-hydroxysulfides in high yields. Reaction with cycloalkene oxides led to stereoselective formation of the trans -2-hydroxysulfides. Excellent regioselectivity was observed for unsymmetrical epoxides. In case of styrene oxide, the hydroxysulfide from nucleophilic attack at the benzylic carbon of the epoxide was the major product. Preferential nucleophilic attack by thiophenol took place at sterically less hindered position of the epoxide ring of unsymmetrical non-styrenoid alkene oxides. Epichlorohydrin exemplified a case of chemo- and regioselective reaction with no detectable (GC–MS) side product formation by direct displacement of the chlorine atom. The methodology was extended for an efficient synthesis of the key intermediate of diltiazem.

A novel Ti–O–Ti bonding complex constructed in the monomeric, mono-lacunary α-Keggin polyoxotungstate, [{Ti(OH2)(ox)}2(μ-O)(α-PW11O39)]5− (1) can act as a precatalyst for the epoxidation of cyclooctene, cyclohexene, and 1-octene with aqueous H2O2 at 25 °C in a homogeneous system. The catalytic activities of complex 1 were considerably higher than those of dimeric mono-, di-, and tri-titanium(IV)-substituted Keggin polyoxotungstates [(α-PTiW11O39)2O]8− (2), [(α-1,2-PW10Ti2O38)2O2]10− (3), and [(α-1,2,3-PTi3W9O37)2O3]12− (4).

Cyclohexene and tetralin can be oxidized to a slight extent by N 2 O in the presence of quaternary ammonium salt promoters under mild experimental conditions. In non-polar solutions, the higher yields of the oxidations of cyclohexene and tetralin are influenced by the donor–acceptor properties of the solvents. The changes in the IR spectrum of N 2 O lend further support to the assumption that ion-pair interactions between the solvated oxidant and the onium salts result in an enhanced rate of O-transfer from the oxidant. Onium-decavanadate ion-pair complexes are more effective promoters than simple onium salts.

The Keggin-type di-vanadium-substituted silicotungstate [γ-1,2-H 2 SiV 2 W 10 O 40 ] 4− with the {VO-(μ-OH) 2 -VO} core catalyzes the epoxidation of various alkenes using only 1 equiv. H 2 O 2 with the high epoxide yield and high efficiency of H 2 O 2 utilization under very mild reaction conditions. Notably, this system shows unique stereospecificity, diastereoselectivity, and regioselectivity, which are quite different from those reported for the epoxidation systems including [γ-SiW 10 O 34 (H 2 O) 2 ] 4− .

Photocatalytic oxidation of cyclopentene was performed over a series of structure different titanium(IV) oxide catalysts. The reaction was carried out with a special attention to limit the extent of the cyclic alkene total decomposition to water and carbon dioxide. It was shown that variable surface catalytic structures of titania acting together with active surface species (e.g., surface hydrogen peroxide, hydroxyl radicals, singlet oxygen) may significantly affect the course of the partial photooxidation. Reactions were carried out in liquid phase, isothermally and at atmospheric pressure with oxygen in the quartz reactor fitted with a source of UV. The catalysts’ structure dependent selectivity profiles were compared with similar kinetic data obtained previously in partial photocatalytic oxidation of cyclohexene.

The epoxidation of cyclopentene with hydrogen peroxide catalyzed by 12-heteropolyacids of molybdenum and tungsten (H3PMo12−nWnO40, n = 1–11), 12-tungstophosphoric acid and 12-molybdophosphoric acid combined with cetylpyridinium bromide as a phase transfer reagent was carried out in acetonitrile. Among 13 heteropolyacids investigated, catalyst of H3PMo6W6O40 showed the highest activity, giving a conversion of 60% and a selectivity of 95% in the epoxidation of cyclopentene. The fresh catalysts and the catalysts under reaction condition were characterized by UV–vis, FT-IR and 31P NMR spectroscopy, which has revealed that all of the molybdotungstophosphoric acids were degraded in the presence of hydrogen peroxide to form a considerable amount of phosphorus-containing species. The active species resulted from H3PMo6W6O40 are new kinds of phosphorus-containing species, which is different from {PO4[WO(O2)2]4}3−.

Vanadium containing MCM-41(V-MCM-41) was synthesized by one pot synthesis and characterized by spectroscopic techniques. The oxidation of olefins such as 1-hexene, cyclohexene, cyclopentene, norbornene and trans-2-hexene-1-ol with tertiary butyl hydroperoxide (TBHP) in the presence of V-MCM-41 as catalyst in different solvents(CH2Cl2, CH3CN, CH3OH·CHCl3) is described. It was found that V-MCM-41 in refluxing CHCl3 was very reactive for epoxidation of trans-2-hexene-1-ol with 52% reactivity and 100% selectivity. Oxidation of trans-2-hexene-1-ol to the corresponding epoxide in the absence of solvent was successfully carried out with the enhancement of reactivity to 94%.

Ruthenium-catalyzed ROM–RCM and CM were carried out. In the case of ROM–RCM of cycloalkene-yne, various cyclized compounds were reconstructed from the corresponding cycloalkene having alkyne in a tether using the second-generation ruthenium–carbene complex.

Six dioxomolybdenum(VI) complexes of Schiff-bases derivatives of trans-1,2-diaminocyclohexane and R-salicylaldehyde as well as 2-hydroxynaphthaldehyde have been synthesised and characterized by IR, UV-Vis and NMR-spectroscopic methods. The catalytic activities of the complexes in the reaction of epoxidation of cyclohexene and 1-octene with tert-butyl hydroperoxide (TBHP) as oxidant have been studied.

The aldimines and ketimines reacted with alkenes under a rhodium catalyst [Rh(coe) 2 Cl] 2 and Cy 3 P to give mainly the double alkylated products with moderate to high yields. The aldimines bearing H, p -CH 3 O, p -CH 3 , p -Cl, p -F, p -CF 3 and o -CH 3 groups have high reactivities, but m -CH 3 O, m -Cl and m -F exhibit moderate reactivities. However, o -Cl, o -NO 2 and p -NO 2 groups did not work. The ketimine 9 gave the mono-alkylated products predominantly. 1-Naphthyl and heteroaromatic aldimines showed good regioselectivities.

Cyclohexene oxidation using tert-butylhydroperoxide (TBHP) or chloroperoxybenzoic acid (CPBA) in the presence of iron(II) polychlorophthalocyanine (Cl16PcFe), iron(II) phthalocyanine (PcFe) and cobalt(II) phthalocyanine (PcCo), results in the formation of the following products: cyclohexene oxide, 2-cyclohexene-1-ol and 2-cyclohexene-1-one. Adipic acid was also formed after long reaction times. The selectivity for 2-cyclohexene-1-one is favoured when Cl16PcFe or PcCo catalysts are employed, while PcFe is selective towards the formation of 2-cyclohexene-1-ol. The Cl16PcFe catalyst is transformed into a μ-oxo dimer (Cl16PcFeIIIOIIIFePcCl16) during the oxidation process. The catalytic process using the unsubstituted PcCoII and PcFeII catalysts involved PcMIII species as an intermediate. The active form of the Cl16PcFe catalyst was stable to degradation in that it was still active even after 4 weeks of continued catalysis.

High trans and mainly cis directing Grubbs Ru initiators, I–III, and IV, respectively have been investigated as catalysts for metathesis copolymerization of norbornene and cyclopentene. When the Lewis acid, MoCl5 or WCl6, is added to these Lewis bases initiators, I–III, a cage effect develops such that the polymers become alternating caused by the severe or almost total denial of access of norbornene to the propagating metallacarbenes. Addition of ethers destroys the cages and removes the effect. In marked contrast the N-heterocyclic ligand Grubbs initiator, IV, does not show the effect, as addition of MoCl5 only seems to retard the overall reaction, but does not change the copolymer composition.

A new one pot reaction of hydroformylation–cyclotrimerization of cyclopentene 1a and cyclohexene 1b was selectively catalyzed by Rh6(CO)16 and H3PW12O40·xH2O (HPA-W12) in THF as a solvent at 40 atm (CO/H2 = 1/1) to give 2,4,6-trisubstituted-1,3,5-trioxanes 3a and 3b as major products along with the corresponding aldehydes 2a and 2b. © 2003 Elsevier Science B.V. All rights reserved.

The kinetics of the epoxidation of cis-cyclooctene, 2-norbornene and limonene catalyzed by cis-[RuCl2(dppb)(2,2′-bipy)] (1) or trans-[RuCl2(dppb)(2,2′-bipy)] (2) (where, dppb: 1,4-bis(diphenylphosphino)butane; 2,2′-bipy: 2,2′-bipyridine) in the presence of iodosylbenzene (PhIO) follow a Michaelis–Menten type mechanism. The performance of 1 and 2 in the epoxidation of cis-cyclooctene, 2-norbornene and limonene are respectively (1) Vmax=8.62, 11.6 and 4.98 mol l−1 min−1 and (2) Vmax=4.28, 7.55 and 5.66 mol l−1 min−1. The activation energies of the epoxidations catalyzed by 1 are 1.5–3.3 kcal mol−1 lower than those measured for 2.

New Mn(II), Co(II), Ni(II) and Cu(II) complexes of a tetradentate Schiff base ligand [bis(2-hydroxyanil)acetylacetone],“2-[{1-methyl-3-[(2-hydroxyphenyl)imino]butylidene}amino]phenol”, H 2 haacac, have been prepared and characterized by elemental analyses, IR and conductometry. The results suggest that the Schiff base is a bivalent anion with tetradentate ONNO donors derived from the phenolic oxygen and azomethine nitrogen. The formulae was found to be [M(haacac)] for the 1:1 non-electrolytic complexes. Alumina-supported [M(haacac)] complexes catalyze the oxidation of cyclohexene with tert -butylhydroperoxide (TBHP). The major products of the reaction were 2-cyclohexene-1-ol (OH), 2-cyclohexene-1-one (CO) and 2-cyclohexene-1-( tert -butylperoxy) (OO t Bu). The influence of temperature, solvent and time for the oxidation reaction has been studied. The selectivity of 2-cyclohexene-1-( tert -butylperoxy) varied with reaction temperature. Mn(haacac)-alumina shows significantly higher catalytic activity than other alumina-supported complexes.

In this study, in situ FT-IR spectroscopy and ex situ GC and GC–MS were employed to investigate the photooxidation of cyclohexane and cyclohexene in BaY. Cyclohexane and cyclohexene were oxidized using molecular oxygen and photochemically produced tert-butyl hydroperoxide (TBHP) in BaY. The main products formed after photooxidation of cyclohexane with molecular oxygen were cyclohexanone and cyclohexanol. Cyclohexane did not react with TBHP in BaY. The main product formed after photooxidation of cyclohexene and molecular oxygen in BaY was 2-cyclohexen-1-one and the main product formed after reaction of cyclohexene with TBHP in BaY was 1,2-epoxy cyclohexane. In general, it was found that the photooxidation of cyclohexene using O2 or TBHP gave consistently higher activity but lower selectivity than that found for cyclohexane photooxidation, due to the presence of two active reaction centers (–H and C=C bond) in cyclohexene. It was also shown that for cyclohexene oxidation in BaY, the choice of oxidant significantly alters the product distribution. © 2002 Elsevier Science B.V. All rights reserved.

The catalysed oxidations of hydrocarbons were found to involve radicals and to be inhibited effectively by phenolic scavengers. The dependences of the activities of the catalysts on their concentrations are explained by the structural changes in the inverse micelles, from the first small spherical associates through an open-layered more active structure, which finally folds back by forming a hollow spherical closed structure, with a fall in the rate. The 51 V NMR spectral behaviour of the ion-pair catalysts and the colour changes in the solutions are discussed. The decavanadate structure is not destroyed entirely during the catalysed oxidation, in spite of the partial reduction of the V(V) centres and some structural deformations. The essential role of water and the influence of the products of oxidation by O2 on the courses of the reactions are also discussed.

Two novel molybdenum-containing organic complexes based on 3,4-dihydroxy-3-cyclobutene-1,2-dione (“squaric acid”), 1-phenyl-1-ethanamine and 1,3-diamino-2-propanol (DAP), respectively, have been synthesized in aqueous medium and characterized by infrared (FT-IR) spectroscopy, thermogravimetric (TGA) and elemental analyses. The catalytic activities and selectivities of these complexes in the epoxidation of cyclohexene with t-butylhydroperoxide (TBHP) were, approximately, the same as those of similar complexes prepared previously in the same manner.

trans-RuCl2[κ3-1R,2R-P(NH)(NH)P](PPh3) was synthesized and used in the oxidation of cyclohexene at 80–130 °C by molecular oxygen with very high activity to the products including 2-cyclohexen-1-one, 2-cyclohexen-1-ol and 1,2-cyclohexandiol. The addition of carbon nanotubes (CNTs), which were synthesized by Fe-Cu/SiO2 catalyzed decomposition of ethylene at 550 °C, can enhance the activity of the Ru complex and the selectivity of 2-cyclohexen-1-ol. It was also better for the recycling of the Ru complex, the catalytic activity and selectivity of which still held at a high level after nine times using.

The polymer supported Mn(II) Schiff base complexes were prepared from crosslinked chloromethylated poly(styrene-divinyl benzene) copolymer beads by sequential modification into a Schiff base bearing ligand. These Schiff base bearing polymer on treatment with a solution of MnCl 2 ·2H 2 O gave the corresponding metal complexes. The polymer supported Mn(II) complexes were characterised by elemental analysis, FT-IR, diffuse reflectance, SEM and thermogravimetric analysis. Physicochemical properties such as surface area, bulk density and swelling behaviour in different solvents were studied. The catalytic activity of the supported metal complexes were studied in the epoxidation of norbornene and cis -cyclooctene using tert -butylhydroperoxide (TBHP) as the terminal oxidant. The influence of various reaction parameters such as temperature, solvent, substrate and catalyst concentration, on conversion and selectivity has been studied.

A number of chiral 1,10-phenanthrolines (phens) have been assessed in asymmetric Cu(I)-catalyzed allylic oxidation of cyclohexene. Very effective copper-phen catalysts are obtained only when these ligands bear at least a substituent close to the reactive site of the catalyst. Enantioselectivity up to 36% was obtained.

Ionic Fe(III)porphyrins pentafluorophenyl-derivatives: 5,10,15-tris(pentafluorophenyl)-20-(4-N-methylpyridyl)porphyrin iron(III) ([Fe{M(4-N-MePy)TPFP}]2+), 5,10,15-tris(4-N-methylpyridyl)-20-(pentafluorophenyl)porphyrin iron(III) ([Fe{T(4-N-MePy)MPFP}]4+) and 5,10,15-tris(pentafluorophenyl)-20-(3-sulfonatophenyl)porphyrin iron(III) ([Fe{M(3-SO3P)TPFP}]) immobilised on silica gel (SiO2) and modified silica with sulfonatophenyl (SiSO3−), propylimidazole (IPG), sulfonatophenyl plus propylimidazole (SiSO3−(IPG)), propyltrimethylammonium (SiN+) and propyltrimethylammonium plus propylimidazole (SiN+(IPG)) were studied in the epoxidation of (Z)-cyclooctene by H2O2. The better yields of product, cis-epoxycyclooctane, were achieved with the catalytic systems, [Fe{M(4-N-MePy)TPFP}]-SiSO3(IPG), [Fe{M(3-SO3P)TPFP}]-IPG and [Fe{M(3-SO3P)TPFP}]-SiO2, where is more probable to have available sulfonatophenyl groups. That is, where there is no ionic binding Fe(III)porphyrin-support via sulfonatophenyl. A charge effect supplied by the available sulfonatophenyl residues and a more polar microenvironment provided by the silica-support promote the heterolytic cleavage of the OO bond, which is essential to obtain high yields of products in oxidation reactions. Effects of general acid–base catalysis, as occurs in enzymes, and higher reduction potential provided by electron-withdrawing groups, present on porphyrin ring or axial ligand, as recently reported by Nam and coworkers for homogeneous Fe(III)porphyrins, to promote the heterolysis of the OO bond are ruled out.

Alumina-supported Mn(II) complexes with ligands of acetylacetonato (acac), N , N ′-ethylenebis(salicylideneiminato) (salen), ethylenediamine (en) and 2,2′-bipyridine (bpy) catalyze the oxidation of cyclohexene with tert -butylhydroperoxide (TBHP) and hydrogen peroxide. Oxidation of cyclohexene with TBHP gave 2-cyclohexene-1-ol, 2-cyclohexene-1-one and 1-( tert -butylperoxy)-2-cyclohexene whereas, oxidation with H 2 O 2 resulted in the formation of cyclohexeneoxide and cyclohexene-1,2-diol. Mn(II) catalysts with the nitrogen donor ligands show significantly higher catalytic activity than oxygen donor ligands at the same surface coverage. The mechanism of oxidation has also been discussed.

The ability of certain Fe and Mn metalloporphyrins to catalyse the H 2 O 2 epoxidation of cyclooctene is analysed. The ‘efficiency’ of epoxidation is dissected into contributions due to inherent catalyst epoxidation ability, catalyst H 2 O 2 dismutation ability, and catalyst stability towards the oxidant. It is shown that catalyst stability is a major factor contributing to apparent catalyst ability. The preparation of a sol–gel encapsulated metalloporphyrin is reported and it is shown to exhibit reduced rate of epoxidation, but a much enhanced stability.

With Cu(MeCN) 4 BF 4 as catalyst and benzotrifluoride as solvent, the allylic oxidation of cyclohexene by tert-butyl perbenzoate was performed at room temperature in 75% yield without requiring an axcess of the olefin. The benzoyloxylation of other cycloalkenes in using such a substrate/perester ratio required additives such as DBU, DBN or DMAP, and often an increase of the reaction temperature.

The complexes of rhodium with N-phenyl anthranilic acid and anthranilic acid were synthesised and their structure was investigated with infrared spectroscopy. It appears that rhodium interacts with N-phenyl anthranilic acid via the carboxyl and the amine groups. With anthranilic acid, the bond with the amine could not be unambiguously established. X-ray diffraction and elemental analysis data suggest that the complexes are not pure and that the presence of Rh(0) is likely. Catalytic hydrogenation results and mercury poisoning experiments confirm the presence of Rh(0).

MoO2(acac)2 has been encapsulated in silica matrixes prepared by hydrolysis/condensation of tetraethylorthosilicate. Alternatively, hybrid organic–inorganic matrixes were prepared by adding 3-(triethoxysilyl)propylethylenediamine or 1,4-bis(triethoxysilyl)benzene to the reaction mixture. All systems were tested in the epoxidation of cyclohexene or cis-cyclooctene at

Addition of poly(ethylene oxide) (PEO) to the catalytic system MoO2(acac)2/TBHP/t-butanol used for epoxidation of olefins allowed an easy strategy for catalyst recycling and product recovery. This procedure is based upon catalyst removal by precipitation of a complex with the polymer, being advantageous over other similar recycling methodologies in that there is no requirement for specially prepared catalysts or solvents. Although some catalyst leaching is detected, the epoxidation of cis-cyclooctene was achieved with global turnover numbers close to 650. © 2002 Elsevier Science B.V. All rights reserved.

Attempts have been made to immobilize some molybdenum-containing complexes with low molecular weight organic ligands, including newly synthesized ones, on commercial ion-exchange resins. The catalytic activity of these complexes in the epoxidation reaction of cyclohexene with tert-butyl hydroperoxide was evaluated and compared to that of the molybdenyl acetylacetonate homogeneous catalyst as well as to some polymeric molybdenum- containing catalysts derived from ion-exchange resins and obtained previously.

The liquid-phase epoxidation of a series of cyclic alkenes with H2O2 and TBHP over Na–Tiβ zeolites without undergoing further acid-treatment has been carefully investigated. Many factors such as the time, the conversion, the solvent, the Si/Na ratio, the Si/Ti ratio and the Ti/Na ratio, have been found to take effects on the conversion of cyclohexene and H2O2 as well as the selectivity to epoxide. Lower conversion (about 6.2 mol%) of cyclohexene has shown an improvement for the selectivity to epoxide (about 90%). The solvent having bigger dielectric constant is very helpful to enhance the reactivity of substrate, particularly MeCN is an optimal choice for improving the selectivity to epoxide (up to 59%). The reactivity of cyclic alkenes decreases with increasing carbon number from C6 to C12, the selectivity to corresponding cyclic epoxides is C 12≈ C 8 (100%)> C 7 (71%)> C 5 (20%)> C 6 (1.2%) , where the exception of C5 is related to its low dissolubility and steric conformations of reactant and products molecules. Linear alkene shows the higher reactivity and the lower selectivity to epoxide than cyclic alkene with the same carbon number. TBHP as the oxidant significantly retards the reactivity of C6, C7 and C12, and shows more beneficial to the selective production of epoxide than H2O2.

The cationic manganese porphyrins: manganese(III) 5,10,15-tris(2,6-dichlorophenyl)-20-(4- N -methylpyridyl)porphyrin ([Mn{M(4- N -MePy)TDCPP}] 2+ ), 5,10,15,20-tetra(2,3,5,6-tetrafluoro-4-trimethylammoniumphenyl)porphyrin ([Mn(TF4TMAPP)] 5+ ) and 5,10,15,20-tetra(4- N -methylpyridyl)porphyrin ([Mn{T(4- N -MePy)P}] 5+ ) supported on silica modified with propylimidazole (IPG), sulfonatophenyl (SiSO 3 − ) and both propylimidazole and sulfonatophenyl (SiSO 3 − (IPG)) have been studied as catalysts in the epoxidation of ( Z )-cyclooctene and oxidation of cyclohexane. High yields of products were obtained using PhIO as oxidant without leaching, except for the IPG, of the catalyst from the surface of the support. The catalysts also have been used with H 2 O 2 in the epoxidation of ( Z )-cyclooctene with and without a co-catalyst (imidazole or ammonium acetate). The best catalyst [Mn{T(F4TMAPP)}]-SiSO 3 (IPG) achieved almost 200 turnovers of the product cis -epoxycyclooctane using ammonium acetate as co-catalyst. The analogous homogeneous systems have been studied for comparison, but they did not reach the same efficiency . With these studies the two-fold role of imidazole in oxygenations of hydrocarbons by H 2 O 2 and Mn(III) porphyrins was confirmed. The characterisation of supported metalloporphyrins by UV–VIS spectroscopy is reported too.

The epoxidation of a number of cyclic and linear terminal alkenes by an O 2 –O 3 mixture at room temperatures catalysed by Fe(TMP)Cl is reported. It appears that the alkene forms a primary ozonide which rearranges to a secondary ozonide, and it is the latter which, when catalysed by Fe(TMP)Cl, affects the subsequent alkene epoxidation. A number of other metal complexes were also tested as catalysts, but Fe(TMP)Cl was the most effective.

The use of the water soluble ruthenium clusters Ru 3 (CO) 12− x (TPPTN) x ( x =1 1 , 2 2 or 3 3 ) and H 4 Ru 4 (CO) 11 (TPPTN) 4 (TPPTN=P{ m -C 6 H 4 SO 3 Na) 3 ) as catalyst precursors in the hydrogenation of non-activated alkenes under biphasic conditions is described. Each cluster displays activity under moderate conditions, ca. 60 atm. H 2 at 60°C, with catalytic turnovers up to ca. 500. The trinuclear clusters undergo transformation during reaction but can be reused repeatedly without loss of activity. Other methodologies such as ionic liquid–organic and the use of silica supports have been attempted with these clusters but they are less effective than the aqueous–organic regime.

The oxidation of cyclohexene with tert -butylhydroperoxide (TBHP) in the presence of exchanged zeolite NaY (NaA and HS in some cases) with transition metal elements Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) in refluxing dichloromethane has been investigated. The results showed that the Mn–Na–Zeolite had the highest reactivity and selectivity with the formation of di(2-cyclohexenyl) ether as the main product. The optimum conditions were applied to cyclopentene and 1,1-diphenylethylene which afforded di(2-cyclopentenyl) ether and benzophenone, respectively.

Epoxidation of cis-cyclooctene with iodosylbenzene has been carried out in the absence and presence of metal complex catalysts and light. Increase in the epoxide yield is observed in the presence of light.

Molybdovanadophosphate (NPMoV)/hydroquinone/O 2 system was found to be an efficient reoxidation system in palladium-catalyzed oxidations of alkenes and related compounds. Thus, acetoxylations of cycloalkenes utilizing molecular oxygen as the final oxidant were cleanly performed using the multicatalytic system consisting of Pd(OAc) 2 /hydroquinone/NPMoV to form 3-acetoxy-1-cycloalkenes in good yields. For example, cyclopentene and cyclohexene were converted into the corresponding allylic acetates in almost quantitative yields. Omitting hydroquinone from the catalytic system led to low yields of the acetates. Acetoxylation of cyclooctene was satisfactorily achieved by replacing hydroquinone of the multicatalytic system by chlorohydroquinone. Molybdovanadophosphates, which catalyze the smooth dehydrogenation of hydroquinone to benzoquinone with dioxygen, were found to rapidly promote the present Pd(II)-catalyzed acetoxylation of cycloalkenes. By the use of a mixed solvent of ethanol and water under these conditions, Wacker type oxidations of cyclohexene and styrene were accomplished in fair to good yields. Monosubstituted alkenes such as ethyl acrylate and acrylonitrile underwent the acetalization by the present catalytic system to give the corresponding acetals in quantitative yields.