Iron phthalocyanine as catalyst

A variety of aUcenes can be converted to aziridines with PhINTs in good yields (48-90%) using iron phthalocyanine as catalyst (Scheme 24) [79]. It is noteworthy... 

A practical method of modification of polysaccharides by clean oxidation using H2O2 as oxidant and cheap iron phthalocyanine as catalyst has been developed. Since no acids, bases or buffers and no chlorinated compounds were used, a pure product can be recovered without additional treatment. Importantly, this flexible method provides materials with a wide range of DScho and DScooh just by an appropriate choice of the reaction conditions. Oxidized polysaccharides thus obtained possess various, tailormade hydrophihc/hydrophobic properties which have been tested successfully in cosmetic and other apphcations. 

Benzyl phenyl sulphide was oxidized to benzyl phenyl sulphone quantitatively in 6h with iron phthalocyanine as catalyst. Experiments were similarly carried out with other metal phthalocyanines using phenyl and benzyl phenyl sulphides. Experiments using copper phthalocyanine, nickel phthalocyanine and no catalyst, were carried out for 24 h and the products analysed by HPLC. These results are presented in Table-1. In these experiments... 

Ahmed J, Yuan Y, Zhou L, Kim S (2012) Carbon supported cobalt oxide nanoparticles-iron phthalocyanine as alternative cathode catalyst for oxygen reduction in microbial fuel cells. J Power Sources 208 170-175... 

Baker R, Wilkinson DP, Zhang J (2009) Facile synthesis, spectroscopy and electrochemical activity of two substituted iron phthalocyanines as oxygen reduction catalysts in an acidic... 

Bala M, Verma PK, Singh B (2013) Iron phthalocyanine as an efficient and versatile catalyst for N-alkylation of heterocyclic amines with alcohols one-pot synthesis of 2-suhstituted benzimidazoles, benzothiazoles and benzoxazoles. Green Chem 15(6) 1687-1693... 

Air oxidation of dyestuff waste streams has been accompHshed using cobalt phthalocyanine sulfonate catalysts (176). Aluminum has been colored with copper phthalocyanine sulfonate (177,178). Iron phthalocyanine can be used as a drier in wood oil and linseed oil paints (179). 

Previous studies by Sorokin with iron phthalocyanine catalysts made use of oxone in the oxidation of 2,3,6-trimethylphenol [134]. Here, 4 equiv. KHSO5 were necessary to achieve full conversion. Otherwise, a hexamethyl-biphenol is observed as minor side-product. Covalently supported iron phthalocyanine complexes also showed activity in the oxidation of phenols bearing functional groups (alcohols, double bonds, benzylic, and allylic positions) [135]. Besides, silica-supported iron phthalocyanine catalysts were reported in the synthesis of menadione [136]. 

Iron phthalocyanine is an efficient catalyst for intermolecular amination of saturated C-H bonds. With 1 mol% iron phthalocyanine and 1.5 equiv. PhlNTs, amination of benzylic, tertiary, and ally lie C-H bond have been achieved in good yields (Scheme 31). With cyclohexene as substrate, the allylic C-H bond amination product was obtained in 75% yield, and the aziridination product was found in minor amount (17% yield) [79]. 

The heterogeneous catalytic system iron phthalocyanine (7) immobilized on silica and tert-butyl hydroperoxide, TBHP, has been proposed for allylic oxidation reactions (10). This catalytic system has shown good activity in the oxidation of 2,3,6-trimethylphenol for the production of 1,4-trimethylbenzoquinone (yield > 80%), a vitamin E precursor (11), and in the oxidation of alkynes and propargylic alcohols to a,p-acetylenic ketones (yields > 60%) (12). A 43% yield of 2-cyclohexen-l-one was obtained (10) over the p-oxo dimeric form of iron tetrasulfophthalocyanine (7a) immobilized on silica using TBHP as oxidant and CH3CN as solvent however, the catalyst deactivated under reaction conditions. 

A mild aerobic palladium-catalyzed 1,4-diacetoxylation of conjugated dienes has been developed and is based on a multistep electron transfer46. The hydroquinone produced in each cycle of the palladium-catalyzed oxidation is reoxidized by air or molecular oxygen. The latter reoxidation requires a metal macrocycle as catalyst. In the aerobic process there are no side products formed except water, and the stoichiometry of the reaction is given in equation 19. Thus 1,3-cyclohexadiene is oxidized by molecular oxygen to diacetate 39 with the aid of the triple catalytic system Pd(II)—BQ—MLm where MLm is a metal macrocyclic complex such as cobalt tetraphenylporphyrin (Co(TPP)), cobalt salophen (Co(Salophen) or iron phthalocyanine (Fe(Pc)). The principle of this biomimetic aerobic oxidation is outlined in Scheme 8. 

The oxidation of starch in aqueous suspension with H202 in the presence of iron phthalocyanine gives both carboxylic and carbonyl groups (Table 3.1). The best yields were obtained with a molar ratio 12900/1 (0.0078 mol%), but the oxidation was still quite efficient with 0.0039 mol% of catalyst [25800 per anhydroglucose unit (AGU)/catalyst ratio]. The oxidized starch had almost the same final Fe-content as the initial potato starch. Still, the efficiency of this method in view of scaling up was limited by comparatively low activity and product isolation problems. 

The first chelate found to be electrocatalytic was cobalt phthalocyanine x>, which functions as an oxygen catalyst in alkaline electrolytes. Soon afterwards we were able to show 3,4,10,11) -that several phthalocyanines are also active in commercially important, sulfuric acid containing media. A comparison of various central atoms showed that activity increased in the order Cu Ni iron phthalocyanine, the nature of the carbon substrate plays a very important part FePc is more active on a carbon substrate with basic surface groups than on one with acid surface groups3). This property is however specific to phthalocyanines (Pc). 

Weber e.t al. utilized dinuclear (i-oxo iron(III) phthalocyanines 18 as catalysts in the aerobic oxidation of a-pinene lg, resulting in the formation of trans-verbenol 2g, verbenone 3g and a-pinene oxide 4g in almost equimolar amounts. Additionally, 3-pinen-2-ol 19 was obtained (Scheme 3.28) [119]. 

A variety of different metal complexes have been screened as catalysts for allylic amination using phenyl hydroxylamine 108 as the nitrogen fragment donor, and it was found that iron-complexes have better redox capacity compared to molybdenum [64]. With the iron compounds, higher yields and a lower amount of hydroxylamine-derived byproducts are obtained. These byproducts constitute one of the problems in this type of allylic amination reactions in general, as their formation is difficult to suppress. The allylic amination reaction of a-methyl styrene 112 with 108 can, e.g., be catalyzed by the molybdenum dioxo complex 107, iron phthalocyanine 114, or by the combination of the iron chlorides 115 [64,65]. It appears from the results in... 

Figure 45. FTIR spectra recorded on iron phthalocyanine catalyst dispersed on carbon during the ORR at 0.5 V vs RHE. A low hydrated Nafion membrane was used as electrolyte.

One of the most smdied examples is the mimic of the enzyme cytochrome P-450 in the pores of a faujasite zeolite [196,204,225], The iron-phthalocyanine complex was encapsulated in the FAU supercage and is used as oxidation catalyst for the conversion of cyclohexane and cyclohexanone to adipic acid, an important intermediate in the nylon production. In this case the two step process using homogeneous catalysts could be replaced by a one step process using a heterogeneous catalyst [196]. This allowed better control of the selectivity and inhibited the auto oxidation of the active compound. In order to simulate a catalyst and the reaction conditions which are close to the enzymatic process, the so obtained catalyst was embedded in a polydimethylsiloxane membrane (mimics the phospholipid membrane in the living body) and the membrane was used to limit oxygen availability. With this catalyst alkanes were oxidized at room temperature with rates comparable to those of the enzyme [205]. 

Over iron-phthalocyanine encaged in zeolite Y and using tertiary-butylhydroperoxide (t.-BHP) as oxidant, even cyclohexane can be converted to adipic acid. Selectivities of up to 35 % at conversions around 85 % have been reported. Unfortunately, however, a reaction time of 33 hours at 60 °C was required to achieve this conversion. Although the activity of the latter catalyst is certainly much too low to compete with the conventional catalytic systems for adipic acid synthesis, it provides interesting prospects for further developments. For the near future, we perceive that more and more groups will be working in this interesting field of catalysis by zeolite inclusion compounds. 

In Parton et al., a new type of heterogeneous catalyst was proposed consisting of a solid catalyst (iron phthalocyanine zeolite Y) dispersed in a dense PDMS (polydimethylsiloxane) polymer matrix.[l] The system resulted in strongly increased catalytic activities in the oxidation of cyclohexane.[2] Other systems, such as Mn(bipy)2-Y (mangtuiese bipyridine zeolite Y) were also proven to benefit from such incorporation.[3,4] The results presented here using Ti-MCM-41 confirm this for the epoxidation of olefins, an important route for the production of fine chemicals.[5] The influence of the polymer on the reaction activity and selectivity is shown by using different oxidants and solvent conditions in the epoxidation of 1-octene. It will enable the deduction of the advantages and limitations of the reported membrane occluded catalyst system. 

Results in Table-1 show that with iron phthalocyanine (Fe(II)Pc), manganese phthalocyanine (Mn(II)Pc) and cobalt tetrasulphonatophthalocyanine (Co(II)TSPc) as catalyst both phenyl and benzyl phenyl sulphides could be quantitatively oxidized to corresponding sulphones in 3-6 h. However, oxidation of benzyl phenyl sulphide to the corresponding sulphone with vanadyl phthalocyanine took 18h. In case of copper phthalocyanine (Cu(II)Pc) and nickel phthalocyanine (Ni(II)Pc), no sulphone formation was detected even after 24h, and the products analysis by HPLC showed the formation of 61% and 4.2% benzyl phenyl sulphoxide, respectively. The results for the oxidation of benzyl phenyl sulphide with Ni(II)Pc as catalyst and without any catalyst (entry 9, 10 Table-1) show that Ni(II)Pc rather gave negative effect in these oxidations. 

Iron phthalocyanine encapsulated in zeolites was used as oxygen activating catalysts in the triple catalytic aerobic oxidation of hydroquinone to benzoquinone, in the allylic oxidation of olefins and in the selective oxidation of terminal olefins to ketones. The catalyst proved active in the above reactions. It is stable towards self-oxidation and can be recovered and reused. 

Zeolites are well suited for the preparation of encapsulated complexes by virtue of the large supercages. Metallo-phthalocyanines encaged in zeolites have been proposed as enzyme mimics [7,8 Zeolite-encapsulated iron phthalocyanine catalysts have been used in hydrocarbon oxidations it was found that the resistance of the zeolite-encaged complexes against oxidative destruction by far exceeded that of free iron phthaTocyanines [9,10]. In the present work, zeolite-encaged phthalocyanine catalysts were studied in the triple catalytic oxidation of olefins. 

Analysis of the iron content allowed determination of the amount of iron phthalocyanine present in the zeolite. It was found that the metal macrocycle content of the zeolite was 0.02 mmol Fe(Pc)/g catalyst. The I.R. and the nitrogen analysis data showed, that the amount of Ho-phtnalocyanine was much higher than the amount of Fe(Pc), just as it was published by Parton and coworkers [10]. This is not surprising, because 1,2-dicyanobenzene was used in large excess over ferrocene. 

The oxidation of hydroquinone to benzoquinone is regarded as a test reaction for evaluation of the catalytic activity of the metal macrocycle oxygen-activating complexes. The oxygen uptake for the oxidation of hydroquinone catalyzed by the free iron phthalocyanine catalyst is depicted in Fig. 1. The catalytic activity of the free iron phthalocyanine was similar to that observed by Backvall, Hopkins, Grennberg, Mader and Awasthi [5]. 

The zeolite-encapsulated iron phthalocyanine catalyst was also active in this reaction and the catalytic activity was similar to that of the free complex. After the injection of a new portion of hydroquinone, the catalyst showed almost the same activity as in the first run, indicating that there was no catalyst deactivation during the reaction. The supported catalyst can be filtered off and used in new experiments. 

The zeolite-encapsulated iron phthalocyanine catalyst exhibited a similar behavior. When the oxygen uptake in the first run had ceased, 1-decene was injected into the reactor (second run), and the oxygen uptake was measured again. A similar rate was measured in the second run as in the first one, i.e. the catalytic activity did not decrease during the oxidation reaction, in spite of the presence of the strong acid HCIO4 in the reaction mixture. 

The reaction of cyclohexene in acetic acid in the presence of oxygen with cataiytic amounts of Pd(OAc)g, hydroquinone and iron phthalocyanine catalyst at 333 K resulted in a smooth oxidation (Fig. 4.). The iron phthalocyanine complex had a similar activity as that reported by B ckvell and coworkers [5]. 

The first example of FB oxidation of sulfides dates back to 1995 dibenzothiophene and diphenyl stdfide gave the corresponding sulfones in low yields (1.4% and 10%, respectively) upon treatment with O2 at 100 °C in the presence of a not fully characterized perfluorocarbon-soluble iron—phthalocyanine [19]. Following this earlier report, Co(ll)—tetraarylporphyrin Co-5 and Co(I I [—phthalocyanine Co-12 (cf Stmcture) were tested as catalysts for the FB oxidation of methyl phenyl sulfide and para-substituted aryl methyl sulfides with O2 and a sacrificial aldehyde (Table 3) [20]. 

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