Iron Phthalocyanine

Cédric Colomban was born in Briançon, France, in 1986. He studied bio-organic and bio-inorganic chemistry at University Joseph Fourier, Grenoble, France. He is currently pursuing a Ph.D. at University Claude Bernard (Lyon, France) under the guidance of Dr. Alexander Sorokin and Dr. Pavel Afanasiev. His research is focused on oxidative dehalogenation of polyfluorinated and polychlorinated aromatics using single-atom-bridged diiron macrocyclic complexes.

Introduction

Iron phthalocyanine (FePc) complexes are structurally related to porphyrin complexes; phthalocyanines have been used as alternative catalysts because they are cheaper and more stable to degradation. FePc is widely used in a variety of catalytic transformations,[1] including N-alkylation,[2] C–H amination,[3] C–C bond formation,[4] preparation of esters[5] and oximes,[6] reduction,[7] oxidation,[8] [9] and radical reactions.[10] Although FePc is particularly studied as a catalyst for organic reactions, this particular reagent is also described in many other applications. For example, FePc complexes are efficient catalyst for the charge/discharge process in lithium–oxygen large-capacity batteries.[11] The following literature data indicate that FePc displays a strong bibliographic background in a wide variety of reactions and is currently considering as an active and ‘hot’ research topic. On overview of typical iron phthalocyanine syntheses is shown in Scheme [1].

Scheme 1 Preparation of FePc complexes from cyclotetramerization of common precursors. Reagents and conditions: (a) iron salt, Δ; (b) iron salt, urea, catalyst, Δ.

Abstracts

(A) FePc has been reported as an efficient and versatile catalyst for the N-alkylation of amine-substituted heterocycles with alcohols. The one-pot syntheses of ortho-amino-substituted benzimidazoles, benzothiazoles, and benzoxazoles are achieved by using FePc in combination with a base. The best reaction conditions were found to be t-BuONa in toluene.[2]
(B) Intramolecular C–H amination is catalyzed by FePc in the presence of AgSbF6 under mild reaction conditions. Allylic C–H amination is preferred over aziridination. Interestingly, this very selective amination is due to the difference in reactivity, closely paralleling C–H bond dissociation energies (allylic > benzylic > ethereal > tertiary > secondary C–H bonds). C–H aminations are particularly important reactions because may biologically active moleculs are amines.[3]
(C) Lamar and Nicholas developed an efficient method for the direct synthesis of 3-arylindoles catalyzed by FePc. 3-Arylindoles are produced in moderate to excellent yields via annulation of aryl hydroxylamines with alkynes in the presence of FePc in refluxing toluene.[4]
(D) The preparation of various esters from a wide range of alcohols and carboxylic acids is achieved through the aerobic activation of Ph3P catalyzed by FePc. The reaction is accelerated in the presence of pyridine N-oxide derivatives such as 4-methoxypyridine N-oxide (MPO). It is noteworthy that the only phthalocyanine derivative able to catalyze this reaction is the iron complex thanks to the ability of FePc to use O2 for the activation of Ph3P.[5]
(E) Beller and co-workers reported the first iron-catalyzed synthesis of oximes from olefins. The treatment of substituted styrenes with tert-butyl nitrite and NaBH4 in the presence of FePc affords oximes in moderate to high yields.[6]
(F) Iron tetrasulfophthalocyanine (FePcS) catalyzes the reduction of nitrite (NO2 –) by dithionite or sulfoxylate in aqueous alkaline solution. Interestingly, different products can be obtained depending on the choice of the reductant. Using dithionite, NO2 – is reduced to N2O, while the use of sulfoxylate as reductant lead to ammonia as the product.[7]
(G) Boger and co-workers extended the initial work of Kasuga on the oxidation of styrenes[8] to the first oxidation of unactivated alkenes by a FePc–NaBH4–O2 system. The oxidation of a range of alkenes to the corresponding alcohols is achieved by using a cata­lytic amount of FePc. In this system, O2 acts as metal oxidant and as a radical trap.[9]
(H) The radical cyclization of 1,6-dienes to give functionalized cyclic compounds is catalyzed by FePc in the presence of NaBH4 and O2 in EtOH at room temperature. The reaction gives five-membered carbo- or heterocyclic compounds with a hydroxyl group.[10]

• References

• 1 Sorokin AB. Chem. Rev. 2013; 113: 8152
• 2 Bala M, Verma PK, Sharma U, Kumar N, Singh B. Green Chem. 2013; 15: 1687
• 3 Paradine SM, White MC. J. Am. Chem. Soc. 2012; 134: 2036
• 4 Lamar AA, Nicholas KM. Tetrahedron 2009; 65: 3829
• 5 Taniguchi T, Hirose D, Ishibashi H. ACS Catal. 2011; 1: 1469
• 6 Prateeptongkum S, Jovel I, Jackstell R, Vogl N, Weckbecker C, Beller M. Chem. Commun. 2009; 1990
• 7 Kudrik E, Makarov SV, Zahl A, van Eldik R. Inorg. Chem. 2005; 44: 6470
• 8 Sugimori T, Horike SI, Tsumura S, Hande M, Kasuga K. Inorg. Chem. Acta 1998; 283: 275
• 9 Leggans EK, Barker TJ, Duncan KK, Boger DL. Org. Lett. 2012; 14: 1428
• 10 Taniguchi T, Goto N, Nishibata A, Ishibashi H. Org. Lett. 2010; 12: 112
• 11 Sun D, Shen Y, Zhang W, Yu L, Yi Z, Yin W, Wang D, Huang Y, Wang D, Goodenough JB. J. Am. Chem. Soc. 2014; 136: 8941