Effect of imidazole on biomimetic cyclohexane oxidation by first-, second-, and third-generation manganese porphyrins using PhIO and PhI(OAc)2 as oxidants

This review describes new reactions catalyzed by recently discovered types of metal complexes and catalytic systems (catalyst + co-catalyst). Works of recent years (mainly 2010-2016) devoted to the oxygenations of saturated, aromatic hydrocarbons and other carbon-hydrogen compounds are surveyed. Both soluble metal complexes and solid metal compounds catalyze such transformations. Molecular oxygen, hydrogen peroxide, alkyl peroxides, and peroxy acids were used in these reactions as oxidants.

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“…Metalloporphyrins [175][176][177][178] play a very important role in such studies; they are models of enzyme reaction centers.…”

Section: New Types Of Ligands and Catalystsmentioning

confidence: 99%

New Trends in Oxidative Functionalization of Carbon–Hydrogen Bonds: A Review

Shul’pin

2016

Catalysts

174

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“…DMAP exhibited lower values for K 1 and K 2 when compared to TBAB. DMAP is an aminopyridine‐type ligand known to be less effective than imidazole‐type ligands, although K 1 and K 2 values obtained in this work are comparable to axial coordination of imidazole in second‐generation Mn(III)‐porphyrins . This observation could be justified by the resonance effect promoted by the lone electron pair on the amino substituent which makes the pyridinic nitrogen a good σ‐ and π‐ donor in DMAP …”

Section: Electronic Spectra and Mechanistic Considerationsmentioning

confidence: 60%

“…Metalloporphyrins MnP1‐6 are five‐coordinated complexes with a square pyramidal geometry (Figure ), so there is a free vacant site at the metallic center where the epoxide should coordinate to suffer the cycloaddition. When 1‐methylimidazole and DMAP are in the system, there is a competition between the base and epoxide; the more favorable and strong coordination between Mn(III) and nitrogen donor ligands turns the active catalyst in a hexacoordinated dormant species and no conversion is observed (see mechanistic considerations).…”

Section: Resultsmentioning

confidence: 99%

“…When 1‐methylimidazole was used as cocatalyst instead of DMAP, similar behavior was observed (0 % of conversion). Da Silva and co‐workers have studied similar Mn(III)‐porphyrins ([Mn III (TPP)Cl], [Mn III (APTPP)Cl], [Mn III (Br 9 APTPP)Cl], [Mn III (T4CMPP)Cl] and [Mn III (Br 8 T4CMPP)Cl]) in the presence of imidazole. Similarly, the authors have made a spectrophotometric titration of Mn(III)‐porphyrins and calculated K 1 and K 2 , in equilibria quite similar to Scheme .…”

Section: Electronic Spectra and Mechanistic Considerationsmentioning

confidence: 99%

“…[7d,9] Among these systems, heterocyclic macrocycle metal complexes, such as metalloporphyrins [10] and metallocorroles, [8b,11] are promising catalysts due to the possibility of altering electronic and steric characteristics by modifications of their framework. [12] Also, in square pyramidal metalloporphyrins the axial counterion may influence the stability and catalytic activity and additionally can be readily replaced. [10c,13] Metalloporphyrins (MP) have been studied lately for this transformation and some outstanding results were reported.…”

Section: Introductionmentioning

confidence: 99%

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Mn^III Porphyrins: Catalytic Coupling of Epoxides with CO₂ under Mild Conditions and Mechanistic Considerations

et al. 2019

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A series of 5,10,15,20‐tetrakis(2,3‐dichlorophenyl)porphyrinate complexes of manganese(III) [MnIII(T2,3DCPP)X] with six different axial ligands (X=NO3−, AcO−, IO3−, Br−, Cl−, HO−) were investigated as catalysts in the cycloaddition reactions of CO2 and styrene oxide (SO), under mild conditions, i. e., atmospheric pressure and 60 °C. [MnIIIT(2,3DCPP)IO3] showed the best catalytic performance, selectively producing the respective cyclic carbonate from diverse epoxides using tetrabutylammonium bromide as a nucleophile source. Mechanistic considerations were inferred from electronic spectra and spectrophotometric titrations, showing that there are a series of equilibriums involved in the formation of the catalytic active species. Stability constants for the proposed equilibrium models were determined using SQUAD software. A catalytic cycle has been proposed based on those observations.

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Exploring manganese pyridylporphyrin isomers for cyclohexane oxidation: First‐generation catalysts are better than third‐generation ones

Meireles

Guimarães

Querino

et al. 2021

Applied Organom Chemis

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Manganese porphyrins are widely studied as catalysts for oxidation reactions of different organic substrates. In this work, we evaluate the catalytic activity of manganese complexes derived from meso-tetrakis(2-, 3-, or 4-pyridyl) porphyrin isomers, [Mn(TXPyP)]Cl (X = 2, 3, or 4), and the respective β-octabrominated counter-parts, [Mn(Br 8 TXPyP)], for oxidation of cyclohexane by PhI(OAc) 2 . At first, we describe the synthesis and characterization of a new third-generation manganese porphyrin, [Mn(Br 8 T4PyP)]. It presented a more positive value of half-wave potential (À0.287 V vs. Fc + /Fc) and a lower solubility in organic solvents among the isomers. In general, the third-generation catalysts [Mn(Br 8 TXPyP)] showed lower catalytic activity than those of the first-generation [Mn(TXPyP)]Cl in all systems studied. In addition, the use of water or imidazole as cocatalysts did not increase the yield or selectivity of the systems. Finally, when evaluating the use of the classic oxidant PhIO, there was a decrease in yield for all systems, indicating that PhI(OAc) 2 is a good substitute for this oxidant in catalytic systems.

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Effect of imidazole on biomimetic cyclohexane oxidation by first-, second-, and third-generation manganese porphyrins using PhIO and PhI(OAc)2 as oxidants

Cited by 23 publications

References 46 publications

New Trends in Oxidative Functionalization of Carbon–Hydrogen Bonds: A Review

New Trends in Oxidative Functionalization of Carbon–Hydrogen Bonds: A Review

Mn^III Porphyrins: Catalytic Coupling of Epoxides with CO₂ under Mild Conditions and Mechanistic Considerations

Exploring manganese pyridylporphyrin isomers for cyclohexane oxidation: First‐generation catalysts are better than third‐generation ones

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Effect of imidazole on biomimetic cyclohexane oxidation by first-, second-, and third-generation manganese porphyrins using PhIO and PhI(OAc)2 as oxidants

Cited by 23 publications

References 46 publications

New Trends in Oxidative Functionalization of Carbon–Hydrogen Bonds: A Review

New Trends in Oxidative Functionalization of Carbon–Hydrogen Bonds: A Review

MnIII Porphyrins: Catalytic Coupling of Epoxides with CO2 under Mild Conditions and Mechanistic Considerations

Exploring manganese pyridylporphyrin isomers for cyclohexane oxidation: First‐generation catalysts are better than third‐generation ones

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Mn^III Porphyrins: Catalytic Coupling of Epoxides with CO₂ under Mild Conditions and Mechanistic Considerations