Iron(III)-catalyzed oxygenation of catechols. Structure of (nitrilotriacetato)(3,5-di-tert-butylcatecholato)ferrate(III) dianion

Abstract

Der Fe(III)‐l(omplex von Nitrilotriessigsäure in einer Mischung eines organischen Lösungsmittels mit einem Boratpuffer stellt ein System dar, das eine Aktivität gegenüber einer oxida‐ tiven Spaltung von Brenzcatechinen zeigt.

Catecholase biomimetic catalytic activity of copper(II) complexes with 2-methyl-3-amino-(3H)-quinazolin-4-one

“…The kinetic activity of SQ is presumably the spark for initiation of the oxidation catalytic cycle towards the aerobic conversion of catechol to the interadiol cleavage product. In this proposed mechanism the semiquinone substrate may coordinate to the copper(II) center in a bidentate [36] to give a peroxy derivative of the substrate, which remains coordinated to the copper(II) center. The subsequent rearrangement of this peroxy intermediate yields the muconic acid anhydride.…”

Iron-Containing Models of Catechol Dioxygenases

“…Indications that this reaction step does not proceed via a dioxetane intermediate were provided by the reaction of [Fe(nta)(dbc)] 2~ with 18 02, where a single l8 0 label is incorporated in the 3,5-di-/erf-butyl-5-carboxymethyl-2-furanone derivative. 47 Similar labeling experiments with the enzyme 1,2-CTD showed the loss of some l8 0-labeled atoms in the product due to the solvent exchange reaction of the iron(III) hydroxide species with H 2 16 0. 61 In addition, with faster reacting model complexes in less nucleophilic solvents, 3,5-di-rerr-butylmuconic anhydride (4) can be obtained as the main product, providing definite evidence for the occurrence of a Criegee rearrangement in the reaction mechanism.…”

“…X-ray structure determinations were carried out on a number of model complexes. [47][48][49][50][51][52][53] For example, the perspective view of the complex cation [Fe(L-N4Me 2 )(dbc)] + is shown in Fig. 8.6.…”

Mononuclear non-heme iron(III) complexes of linear and tripodal tridentate ligands as functional models for catechol dioxygenases: Effect of N-alkyl substitution on regioselectivity and reaction rate

“…On adding one equivalent of H 2 DBC to 1-7 in DCM solution a new wave appears in the CV and DPV responses, which corresponds to DBSQ/DBC 2− couple 53-55,58-62 of [Fe(L)(DBC)(Cl)] species generated. On adding two equivalents of Et 3 N to deprotonate the catechol the reduction current of this couple increases and the Fe III /Fe II redox wave tend to vanish completely, which is expected [53][54][55][58][59][60][61][62] to be shifted to a more negative potential due to chelation of DBC 2− . Also, the redox potential of DBSQ/DBC 2− couple of [Fe(L)(DBC)(Cl)] species is observed in the range −0.075 − −0.009 V, which is less negative than that of free DBSQ/DBC 2− couple (E pc , −1.34 V vs. SCE).…”

“…of Et 3 N to the iron(III) complexes 12-19 in DMF solution. [53][54][55][58][59][60][61][62] The positions of both the low-and high-energy bands depend on the nature of substituents on the catecholate ring and are shifted to higher energies when the substituents are varied from electron-donating to electron-withdrawing. In DMF solvent both the low-and high-energy LMCT bands exhibit a remarkable dependence on the number of N -alkyl substituents in the complexes of 3N ligands and their energies decrease in the order: 12 > 13 > 14 > 16 > 17 ≥ 18 > 19 and thus, on increasing the number of N -alkyl substituents along the above series, the lower energy band shifts from 781 to 810 to 848 nm in DMF solvent.…”