Bio-inspired arenecis-dihydroxylation by a non-haem iron catalyst modeling the action of naphthalene dioxygenase

Abstract

Reported in this paper is the first example of a biomimetic iron complex, ([Fe(II)(TPA)(NCMe)(2)](2+) (TPA = tris(2-pyridylmethyl)amine), that catalyses the cis-dihydroxylation of an aromatic double bond, mimicking the action of the non-haem iron enzyme naphthalene dioxygenase and shedding light on its possible mechanism of action.

Iron‐Promoted ortho‐ and/or ipso‐Hydroxylation of Benzoic Acids with H2O2

“…[44] Although it may be argued that a direct electrophilic attack of the aromatic ring by 2 b is plausible, particularly for benzoic acids with electron donating substituents, the broad scope of both ortho-and ipso-hydroxylation reactions promoted by 1 and 2 suggests that a highly electrophilic intermediate is likely to be involved, which we propose is 1 e or 2 e. A similar oxidant has been proposed for the 2-catalyzed self-hydroxylation of aryl peroxyacids, [37] for the intramolecular hydroxylation of the aromatic ring covalently appended to the analog of 1, [33] and for the ortho-hydroxylation of benzyl alcohol by another aminopyridine iron complex. [74] Although only one non-heme iron(V)-oxo complex has been directly observed at low temperature as a transient species and characterized by a variety of spectroscopic methods, [75] indirect evidence supporting participation of non-heme Fe V -oxo intermediates in oxidations of alcohols, [76] olefins, [43,76,77] and arenes [33,74,78] continues to accumulate. The coordination of the carboxylate cis to the oxo moiety in the putative oxoiron(V) oxidant 1 e or 2 e [77] positions the aromatic ring well for the attack of the oxo group at the carbon atom ortho to the carboxylate function.…”

Site‐Directed Mutagenesis Studies on the Toluene Dioxygenase Enzymatic System: Role of Phenylalanine 366, Threonine 365 and Isoleucine 324 in the Chemo‐, Regio‐, and Stereoselectivity

“…IPTG was added to a final concentration of 10 mg/L 12 hours after inoculation to induce enzyme expression, and stirrer speed was set to 900 rpm. After the culture reached the stationary phase (c.a.26 h, 30 g/ L cdw aprox) cells were harvested by centrifugation (4000rpm, 20 min, 4 8C), and the pellet was resuspended in isotonic phosphate buffer (KH 2 PO 4 3 g/L, NaHPO 4 12 g/L, NaCl 0.7 g/L) to a final OD 600 = 30. Biotransformations were performed using resting cells, thus, 100 mL of this cell suspension were placed in 500 mL Erlenmeyer flasks and supplemented with glucose to a final concentration of 5 g/L.…”

“…[3] To date, no other non-biocatalytic chemical method for their production at a preparative scale is known. [4] Rieske non-heme iron dependent dioxygenases are multicomponent enzymes constituted by a reductase, an oxygenase and in some cases a ferredoxin, and are well known for their ability to activate molecular oxygen to oxidize organic compounds. [3d] Besides the dioxygen addition to aromatic rings, Rieske dioxygenases are also able to catalyse other reactions, such as sulfoxidation, benzylic oxidation, dehydrogenation, and O-and N-dealkylations.…”

Fe-Catalyzed Oxidation Reactions of Olefins, Alkanes, and Alcohols: Involvement of Oxo- and Peroxo Complexes

“…Lately, TPA ligands were used also as model for NDO (naphthalene 1,2-dioxygenase), which catalyzes the conversion from naphthalene to cis-(1R,2S)-1,2-dihydro-1,2-naphthalenediol [63]. Another tetradentate N 4 -ligand family was examined by Costas and coworkers in 2008 based on the methylpyridine-derivatized triazacyclononane (TACN) backbone.…”