Iron complexes amides

With the iron complex [Fe(Cl3terpy)2]( 104)2 (Clsterpy = 4,4, 4"-trichloro-2,2 6, 2"-terpyridine) as catalyst, sulfamate esters react with Phl(OAc)2 to generate iminoiodanes in situ which subsequently undergo intramolecular nitrenoid C-H insertion to give amidation products in good yields (Scheme 30) [48]. 

The EFF calculations yielded a single Cs-symmetric conformation for each type of ferrichrome analog (Figure 4), both with a A-cis configuration of the hydroxamates about the metal when L-amino acids were used. Taken together with the spectroscopic data, pronounced differences were observed for the conformations of these iron complexes. Inspection of the calculated conformations showed that the backbone amide groups may... 

Recently Liu and coworkers used (porphyrin)iron(III) chloride complex 96 to promote 1,5-hydrogen transfer/SHi reactions of aryl azides 95, which provided indolines or tetrahydroquinolines 97 in 72-82% yield (Fig. 24) [148]. The reaction starts probably with the formation of iron nitrenoids 95A from 95. These diradicaloids undergo a 1,5- or 1,6-hydrogen transfer from the benzylic position of the ortho-side chain. The resulting benzylic radicals 95B react subsequently with the iron(IV) amide unit in an Sni reaction, which liberates the products 97 and regenerates the catalyst. /V,/V-Dialkyl-w// o-azidobenzamides reacted similarly in 63-83% yield. For hydroxy- or methoxy-substituted indolines 97 (R2=OH or OMe) elimination of water or methanol occurred from the initial products 97 under the reaction conditions giving indoles 98 in 74—78% yield. 

They formally contain Fe(IV) and Fe(V) centers and represent examples of discrete high-oxidation state molecular iron complexes. Short Fe—S ( 218 pm) and Fe—N ( 184 pm) distances indicate that in both complexes n donation from thiolate and amide donors is effective in reducing the electron deficiency at the Fe centers and stabilizing their high-oxidation states. 

Bleomycin, an antitumour antibiotic, binds iron in the reduced, divalent state to its secondary amide group. It binds low molecular weight iron ions (often loosely referred to as free iron) in forms that catalyse free radical reactions (Gutteridge et al., 1981) but not iron bound within native, functional protein structures, such as ferritin, transferrin, lactoferrin, haemoglobin, myoglobin, cytochromes etc. The resulting bleomycin-iron complex is capable of degrading DNA... 

N, 6-N-di(2,3-dihydroxybenzoyl)-L-lysine (58) is a siderophore produced by Azotobacter vinelandii which has only two catechol groups. However, of the catecholate siderophores by far the best studied is enterobactin. A major difference between hydroxamate and catecholate siderophores occurs in their utilization as transport agents. For the former, the iron complex is taken up by the bacterial cell, the iron released, and the hydroxamate siderophore re-secreted for additional iron chelation. In contrast, enterobactin is destroyed by enzymatic hydrolysis within the cell and therefore the ligand is not recycled. This hydrolysis of the amide linkages of the iron(III) enterobactin lowers the redox potential of the chelate complex sufficiently to allow iron reduction — and thus uptake of iron into the cell metabolism (59, 60). 

A very different, but similarly effective, auxiliary is the chiral carbonyl(t/5-cyclopentadienyl)(tri-phenylphosphine)iron moiety. When the z./i-unsaturated acyl-iron complex ( -)-(/ )-11 is treated by a modified Simmons Smith reagent, a 91 9 mixture of cyclopropane diastereomers is isolated in good yield73. Precomplexation of the starting iron complex by the Lewis acid zinc(II) chloride seems to be necessary to obtain good selectivity. The chiral iron moiety can then be removed oxidatively by bromine treatment, and the intermediate acyl bromides converted into amides by reaction with (/ )- -phenylethylamine. 

Polyaromatics (anthracene and phenanthrene) have also been oxidized by FePcS/H202. This catalytic system is highly influenced by the presence of an organic co-solvent and phosphate ions. Iron tetra-amide complexes are also able to efficiently catalyze the oxidative cleavage of TCP with hydrogen peroxide at basic pH values. ... 

In continuation of their research on N-hydroxypeptides Akiyama s group obtained the anilide hexapeptide with a 6-aminohexanoyl-3-(hydroxyamino)propanoyl sequence (225). This linear tri-N-hydroxy-amide bears a structural resemblance to the natural siderophores fer-rioxamines. Cyclic voltametry and UV spectrometry were used for the study of its iron complex. The key substrate was obtained by the addition of benzyloxyamine to / -nitrophenyl acrylate. 

Katayama Y, Yoshihara M, Miura T (2014) Electrochemical reaction of tris(l,10-phenanthroline)iron complexes in some amide-type ionic liquids. ECS Trans 64(4) 109-118... 

In 2011, Sortais and Darcel described the activity of the related nonlinked half-sandwich iron complex [CpFe(IMes)(CO)2]I [IMes = l,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene] (Fig. 10.15c) in the hydrosilylation of aldehydes and ketones [73], and more recently, they extended these studies to the reduction of amides [74], nitriles [74], imines... 

Another auxiliary that became well known in enolate chemistry is chiral acyl iron complexes for alkylation, aldol reactions, and conjugate additions indeed, so-called Davies-Liebeskind enolates [60] can be generated either by deprotonation of alkanoyl complexes 124a or conjugate addition of strong nucleophiles like alkyllithium compounds or lithium amides to alkenoyl complexes 127. 

Similarly, the reaction of 3-halo-1-alkenes with tetrabutylammonium tricarbonyl-(nitrosyl)ferrate (TBAFe) gives T -allyl(tricarbonyl)(nitrosyl)iron complexes. Treatment of Y-bromo-a,p-unsaturated esters or amides with potassium tricarbonyl-(nitrosyl)ferrate provides planar chiral T] -allyl(dicarbonyl)(nitrosyl)iron complexes. Enantiopure amides as starting materials lead to a low diastereoselectivity, whereas no diastereoselectivity is observed for the chiral esters. The diastereoisomers of the amide-substituted allyliron complexes can be conveniently separated by column chromatography (Scheme 4-80). ... 

Alternatively, (trimethylenemethane)iron complexes can be synthesized by disproportionation of tricarbonyl(2-methallyl)ironJ Enantiomerically pure tricarbonyl-(trimethylenemethane)iron complexes can be obtained by resolution of the racemic mixture via diastereomeric esters or amides. (5)-(-)-Ethyl lactate and (/ I)-(+)-a-methyl-benzylamine are employed as resolving reagents for this piupose. The chiral auxiliaries can be removed by a variety of reagents leaving the (trimethylenemethane)iron fragment unaffected. Treatment of both the corresponding Boc-protected amides and the chiral esters with diisobutylaluminum hydride (DIBAL) or methyllithium provides the primary or tertiary alcohols, respectively. Saponification of the ester with lithium hydroxide in methanol and subsequent acidification of the mixture affords the methyl ester. Treatment of the ester with triethylsilane leads to complete reduction of the functionality to leave a methyl group (Scheme 4—85). ... 

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