Iron amides

Treatment of the yellow chloride 159 with lithium diphenylamide gave rise to a thermally stable red iron amide complex [PhB(CH2PiPr2)3]FeNPh2, which was characterized structurally <2004JA6252>. 

The nine-membered lactam representing an intermediate between cis and irons lactams was assumed to be sufficiently flexible to allow the more stable irons amide group to co-exist with the strainless cis form [47]. However, a strainless planar irons form is not possible and the actual conformation is rather a skew structure which drastically reduces the jo—tt overlap and decreases resonance stabilization of the amide group. Therefore, an increased amount of delocalization energy is released in the... 

The iron-amide complex is an extremely air- and moisture-sensitive light green solid and must be stored under a strictly inert atmosphere. Handling in a glovebox... 

Anhydrous liquid ammonia (note 2) (900 ml) was drawn from a cylinder and introduced into the flask. Iron(III) nitrate (lOO mg) was added and, as soon as a uniformly brown solution had formed (after stirring for a few seconds), about 0.7 g of lithium (from the starting amount of 7 g) was cut into two or three pieces and immediately introduced into the flask. After 10-15 min the blue colour had disappeared completely and a white suspension of lithium amide had formed. The remainder of the 7 g (1 mol) of lithium was then cut up and introduced. In most cases the conversion was finished v/ithin about 30 min (note 3). 

In contrast to the reaction with lithium amide, the sodium amide suspension immediately settles out after stopping the stirring and the supernatant ammonia has a grey or black colour, due to colloidal iron. In some cases it took a long time before all of the sodium had been converted (note 4). A further 0.1 g of iron(III) nitrate was then added to accelerate the reaction and some liquid ammonia was introduced to compensate for the losses due to evaporation. 

Adiponitrile undergoes the typical nitrile reactions, eg, hydrolysis to adipamide and adipic acid and alcoholysis to substituted amides and esters. The most important industrial reaction is the catalytic hydrogenation to hexamethylenediarnine. A variety of catalysts are used for this reduction including cobalt—nickel (46), cobalt manganese (47), cobalt boride (48), copper cobalt (49), and iron oxide (50), and Raney nickel (51). An extensive review on the hydrogenation of nitriles has been recendy pubUshed (10). 

Analytical Procedures. Standard methods for analysis of food-grade adipic acid are described ia the Food Chemicals Codex (see Refs, ia Table 8). Classical methods are used for assay (titration), trace metals (As, heavy metals as Pb), and total ash. Water is determined by Kad-Fisher titration of a methanol solution of the acid. Determination of color ia methanol solution (APHA, Hazen equivalent, max. 10), as well as iron and other metals, are also described elsewhere (175). Other analyses frequendy are required for resia-grade acid. For example, hydrolyzable nitrogen (NH, amides, nitriles, etc) is determined by distillation of ammonia from an alkaline solution. Reducible nitrogen (nitrates and nitroorganics) may then be determined by adding DeVarda s alloy and continuing the distillation. Hydrocarbon oil contaminants may be determined by ir analysis of halocarbon extracts of alkaline solutions of the acid. 

Homolytic oxaziridine decomposition can be easily initiated by iron(II) ion in acidic media. Catalytic amounts are sufficient because chain reactions proceed. The reaction proceeds obviously in the case of 2-r-alkyloxaziridines like (56), where it yields the isomeric acid amide (111) (57JA5739). 

When )3-scission can occur in the radical, further reactions compete with acid amide formation. Thus oxaziridine (112) with iron(II) ion and acid yields stabilization products of the isopropyl radical. If a-hydrogen is present in the Af-alkyl group, radical attack on this position in (113) occurs additionally according to the pattern of liquid phase decomposition. 

An earlier report (126) which assigned the irons configuration to the enamine (175) derived from the cyanamine (176) upon reaction with potassium amide in liquid ammonia has been questioned by Munk and Kim (725). They also have doubts about the structures (177 and 178) proposed for the products obtained by the reduction of acetonitrile with sodium (727). 

The antiparasitic drug clorsulon (206), contains a rather unusual trichloroethylene group. This function is established early in the syntliesis by treatment of the perhalogenated compound 203 obtained from reduction of 202 with iron powder. Chlorosulfonation of 204 by means of chloro-sulfonic acid, followed by conver.sion of. sulfonyl chloride 205 to the amide, gives clorsulon (206) 153],... 

Amides are produced if iron - acyl complexes are oxidized in the presence of a secondary or primary amine25 52 59 60. This reaction, usually conducted at low temperatures, employs /Y-bromosucciniinide or bromine as the oxidant (see Table 6). 

Table 6. Amides 13 by Removal of the Chiral Auxiliary from Iron-Acyl Complexes 12 n1 R4 R1...

The chemistry of indium metal is the subject of current investigation, especially since the reactions induced by it can be performed in aqueous solution.15 The selective reductions of ethyl 4-nitrobenzoate (entry 1), 2-nitrobenzyl alcohol (entry 2), l-bromo-4-nitrobenzene (entry 3), 4-nitrocinnamyl alcohol (entry 4), 4-nitrobenzonitrile (entry 5), 4-nitrobenzamide (entry 6), 4-nitroanisole (entry 7), and 2-nitrofluorenone (entry 8) with indium metal in the presence of ammonium chloride using aqueous ethanol were performed and the corresponding amines were produced in good yield. These results indicate a useful selectivity in the reduction procedure. For example, ester, nitrile, bromo, amide, benzylic ketone, benzylic alcohol, aromatic ether, and unsaturated bonds remained unaffected during this transformation. Many of the previous methods produce a mixture of compounds. Other metals like zinc, tin, and iron usually require acid-catalysts for the activation process, with resultant problems of waste disposal. 

Firstly there is nucleophilic attack of the nitrile carbon atom by hydroxylamine. An amide oxime is produced this then forms an intensely colored complex with the iron(III) chloride. 

A relationship between the redox state of an iron—sulfur center and the conformation of the host protein was furthermore established in an X-ray crystal study on center P in Azotobacter vinelandii nitroge-nase (270). In this enzyme, the two-electron oxidation of center P was found to be accompanied by a significant displacement of about 1 A of two iron atoms. In both cases, this displacement was associated with an additional ligation provided by a serine residue and the amide nitrogen of a cysteine residue, respectively. Since these two residues are protonable, it has been suggested that this structural change might help to synchronize the transfer of electrons and protons to the Fe-Mo cofactor of the enzyme (270). 

The dehydration of primary amides with hydrosilane catalyzed by iron carbonyl clusters, such as [Et3NH][HFe3(CO)n] and Fe2(CO)9, was achieved by Seller and coworkers in 2009 (Scheme 43) [145]. This reaction shows good functional group tolerance (e.g., such as aromatic, heteroaromatic, and aliphatic substrates). 

The addition of acetic acid (0.5 equiv. to the substrate) to the catalyst system led to increased activity (doubling of yield) by maintaining the selectivity with 1.2 equiv. H2O2 as terminal oxidant. Advantageously, the system is characterized by a certain tolerance towards functional groups such as amides, esters, ethers, and carbonates. An improvement in conversions and selectivities by a slow addition protocol was shown recently [102]. For the first time, a nonheme iron catalyst system is able to oxidize tertiary C-H bonds in a synthetic applicable and selective manner and therefore should allow for synthetic applications [103]. 

High-valent iron-imido complexes have also been proposed as reaction intermediates in several reactions of the iron catalysis. Que and coworkers have provided evidence for Fe(IV) imide as a reaction intermediate in the reaction of [(6-PhTPA)-Fe°(CH3CN)2] " with PhI=NTs. Borovik and coworkers have also reported the formation of an amide product involving the generation of a putative iron(IV) imide [36] (Scheme 7). 

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]. 

Allyl groups attached directly to amine or amide nitrogen can be removed by isomerization and hydrolysis.228 These reactions are analogous to those used to cleave allylic ethers (see p. 266). Catalysts that have been found to be effective include Wilkinson s catalyst,229 other rhodium catalysts,230 and iron pentacarbonyl.45 Treatment of /V-allyl amines with Pd(PPh3)4 and (V,(V -dimethylbarbi Lurie acid also cleaves the allyl group.231... 

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