Conjugate iron complex

Alkyl iron complexes behave as electrophiles in the presence of nucleophiles. Rosenblum and co-worker showed, for example, that the ethene complex of cyclopentadienyl dicarbonyl iron (abbreviated as Fp), Fp-ethene (482), reacted with dimethyl lithiomalonate to give 486.3 4 Conjugated iron complexes can also be... 

Other Reactions. Due to the highly reactive conjugated double bonds, butadiene can undergo many reactions with transition metals to form organometaHic complexes. For instance, iron pentacarbonyl reacts with butadiene to produce the tricarbonyl iron complex (10) (226). This and many other organometaHic complexes have been covered (227). 

Cycloaddition of 2-alkoxy-l,3-butadienes, H2C=C(OAlk)CH=CH2, and nitrile oxides to give isoxazolines 51 proceeds with the participation of only one of the conjugated C=C bonds. With benzonitrile oxide, only the vinyl group in alkoxydienes participates in cycloaddition reactions while in the case of phenyl-glyoxylonitrile oxide both double bonds react (222). Nitrile oxides RC=NO react with iron complexed trienes 52. The reaction proceeds with good yield and diastereoselectivity ( 90/10) to give isoxazolines 53 (223). 

B. Iron Complex of a Crown Ether-Porphyrin Conjugate Suitable for... 

As well as organic chiral auxiliaries, organometallic fragments have found some application as chiral auxiliaries in conjugate addition reactions. Particularly noteworthy are chiral molybdenum allyl complexes [69], chiral iron complexes [70], and planar chiral arene chromium species [71]. 

Nucleophilic additions of alcohols, amines, thiols, and selenols to Group 8 buta-trienylidene intermediates [M]=C=C=C=CR2 have also been used in the preparation of stable heteroatom-conjugated allenylidene complexes. Thus, activation of trimethylsilyl-l,3-butadiyne HC=C-C=CSiMe3 by the iron(II) complex [FeClCp (dppe)], in methanol and in the presence of NaBPh4, resulted in the high-yield formation of the methoxy-allenylidene [FeCp =C=C=C(OMe)Me ... 

A recently described method for insertion of a carbon monoxide molecule into the monoepoxide of a conjugated diene gives /3-lactones in high yield. This is achieved by reaction of iron pentacarbonyl with the starting vinyloxirane to give the 7r-allyl iron complex (66), which on oxidation with cerium(IV) ammonium nitrate gives the /3-lactone. In some cases, y-Iactone products can also be obtained from this reaction (8lJCS(Pi)270). 

While sluggish under thermal conditions,274-275 the asymmetric conjugate addition of amines to alkyl crotonates is achieved at room temperature under high pressure (15 kbar).276 Thus, benzylamine can be added to the crotonate derived from 8-p-naphthyl menthol, with virtually complete diastereoselectivity. A related intramolecular 1,4-addition of an amine to a chiral enoate was used in a total synthesis of the alkaloid (-)-tylophorine.277 Additions of amines to chiral iron complexes of type (116) proceed with excellent selectivity and allow the preparation of homochiral p-lactams.l27128,l3() l32 In contrast, the addition of amine nucleophiles to chiral vinylic sulfoxides278-2811 and to chiral vinylsulfoximines281 proceeds with comparably low selectivities. 

Complementary to the conjugate substitution reaction in which the nucleophile is transferred directly from the tetraalkyl ferrate to the allylic ligand, preformed low-valent Fe complexes can form reactive allyl-iron complexes via an SN2 -type mechanism (path C, Equations (7.8) and (7.9), Scheme 7.16], These complexes react with incoming nucleophiles and electrophiles in a substitution reaction. Depending on the nature ofthe iron complex employed in the reaction, either o- or Jt-allyl complexes are generated. 

Another approach for the ring expansion of epoxides uses low-valent iron complexes which open epoxides under reductive conditions, as reported by Hilt et al. [106]. The iron complexes are reduced and after coordination of the epoxide to the iron center an electron transfer initiates the radical-type ring opening of the epoxide. Under formal insertion of an alkene, regioselective formation of tetrahy-drofurans was observed (Scheme 9.46). The reaction is applicable to a broad range of acceptor-substituted alkenes bearing another double or triple bond system in conjugation with the inserted carbon-carbon double bond. 

The molecular ion of the tricarbonyl (dienamine) iron complex 25 (cross-conjugated) is more abundant than that of 26 (linear) (Scheme 20) confirming their different relative stabilities18. They fragment essentially by successive losses of 3 CO and CH4 molecules leading to an abundant ion m/z 231 [Fe(C12H17N)] + ... 

Dehydration of (2-hydroxymethyl-1,3-butadiene)iron complexes or (hydroxymethyltrimethylenemethane)iron complexes with fluorosulfonic acid/liquid sulfur dioxide generates the corresponding (cross-conjugated dienyljiron cations (194) (equation 72). The H and NMR spectral data for these cations favor an " -TMM-methyl cationic structure (282) over an ) " -isoprenyl cationic stmcture (283). These cations react with water or alcohols to afford butadiene products via nucleophilic attack at C-5. As indicated earlier (Section 6.1.1), the cross-conjugated dienyl cations are believed to be intermediates in the substitution of (193) with weak carbon nucleophiles (Scheme 53). In these cases, nucleophihc attack occurs on C-4 to give predominantly TMM products. ... 

Conjugate addition reactions of N-nucleophiles with double stereodifferentiation are known in some cases11-116. While direct reaction of chiral amines with chiral enones11 leads to poor enantiomeric excess of the resulting /l-amino acids, reaction of chiral amines116 with acylated chiral iron complexes gives /J-amino acids with a high enantiomeric excess. 

Deferiprone is an alpha-ketohydroxypyridine compound with metal-chelating properties (1). It is absorbed within minutes after oral administration and reaches maximum blood concentrations within 1 hour. It has a half-life of 1-2 hours, and is almost completely undetectable in blood within 5-7 hours after a single dose. Deferiprone is mostly metabolized to a glucuronide conjugate that reaches maximum blood concentrations within 1.0-1.5 hours. Deferiprone, its iron complex, and its glucuronide conjugate are detectable in the urine, and in most instances the total amount of all three accounts for almost 100% of the... 

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