Iron catalysis substitution

Organolithium reagents47 instead of organoaluminum derivatives48, 9 have been used for the carbometallation of unactivated alkynes under iron catalysis (Scheme 9). Thus, variously substituted alkynes 30 and 32, bearing a tertiary... 

Ferric (III) acetylacetonate [Fe(acac)3, iron(III) tris(2,4-pentadionate)] [14024-18-1] M 353.2, m 181.3-182.3°. When recrystallised twice from benzene/petroleum ether, it has m 181.3-182.3° corr [Firm et al. J Chem Soc 1256 1938]. However, when reciystallised from EtOH or Et20 it has m 179° [Hantzsch Desch Justus Liebigs Ann Chem 323 13 1902]. Recrystallisation from absolute EtOH also gives material with m 159.5° [Emmett Jacob Chem Ber 67 286 1934], Dry it for 1 hour at 120°. [Beilstein 11404,1II 836,1IV 3675.] Fe(acac)3 catalyses a large variety of chemical reactions such as aromatic substitution, cross-coupUng, Friedel-Crafts etc [see B. Pleitker (ed). Iron Catalysis in Organic Chemistry Wiley-VCH, 2008, ISBN 978-3-527-31927]. 

Substitution reactions of [Fe (CO) (y -PPh)can be Induced by electron-transfer catalysis (ETC) under conditions in which thermal reactions do not occur. Reactions using P-donor ligands take place sequentially at the three iron centres. Substitutional lability of the generated radical anion [Fe,(CO) (n -PPh) ] is a... 

Various propargylic dithioacetals react with organomagnesium compounds to yield substituted allenes. Alkynyl oxiranes like 137 lead to 2,3-allenols of type 138 under iron catalysis with good chirality transfer (Scheme 2-50). ... 

Whereas the Prins-type cyclizations reported in this and the preceeding chapter were performed using stoichiometric amounts of Fe salts as Lewis acids, a breakthrough in the field of catalysis was reported in 2009 when the first iron-catalyzed Prins- and aza-Prins cyclization was reported. The catalytic system, which is obtained by combining catalytic amounts of an iron salt with trimethylsilyl halides as a halide source, is widely applicable and promotes the construction of substituted six-membered oxa- and aza-cycles (Scheme 33) [44]. 

Keywords Allylic substitution Catalysis Cross-coupling Cycloaddition Cycloisomerisation DNIC Ferrate Hydrogenase Iron... 

A mechanistic study of acetophenone keto-enol tautomerism has been reported, and intramolecular and external factors determining the enol-enol equilibria in the cw-enol forms of 1,3-dicarbonyl compounds have been analysed. The effects of substituents, solvents, concentration, and temperature on the tautomerization of ethyl 3-oxobutyrate and its 2-alkyl derivatives have been studied, and the keto-enol tautomerism of mono-substituted phenylpyruvic acids has been investigated. Equilibrium constants have been measured for the keto-enol tautomers of 2-, 3- and 4-phenylacetylpyridines in aqueous solution. A procedure has been developed for the acylation of phosphoryl- and thiophosphoryl-acetonitriles under phase-transfer catalysis conditions, and the keto-enol tautomerism of the resulting phosphoryl(thiophosphoryl)-substituted acylacetonitriles has been studied. The equilibrium (388) (389) has been catalysed by acid, base and by iron(III). Whereas... 

Yamamoto and coworkers studied the substitution of ally lie phosphates by Grignard reagents in the presence of copper or iron salts. Only the Sn2 product is formed under copper catalysis whereas, in the presence of iron(III) acetylacetonate, the Sn2 product is generally obtained with an excellent selectivity (Scheme 49). It should be noted that aryl-, alkenyl-, aUcynyl- and aUcyhnagnesium halides can be used successfully. 

Gu, Y., Lee, H., and Hudson, R.A., Bis-catechol-substituted redox-reactive analogs of hexam-ethonium and decamethonium stimulated affinity-dependent reactivity through iron peroxide catalysis, /. Med. Chem., 37, 4417, 1994. 

In relation to enzymic cytochrome P-450 oxidations, catalysis by iron porphyrins has inspired many recent studies.659 663 The use of C6F5IO as oxidant and Fe(TDCPP)Cl as catalyst has resulted in a major improvement in both the yields and the turnover numbers of the epoxidation of alkenes. 59 The Michaelis-Menten kinetic rate, the higher reactivity of alkyl-substituted alkenes compared to that of aryl-substituted alkenes, and the strong inhibition by norbornene in competitive epoxidations suggested that the mechanism shown in Scheme 13 is heterolytic and presumably involves the reversible formation of a four-mernbered Fev-oxametallacyclobutane intermediate.660 Picket-fence porphyrin (TPiVPP)FeCl-imidazole, 02 and [H2+colloidal Pt supported on polyvinylpyrrolidone)] act as an artificial P-450 system in the epoxidation of alkenes.663... 

A titanium complex derived from chiral /V-arencsulfonyl-2-amino-1 -indanol [20], a cationic chiral iron complex [21], and a chiral oxo(salen)manganese(V) complex [22] have been developed for the asymmetric Diels-Alder reaction of oc,P-unsaturated aldehydes with high asymmetric induction (Eq. 8A.11). In addition, a stable, chiral diaquo titanocene complex is utilized for the enantioselective Diels-Alder reaction of cyclopentadiene and a series of a.P Unsaturated aldehydes at low temperature, where catalysis occurs at the metal center rather than through activation of the dienophile by protonation. The high endo/exo selectivity is observed for a-substituted aldehydes, but the asymmetric induction is only moderate [23] (Eq. 8A. 12). 

The application of transition metal catalysis provided new opportunities to introduce diverse functionality to the diazepine ring system. Iron-catalyzed cross-coupling of Grignard reagents with the imidoyl chloride 40 provided a convenient and efficient method for substituting the heterocyclic ring (Scheme 9) <20060L1771>. 

The oxidative imination of sulfides and sulfoxides via nitrene transfer processes leads to N-substituted sulfilimines and sulfoximines. This reaction is interesting as chiral sulfoximines are efficient chiral auxiliaries in asymmetric synthesis, a promising class of chiral ligands for asymmetric catalysis and key intermediates in the synthesis of pseudopeptides [169]. However, very few examples of such iron-catalyzed transformations have been described. 

Recently, Taillefer et al. reported an Fe/Cu cooperative catalysis in the assembly of N-aryl heterocycles by C—N bond formation [90]. Similarly, Wakharkar and coworkers described the N-arylation of various amines with aryl halides in the presence of Cu—Fe hydrotalcite [91]. Interestingly, Correa and Bolm developed a novel and promising ligand-assisted iron-catalyzed N-arylation of nitrogen nucleophiles without any Cu co-catalysts (Scheme 6.19) [92]. Differently substituted aryl iodides and bromides react with various amides and N-heterocycles. The new catalyst system consists of a mixture of inexpensive FeCl3 and N,N -dimethylethylenediamine (dmeda). Clearly, this research established a useful starting point for numerous future applications of iron-catalyzed arylation reactions. 

---