Iron, carbonyl compounds methylation

The iron-catalyzed [3 + 2]-cycloaddition (Huisgen reaction) of nitriles and carbonyl compounds as reported by Itoh et al. is one of the rare examples reported where an iron reagent can be utilized for the synthesis of 1,2,4-oxadiazoles (Scheme 9.35) [93]. In this reaction, methyl ketones are nitrated at the a-position by Fe(N03)3 to generate an a-nitro ketone. This intermediate rearranges to an acyl cyanate, which reacts further with the nitrile to give the heterocyclic product 48 in good to excellent yields (R1 = Ph, R2 = CH3 95% yield). 

Iron complexes can also catalyze allylic amination [31,32]. Enders et al. have demonstrated the nucleophilic addition of various acyclic and cyclic amines to the optically active l-methoxycarbonyl-3-methyl-(T)3-allyl)-tetracarbonyliron cation 49 formed in high yield from reaction of 48 with iron carbonyls. Oxidative removal of the tetracarbonyliron group by reaction with CAN gives 50 with high optical purity and retention of the stereochemistry (Eq. (12)) [31]. The reaction proceeds well for the different amines, and has been used for the synthesis of a compound showing cytotoxic activity against diverse cell lines [31b]. 

Decomposition of methanesulphonyl azide in aromatic solvents (methyl benzoate or benzotrifluoride), in the presence of transition metal compounds (e.g. copper(ri) acetylacetonate, manganese(ii) acetylacetonate, di-cobalt octacarbonyl, tri-iron dodecacarbonyl, and iron pentacarbonyl) led to a marked decrease in the aromatic substitution product compared with thermolysis, and, with the iron carbonyls, to an increased yield of methanesulphonamide . In addition, the aromatic substitution products shifted from mainly ortAo-substitution with no additives to mainly w ia-substitution in the presence of the additives mentioned above. 

Various metal-metal single o-bonded complexes have been obtained by the reaction of metal carbonyls with metal-carbon o-bonded porphyrins or by the reaction of metal carbonyl anions and chlorometalloporphyrins (Scheme 14). For example, the reaction of dimanganese carbonyl and methyl indium(III) porphyrin gives manganese pen-tacarbonyl indium porphyrin In(Por)Mn(CO)5. The same compound is isolated when chloroindium porphyrin is allowed to react with the manganese pentacarbonyl monoanion. Various iron, cobalt, tungsten, and molybdenum complexes have been prepared by these two methods. 

Ford used HP-IR to investigate an acyliron migratory insertion intermediate formed by flash photolysis. Thus, flash photolysis of (7 -Cp)Fe(C0)2C(0)GH3 affords coordinatively unsaturated ( -Gp)Fe(C0)C(0)CH3. Trapping of the latter with CO in the reverse reaction was studied, and the second-order rate constant could be determined for this reaction under the high CO pressures employed. Variable-temperature studies allowed calculation of activation parameters for methyl migration. Iron cluster compounds have been studied for the carbonylation of methanol to methyl formate. Consistent kinetics and a first-order dependence on cluster concentration confirmed the HP-IR results which showed that the cluster remained intact through the catalytic process. 

Various carbonyl compounds and decomposition products of methyl linolenate hydroperoxides were tested for their interaction with DNA by measuring fluorescence in the presence of ferric chloride and ascorbic acid. 2,4-Alkadienals and 2,4,7-decatrienals were among the most active decomposition products of linolenate hydroperoxides (Table 5.8). To determine the type of reactive species involved in fluorescence formation with DNA, the effect of free radical antioxidants and a singlet oxygen quencher were examined. )3-Carotene, a-tocopherol and phenolic antioxidants strongly inhibited DNA fluorescence formed by decomposition of linolenate hydroperoxides in the presence of ferric chloride and ascorbic acid (Table 5.9). These results indicate that singlet oxygen and free radical species are important intermediates in the interaction of linolenate hydroperoxides with DNA in the presence of iron and ascorbic acid. 

Reactions between alkynes and transition metal compounds yield a surprising variety of products (76, 77), indicating nonspecific mechanisms of formation. At least for the reaction of alkynes with metal carbonyls any simple polar mechanism must be excluded, in view of the insensitivity of the reactions to the degree of polarity of the solvents. A radical mechanism would perhaps be better suited for a general description but this has so far been rejected, since inhibition of the reactions with f-butylphenol or hydroquinone proved unsuccessful (78). Likewise, iron carbonyls react with diphenylacetylene, using ethyl acrylate, vinyl methyl ketone or vinyl acetate as the solvent, without polymerization of the vinyl compounds (79). These experiments, however, do not fully eliminate the possibility of a radical mechanism. 

Other complex iron carbonyl tellurides can be obtained by solvothermal reactions. Compound 53, (Me4N)2[Fe4(Te2)2(Te)2(TeMe)2(CO)g], is produced when Fe3(CO)i2, Na2Te2, and Me4NBr are mixed with a small amount of methanol and heated at 110°C. This complex exhibits solvent-derived methylation of Te ions, which was not expected. 

Iron pentacarbonyl can regenerate carbonyl compounds from oximes under aprotic conditions (Alper and Edward, 1967). The presence of boron trifluoride etherate affords products in 55-81% yields although the reaction can take place—sometimes in reduced yields—in the absence of the Lewis acid (XXXIII - XXXIV) (Alper and Edward, 1969). The intermediate was isolated using the sterically hindered reactant, methyl mesityl ketoxime (Dondoni and Barbaro, 1975). 

Earlier catalysts were based on cobalt, iron, and nickel. However, recent catalytic systems involve rhodium compounds promoted by methyl iodide and lithium iodide (48,49). Higher mol wt alkyl esters do not show any particular abiUty to undergo carbonylation to anhydrides. 

Bis[iV,iV -di(2-pyridyl)-imidazol-2-ylidene]aurate(I) tetrafluoroborates, preparation, 2, 292-293 Bis[iV,iV -di(2-pyridyl-methyl)-imidazol-2-ylidene]aurate(I) tetrafluoroborates, preparation, 2, 292-293 Bis(diselenolate) complexes, dinuclear iron compounds, 6, 242 Bis(dithiolene) compounds, in tungsten carbonyl and isocyanide complexes, 5, 644 Bis(enolato) complexes, with bis-Cp Ti(IV), 4, 589 Bis(enones), in reductive cyclizations, 10, 502 Bis(ethanethiolato) complexes, with bis-Cp Ti(IV), 4, 601 Bis(ethene)iridium complexes, preparation, 7, 328-329 -Bis(fluorenyl)zirconocene dichlorides, preparation,... 

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