Iron carbonyls synthesis

Reactions with iron carbonyl Synthesis of silanes and ethylenesilanes from ethylene derivatives... 

The attraction of this methodology is the rapid access it provides to optically pure diene complexes which have subsequently been converted to dienyl iron complexes. Using Birch substrates as starting materials for diene iron carbonyl synthesis requires a resolution step in order to obtain optically pure material, and to date no efficient method for performing this resolution has been devised. 

Direct substitution of the carbonyls themselves is of course possible. Besides Group 15 donor ligands, unsaturated hydrocarbons give especially interesting products. The iron carbonyl acetylenes provided early examples of the use of carbonyls in organic synthesis. From them a wide variety... 

Rhodium and cobalt carbonyls have long been known as thermally active hydroformylation catalysts. With thermal activation alone, however, they require higher temperatures and pressures than in the photocatalytic reaction. Iron carbonyl, on the other hand, is a poor hydroformylation catalyst at all temperatures under thermal activation. When irradiated under synthesis gas at 100 atm, the iron carbonyl catalyzes the hydroformylation of terminal olefins even at room temperatures, as was first discovered by P. Krusic. ESR studies suggested the formation of HFe9(C0) radicals as the active catalyst, /25, 26/. Our own results support this idea, 111,28/. Light is necessary to start the hydroformylation of 1-octene with the iron carbonyl catalyst. Once initiated, the reaction proceeds even in the... 

In contrast to thermal uncatalyzed reactions of /V-acylsulfinylamines with aryl isocyanates which give rise to azoarenes,188 the cobalt or iron carbonyl-catalyzed process gives additionally 3,5-dioxo-l,2,4-triphenyl-1,2,4-triazolidine (Scheme 124).189 The only possible restriction on this simple urazole synthesis would be the expectation that the substituents on the reactants must be the same to prohibit exchange. 

The present paper focuses on the interactions between iron and titania for samples prepared via the thermal decomposition of iron pentacarbonyl. (The results of ammonia synthesis studies over these samples have been reported elsewhere (4).) Since it has been reported that standard impregnation techniques cannot be used to prepare highly dispersed iron on titania (4), the use of iron carbonyl decomposition provides a potentially important catalyst preparation route. Studies of the decomposition process as a function of temperature are pertinent to the genesis of such Fe/Ti02 catalysts. For example, these studies are necessary to determine the state and dispersion of iron after the various activation or pretreatment steps. Moreover, such studies are required to understand the catalytic and adsorptive properties of these materials after partial decomposition, complete decarbonylation or hydrogen reduction. In short, Mossbauer spectroscopy was used in this study to monitor the state of iron in catalysts prepared by the decomposition of iron carbonyl. Complementary information about the amount of carbon monoxide associated with iron was provided by volumetric measurements. 

A viable iron carbonyl-mediated reduction process converts acid chlorides and bromoalkanes into aldehydes [3, 6]. Yields are high, with the exception of nitro-benzoyl chloride, and the procedure is generally applicable for the synthesis of alkyl, aryl and a,(i-unsaturated aldehydes from the acid chlorides. The reduction proceeds via the initial formation of the acyl iron complex, followed by hydride transfer and extrusion of the aldehyde (cf. Chapter 8). 

Since the pioneering work by Sarel and co-workers on the iron carbonyl promoted transformation of vinylcyclopropanes and related compounds [1], a variety of transition metal complexes have been examined to achieve effective activation of the vinylcyclopropane-cyclopentene rearrangement which usually requires pyrolytic conditions. These reactions have been applied to natural product synthesis in some cases and have already been reviewed in several excellent articles [2-4]. 

The synthesis of metal-coordinated 1-azirines and the reactions of azirines induced by metals have opened a new area in the chemistry of this small ring heterocycle. Many of the reactions encountered bear resemblance to previously discussed thermally and photo-chemically induced reactions of 1-azirines. The reaction of a series of diiron enneacarbonyls in benzene results in coupling and insertion to give diimine complexes and ureadiiron complexes as well as pyrroles and ketones (76CC191). A mechanism for the formation of these products which involves initial 1,3-bond cleavage and generation of a nitrene-iron carbonyl complex as an intermediate was proposed. 

Orgel (23). Subsequently, Hubei and co-workers (24) obtained, among other products, tricarbonyl-7r-tetraphenylcyclobutadiene iron by the reaction of tolane with iron carbonyls. More recently, a general synthesis of tetra-phenylcyclobutadiene-metal complexes using ligand transfer from tetra-phenylcyclobutadiene palladium(II) halides (25) to a metal carbonyl has been described (26). It is also possible to obtain complexes containing... 

Only two diantimony-iron carbonyl clusters are known. Whitmire (775) has described the synthesis of [Fe3(CO)9 /r3-SbFe(CO)4 2]2 (134) from the reaction between NaSb03 and methanolic [Fe(CO)5j. The structure is similar to that of 132 except that in 132 only one bismuth carries an Fe(CO)4... 

Oxanorbomane, 2,3,5,6-tetrakis(methylene)-adduct with benzoquinone, 1, 414 7-Oxanorbomanes iron carbonyl complexes structure, 4, 550 l70 NMR, 4, 580, 581 photoelectron spectroscopy, 4, 586 structure, 4, 547 Oxapenams synthesis, 7, 353... 

Iron carbonyls have been used in stoichiometric and catalytic amounts for a variety of transformations in organic synthesis. For example, the isomerization of 1,4-dienes to 1,3-dienes by formation of tricarbonyl(ri4-l,3-diene)iron complexes and subsequent oxidative demetallation has been applied to the synthesis of 12-prostaglandin PGC2 [10], The photochemically induced double bond isomerization of allyl alcohols to aldehydes [11] and allylamines to enamines [12,13] can be carried out with catalytic amounts of iron carbonyls (see Section 1.4.3). 

Iron carbonyls also mediate the cycloaddition reaction of allyl equivalents and dienes. In the presence of nonacarbonyldiiron a,a -dihaloketones and 1,3-dienes provide cycloheptenes (Scheme 1.5) [14,15]. Two initial dehalogenation steps afford a reactive oxoallyliron complex which undergoes a thermally allowed concerted [4 + 31-cycloaddition with 1,3-dienes. The 1,3-diene system can be incorporated in cyclic or heterocyclic systems (furans, cyclopentadienes and, less frequently, pyrroles). Noyori and coworkers applied this strategy to natural product synthesis, e.g. a-thujaplicin and P-thujaplicin [14, 16]. 

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