Pentacarbonyl, iron, reaction with dienes

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). 

DIBAL-H/n-butyllithium, in cyclic and acyclic systems with iron pentacarbonyl, in cyclodecanes with lithium dihydrodimethoxyaluminate(III)/copper(I) iodide, and in cyclohexane and cyclopentane systems with NaH/sodium r-butylpentyl/Ni(OAc)2. ° The monoreduction of 1,3-diketones can be carried out under similar conditions, as illustrated by the reaction of a substituted cyclohexane-1,3-dione with oxalyl chloride to give the corresponding 1-chlorocyclohexenone, which was subsequently reduced to the enone with zinc-silver couple (Scheme 45). Kropp et al. have reported the photolytic reduction of vinyl iodides in acyclic systems however, when an a-hydrogen is present, formation of the diene product is a limiting side reaction (Scheme 46). For a more extensive discussion of vinyl halide reductions, see the preceding chapter in this volume. 

A pure sample of (94, R = R = H cis) could be obtained (30°C, 60% yield) by treatment of (91) with (92 R = R = H) using molybdenum hexacarbonyl as mediator. Interestingly, with iron pentacarbonyl and 2,3-dimethyl-1,3-butadiene (92 R = R = Me), (91) formed only the alkylidene products (93 R = R = Me). The corresponding alkene (94, R = R = Me) did result exclusively from photochemical treatment of (91) with W(CO)6 at 0°C. Exposure of this alkene to Fe(CO)slhv isomerized it quantitatively to (93 R = R = Me), explaining the initial result. These, and other, findings allowed the authors to conclude that the mechanism involved an unusual 1,1-addition where the two silicon atoms added to the same carbon. Cl, of the diene, and the hydrogen atoms were shifted from Cl to C4 and C3. In addition, it was concluded that, in these reactions, a n-... 

An oxidizer. The liquid is a sensitive explosive. Explosive reaction with carbon disulfide (when ignited), methanol (when ignited), pentacarbonyl iron (at 50°C), phosphine + oxygen, sodium diphenylketyl, dichlorine oxide, fluorine, nitrogen trichloride, ozone, perchloryl fluoride (at 100-300°C), vinyl chloride. Reacts to form explosive products with dienes (e.g., 1,3-butadiene, cyclopentadiene, propadiene). 

Iron carbonyl complexes are obtained by irradiation of iron pentacarbonyl with vinylcyclopropanes. The principal modes of reaction are (i) metal insertion into a strained bond with hydrogen migration to give diene-Fe(CO)3 complexes, (ii) metal carbonyl insertion to give a n-allyl-complexed acyl iron tricarbonyl, and (iii) cycloinsertion of CO across the homodiene to give a cyclohexenone. Similar types of... 

The photochemical reaction of Group VI metal hexacarbonyls with mono-enes was studied several years ago, but only recently has the reaction of one of the hexacarbonyls, W(CO)s in fact, with conjugated dienes been investigated. The W(CO)6 proves to be an effective catalyst for cis trans isomerization of such dienes compounds of the type W(CO)6(diene), which must act as intermediates in such isomerizations, have been isolated and their reactions studied. Under normal conditions iron pentacarbonyl reacts with acetylene to produce a complicated mixture of products, but under irradiation in an argon matrix at — 256 °C the product is but-l-en-3-yne, complexed to the iron through the carbon-carbon triple bond only. This iron-alkyne-carbonyl compound is presumably an intermediate in the reaction under normal thermal conditions. In an argon matrix at — 256 C, iron pentacarbonyl reacts with ethylene to give Fe(CO)4(QH4). ... 

Corey-Winter elimination dibenzobarralene (442). In a similar way, spirohex-4-ene was obtained in 80% yield from (443). Daub and his co-workers have synthesized several uncommon olefins, among these (442), from parent cyclic thionocarbonates, using iron pentacarbonyl as the efficient elimination promoter. Semmelhack and Stauffer have reported that bis-(cyclo-octa-l,5-diene)nickel (444) converts thionocarbonates of vic-diols into the corresponding olefins in excellent yields and with a high degree of stereospecificity. In connection with a discussion of the mechanistic pathways of this reaction, the authors presented evidence for the intermediacy of the carbene complex (445). 

Many diene iron tricarbonyl complexes are known.f Butadiene iron tricarbonyl was first prepared in 1930 by Reihlen and co-workers [60], by treatment of iron pentacarbonyl with butadiene under pressure. It is a typical diene iron carbonyl complex being a yellow-brown oil which distils slowly at 60° in high vacuum. It is soluble in the common organic solvents and reacts with chlorinated hydrocarbons. The pure oil and its solutions are oxidized in air within hours, forming iron oxides. The diene system resists hydrogenation and does not undergo the Diels-Alder reaction [5]. 

Iron pentacarbonyl isomerizes cu-substituted conjugated dienes giving ironr-substituted products [42]. It has been suggested that the tram-substituted olefins are the stable products of these reactions since in this configuration the substituents would interact less with the metal examples are ... 

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