Iron-tricarbonyl complex

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). 

Diels-Alder reactions, 4, 842 flash vapour phase pyrolysis, 4, 846 reactions with 6-dimethylaminofuKenov, 4, 844 reactions with JV,n-diphenylnitrone, 4, 841 reactions with mesitonitrile oxide, 4, 841 structure, 4, 715, 725 synthesis, 4, 725, 767-769, 930 theoretical methods, 4, 3 tricarbonyl iron complexes, 4, 847 dipole moments, 4, 716 n-directing effect, 4, 44 2,5-disubstituted synthesis, 4, 116-117 from l,3-dithiolylium-4-olates, 6, 826 electrocyclization, 4, 748-750 electron bombardment, 4, 739 electronic deformation, 4, 722-723 electronic structure, 4, 715 electrophilic substitution, 4, 43, 44, 717-719, 751 directing effects, 4, 752-753 fluorescence spectra, 4, 735-736 fluorinated derivatives, 4, 679 H NMR, 4, 731 Friedel-Crafts acylation, 4, 777 with fused six-membered heterocyclic rings, 4, 973-1036 fused small rings structure, 4, 720-721 gas phase UV spectrum, 4, 734 H NMR, 4, 7, 728-731, 939 solvent effects, 4, 730 substituent constants, 4, 731 halo... 

Another recent example of sonochemical substitution is in the preparation of 7r-allyllactone(tricarbonyl)iron complexes, which are useful synthetic intermediates in the synthesis of lactones and lactams (185). Upon... 

Tricarbonyl)iron complexes of 1,2-diazepines do not show the rapid isomerization found in their azepine counterparts (Scheme 41) the iron forms a diene complex with the C = C double bonds in the 4- and 6-positions. The chemistry of the 1,2-diazepine complexes is similar to that of the azepine complexes (CHEC 5.18.2.1) (81ACR348). 

The method involves a highly enantioselective rearrangement of an epoxide and a subsequent Ireland-Claisen rearrangement (see Scheme 31). The enolate Claisen rearrangements of [4-7- /4-4-(l-acyloxy-2,4,6-octatrienyl)]tricarbonyl iron complexes... 

P. Vogel s group studied exhaustively the 5,6,7,8-tetramethylidenebicyclo[2.2.2]octane system and its metal carbonyl complexes. The preparation and CD spectra of tricarbonyl-iron complexes (144-147) were reported333. The chirality of complexes 144 and 146 is due uniquely to the coordination of Fe(CO)3 moieties. The signs of the Cotton effects for (+)-144 and (+)-146 obey the octant rule, as the endo-Ft(CO)j, of 144 and 146 fall in a positive octant, while the second exo-Fe(CO)3 (syn to the carbonyl) lies almost on the XY nodal plane, and thus its contribution is expected to be small. The deuterium-substituted free tetraenone 148, however, showed an anti-octant behavior. The CD spectra of 144 and 146 are strongly temperature and solvent dependent. 

Selective osmylation of trienes.10 The (tricarbonyl)iron-complexed triene 2, prepared from the butadiene-tricarbonyliron 1 (11, 222), undergoes osmylation to give a single racemic, cij-diol 3 in 96% yield. Reaction of 3 with N,N -carbonyldi-nnidazole provides the single carbonate 4." Related carbonates, prepared from d-... 

Azepine derivatives form a diene complex with (tricarbonyl)iron, leaving the third of the double bonds uncomplexed. If the 3-position is substituted, two different such complexes are possible and are in equilibrium, as seen in the 11 NMR spectrum. An ester group in the 1-position of the complex can be removed by hydrolysis to give an NH compound that, in contrast to the free 1 //-azcpinc, is stable (Scheme 82). The 1-position can then be derivatized in the manner usual for amines. The same (tricarbonyl)iron complex can, by virtue of the uncomplexed 2,3-double bond, serve as a dienophile with 1,2,4,5-tetrazines. The uncomplexed N-ethoxycarbonylazepine also adds the tetrazine, but to the 5,6-double bond. Thus, two isomeric adducts can be synthesized by using or not using the complex (Scheme 83). 

The complexation of chiral dienes leads to the formation of diastereomeric j -diene iron tricarbonyl complexes. An early example was actually carried out for the protection of the diene unit found in the steroid B-ring of ergosteryl acetate (equation 53) neither the stereochemical assignment nor the diastereomer ratio were estabhshed. Similarly, the tricarbonyl iron complex of calciferol was also prepared. ... 

Tricarbonyl)iron complexes of a ,/3-enones (253) and vinylimines (254) may be prepared by reaction of the organic ligand thermally with (2) or photo chemically with (1). X-ray diffraction analysis of these complexes clearly indicates that the ligand is nearly planar and that iron is bound to all four atoms of the functionality. The heterodiene ligand may be... 

Hydride abstraction from dienyl tricarbonyl iron complexes furnishes cationic dienyl tricarbonyl iron complexes. For example, reaction of the diene-iron tricarbonyl complex (115) with triphenyhnethyl hexafluorophosphate followed by trimethylsilyl cyanide furnished with excellent regio- and stereoselectivity a new diene iron tricarbonyl complex (116) (Scheme 170). Excellent regio- and stereoselectivity is seen upon reaction of the cationic complex (116) with trimethylsilyl cyanide (TMS-CN) (Scheme 170). Reduction of the nitrile affords a spirocyclic lactam complex. Intramolecular cyclization of in situ formed enols furnishes spirocyclic compounds again with excellent stereoconfrol (Scheme 171). An interesting example of hydride transfer from a cyclohexadiene ring to a pendant aldehyde followed by nucleophilic addition is seen in Scheme 172. 

Although the reaction of bis(trifluoromethyl)tetramethylbi-cyclo[2.2.2]octatriene with Mo(CO)(j or Co(CO)2(C5H5) gives a single product, e.g., (168), its reaction with Fe(CO)5 produces two tricarbonyl-iron complexes, one with a structure analogous to (168) and another with structure (135), the latter being the major product (343). Similarly, reaction of Fe(CO)5 or Fe3(CO)i2 with tetrafluorobenzobicyclo[2.2.2]-octatriene under reflux produces an orange-yellow complex (136) (373). 

Oxidation of tri-terr-butylcyclobutadiene(tricarbonyl)iron complex with ammonium ce-rium(IV) nitrate or iron(III) nitrate in acetone did not afford the expected dimer of ix i-tert-butylcyclobutadiene, but gave exclusively l,2-di-ter/-butyl-3-(2,2-dimethyl)propanoylcyclo-propene (4), in quantitative yield. ... 

Diene)tricarbonyliron complexes have found use as synthons for the preparation of functionalized dienes. Substituted 4-vinylcyclohexene derivatives are isomerized by pen-tacarbonyliron into a mixture of conjugated cyclohexadiene tricarbonyl iron complexes . When the 4-vinyl cyclohexene 90 was refluxed with 1.2 equivalents of fclCOjs in di-n-butyl ether, a 3 1 mixture of cyclohexadiene isomers 91 and 92 was acquired in 75% overall yield (equation 48). 

Decomplexation of 2-ethoxycarbonyl-l,3-butadiene-tricarbonyl iron complex 67 in the presence of an excess of cyclopentadiene affords the endo-adduct 68 stereospecifically, which readily undergoes Cope rearrangement to the bicyclo[4.3.0] derivative 69l073. 

Tricarbonyliron diene complexes have found many uses in synthetic chemistry but their synthesis is often not easy. Knolker has developed a range of tricarbonyl(7] -l-aza-l,3-butadiene) iron complexes that are excellent transfer agents for the Fe(CO)3 complexation of 1,3-dienes, and showed their versatility. As an extension to this work, Knolker and Gonser have prepared a polymer-supported l-aza-l,3-butadiene 321 by reaction of Merrifield s resin with phenolic l-aza-l,3-butadiene 320, formed from cinnamaldehyde and /> ra-hydroxyaniline (Scheme 105). The corresponding tricarbonyl iron complex 322 was formed by treatment of 321 with an excess of Fe2(CO)9 in THF using ultrasound. The iron complex was subsequently used efficiently as a transfer agent for the tricarbonyliron complexation of 1,3-dienes. 

R = Me) with AT-phenyltriazolinedione and the tricarbonyl iron complex of 1,6,7,8-tetramethylbicyclo[4,2,0]octa-2,4,7-triene with benzylideneacetoneiron tricarbonyl,... 

This otherwise unstable compound may be isolated as its tricarbonyl iron complex [Eq. (166) (Landesberg and Sieczkowski, 1968,1969)]. The free ligand appears to be generated in situ on photolysis of the complex. 

Cycloaddition.— Reactions of electrophilic olefins and acetylenes with tricarbonyl-iron complexes of cycloheptatriene and cyclo-octatetraene lead to 1,3-exo-products. Troponetricarbonyliron and tcne, however, have now been found to give complex (20) which results from previously unobserved 1,5-exo-cycloaddition. A dipolar intermediate (21) resulting from initial attack by the electrophile on the hydrocarbon... 

The first C-unsubstituted germole, 1,1-dimethylgermole (8), was prepared in 1981 by Dubac and coworkers by dehydration in the gas phase of 1,1-dimethyl-l-germacyclopent-4-en-3-ol (Scheme 2). At room temperature, as in the case of 1,1-dimethylsilole, the [2-1-4] dimer is formed. At low temperature, the monomer gives a Diels-Alder adduct with maleic anhydride, and forms a -tricarbonyl iron complex -. The indirect dehydration of the same alcohol, via its Af-phenylcarbamate, also produces the germole (Scheme 2). 

Caution All procedures must be carried out in an efficient fume hood. Eye protection must be worn at all times. Chemical resistant gloves must be worn when handling iron pentacarbonyl, tricarbonyl iron complexes and their solutions. 

Tricarbonyl iron complexes of a number of substituted dihydroanisic esters have been prepared. Several undergo hydride abstraction to yield [(cyclo-hexadienyl)Fe(CO)3]+ salts, which react with malonate in the expected manner to give the 5-substituted (l,3-chd)Fe(CO)3 derivative. Hydrolysis of the parent salt (63) yields (cyclohexa-2,4-dienone)Fe(CO)3 containing the keto-isomer of phenol, and (63) may also be alkylated with dimedone to yield the 5-substituted (l,3-chd)Fe(CO)s complex. The bicyclic analogue (64) and... 

Bicyclo[4.1.1] or [3.2.1]octenones and cyclopropanes have resulted from decomplexation of the iron tricarbonyl group from the alkyl-allyliron tricarbonyl complex, using oxidative (i.e., GO atmosphere) or carbonylative methods for the bicyclooctenones and ceric ammonium nitrate (GAN) for the cyclopropanes. Photolysis of analogous tricarbonyl iron complexes leads to monoolefmic hydrocarbons or aldehydes. The kinetics of GO substitution in reactions of 77 -cyclopropenyl complexes of iron is also reported. " A number of comprehensive reviews have appeared since 1992, illustrating the chemistry of ry -allyliron complexes. 

Grubb s ruthenium carbene catalyst to afford medium-sized carbocycles (Equation (10))." Iron tricarbonyl systems containing diazoketones tethered to the terminal position of the acyclic coordinated diene have been utilized to effect ring formation, via inter- and intramolecular carbene reactions, affording new cyclohexa-2,4-dienone and cyclopent-2-enone tricarbonyl iron complexes. ... 

Recently, Sherburn and coworkers [87] attempted to use Wittig olefination to synthesize 1-substituted [3]dendralenes, only to determine that [3]dendralenes featuring a l -conjugating substituent underwent rapid DA dimerization and could not be isolated. The Wittig reaction furnished only an isolated example of a IZ-phenyl substituted [3]dendralene in low yield (20%), along with a mixture of three Diels-Alder dimerization products. This led to the development of a cross-metathesis approach involving tricarbonyl-iron complexed dendralenes, which is discussed in Section 1.4. 

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