Iron complexes cycloheptatriene

The following compounds have been obtained from thiete 1,1-dioxide Substituted cycloheptatrienes, benzyl o-toluenethiosulfinate, pyrazoles, - naphthothiete 1,1-dioxides, and 3-subst1tuted thietane 1,1-dioxides.It is a dienophile in Diels-Alder reactions and undergoes cycloadditions with enamines, dienamines, and ynamines. Thiete 1,1-dioxide is a source of the novel intermediate, vinylsulfene (CH2=CHCH=SQ2). which undergoes cyclo-additions to strained olefinic double bonds, reacts with phenol to give allyl sulfonate derivatives or cyclizes unimolecularly to give an unsaturated sultene. - Platinum and iron complexes of thiete 1,1-dioxide have been reported. 

A related >/4-norcaradiene tricarbonyliron complex is obtained upon reaction of tricy-clo[4.3.1.0l6]deca-2,4-diene with Fe3(CO)12 in boiling benzene (equation 143). However, the [4.3.1]propellane ring system is not retained in the analogous tricarbonylchromium complex. Instead, as suggested from solution NMR and solid state X-ray analyses, the complex assumes a homoaromatic structure, which is intermediate between a norcaradi-ene and a cycloheptatriene system (equation 144)193,194. It is noteworthy that the Cr(CO)3 group prefers the same conformation as the Fe(CO)3 group in the analogous norcaradiene iron complex. 

Various unsaturated cyclic 7t-ligands undergo, within a transition-metal complex, cycloaddition reactions and rearrangements with simultaneous formation of cyclopropane subunits. This is observed with cycloheptatriene ehromium and iron complexes such as 4 which give cycloaddition products, e.g. 

In the cycloheptatriene complex 10.43, one of the three double bonds is uncomplexed. This double bond is more reactive towards electrophiles (Scheme 10.13). Thus, acylation of the complex gives the Friedel-Crafts product as an if-dienyl complex 10.44 that can be converted to the V-diene complex 10.45 by addition-elimination of methoxide. Intramolecular molecular acylation of iron complexes is also possible (Scheme 10.14). ... 

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 reaction sequence includes a variety of different iron complexes and utilizes their specific nucleophilic and electrophilic properties. Nucleophilic addition ofri -allyl-Fp to a tricarbonyliron complexed cationic ri -cycloheptatrienyl system leads to an intermediate (Tj -cycloheptatriene)iron complex bearing an exocyclic cationic (Ti -alkene)iron unit. The latter is attacked by the uncomplexed alkene moiety with concomitant cyciization to leave an alkyl-Fp and an (ri -cycloheptadienylium)iron fragment in the molecule. Reduction with sodium borohydride and subsequent oxidative demetalation in the presence of carbon monoxide provides the hexahydroazulene derivative. 

Addition of an T -allyl-Fp complex to this compound affords an T -aIlyl-Fp-substituted cycloheptatriene system. Two double bonds are involved in an (T -diene)iron complex. The remaining free double bond of the silyl enol ether attacks as a nucleophile at the cationic r -alkene-Fp moiety to form an (Tj -diene)iron complexed cyclopentane annulated cycloheptadienone. Treatment with CAN in methanol under carbon monoxide atmosphere releases the methoxycarbonyl-substituted free ligand (Scheme 4-25). Reaction of the Ti -dienyliumiron intermediate of Scheme 4-25 with an ( , Z)-isomeric mixture of ri -crotyl-Fp proceeds with high diastereoselectivity. Four new stereogenic centers are formed in the course of this formal [3+2] cycloaddition. A hetero [3+2] cycloaddition is also feasible between T -ailyl-Fp complexes and aromatic aldehydes in the presence of zinc chloride or titanium(IV) chloride to provide tetrahydrofuran derivatives (Scheme 4-26). A 1,2-shift of the iron complex fragment occurs in the course of this reaction. Employment of imines affords the corresponding pyrrolidines. ... 

This method can be employed to the formation of acyclic and cyclic Ti -dienyl-iumiron complexes. T) -Cycloheptadienyliumiron and n -qrclooctadienyliumiron complex salts are readily available using this procedure starting from T -cycloheptatriene- or (T -cyclooctatriene)iron complexes, respectively. Protonation of tricarbonyl(cyclooctatetraene)iron by noncoordinating acids is known to afford cyclopropane annulated Ti -cycloheptadienyliumiron complexes. This procedure has been exploited for the synthesis of c -2-(2 -carboxycyclopropyl)glycines. ... 

The metal-mediated and metal-catalyzed [6 + 2]- and [6 + 4]-cycloaddition reactions, pioneered by Pettit and co-workers105 106 and Kreiter and co-workers,107 respectively, involve the cycloaddition of metal-complexed cyclic trienes with 7r-systems such as alkenes, alkynes, and dienes. The [6 + 2]-reactions produce bicyclo[4.2.1]nonadiene derivatives and the [6 + 4]-reactions produce bicyclo[4.4.1]undecatrienes (Scheme 32). Trienes complexed to chromium, which can be prepared on large scale (40 g) as reported by Rigby and co-workers,108 react with 7r-systems upon thermolysis or irradiation.109-111 Chromium and iron-catalyzed [6 + 2]-reactions of cycloheptatrienes and disubstituted alkynes... 

Reaction of (CN C—C(CF3)2 with [Fe(cycloheptatriene)(CO)3] yields adduct (39), which under CO pressure gives tricyclic ketone (40) presumably via iron-acyl complex (41 equation 16).47... 

We have thus been able to show that the acetonitrile-pentacarbonyl complexes M(CO)5NCMe (M = Cr, Mo, W) and cycloheptatriene-iron-tricarbonyl C7H3Fe(CO)3 are deprotonated as follows, without attack at the CO ligands (151). 

When this hydride abstraction was tried with the iron-cycloheptatriene analog, a carbonium ion complex was formed, but by trityl alkylation. 

Diene iron tricarbonyl complexes are prepared by thermal or photochemical reaction of conjugated dienes with iron pen-tacarbonyl in the presence of TMANO, triiron dodecacarbonyl, ()]" -benzylidenacetone)iron tricarbonyl, diiron nonacarbonyl, or diiron nonacarbonyl absorbed on silica gel in the absence of solvent. The latter method is particnlarly usefiil for the preparation of complexes from polar electron-rich dienes and heterodienes. A reductive complexation of cycloheptatrienes using iron tricarbonyl and sodium borohydride to give cyclo-heptadiene iron tricarbonyl has been developed (Scheme 126). 

Double bonds adjacent to complexed dienes can be cyclopropanated using diazomethane, methyl diazoacetate, or sulfur-based ylids. Cycloheptatriene iron tricarbonyl undergo a [2 -F 2] cycloaddition with chloroketene derived from trichloroacetyl chloride (Scheme 161). 

Cycloheptadiene complexes are useful synthetic building blocks in the preparation of complex organic and natural products. A variety of substituted cycloheptadiene complexes can be prepared via catalytic hydrogenation of the respective cycloheptatriene-Fe(CO)3 complex. Subsequent oxidation liberates the iron carbonyl moiety affording the uncomplexed substituted cycloheptadiene complex (Scheme 34). 

C7Hg)Fe(CO)3 but also the diene complex (C7Hio)Fe(CO)3 (60) and a trinuclear complex for which structure (110) has been suggested (470). Formation of the diene complex in this reaction obviously involves a rather uncommon intermolecular hydrogen transfer (470). The reaction of Fe2(CO)9 with either 1,3,5-cycloheptatriene or its 7-methoxy derivative yields the complex (triene)Fe2(CO)8 (190), the Mossbauer spectrum of which shows chemically equivalent iron atoms. This, with... 

C7H7)Fe.,(CO)6]+, obtained by reaction of the cycloheptatriene complex with trityl tetrafluoroborate, shows in solution a rapid valence tautomerisrn involving diene bonding to an iron atom and Tr-allylic bonding to the other. 

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