Of tricarbonyls

Methylthiophene is metallated in the 5-position whereas 3-methoxy-, 3-methylthio-, 3-carboxy- and 3-bromo-thiophenes are metallated in the 2-position (80TL5051). Lithiation of tricarbonyl(i7 -N-protected indole)chromium complexes occurs initially at C-2. If this position is trimethylsilylated, subsequent lithiation is at C-7 with minor amounts at C-4 (81CC1260). Tricarbonyl(Tj -l-triisopropylsilylindole)chromium(0) is selectively lithiated at C-4 by n-butyllithium-TMEDA. This offers an attractive intermediate for the preparation of 4-substituted indoles by reaction with electrophiles and deprotection by irradiation (82CC467). 

C. 7 ricar6oni/Z[( 1,2,3,4,5-jj)-l-and 2-methoxy-2,4 -cydohexadien-l-yl]-irTriphenylmethyl tetrafluoroborate [Methylium, triphenyl-, tetrafluoroborate] (34 g., 0.103 mole) (Note 20) is dissolved in a minimum volume of dichloromethane and 18 g. (0.072 mole) of tricarbonyl (1- and 2-methoxy-l,3-cyclohexadiene)iron dissolved in a like volume of dichloromethane is added. The resulting dark solution is left for 20-30 minutes and then added with stirring to three times its volume of ether (Note 21). The precipitate is collected and washed with ether to 5ueld 21-22 g. (87-91%) of product as yellow solid (Note 19). 

Syntheses of heterocycles, among them carbazole alkaloids, with participation of tricarbonyl(Ti -diene)iron complexes 99CSR151. 

Irradiation of tricarbonyl(r(4-cyclobutadienc)iron(0) with ethyl 1//-azepine-l-carboxylate results in the formation of the novel sandwich compound (t 4-cyclobutadiene)[l-(ethoxycar-bonyl)-1 //-azepine]iron(0) (27).223... 

Irradiation of complex 6 in the presence of ethyl acrylate provides the [6 + 2] 7t-adduct 9 as the single enrfo-diastereomer,276 which may also be obtained by heating a mixture of methyl l//-azepine-l-carboxylate with the ester in the presence of a catalytic amount of tricarbonyl(>]6-naphthalene)chromium(O).277... 

Reaction of Tricarbonyl(diazepine)iron 16 with Dimethyl Acetylenedicarboxylate and Decomplexation of the Products Typical Procedure ... 

In 1989, Thomas reported3 the novel synthesis of tricarbonyl(774-vinylke-tene)iron(O) complexes (221) from the corresponding 774-vinylketones (222). Nucleophilic attack by methyllithium on a carbonyl ligand is thought to produce the anionic complex 223, which then carbonylates to give the rf-... 

Although Eq. (3) indicates that CO absorption is required for aldehyde formation, it has been shown by Karapinka and Orchin 18) that at 25° and with a moderate excess of olefin the rate of reaction and the yield of aldehyde are similar when either 1 atm of CO or 1 atm of Nj is present. Obviously CO is not essential for the reaction and a CO-deficient intermediate, probably an acylcobalt tricarbonyl, can be formed under these conditions. The relative rates of HCo(CO)4 cleavage of tricarbonyl and tetracarbonyl are not known, and thus the stage at which CO is absorbed in the stoichiometric hydroformylation of olefins under CO is not known with certainty. Heck (19) has shown conclusively that acylcobalt tetracarbonyls are in equilibrium with the acylcobalt tricarbonyl ... 

Annulation of tricarbonyl cyclobutadiene iron to tropone and tropylium ion to give complexes 282 and 285 is achieved by Wittig cycloolefination of dialdehyde 281 with biphosphonium salts, 280 and 283, respectively (Scheme 71 77JA513 78AJC1607). 

The crystal structure of tricarbonyl-(2,4,6-triphenylphosphorin)chromium (57) has been reported. The Cr(CO)3 group has a central position above the... 

Recently a compound with three PH3 ligands bonded to a central atom was reported. Phosphine reacted rapidly and quantitatively at room temperature with a solution of tricarbonyl-hexamethylborazine chromium(O) in cyclohexane to give the octahedral tricarbonyltris(phosphine)chromium(0) in the cis configuration... 

Some further examples of stereoselective deprotonation/alkylation reactions of tricarbonyl-chromium complexed (V-methyl tetrahydroisoquinolines have been reported27. Starting with the enantiomerically pure (35)-methyl tetrahydroisoquinoline reaction with hexacarbonyl-chromium led to a mixture of endo- (40%) and exo- (60%) complexes, which were deprotonated with butyllithium and subsequently methylated with iodomethane. In this way methylation occurred firstly at the 4- and secondly at the 1-position. In all cases, the methyl group entered anti to the chromium complexed face. After separation of the alkylated complexes by chromatography and oxidative decomplexation, the enantiomerically pure diastereomers (—)-(l 5,35,47 )-and ( + )-(17 ,35,45)-1,2,3,4-tetrahydro-l,2,3,4-tetramethylisoquinolme were obtained, benzylic amines such as tetrahydroisoquinoline to 2-amino-4,5-dihydrooxazoles. Deprotona... 

No racemization occurs at the phenylglycine moiety throughout the entire sequence. With more complex arenetricarbonylmanganese complexes, such as that derived from the methyl ester of iV-acetyl-O-phenyltyrosine 5, two equivalents of the lithiated dialkoxydihydropyrazine 1 have to be used30. If not, no arylaled dialkoxydihydropyrazine is formed and the loss of tricarbonyl-manganese is observed. 

In view of the extensive nature of this field, remarkably few complexes of heterocyclic systems have been reported. One of the first to be isolated was tricarbonyl-7r-thiophene chromium 28), and the preparation of tricarbonyl-7r-pyrrolyl manganese has recently been reported (29). 

To a 125-mL Erlenmeyer flask containing a stirring bar is added 1.078 g (2.000 mmol) of tricarbonyl(hydrido)[l,2-bis(diphenylphosphino)ethane] manganese in 60 mL of methylene chloride. To the stirred solution, 2.11 g (11.1 mmol) of solid p-toluenesulfonic acid hydrate is added in small increments. The theoretical quantity of dihydrogen is evolved in less than 10 min. The suspension is washed twice with equal volumes of water, then with dilute sodium bicarbonate solution, then with water again. The methylene chloride is evaporated to dryness and the product is crystallized from benzene methylene chloride (2 1) to give yellow crystals in 77% yield. 

Butanaminium, NW-tributyl-, stereoisomer of tricarbonyl-[tetrakis[(methylthio)methyllborato( 1 -)-S, yS"]molybdate( 1 -), 32 111-12... 

Several other dicarbonyltris(phosphane)iron complexes are mentioned as coproducts in the reaction of tricarbonyl( 1,2,3,6,->/-cyclooctenediyl)iron with phosphanes, but only the P(OC2H5)3 derivative could be isolated (60%).12... 

The properties of tricarbonyl compounds are for the most part as expected, except when the three groups are contiguous to one another, as in diphenyl-propanetrione. With such compounds, the central carbonyl group is highly reactive it is lost, as carbon monoxide, in the presence of acidic catalysts such as aluminum chloride, and adds water readily to give a monohydrate ... 

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. 

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). 

Chemoselective oxidation of 4-methoxyanilines to quinonimines can be achieved in the presence of tricarbonyl(ri4-cyclohexadiene)iron complexes. This transformation has been used for the synthesis of carbazoles via intermediate tricarbonyliron-coordinated 4b,8a-dihydrocarbazol-3-one complexes (Scheme 1.24) [57]. 

The first aspect is illustrated by the synthesis of tricarbonyl(ri4-l,3-diene)iron complexes from pentacarbonyliron in the presence of catalytic amounts of a 1-azabuta-... 

Fig. 16. Views of tricarbonyl(l-Mro-fluoro-l-methyl-2,3,4,5-tetraphenyl-l-germacy-clopentadienyDiron, (a) perpendicular to the C4Ge plane and (b) perpendicular to the Fe ring interaction (phenyl groups omitted for clarity).

---