TRICARBONYL HEXAFLUOROPHOSPHATE

An alternative method for the oxidative cyclization of the arylamine-substituted tricarbonyl(r -cyclohexa-l,3-diene)iron complex (725) is the iron-mediated arylamine cyclization. Using ferricenium hexafluorophosphate in the presence of sodium carbonate provided hyellazole (245) directly, along with the complex 727, which was also converted to the natural product (599,600) (Scheme 5.71). 

Retrosynthetic analysis of the carbazomycins C (263) and D (264) based on the iron-mediated construction of the carbazole framework leads to tricarbonyl [3-methoxy-(l-5-ri)-cyclohexadienyl]iron hexafluorophosphate (779) and the aryl-amines 780a and 780b (see Scheme 5.84) as synthetic precursors (611). The arylamines 780a and 780b have been used previously as precursors for the total syntheses of carbazomycin A (260) and B (261) (see Schemes 5.86, 5.87 and 5.88). 

E. Tricarbonyl[(l,2,Z,, 5-r))-2-methoxy-2,4 -cyclohexadien-l-yT -iron(l +) Hexafluorophosphate(l —). To the aqueous layer from Part D is added with swirling 7.1 g. (0.044 mole) of ammonium hexafluoro-phosphate (Note 23) in 30 ml. water. After 30 minutes, the light-yellow product is filtered, washed with water, and air dried the yield is about 9-10 g. (35-44%) (Notes 19, 24). 

HYDROGENATION CATALYSTS Aretie-chnomium tricarbonyls. (1,5-Cycloocta-diene)(pyridine)(tricyclohexyl-phosphine)iridium(I) hexafluorophosphate. Di-fi.-chlorobis( 1,5-hexadlene)dirhodium. Lindlar catalyst. Palladuim(II) acetate-So-dium hydride-/-Amyl alkoxide. Rhodium catalysts. 

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. 

The methylation of (/r-tellurido)bis[7r -cyclopentadienyl(tricarbonyl)]chromium by methyl trifluoromethanesulfonate in diethyl ether at 20 produced a methyltelluro-bridged complex that was isolated as the hexafluorophosphate. The red-brown solid forms needles that are stable in air for a short time only. 

Dicarbonyl-/i5-cyclopentadienylnitrosylmanganese(l + ) hexafluoro-phosphate(l —) is usually prepared1 by the reaction of tricarbonyl-fi5-cyclopentadienylmanganese with sodium nitrite and hydrochloric acid in refluxing ethanol. The cationic nitrosyl is isolated by the addition of ammonium hexafluorophosphate to the reaction mixture. This procedure yields up to 50 % of the product in a total reaction time of several hours. A more efficient preparation is the direct reaction of [Mn(C5H5)(CO)3] with [NO][PF6] in acetonitrile, which allows the isolation of the cationic complex in quantitative yield in less than one hour. 

The reaction is conducted in an atmosphere of dry nitrogen, and the acetonitrile must be dried before use (molecular sieves are satisfactory), since nitrosyl hexafluorophosphate is easily hydrolyzed. To 2 g. of tricarbonyl- -cyclopentadienylmanganese1 in 100 ml. of acetonitrile is added dropwise, and with rapid stirring, a solution of 1.9 g. [NO] [PF6] in 30 ml. of acetonitrile. Carbon monoxide is evolved, and the solution becomes darker yellow. After the addition of the [NO][PF6] solution is complete (5 minutes), stirring is continued for 10 minutes to ensure complete reaction. The volume of the solvent is reduced to approximately 20 ml. by evaporation,... 

Miscellaneous Systems Other systems have been described [li,m] ferrocene/ carbon tetrachloride (a trichloromethyl radical is formed), ferrocene/carbon tetrabromide, metal carbonyl/onium salts (e.g., the [cyclopentadienyl Fe (CO)2]2/ diaryliodonium hexafluorophosphate combination where a phenyl radical is generated), benzene chromium tricarbonyl/halide derivative, and so on. 

The reaction of nucleophiles with chloroarene-Mn(CO)3 and fluoro arene-Cr(CO)3 complexes has been employed for the synthesis of diaryl ethers and has been particularly applied (ref. 55) to the selective arylation of polyfunctional phenols by reaction of the phenoxide formed from NaH in dimethylformamide with the 4-chlorotoluene-manganese tricarbonyl cation (as the hexafluorophosphate) in acetonitrile at ambient temperature over 18 hours. 

FjFeMoOjP2C34H2g, Iron(l+), p-acetyl-2k C lK0-tetracarbonyl-lK C,2K C-bis[ 1,2-(Ti -cyclopentadienyl)l(tri-phenylphosphine-licP)molybdenum-, hexafluorophosphate(l-), 26 241 FjFeMoOgPCijHij, lron(l+), p-acetyl-2K-C icO-pentacarbonyl-li C,2K C-bisl 1,2-(tl -cyclopentadienyl)]molybdenum-, hexafluorophosphatefl—), 26 239 FgFe02PC, H j, Iron(l+), (ii -cyclopenta-dienyl)dicarbonyl(tetrahydrofuran)-, hexafluorophosphatefl—), 26 232 F4Fe204P2CjjH28, lron(l+), p-acetyl-2K-C 1 KO-tricarbonyl-1 x, 2KC-bis [ 12-(il -cyclopentadienyl))(tripheiiylphos-phine-2icP)di-, hexafluorophos-phate(l-), 26 237... 

FjFe02PCi,H,3, Iron(H-X ( ( -cyclopenta-dienyl)dicarbonyl(tetrahydrofuran)-, hexafluorophosphate(l —X 26 232 F6Fe204PjC3,H2g, Iron(l-t-X / -acetyl-2kC 1 KO-tricarbonyl-1 K C,2KC-bis [ 1,2-... 

CliHi3F6N2O3PW, (Acetone hydrazone)tricarbonyl( -cyclopentadienyl)-tungsten hexafluorophosphate, 44B, 758 CiiHi3FeP, 3,4-DimethyIphospholyl-cyclopentadienyliron, 43B, 1063 Cl iHi 303ReSi, TricarbonyK (trimethylsilyl)-7r-cyclopentadienyl)-rhenium, 38B, 781... 

Cyclohexadienyl iron tricarbonyl cations are best isolated as their relatively stable hexafluorophosphate salts. These are easily formed by addition of a saturated aqueous solution of ammonium hexafluorophosphate to an aqueous solution containing the cationic complex arising from either hydride or methoxide abstraction. The following protocol for the hydride abstraction from tricarbonyl(l-methoxy-4-methylcyclohexa-l,3-diene)iron 34 is representative. 

Synthesis of tricarbonyl(4-methoxy-1-methylcyclohexadienylium)iron hexafluorophosphate (Structure 45) ... 

Add the solution of ammonium hexafluorophosphate to the saturated tetrafluoroborate solution, and leave standing at room temperature for 30 min. Filter the resultant precipitate, wash with water (2x5 mL) and dry under vacuum to give in the order of 6 g of tricarbonyl(4-methoxy-1-methylcyclo-hexadienylium)iron hexafluorophosphate as a yellow solid, displaying appropriate spectroscopic data. ... 

Oxidative cyclization of alkylamines tethered to tricarbonyl-cyclohexadiene complexes facilitates an easy route to synthesis of indole derivatives. The ring closure is brought about using a single-electron-transfer (SET) agent, such as ferricenium hexafluorophosphate. Yeh et al. reported the first intramolecular radical cyclization of jf-diene)Fe(GO)3 complexes, to afford racemic cyclic tertiary alcohols. 

High-frequency shoulders on Vs(CO) and Vas(CO) bands in the FTIR spectra of an organometallic probe derived from tricarbonyl(l-4- n -5-pyridinocyclohexa-l,3-diene)iron hexafluorophosphate have been observed io on incubation with a-chymotrypsin and were assigned to an iron-complex covalently bonded to enzyme-NH2 groups. Curve-fitting analysis of the spectra enabled the bound complex to be detected even in the presence of the unbound probe and its FTIR spectrum to be calculated and compared with spectral data arising from similar interactions between the tricarbonyliron moiety and twelve aminoacids and polylysine. 

Tricarbonyl( p -l,3-dimethoxycyclohexadiene)iron (5 g, 18 mmol) is stirred in trifluoroacetic acid (10 mL) at 0 °C for 1 h and then at 10 °C for 10 min. The mixture is cooled to -50 °C and an ice-cold solution of ammonium hexafluorophosphate (5 g, 35 mmol) in water (10 mL) is added. After the mixture has reached ambient temperature, the precipitated yellow salt is filtered off, washed with cold water, and air-dried. The solid is purified by precipitation (acetone/diethyl ether) to give tricarbonyl-3-methoxycyclo-hexadienyliumiron hexafluorophosphate 4.9 g (70%). ... 

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