Dicarbonyl tetrafluoroborate

A 100-mg. (0.2-mmole) sample of ju-chloro-bis(cyclopenta-dienyliron dicarbonyl) tetrafluoroborate is dissolved in 2 ml. of acetone, and 0.5 ml. (10 mmoles) of acetonitrile is added to the dark red solution. The reaction mixture is heated to 20-30°C. for 1 hours. During that time the color changes to red-orange. Solvent and excess acetonitrile are removed under vacuum. The oily residue is treated with ether, and a yellow solid forms. The yellow solid is removed by filtration and is dissolved in 2 ml. of acetone. The solution is filtered then ether is added dropwise to the filtrate until no more precipitate separates. After the yellow crystalline product is dried under high vacuum, the yield is about 60%, based on [ CtH5Fe(CO)2 2Cl]BF4. Anal. Calcd. C, 29.78 H, 2.23 Fe, 15.39 N, 3.86. Found C, 29.86 H, 2.46 Fe, 15.47 N, 3.48. 

Cyclopentadienyl)(isobutenyl)iron dicarbonyl tetrafluoroborate, [Fp(ole-fin)] BF4" (1). Mol. wt. 319.87, yellow-orange crystals, stable for some time at 20°. 

ALKENES (Cyclopentadienyl)(isobutenyl)iron dicarbonyl tetrafluoroborate. 

ALKENES (Cyclopentadlenyl)(isobutenyl)iton dicarbonyl tetrafluoroborate. 

Several interesting reactions have been described for quinolizine-3-diazonium tetrafluoroborate 121. Thus, its treatment with secondary amines gave the corresponding triazenes 122 <2004ZNB380>, while its reaction with 1,3-dicarbonyl compounds gave the corresponding hydrazones. In the case of alkyl 4-chloro-3-oxobutanoates, the intermediate hydrazone 123 furnished a pyrazole derivative 124, as shown in Scheme 17 <2002H(57)2091>. 

Cyclopentene annelation.1 The reaction of the anion of a 1,3-dicarbonyl compound with l-decynyl(phenyl)iodonium tetrafluoroborate results in an annelated 3-pentylcyclopentene in reasonable yield. The product is considered to result from... 

Putilova ES, Troitskii NA, Zlotin SG (2005) Reaction of aromatic aldehydes with beta-dicarbonyl compounds in a catalytic system piperidinium acetate - l-butyl-3-methylimida-zolium tetrafluoroborate ionic liquid. Russ Chem Bull 54 1233-1238... 

Dicarbonyl(cyclopentadienyl) (ethyl vinyl ether)iron tetrafluoroborate Iron(l+), dicarbonyl (n -2,4-cyclopentadien-l-yl )[(l,2-Ti)-ethoxyethene]-, tetrafluoroborate(l-) (10) (75182-42-2)... 

Dicarbonyl(cyclopentadienyl)(ethyl vinyl ether)1ron tetrafluoroborate,... 

Dicarbonyl(cyclopentadienyl)(trans-3-methyl-2-vinylcyclohexanone)iron tetrafluoroborate, 66, 97... 

BF4MoOPCwH](), Molybdenum(l +), car-bonyl-(-n5-cyclopentadienyl)-(diphenylacetylene)-(triphenylphosphine)-tetrafluoroborate(l -), 26 104 BF4MoO2PC25H20, Molybdenum, dicarbonyl-(T) -cyclopentadienyl)-[tetrafluoroborato(l -)] (triphenylphosphine)-, 26 98 BF4MoOjCbH5, Molybdenum, tricarbonyl-(ry -cyclopentadienyl) [tetrafluorobor-ato (1-)]-, 26 96... 

Dicarbonyl(cyclopentadienyl)[(dimethylsulfoniuni)methyl]iron(II) tetrafluoroborate... 

Dicarbonyl(cyclopentadienyl)[(dimethylsulfonium)methyl]iron(ll) tetrafluoroborate, Cp(CO)2FeCH2S(CH3)2BF4 (1). 

Dicarbonyl(cyclopentadienyl)-[(dimethylsulfonium)methyl]-iron(II) tetrafluoroborate, 98 Diiodomethane-Diethylzinc, 276 Diiodomethane-Triisobutylalu-minum, 114... 

Tributyltin hydride, 316 Tributyltinlithium, 319 Trichloroacetonitrile, 321 Other carbohydrates (Diethylamino)sulfur trifluoride, 110 Triethyloxonium tetrafluoroborate, 44 Carbonates (see also Enol carbonates) Carbon dioxide, 65 Di-/-butyl dicarbonate, 94 Carboxylic acids (see also Dicarbonyl compounds, Unsaturated carbonyl compounds)... 

Bromopentacarbonylmanganese, 49 tom -Bromotetracarbonyl(methyl-methylidyne)chromium, 50 frmethylidyne)tungsten, 49 Carbonylhydridotris(triphenylphosphine)-rhodium(I), 329 Chromium carbonyl, 51 Decacarbonyldimanganese, 49 Dicarbonylcyclopentadienylcobalt, 96 Dicarbonyl(cyclopentadienyl)[(dimethyl-sulfonium)methyl]iron(II) tetrafluoroborate, 98... 

It has been shown that selective a-vinylation of enolate anions derived from 1,3-dicarbonyl compounds can be achieved by reaction with 4-/-butyl-1 -cyclohcxcnyl-(aryl)iodonium and 1 -cyclopentenyl(aryl)iodonium tetrafluoroborates without competing a-arylation, provided that the alkenyliodonium salt used bears a / -mcthoxyphcnyl, rather than phenyl, group.24... 

The retrosynthetic analysis of 2,4,6-triphenylpyrylium tetrafluoroborate (86), involving an initial reduction followed by a disconnection of one carbon-oxygen bond (cf. disconnection of 2,5-dimethylfuran, Section 8.3.1, p. 1146), reveals the substituted 1,5-dicarbonyl compound (89). Further rational disconnection then reveals acetophenone and l,3-diphenylprop-2-en-l-one (chalcone) clearly the latter may originate from acetophenone and benzaldehyde (cf. Section 6.12.2, p. 1032). 

Alkynyl(phenyl)iodonium salts can be used for the preparation of substituted alkynes by the reaction with carbon nucleophiles. The parent ethynyliodonium tetrafluoroborate 124 reacts with various enolates of /J-dicarbonyl compounds 123 to give the respective alkynylated products 125 in a high yield (Scheme 51) [109]. The anion of nitrocyclohexane can also be ethynylated under these conditions. A similar alkynylation of 2-methyl-1,3-cyclopentanedione by ethynyliodonium salt 124 was applied in the key step of the synthesis of chiral methylene lactones [110]. 

If cyclopentadienyliron dicarbonyl halides are allowed to react with themselves in the presence of Lewis acids, cations are formed in which the new substituent is the cyclopentadienyliron dicarbonyl halide itself, for example, [CjH6Fe(CO)i-X-(CO)2-FeC8H8]+ (X = Cl, Br, I). All three cations can be prepared best by treatment of the corresponding halides with boron trifluoride diethyl etherate all are isolated as tetrafluoro-borates.18 The bromine complex can also be obtained by a more complicated procedure by the reaction between C8H8Fe-(CO)2Br and AlBr3 in liquid sulfur dioxide 16 the iodine cation can be isolated from a melt of cyclopentadienyliron dicarbonyl iodide and aluminum chloride.17 In the latter two cases the hexafluorophosphate salts can be obtained. These binuclear cations are of special interest, because they are cleaved by electron donors,16-17 e.g., aniline, pyridine, benzonitrile, acetonitrile, acrylonitrile, with the formation of the corresponding [C8H8Fe(CO)2L]+ cations and the parent halide. Equations for preparation of the tetrafluoroborate are ... 

Despite the synthetic possibilities suggested by this early study, the chemistry of the alkynyliodonium salts lay dormant until the mid-1980s. In 1986, Ochiai and his coworkers published an important communication which shaped much of the later thinking on the reactions of alkynyliodonium ions with nucleophiles28. When / -dicarbonyl enolates are treated with alkynyliodonium tetrafluoroborates containing a long (> three carbons) alkyl chain, derivatives of cyclopentene are produced. This is illustrated in equation 41 for the... 

When / -dicarbonyl enolates are allowed to react with alkynyliodonium salts, typically in ter/-butyl alcohol or THF, alkynyl- and/or cyclopentenyl- -dicarbonyl compounds are obtained. The product compositions are largely regulated by the migratory aptitude of R in the alkynyl moiety and the availability of alkyl side chains for the MC-insertion (MCI) pathway (equation 45). These divergent modes of reactivity are nicely illustrated by the reactions of the 2-phenyl-1,3-indandionate ion with ethynylfphenyl)- and 4-methyl-1-hexynyl(phenyl)iodonium tetrafluoroborates (equation 1 15)27 2. 

Because the hydrogen atom and phenyl group migrate so readily, the reactions of / -dicarbonyl enolates with ethynyl- and (phenylethynyl)iodonium salts can be expected to result in alkynylation. It has already been noted that the 2- -hexyl-l,3-indandionate ion undergoes alkynylation with (phenylethynyl)phenyliodonium tetrafluoroborate (equation 43), despite the availability of the -hexyl group for [2 + 3] annulation. Ethynylations of six / -dicarbonyl enolates and the anion of 2-nitrocyclohexane with ethynyl(phenyl)-iodonium tetrafluoroborate in THF have also been reported27. For example, admixture of the ethynyliodonium salt and the anion of ethyl 2-cyclopentanone-l-carboxylate in THF affords the 1-ethynyl derivative in 71% isolated yield (equation 124)27. 

Cyclopentadienyl dicarbonyl ruthenium dimer 132 reacts with silver tetrafluoroborate and diphenylacetylene to afford the cyclobutadiene ruthenium complex 133 (Scheme 12). Irradiation of 133 in dichloro-methane in the presence of several alkynes leads to the arene cyclopentadienyl ruthenium complexes 125 in high yield. This reaction appears to be a general route to sterically crowded ruthenium arene cations (55). 

Treatment of 1,3-dicarbonyl compounds with DBP in a methoxide/methanol system affords 2-alkyl-4-[(phenylsulfonyl)methyl]furans, where reaction proceeds by Initial addition-elimination on the vinyl sulfone moiety. In contrast, silyl enol ethers in the presence of silver tetrafluoroborate resulted in products derived from Sn2 displacement at the allylic site.11 Anions derived from 1,3-dicarbonyls substituted at the C-2 position are found to induce a complete reversal in the mode of ring closure.12 The major products obtained are 3-[(phenylsulfonyl)methyl]-substituted cyclopentenones. The internal displacement reaction leading to the furan ring apparently encounters an unfavorable Ai -interaction in the transition state when a substituent group is present at the 2-position ol the dicarbonyl compound. This steric Interaction is not present in the transition state leading to the cyclopentenone ring. 

---