Naphthalene dissolving metals

Exposure of naphthalene dissolved in liquid ammonia to europium metal immediately results in the characteristic green color of naphthalene anion-radical. ESR analysis reveals a signal that comes from an unpaired electron interacting with Eu and Eu nuclei. No hyperfine coupling with naphthalene protons is observed, although treatment with water leads to 1,4-dihydronaphthalene (Stevenson et al. 1999). This means that naphthalene has indeed been reduced to its anion-radical and undergone a normal Birch reaction. These results are consistent with the initial donation of two... 

Reduction is defined as acceptance of electrons. Electrons can be supplied by an electrode - cathode - or else by dissolving metals. If a metal goes into solution it forms a cation and gives away electrons. A compound to be reduced, e.g. a ketone, accepts one electron and changes to a radical anion A. Such a radical anion may exist when stabilized by resonance, as in sodium-naphthalene complexes with some ethers [122], In the absence of protons the radical anion may accept another electron and form a dianion B. Such a process is not easy since it requires an encounter of two negative species, an electron and a radical anion, and the two negative sites are close together. It takes place only with compounds which can stabilize the radical anion and the dianion by resonance. 

Exposure of naphthalene dissolved in liquid ammonia to europium metal immediately results in the characteristic green color of the naphthalene anion radical. ESR analy-... 

In addition to being more selective, dissolved calcium metal functions in a similar way to lithium and sodium metals towards organic functional groups [45]. Tab. 4.2 lists reductions giving the same products by the three dissolved metals. Among these, calcium affords the highest yields for some substrates (entries 1-3). The compounds in Tab. 4.2 include an aldehyde, indole [46], aryl ketone, enone, naphthalene [47], pyridine N-oxide [48], benzyl alcohol, styrene, and buckminster-fullerene. 

Electrides are synthetically useful and form the basis of so-called dissolving metal reactions, of which the Birch reduction of aromatic compounds is the paradigm, shown below for benzene and naphthalene ... 

Naphthalene sodium prepared in dimethyl ether or another appropriate solvent, or metallic sodium dissolved in Hquid ammonia or dimethyl sulfoxide, is used to treat polyfluorocarbon and other resins to promote adhesion (138—140). Sodium, usually in dispersed form, is used to desulfurize a variety of hydrocarbon stocks (141). The process is most useful for removal of small amounts of sulfur remaining after hydrodesulfurization. 

Under N2, clean Li metal (0.17 g, 25 mmol) was placed in a round-bottom flask with a solvent mixture of MeOH (3 mL) and pcntan-t-ol (17 mL). The mixture was heated under N, until the reaction with Li was complete. Then, naphthalene-2,3-dicarbonitrilc (2 g, 11 mmol) was added to the mixture which turned green-brown the mixture was refluxed for 3h. The brown powder, obtained after cooling and removal of the solvent under reduced pressure, was dissolved in anhyd acetone (20 mL) and then hexane (70 mL) was added. The green precipitate was separated from the brown solution by filtration. This purification by precipitation was repeated twice. The green precipitate was placed in a Soxhlet extractor and extracted for 3 h with acetone (200 mL) in order to separate the product from the insoluble metal-free species and LiOH. The acetone solution was evaporated down to a volume of 20 mL. The product precipitated after the addition of hexane (70 mL). This latter purification step was performed several times yield 1.29 g (64%). 

DMA in 500 ml ether mix rapidly with 270 ml 0.9 M phenyl-Li, boil fifteen hours and extract as for (VI) or as described previously to get 8 g oily 4-methoxy-indoline (or its 1-methyl derivative) (VII). Alternatively, add 36 g naphthalene to 300 ml tetrahydrofuran and add 11 g Na metal cut in small pieces. Reflux and stir three hours and add 18 g (VI) and 8 g DEA in 200 ml tetrahydrofuran rapidly and boil twelve hours. Evaporate in vacuum, dissolve the oily residue in 2N HCI and extract with ether. Proceed as described to get (VII). 4 g (VII) in 200 ml dry pyridine add to 6 g Cu chloride in 400 ml pyridine and reflux 1 xh hours. Pour on water and extract with ether. Wash extract with 4N HCI and then water and dry and evaporate in vacuum the ether to get 2 g of the indole (VIII). Alternatively, dissolve 4 g (VII) and 9.5 g cinnamic acid in 700 ml mesitylene, add 1 g 5% palladium-carbon and reflux five hours. Filter, wash with HCI and NaHC03 and dry and evaporate in vacuum the mesitylene to get the red, oily (VIII) (can chromatograph on alumina and elute with benzene-petroleum ether). 

By and large, a hnely divided precipitate of a metal is a very effective one-electron reducer. For example, a hnely divided precipitate of Zr(0) was obtained on mixing naphthalene sodium derivative in THF with ZrCl4. The Zr(0) precipitate dissolved on addition of anthracene or benzophenone to form the corresponding zirconium salts of the anion-radicals (Terekhova et al. 1996). 

When sodium metal is dissolved in a solution of naphthalene in THF, a green solution of a radical anion is produced. What is its structure k... 

To a stirred solution of naphthalene (0.045 mol) dissolved in 50 ml dimethoxyethane was added sodium metal (0.039 mol) and the mixture stirred 4 hours until a dark green color persisted. The product from Step 2 (0.016 mol) dissolved in 20 ml dimethoxymethane was added, the reaction stirred 2 hours, and then quenched with saturated 70 ml brine. The mixture was partitioned between 250 ml apiece EtOAc and 10% HCl, the organic layer discarded, and 10% NaOH added to the aqueous layer until pH 7 obtained. The aqueous layer was extracted twice with 100 ml CH2CI2, dried, filtered, concentrated at 25 °C at 150 torr, and the product isolated in 86% yield. and C-NMR, IR, MS and elemental analysis data supplied. 

Ishizu et al.194 synthesized hyperbranched macromolecules that resemble dendrimers. The synthetic approach involved the preparation of poly(4-methyl-styrene-b-PS-b-poly(4-methylstyrene) triblock copolymer by using naphthalene lithium as difunctional initiator. The 4-methyl groups of the terminal blocks were metalated with s-BuLi/tetramethylethylenedi-amine (TMEDA) complex in a molar ratio of 1 2. After removal of the excess s-BuLi by repeated precipitation of the living polymer and transfer of supernatant solution to another flask under high vacuum conditions, the polymer was dissolved in THF and was used as the initiator of a-methylstyrene at —78 °C. After the polymerization of a-methylstyrene, a small amount of 4-methylstyrene was added. The procedure of metalation of the a-methyl groups and polymerization of a-methylstyrene can be repeated many times to form a dendritic type hyperbranched polymer (Scheme 99). The characterization of the inter-... 

Naphthalene does not react with sodium in ether, but Scott found that when sodium is introduced to a solution of naphthalene in dimethyl ether or in ethylene glycol dimethyl ether the metal dissolves to give a deep green solution. Carbonation of the green solution gave a mixture of naphthalene, A -dialin-3,4-dicarboxylic acids, and A"-dialin-l, 4-dicarboxylic acids, and the result led Scott to infer that the solution contains the complex (C,(,HaNa.)C oH8. However, a quantitative study of the reaction in tetrahydrofurane by Paul" indicated that the metal dissolves by... 

Calcon carboxylic acid [3-bydroxy-4-(2-hydroxy-4-sulfo-l-naphthylazo)naphthalene-2-carboxylic acid] [3737-95-9] M 428.4, m 300", Xmax 560nm, pKi 1.2, pK2 3.8, PK3 9.26, PK4 13.14. Purify it via its / -toluidinium salt, viz dissolve the dye in warm 20% aqueous MeOH, treat with an equivalent of / -toluidine and cool to precipitate the salt. Finally recrystallise the acid from hot water. [Itoh Ueno Analyst (London) 95 583 1970.] It is an indicator and complexes with Ca " " in presence of Mg + and other metal ions [Patton Reeder Ana/ Chem 28 1026 1956, Prentoe Prentoe Analyst 106 227 1981]. 

---