Phenyllithium from benzene

Optimum Conditions for Preparing Phenyllithium from Benzene. The optimum procedure for metalation of an aromatic compound in high yield was to use the aromatic compound itself as the solvent. The alkyl-lithium compound used mainly in this study was n-butyllithium because it was convenient and economical. 

Phenyllithium from Benzene and BuLi - TMEDA in Hexane... 

Other reactions typical of aromatic systems, such as nitration and bromination, arc not feasible with metallocenes because of their sensitivity to oxidation.,h- However. many of the derivatives that would be produced in these types of reactions can be made indirectly by means of another reaction typical of aromatic systems mctalla-lion. Just as phenyllithium can be obtained from benzene, analogous ferrocene compounds can be prepared ... 

Recently methyltriphenylammonium tetrafluoroborate was prepared from triphenylamine and trimethyloxonium fluoroborate. Demethylation was affected by butyllithium in hexane or methylene chloride and with phenyllithium in benzene or ether. No evidence for biphenyl or diphenyl-methylamine was noted and only triphenylamine was characterized. In demethylation reactions with potassium methoxide in methanol-O-d, no exchange of methyl hydrogen for deuterium was observed. Thus, no proton abstraction processes occurred in these decompositions 114>. 

The reaction is carried out in a manner similar to that described above (Chapter 11, Section II). In a 250-ml flask fitted with stirrer, condenser, and dropping funnel is placed a solution of 19.25 g (0.0505 mole) of the phosphonium salt in 180 ml of THF. The nitrogen atmosphere is established and 0.05 mole of phenyllithium added (as a solution in benzene, available from Foote Mineral Co.). The mixture is stirred for 45 minutes at room temperature and then refluxed for 15 minutes. To the red-brown solution is added dropwise over 20 minutes 4.91 g (0.05 mole) of distilled cyclohexanone stirring is continued for 24 hours. The mixture is then concentrated by distillation at... 

Diphenyl ditelluride (typical procedure) To a suspension of powdered Te (25.5 g, 0.2 mol) in anhydrous THF (300 mL), 2.0 M phenyllithium (100 mL, 0.2 mol) is added dropwise, with stirring and under argon. The resultant mixture is stirred at room temperature for 2 h and under reflux for 1 h. The reaction mixture, which should contain only a small amount of unreacted Te, is allowed to cool to 20°C, and is poured into 1 L of H2O. Oxygen (or air) is bubbled for 1 h through the mixture, which is then extracted with benzene (100 mL). The benzene solution is washed three times with H2O, dried (Na2S04) and evaporated. The residue is recrystallized from EtOH (77% m.p. 63.8-65.0°C). 

Pentacarbonyl(a-methoxybenzylidene)tungsten(0)7 (0.89 g, 2.0 mmole) and a magnetic stirring bar are placed in a flame-dried, 100-mL, round-bottomed flask fitted with a rubber septum. The flask is flushed with nitrogen, 50 mL of diethyl ether (freshly distilled from sodium and benzophenone) is added, and the resulting red solution is cooled to -78°. A double-titrated8 solution of phenyllithium in 70 30 benzene/diethyl ether (1.25 mL, 1.85 M, 2.31 mmole, 2.10 M total base, 2.63 mmole) is added by syringe to the well-stirred solution. The anionic intermediate formed is thermally unstable at room temperature and is kept at -78° (Dry Ice-acetone) to avoid decomposition. 

Ethereal phenyllithium, prepared from lithium and bromo-benzene,3 may be standardized by adding an aliquot to water and titrating with standard sulfuric acid. 

The phenyl lithium solution was purchased from Aldrich Chemical Company, Inc. The checkers used 64 mL (0.115 mol) of 1.8 M phenyllithium in 75 25 benzene-ether which was purchased from Alpha Products, Morton/Thiokol Inc. 

The interaction between pyridine and organolithium compounds in benzene was first reported by Ziegler and Zeiser129 and was attributed to the formation of 1 1 adducts. Indirect evidence for intermediates of this kind was based on the formation of dihydropyridines by treatment of the reaction mixture with water. More definite evidence was obtained with quinoline, isoquinoline, and acridine.130 Phenyllithium reacts quantitatively with quinoline in ether to yield an adduct as a yellow powder that can be recrystallized. In order to define the site of attachment, the adducts were hydrolyzed to dihydro derivatives and the latter dehydrogenated. Because this treatment leads mainly to 2-phenyIquinoIine and l-phenylisoquinoline from quinoline and isoquinoline, respectively, the related adducts can be assumed to have structures 80 and 81. Isolation and characterization of the dihydro derivatives have been carried out, as well as in the case of the reaction of acridine with phenyllithium. 

Methylene triphenylarsorane (//, 31, 34, 39) has been prepared in situ from the salt in ether (34, 39), benzene (34, 39, 60), tetrahydrofuran (31), or dimethyl sulfoxide (II) by reaction with butyl- or phenyllithium (34, 39), sodium hydride (31), methylsulfinylcarbanion (II), or sodamide (102). Ethylidene triphenylarsorane has been prepared by reaction with methylsulfinylcarbanion (II) whereas fluorenylidene-(9)-trimethyl- and fluor-enylidene-(9)-dimethylbenzylarsorane (101) have been made using phenyllithium in ether. Sodium methoxide in methanol has been used successfully (41, 47, 48, 94) to generate ylides from their corresponding salts when R is an electron-withdrawing group (e.g., COOR, COR, or CN). 

When nine moles of phenyllithium in ether acted upon tetraacetyl-glucosyl chloride, the reaction mixture being subsequently decomposed with water, four products resulted. From the ether layer a quantitative yield of methyldiphenylcarbinol was recovered. Acetylation of the residue from the water layer, followed by fractional crystallization led to two crystalline substances and a residual sirup. The first crystalline product was (tetraacetyl-j3-D-glucopyranosyl)benzene (IV). The second m. p. 142-143°, [a]o24 — 2.3° (chloroform), appeared to be isomeric with IV. It oxidized to benzoic acid and deacetylated to give a sirup which consumed two moles of periodate with liberation of one mole of formic acid. While these properties are to be expected for a structure related to IV, this substance differed from both of the anomeric (tetraacetyl-n-glucopyranosyl)benzenes, nor did it appear to be a mixture of them. Its exact constitution is not yet known. 

Materials. The phenyllithium and n-butyllithium used in this work were commercial products supplied by Foote Mineral Co. in ether-benzene and hexane solutions, respectively. Triphenylmethyldifluoramine was obtained from Peninsular Chem Research and purified by recrystallization from methanol, m.p., 80°—81.5° C. er -Butyl iodide was obtained from K and K Laboratories, Jamaica, N. Y., and purified before use either by distillation or by washing with aqueous sodium thiosulfate and drying. 

Quantitative experiments by Huisgen et cd. on the competition of lithium piperidide and phenyllithium for benzyne originating from different halogenobenzenes show that in these reactions benzyne and not a complex of benzene and a halogen atom is an intermediate. 

There are several recent methods for the reduction of azobenzene to hydrazobenzene in near-quantitative yield. Samarium(II) iodide reduces azobenzene to hydrazobenzene rapidly at room temperature. Hydrogen telluride, generated in situ from aluminum telluride and water, reduces both azobenzene and azoxybenzene to hydrazobenzene a mixture of phenyllithium and tellurium powder has been used to reduce azobenzene. A complex of the coenzyme dihydrolipoamide and iron(II) is also effective for the reduction of azo- and azoxy-benzene to hydrazobenzene the reduction probably involves coordination of the azobenzene to iron(II) as shown in structure (1). Electrochemical reduction has been used to prepare a number of hydrazobenzenes from the corresponding azobenzenes. In the presence of an acylating agent a diacylhydrazine (e.g. the pyridazinedione derivative 2) can be isolated from the electrochemical reduction of azobenzene. 

A procedure better adapted to operation on a large scale is described by Bavin. A solution of 1 mole of fluorene in 500 ml. of ether is added with stirring under reflux to an ethereal solution of phenyllithium prepared from 1.5 moles of bromo-benzene. After 1 hr. more the orange solution of metallated hydrocarbon is poured as rapidly as possible into powdered dry ice which has been slurried with ether. The mixture is acidified, the solvent removed by steam distillation, and the solid is dissolved in aqueous potassium carbonate solutioa Clarification with Norit gives a pale yellow solution which is poured into excess 30% hydrochloric acid. The colorless, crystalline product on reaction with methanol and hydrogen chloride gave the pure methyl ester, m.p. 64-65°. The yield was generally over 70% and occasionally reached 90%. ... 

Since considerable trimethylamine was observed, the fate of the phenyl group was examined. It was determined by carbon-14 labeling, that biphenyl results from the reaction of phenyllithium with 5. However, it is most unlikely that the phenyl group can be displaced by phenyllithium in an 5 2 reaction. Therefore, it was suggested 157> that proton abstraction occurs at the ortho carbon of the benzene ring to give benzyne which subsequently reacts with phenyllithium to give biphenyl. 

It might be expected that in the presence of TMEDA or other tertiary diamines anomalous reaction products might be obtained with organolithium compounds such as benzyllithium. A number of reports in the literature disclose instances of the expected reaction products from reactions such as carbonation to the carboxylic acid and addition to benzophenone (I, 3, 4, 12). The phenyllithium-TMEDA (1 1) complex in benzene was allowed to react with benzophenone to give a 95% yield of triphenylcarbinol and with cyclohexanone to yield 59% of the 1-phenylcyclohexanol. The reaction with excess trimethylsilyl chloride is apparently quantitative. The main consideration in using these complexes is to use low temperatures for reaction and aqueous washes of ammonium chloride solution in the work-up to remove all of the tertiary diamine (the odor can be detected in low concentrations.)... 

Optimum Conditions for Preparing Benzyllithium from Toluene. Both the TMEDA and TED complexes of benzyllithium were investigated. Toluene metalation proceeds much faster than does benzene metalation under similar conditions. The benzyllithium complexes were more soluble in hydrocarbon solvents than were the corresponding phenyllithium complexes. This method of preparation of benzyllithium is the most convenient of the few literature procedures available. Other procedures described are the cleavage of benzyl methyl ether with lithium... 

Phenyllithium-TMEDA in Benzene. Benzophenone. Added ben-zophenone dissolved in benzene at 5°C over 1 hr let warm 1 hr hydrolyzed, used extra benzene during work-up recrystallized from 1 1 methanol-ethanol mp 161 °C (lit. mp 162.5°C) 95%, triphenylcarbinol (36). 

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