Benzene lithium derivatives

Isolation. Diimide has been isolated by low-temperature (-196°, liquid Nj) condensation of the pyrolysis products of the lithium derivative of p-toluenesulfonyl hydrazine (2). This is prepared by the reaction of tosyl hydrazine with lithium bis-(trimethylsilyl) amide in benzene at room temperature. Pyrolysis of (2) is carried out under high vacuum (< I0" torr). 

The lithium derivative of the 2-(methoxymethoxy)naphthalene (248) has been treated with diethyl ethoxymethylenemalonate to produce moderate yields of 6,7-benzocoumarin-3-carboxylate esters (249) in a one-pot reaction.The ort/io-lithiation of (methoxymethoxy)benzenes, followed by reaction with DMF... 

Carboranyl derivatives of lanthanum, thulium and ytterbium are formed when the C-mercuro derivatives of methyl- and phenylcarboranes react with the rare earth metals in tetrahydrofuran at 20°C (Suleimanov et al., 1982a), or from the lithium derivatives of methyl- and phenylcarboranes with the rare earth trichlorides in benzene-ether at 20°C (Bregadze et al., 1983) as complexes with THF. A carboranyl derivative with a thulium-boron bond is also described. The reaction (eq. 62) may proceed via the formation of B-Tm-C derivatives, followed by disproportionation. 

The following carboranyl derivatives of La, Tm, and Yb have been prepared by interaction of the lithium derivatives of carboranes with the appropriate rare earth trichlorides in tetrahydrofuran benzene-ether in 1983 by Bregadze et al. MeCBioHioCLaCl2, m.p. 133-135°C,... 

Bimetallic catalysts (lanthanide halides or 3 diketonates and alkyl-aluminium or lithium derivatives) have been reported. SmCp is also a catalyst for the trimerization of acetylenes to substituted benzenes and... 

The protocol described here for the synthesis of RME is basically that reported in (9). The lithium derivative of retinol is first prepared in dry benzene from retinol and butyllithium. The lithium derivative of retinol then undergoes a nucleophilic substitution in the reaction with dimethyl sulfate, giving RME in a one flask process. All manipulations are carried out under dim light. The structures of retinol and RME are presented in Fig. 1. 

A considerably greater easiness of formation of the lithium derivative using position 3 of the thiophene ring compared to halogen substitution in the benzene ring made it possible to accomplish the scheme for the synthesis of photochrome 58 with retention of the chlorine atom preliminarily introduced into the benzene ring [68] (Scheme 23). 

Several helical polycyclic aromatic hydrocarbons bearing aryl substituents at the most sterically hindered position were synthesized in an efficient three-step cascade reaction. The initial benzannulated enediynes were synthesized by the reaction of appropriate lithium acetylenides with an aryl-rert-butyl ketone. This was followed by reduction of the resultant acetylenic propargyl type alcohol with triethylsilicon hydride. This method turned out to be particularly successful for the synthesis of helical molecules. The reaction of ketones 3.588 and 3.590 with the lithium derivative of l-ethynyl-2-(2-penylethynyl)benzene 3.545 or related binaphthyl derivative followed by reduction and three-step sequence of cascade reactions led to polycyclic aromatic compounds 3.589 and 3.591, respectively, in a good yield (Scheme 3.48) [294, 295]. 

Contrary to benzo[b]thiophen, benzo[b]selenophen is acylated at position 2. 2-Bromobenzo[b]selenophen, prepared from the 2-lithium derivative and bromine, is acylated at position 3, and from this derivative the 3-isomers could be synthesized. A large number of 2- and 3-aroylbenzo[b]seleno-phens were synthesized, either by Friedel-Crafts reaction of benzo-[bjselenophencarboxylic acid chlorides and benzenes or from benzol bjselenophens and benzoic acid chlorides. Also the reaction between Grignard reagents and nitriles was used for the synthesis of aroylbenzo[b]selenophens. 4,S-Diaminobenzo[b]selenophen has been synthesized via nitration of 5-aminobenzo[b]selenophen or via the reaction of the diazonium salt derived from the S-amino-derivative with p-sulphanilic acid. From the diamino-derivative, several fused benzo[b]selenophens, e.g. (525), (526), and (527), were prepared. Reaction of the phenyl-... 

Lithium metal in ammonia at high concentration (4 M), with an alcoholic proton donor, will reduce the benzene ring of a phenoxide ion. The lithium salt of estrone is reduced under such conditions in 95% yield to a mixture containing 77% of estr-5(10)-ene-3a,17i -diol and 23% of the derived 5(10)-dihydro derivative. 

Tetrahydro derivatives are formed when either quinoxaline or 6-chloroquinoxaline is reduced with lithium aluminum hydride in ethereal solution. Similar reduction of 2,3-dimethylquinoxaline gives the meso-(cts)-1,2,3,4-tetrahydro derivative. This is shown to be a stereospecific reduction since lithium aluminum hydride does not isomerize the dl-(trans)-compound. Low temperature, platinum catalyzed, hydrogenation of 2,3-dimethylquinoxaline in benzene also gives meso (cis) -l,2,3,4-tetrahydro-2,3-dimethylquinoxaline. ... 

When the hydride ion of lithium alanate is used as nucleophile, cyclohexa-2,4-dien-l-ol is obtained as a labile addition product which eliminates water on standing to give benzene.12 The reaction of an oxepin derivative that possesses a hexamethylene bridge across C3-C6 with sodium methoxide gives an addition product 5 in which the seven-membered heterocyclic system is retained.213 214... 

The lack of a substrate isotope effect suggests very extensive internal return and is readily explained in terms of the fact that conversion of the hydrocarbon to the anion would require very little structural reorganisation. Since koba = k 1k 2/(kLl+k 2) and k 2 is deduced as > k2, then kobs = Kk 2, the product of the equilibrium constant and the rate of diffusion away of a solvent molecule, neither of the steps having an appreciable isotope effect. If the diffusion rates are the same for reactions of each compound then the derived logarithms of partial rate factors (above) become pAT differences between benzene and fluorobenzene hydrogens in methanol. However, since the logarithms of the partial rate factors were similar to those obtained with lithium cyclohexylamide, a Bronsted cor-... 

Reduction of aromatic rings with lithium or calcium " in amines (instead of ammonia—called Benkeser reduction) proceeds further and cyclohexenes are obtained. It is thus possible to reduce a benzene ring, by proper choice of reagent, so that one, two, or all three double bonds are reduced. Lithium triethylborohy-dride (LiBEtsH) has also been used, to reduce pyridine derivatives to piperidine derivatives." ... 

Macomber, R. S. et al., Synth. React. Inorg. Met.-Org. Chem., 1977, 7, 111-122 The dried solid product from interaction of lithium phenoxide and silver perchlorate in benzene (probably largely silver phenoxide) exploded on gentle heating. Other silver alkoxide derivatives were unstable. 

Treatment of the diester 211 (E = CC Et) with lithium IV-benzyltrimethylsilylamide, followed by aqueous acid, yields the cyclopentane derivative 212, the product of an intramolecular Michael addition (equation 104)110. 1-Methylindane is produced in moderate yield by the electrochemical reduction of o-bromo-(3-butenyl)benzene (equation 105)111. 

Metalated benzene derivatives can also be prepared by the reaction of alkynyl lithium reagents with zirconacyclopentadienes (Eq. 2.55) [39]. 

So far, many syntheses of p, or m-silylphenol derivatives were reported(56-60). p-Trimethylsilyloxy trimethylsilyl benzene was synthesized from trimethylsilyl chloride and p-trimethylsilyloxychloro(or bromo)benzene in the presence of Mg, or Na(56,57,59,60). A similar compound was also synthesized from triphenylchlorosilane and p-lithio phenoxy lithium(58). m-Trimethylsilyloxytrimethylsilylbenzene was prepared from m-trimethylsilyloxy bromobenzene and trimethylsilylchloride(59). 

Amination (11) and solution carbonation (8) reactions were carried out as described previously. For solid-state carbonations, a benzene solution of poly(styryl)lithium was freeze-dried on the vacuum line followed by introduction of high-purity, gaseous carbon dioxide (Air Products, 99.99% pure). Analysis and characterization of polymeric amines (11) and carboxylic acids (8) were performed as described previously. Benzoyl derivatives of the aminated polystyrenes were prepared in toluene/pyridine (2/1. v/v) mixtures with benzoyl chloride (Aldrich, 99%). 

It is quite difficult to reduce benzene or pyridine, because these are aromatic stmctures. However, partial reduction of the pyridine ring is possible by using complex metal hydrides on pyridinium salts. Hydride transfer from lithium aluminium hydride gives the 1,2-dihydro derivative, as predictable from the above comments. Sodium borohydride under aqueous conditions achieves a double reduction, giving the 1,2,5,6-tetrahydro derivative, because protonation through the unsaturated system is possible. The final reduction step requires catalytic hydrogenation (see Section 9.4.3). The reduction of pyridinium salts is of considerable biological importance (see Box 11.2). 

Similar results were achieved when benzene was reduced with alkali metals in anhydrous methylamine at temperatures of 26-100°. Best yields of cyclohexene (up to 77.4%) were obtained with lithium at 85° [396]. Ethylamine [397] and especially ethylenediamine are even better solvents [398]. Benzene was reduced to cyclohexene and a small amount of cyclohexane [397, 398] ethylbenzene treated with lithium in ethylamine at —78° gave 75% of 1-ethyl-cyclohexene whereas at 17° a mixture of 45% of 1-ethylcyclohexene and 55% of ethylcyclohexane was obtained [397], Xylenes m- and p-) yielded non-conjugated 2,5-dihydro derivatives, l,3-dimethyl-3,6-cyclohexadiene and 1,4-dimethyl-1,4-cyclohexadiene, respectively, on reduction with sodium in liquid ammonia in the presence of ethanol (in poor yields) [399]. Reduction of diphenyl with sodium or calcium in liquid ammonia at —70° afforded mainly 1-phenylcyclohexene [400] whereas with sodium in ammonia at 120-125° mainly phenylcyclohexane [393] was formed. 

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