Aryl lithium reaction

Mechanisms for Carbyne Formation. Two possible mechanisms for the aryl lithium reaction can be proposed (see Scheme 4). Since two equiva-... 

Uses. The largest use of lithium metal is in the production of organometaUic alkyl and aryl lithium compounds by reactions of lithium dispersions with the corresponding organohaHdes. Lithium metal is also used in organic syntheses for preparations of alkoxides and organosilanes, as weU as for reductions. Other uses for the metal include fabricated lithium battery components and manufacture of lithium alloys. It is also used for production of lithium hydride and lithium nitride. 

In addition to sodium, other metals have found application for the Wurtz coupling reaction, e.g. zinc, iron, copper, lithium, magnesium. The use of ultrasound can have positive effect on reactivity as well as rate and yield of this two-phase reaction aryl halides can then even undergo an aryl-aryl coupling reaction to yield biaryls. ... 

C. Alkyl and Aryl Derivatives.—Reactions of organometallic reagents, such as methyl-lithium, with fluorocyclophosphazenes are, in general,... 

We hope that the results outlined in this review have demonstrated that the chemistry of the tetrahalogenobenzynes is sufficiently different from the chemistry of benzyne to be worthy of study. That four electron with drawing substituents are essential to the high reactivity of arynes in reactions with aromatic systems has been demonstrated by generating the isomeric trifluorobenzynes from the aryl-lithium compounds (135) and (136) in the presence of an excess of benzene 169>. Whereas tetra-fluorobenzyne reacts under similar conditions to give the 1,4-cycloadduct in greater than 50% yield the compounds (137) and (138) are produced in 16% and ca. 1.5% yields respectively. 

When an aminophosphonium species is used with an aryl lithium reagent, cleavage of the amino functionality from phosphorus is observed, producing the parent phosphine.10 This reaction has been used to prepare stable phosphoranes from aminophosphonium species using dilithium reagents (Figure 5.6).10 It should be noted that the... 

The synthesis of metalloporphyrins which contain a metal-carbon a-bond can be accomplished by a number of different methods(l,2). One common synthetic method involves reaction of a Grignardreagent or alkyl(aryl) lithium with (P)MX or (PMX)2 where P is the dianion of a porphyrin macrocycle and X is a halide or pseudohalide. Another common synthetic technique involves reaction of a chemically or electrochemically generated low valent metalloporphyrin with an alkyl or aryl halide. This latter technique is similar to methods described in this paper for electrosynthesis of cobalt and rhodium a-bonded complexes. However, the prevailing mechanisms and the chemical reactions... 

The compounds 2,6-Mes2H3C6PCl2123 and 2,6-Trip2H3C6PCl2124 have been isolated in high yield (>70%) via the reaction of the aryl lithium salt and PC13. The 31P NMR spectra show characteristic resonances at 160.1 and 157.1 ppm, respectively. Although no complete set of structural data has been published for either compound, the P-C distance in... 

Experimental enthalpies of formation for twelve alkyl- and aryl-lithium reagents were derived by Hohn from the enthalpies of reaction 5 in which the organolithium reagents were dissolved or suspended in ether or in petroleum ether. 

Tertiary and aromatic nitroso compounds react with aryl Grignard or aryl-lithium reagents giving the corresponding hydroxylamines . This reaction is useful for preparation of alkyl- and aiylhydroxylamines (e.g. 109, equation 80 and 110, equation 81) and can be considered as complementary to arylation of hydroxy lamines with activated aryl halides. It has been used for functionalization of cyclophanes with the hydroxy amino group. The main limitation of the reaction is the relatively restricted choice of available aliphatic nitroso components, so most of reactions were done with 2-nitroso-2-methylpropane. There is no literature data about the possibility of removal of the tert-butyl group from these compounds. 

An anionic equivalent of the Friedel-Crafts cyclization reaction has been developed for the formation of the C /C-5 bond of the 1,2-benzothiazine structure (Equation 35 Table 5) <1997SL1079>. In this reaction, directed metalation of sulfonamide-substituted aromatic systems 233 with an excess of LDA affords aryl lithium species 234 in a regiocontrolled fashion. This intermediate then reacts in situ with a proximal amide to form l,2-benzothiazine-4-one 1,1-dioxides 235. The yields of this transformation appear to be highly dependent upon the substitution pattern in 233. The authors attribute the low yield when = methyl and = H to a-deprotonation of the amide moiety. 

Table 22 Reactions of Alkyl- and Aryl-lithium Compounds (RLi) with Pyridines and Some 2- or 4-Substituted...

The use of strong bases such as sodamide in liquid ammonia, lithium diisopropylamide and the alkyl- and aryl-lithiums gives essentially quantitative deprotonation at a side-chain alkyl group. The carbanions produced can undergo reactions with a wide range of electrophiles, as exemplified in Scheme 55. 

In the synthesis of concave 1,10-phenanthroline cyclophanes 21 (Scheme 4), the aryl bridgeheads could be easily introduced by the addition of two aryl lithium moieties 16 to 1,10-phenanthroline (15). Although aryl lithium compounds may also be added to pyridine [23], this approach could not be realized for the construction of concave pyridine cyclophanes 29 yet [24]. Therefore another route for the synthesis of the concave pyridines 29 was used (Scheme 5) the cyclization of 1,5-diaryl substituted Cj-units 23 or 27 with ammonia. The resulting 2,6-bis(2,6-dimethoxyphenyl)pyridine 24 [25], the pyridine analogue to the tetramethoxy-1,10-phenanthroline derivative 17, was then treated in the same way. After liberation of the phenol functions, the four OH groups of 28 were reacted with two equivalents of diiodides 19 [25]. As in the synthesis of the concave 1,10-phenanthroline cyclophanes 21, two macrocycles were formed in one reaction step. 

In order to achieve the final cyclisation step in the spherand syntheses, a new synthetic ring-closure procedure was developed, which proceeds according to Equation 3.2 (acac = acetylacetonato, CH(COMe)2 ). The aryl lithium compound produced by action of butyl lithium is oxidised by the Fe (III) complex to give an aryl biradical, which then undergoes a template cyclisation about the Li+ ion (see Section 3.9.1 for an explanation of the template effect). In the case of 3.33, this method resulted in the isolation of the complex in 28 % yield from the reaction shown in Scheme 3.9. 

The stable hemiacetal tetrahydropyranol 94 was used in a Wittig reaction to give the unsaturated ester 95 mostly as the E-isomer. Oxidation, nitroaldol and elimination gave the unsaturated nitro-compound 98. It turns out that the aryl-lithium does conjugate addition without any copper and that it reacts exclusively with the nitroalkene to give 99. 

Reductive coupling of iodonium salts catalysed by a palladium-zinc system also produced biaryls in good yield [38]. Also very effective was the palladium-catalysed cross-coupling of iodonium salts with sodium tetraphenylborate in water [39]. The reaction of 3-indolyl phenyliodonium trifluoroacetate with several alkyl and aryl lithium reagents gave 3-substituted indoles [40] ... 

A first series was reported on the reaction of simple aryl lithium species with 6-(V,(V-dimethylamino fulvene and subsequent transmetallation. Thereby, it was possible to synthesise para-methoxy phenyl (15), /V./V-di methyI -pheny I (16) and benzo[l,3]dioxole phenyl-substituted (17) dimethylamino-functionalised titanocene dichlorides, which show IC50 values in the range of 54 pM [22]. This represents a significant improvement in cytotoxicity compared with the benzyl-substituted titanocenes by a factor of 3 for titanocene 16 (IC50 for the benzyl-substituted analogue 120 pM) and even 10 for titanocene 17 (IC50 for the benzyl-substituted analogue 280 pM). The sole decrease in cytotoxic activity was... 

Scheme 3 Synthesis of dimethylamino-functionalised titanocenes from the carbolithiation reaction of 6-/V,/V-dimcthylamino fulvene and aryl lithium species...

Within this review we describe a second reaction pathway, which includes a carbolithiation reaction and leads to achiral-substituted titanocene dichlorides also. Therefore, aryl lithium species are added to the identical substituted 6-aryl fulvenes. This leads to the formation of highly substituted, but achiral diarylmethyl-functionalised lithium cyclopentadienides as seen in Scheme 5, which can still be used in the transmetallation reaction with titanium tetrachloride. 

The first cyclisations to be put to synthetic use were those of aryl lithiums onto carbonyl compounds, imines and epoxides. These are known as Parham cyclisations , and the method for transforming an aryl bromide to an aryllithium the Parham protocol , after W. E. Parham, who developed the reaction. We will survey the use of Parham cyclisations in synthesis, before assessing intramolecular attack of other electrophiles. The most important of these are the alkenes, and the usefulness of anionic cyclisations onto unactivated double bonds compares very favourably with radical cyclisations, particularly with regard to stereochemical control. 

Commercially available butyl lithium was frequently used to prepare aryl lithium compounds from aryl bromides. In these cases the aryl butyl tellurium compounds were the products isolated from the reaction mixtures. 

These reactions are of synthetic importance only when the aryl alkyl tellurium compounds are easily accessible. Such aryl alkyl tellurium compounds are obtained when an aryl lithium compound generated from an aryl halide and alkyl lithium is treated with tellurium (p. 154, 387). 

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