Aryllithiums, reactions

Reaction of 1,4-benzodioxin with chromium hexacarbonyl gives a 41% yield of the > -arene chromium complex (62). Reaction of this complex with n-butyllithium forms a yellow solution of the aryllithium. Reaction of this with a range of electrophiles gives a series of 5-substituted derivatives in modest yield, which are readily decomplexed by iodine to form the useful 5-substituted 1,4-benzodioxins (63) <89TL5519>. 

Formation of aryl Grignard reagents (Section 14 4) Aryl halides react with magnesium to form the corresponding arylmagnesium halide Aryl iodides are the most reac tive aryl fluorides the least A similar reaction occurs with lithium to give aryllithium reagents (Section 14 3)... 

Alteration of the relative reactivity of the ring-positions of quinoline is expected and observed when cyclic transition states can intervene. Quinoline plus phenylmagnesium bromide (Et20,150°, 3 hr) produces the 2-phenyl derivative (66% yield) phenyllithium gives predominantly the same product along with a little of the 4-phenylation product. Reaction of butyllithium (Et 0, —35°, 15 min) forms 2-butylquinoline directly in 94% yield. 2-Aryl- or 6-methoxy-quinolines give addition at the 2-position with aryllithium re-agents, and reaction there is so favored that appreciable substitution (35%) takes place at the 2-position even in the 4-chloroquinoline 414. Hydride reduction at the 2-position of quinoline predominates. Reaction of amide ion at the 2-position via a cyclic... 

An example of intramolecular conjugate addition of aryllithium generated by halogen metal exchange reaction of 92 is illustrated in equation 7966. 

The reaction gives good yields with primary, secondary, and tertiary alcohols, and with alkyl and aryllithium reagents.Allylic alcohols also couple with certain... 

Organometallic compounds can be hydrolyzed by acid treatment. For active metals such as Mg, Li, and so on, water is sufficiently acidic. The most important example of this reaction is hydrolysis of Grignard reagents, but M may be many other metals or metalloids. Examples are SiRs, HgR, Na, and B(OH)2- Since aryl Grignard and aryllithium compounds are fairly easy to prepare, they are often used to prepare salts of weak acids, for example,... 

The alkylation of heterocyclic nitrogen compounds with alkyllithium reagents is called Ziegler alkylation. Aryllithium reagents give arylation. The reaction occurs... 

Aromatic aldehydes and ketones can be alkylated and reduced in one reaction vessel by treatment with an alkyl- or aryllithium, followed by lithium and ammonia and then by ammonium chloride." ... 

A variation of an approach developed by Meyers was used to prepare nifedipine-type 1,4-dihydropyridines 35 from pyridine 34 using an oxazoline-directed aryllithium 1,4-addition reaction <96H(43)2425>. 

The reactions of aryllithium reagents are accelerated by inclusion of potassium... 

Arylcopper intermediates can be generated from organolithium compounds, as in the preparation of cuprates.95 These compounds react with a second aryl halide to provide unsymmetrical biaryls in a reaction that is essentially a variant of the cuprate alkylation process discussed on p. 680. An alternative procedure involves generation of a mixed diarylcyanocuprate by sequential addition of two different aryllithium reagents to CuCN, which then undergo decomposition to biaryls on exposure to oxygen.96 The second addition must be carried out at very low temperature to prevent equilibration with the symmetrical diarylcyanocuprates. 

Alkoxy groups can be displaced from boron by alkyl- or aryllithium reagents. The reaction of diisopropoxy boranes with an organolithium reagent, for example, provides good yields of unsymmetrically disubstituted isopropoxyboranes.3... 

The aryl bromides undergo facile metalation with butyl lithium to produce aryllithium derivatives with the expected organometallic activity.9 For example, reaction of lithiated PPO with carbon dioxide produces a carboxylated PPO which exhibits unique blending characteristics18. 

An alternative synthesis of a thermally stable cyclopentadienyl functionalized polymer involved ring bromination of poly(oxy-2,6-diphenyl-l,4-phenylene), followed by lithiation with butyl lithium to produce an aryllithium polymer. Arylation of 2-norbornen-7-one with the metalated polymer yielded the corresponding 2-norbornen-7-ol derivative. Conversion of the 7-ol to 7-chloro followed by treatment with butyl lithium generated the benzyl anion which undergoes a retro Diels-Alder reaction with the evolution of ethylene to produce the desired aryl cyclopentadiene polymer, 6. 

To immobilize such anions as borate, organoboron polymers were reacted with aryllithium reagents.31,32 The reaction of alkylborane polymers with n-BuLi was examined first however, the ionic conductivity of the resulting material was very low. Moreover, complicated peaks were observed in the H-NMR spectrum. Conversely, selective lithium borate formation was observed in the nB-NMR spectrum when PhLi was employed (scheme 6). An ionic conductivity of 9.45 X 10 7Scm 1 was observed at 50°C. The observed ionic conductivity was relatively low because of the decreased number of carrier ions compared with dissolved salt systems. However, the lithium transference number of this polymer was markedly high (0.82 at 30°C). 

Reactions of organoboron polymer electrolytes with aryllithium reagents suffered low conversion due to relatively low reactivity of the mesitylborane unit. Moreover, incorporation of aryl substituent in side chains resulted in higher glass-polymer electrolyte-transition temperatures. 

Similarly to the alkyl derivatives, the most common route for arylcopper compounds is the reaction of a copper halide and aryllithium compounds (Equation (4)). Organocuprates with aryl groups are obtained by using an appropriate excess of the lithium reagent. Magnesium aryls have also been employed in transmetallation reactions with Cu(l) salts to yield both arylcopper compounds and arylcuprates (Equations (5) and (6)). 

An aryllithium reagent, prepared from 1-bromo-2,6-diethylbenzene and butyllithium, reacts with SnCl2 in THF at 0°C to produce hexakis(2,6-diethylphenyl)tristannacyclopro-pane, 47, in 50-55% yield883. If the reaction above is performed at 0°C in Et20, the 1-butyl-2,2,3,3,4,5,5,6,6-nonakis(2,6-diethylphenyl)hexastannabicyclo[2,2,0]hexane, 48, can be isolated in 1.5% yield. This compound turns out to be the first example of a polycyclic polystannane88b. 

The reagent is prepared by reaction of (Cp2ZrCl)20 with A1(CH3)3 (75% yield).1 Benzyne zirconocene complexes.1 This reagent reacts with an aryllithium at - 50° to form an intermediate a that loses methane at 25° to give a zirconocene... 

Alkyllanthanum triflates, RLa(OTf)2. Alkyl- or aryllithium reagents are known to cleave tertiary amides to ketones, but yields are low because of a further reaction with the ketone to form a tertiary alcohol. The amides can be cleaved to ketones in high yield by reaction with alkyl- or aryllanthanum triflates, generated in situ by reaction of RLi or ArLi with La(OTf), (equation I). 

The action of chloroamine and bromoamine on organometallic reagents has been reviewed102 and a comprehensive review of electrophilic aminations of carbanions has appeared103. Alkyl, alkenyl and aryllithium compounds are converted into tertiary amines 84 by reaction with the mesityl compounds 83 (R2 = Me or Et Ar = 2,4, 6-MesCeHj)104. 

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