Organolithium reagents aryllithium

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... 

Early work has shown that the reaction of simple organolithium reagents with oxiranes lead mainly to products from a- or -deprotonation and not from the desired ring opening reaction. However, some reactions of methyllithium , aUyllithium , aryllithiums" , and vinyllithium/potassium reagents " with oxiranes are reported (Scheme 36). 

It is sometimes more convenient to prepare organolithium reagents by halogen-lithium exchange between an aryl halide and butyllithium (BuLi). The reaction takes place because the aryllithium is more stable than butyllithium an sp- carbon is better able to stabilize a negative charge than an sp carbon (Scheme 10.2). Butyllithium is available commercially in bulk quantities. 

Grignard reagents or aryllithium reagents to form triazenes, which are converted to primary aromatic amines by hydrolysis with aqueous KOH or HCOOH (equation I). Grignard reagents react directly with 1, but organolithium reagents require 1... 

A solution of methylmagnesium iodide in EtjO, prepared by the reaction of magnesium (243 mg, 10 mmol) and iodomethane (1.42 g, 10 mmol) in dry EtjO (40 mL), was cooled in an ice bath and triturated dropwise with 1-ethoxycyclopropanol (1.02 g, 10 mmol) in EtjO (20 mL). Methane evolved immediately and a white suspension of 4 was formed. This suspension of the reagent can be conveniently used for reactions with organolithium reagents, e.g. aryllithiums, to give 1-aryl-1-cyclopropanols. 

Grignard and organolithium reagents react with tetrachloro-4-methoxypyridine to form 4-alkyl-and 4-aryltetradilorcpyridines.Phenyllithium and tetrachloro-4-methoxypyridine form tetrachloro-4-phenyl- (MI-737, Ar = CgHs) trichloro-4,6-diphenyl- and dichloro-2,4,6-triphenylpyridine. Under mild conditions a series of aryllithium compounds form 4-aryltetra-chloropyridines (XII-737) that react with butyllithium to give 4-aryl-trichloro-3-pyridyllithium (Xn-738). - ... 

Metal-halogen exchange is a rapid reaction and can usually be carried out at -60 to -120°C. This makes it possible to prepare aryllithium compounds containing functional groups such as cyano and nitro which would be reactive with the organolithium reagent at higher temperatures. Entries 6 and 7 in Scheme 6.2 are examples. 

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