Preparation and Properties of Organolithium Compounds

Preparation Using Metallic Lithium. Most simple organolithium reagents can be prepared by reaction of an appropriate halide with lithium metal. The method is applicable to alkyl, aryl, and alkenyl lithium reagents. 

As with organomagnesium reagents, there is usually loss of stereochemical integrity at the site of reaction during the preparation of alkyllithium compounds.25 Alkenyllithium reagents can usually be prepared with retention of configuration of the double bond.26,27 

For some halides, it is advantageous to use finely powdered lithium and a catalytic amount of an aromatic hydrocarbon, usually naphthalene or 4,4 -di- -bu(ylbiphcnyl (DTBB).28 These reaction conditions involve either radical anions or dianions generated by reduction of the aromatic ring (see Section 5.6.1.2), which then convert the halide to a radical anion. Several useful functionalized lithium reagents have been prepared by this method. In the third example below, the reagent is trapped in situ by reaction with benzaldehyde. 

Alkyllithium reagents can also be generated by reduction of sulfides.32 Alkenyl-lithium and substituted alkyllithium reagents can be prepared from sulfides,33 and sulfides can be converted to lithium reagents by the catalytic electron transfer process described for halides.34 

This technique is especially useful for the preparation of a-lithio ethers, sulfides, and silanes.36 The lithium radical anions of naphthalene, 4, 4/-di-f-butyldiphenyl (DTBB) or dimethylaminonaphthalene (LDMAN) are used as the reducing agent. 

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