Preparation of Organolithium and Organomagnesium Compounds

Organolithium compounds are often prepared by the reduction of organic halides with lithium metal. These reductions are usually carried out in ether solvents, and since organolithium compounds are strong bases, care must be taken to exclude moisture. (Why ) The ethers most commonly used as solvents are diethyl ether and tetrahydrofuran. (Tetrahydrofuran is a cyclic ether.) 

The order of reactivity of halides is Rl RBr RCI. (Alkyl and aryl fluorides are seldom used in the preparation of organolithium compounds.) 

For example, butyl bromide reacts with lithium metal in diethyl ether to give a solution of butyUithium  

Several alkyl- and aryllithinm reagents are commercially available in hexane and other hydrocarbon solvents. 

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SECTION 7.1 PREPARATION AND PROPERTIES OF ORGANOLITHIUM AND ORGANOMAGNESIUM COMPOUNDS... 

Organolithium and organomagnesium compounds find their- chief use in the preparation of alcohols by reaction with aldehydes and ketones. Before discussing these reactions, let us first exanine the reactions of these organometallic compounds with proton donors. 

Organolithium and organomagnesium compounds are stable species when prepared in suitable solvents such as diethyl ether. They are strongly basic, however, and react instantly with proton donors even as weakly acidic as water and alcohols. A proton is transferred from the hydroxyl group to the negatively polarized carbon of the organometallic compound to form a hydrocarbon. 

Reaction between quinuclidin-3-one (2) and organolithium or organomagnesium compounds is a general method for preparing tertiary alcohols.47,162,164-168 By dehydration of these alcohols substances with a semicyclic double bond (127) are formed together with A 2-dehydroquinuclidine derivatives (126).165-168 Reduction of unsaturated compounds gave various 3-substituted quinuclidines (128). 

Two of the most common organometallic compounds are organolithium compounds and organomagnesium compounds. Organolithium compounds are prepared by adding lithium to an alkyl halide in a nonpolar solvent such as hexane. 

There are several useful means for preparation of organomercury compounds. The general metal-metal exchange reaction between mercury(II) salts and organolithium or organomagnesium compounds is applicable. The oxymercuration reaction discussed in Section 4.3 provides a means of acquiring certain functionalized... 

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