Methods for the Preparation of Organolithium Compounds

Reactions of Grignard reagents or organolithium compounds with arsenic halides, usually chlorides, have been one of the most frequently used method for the preparation of triorganoarsenic compounds. A wide variety of triorganoarsenic(III) compounds have been prepared as shown in equations 1 , 2 , 3 , 4 , 5 , 6 , 7 and 8 . 

Transmetalation using tin-lithium exchange is an excellent method — even better than mercury-lithium exchange — for the preparation of organolithium compounds, but it works only for compounds being more stable than n-butyllithium. This is also true for the synthesis of polylithiumorganic compounds. Examples are ( , )-1,5-dilithio-1,4-pentadiene 99the (Z,Z)-l,5-dilithio-l,4-pentadiene derivative 101 —... 

The reaction of Grignard reagents and organolithium compounds with aldehydes and ketones is perhaps the most useful method for the preparation of alcohols. The reaction is conducted under basic conditions and proceeds according to the following general mechanism ... 

Recently Yoshida et al. have employed silyl-stabilized a-alkoxy organolithium reagents for the synthesis of a variety of carbonyl compounds. Methoxy(trimethylsilyl)methane and methoxybis(trimethyl-silyl)methane, when deprotonated with Bu Li and Bu"Li respectively, give anions which can be alkylated with a variety of electrophiles. Electrolysis of a solution of the alkylated product in methanol yields, by virtue of the reduced oxidation potential of ethers a-substituted with silicon, either the dimethyl acetal or in the latter case the orthoester. The mildness of the electrolytic process recommends the method for the preparation of a variety of carbonyl compounds. 

In principle, another general method for the preparation of hydroxyl-functionalized polymers is through the reaction of polymeric organolithium compounds with carbonyl compounds. The reaction of polymeric organolithium compounds with the simplest carbonyl compound, formaldehyde, has been reported. ... 

A simple and high-yielding method for the preparation of allylic alcohols and allylic amines by the additions of organolithiums to different a,y3-unsaturated compounds has been described as efficient in the presence of the binary system LiBr-2-methyltetrahydrofuran at 0°C. This protocol provides very high 1,2-regioselectivity with no detection of undesired 1,4-adducts. 

Recently, nitration of organolithiums and Gngnards v/iih has been developed for the preparation of certain kmds of nitro compounds fEqs. 2.14 and 2.15. The success of this process depends on the reaction conthdons (low remperanirei and the stnicnire of substrates. For example, 3-nitrothiophene can be obtained in 70% overall yield from 3-bromothiophene this is far superior to the older method. 3-Nitroveratrole cannot be prepared usefully by classical electrophilic nitradonof veratrole, but it can now be prepared by direct orr/io-lithiadon followed The mechanism is believed to proceed by dirutrogen rathcal, followed by the rathcal s combinadon. 

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