Organolithium reagents Subject

Functionalized organolithium reagents can be prepared and alkylated. The configuration of the dioxanyl reagent 2 proved to be subject to control.85 The kinetically favored trans lithio derivative is converted to the more stable cis isomer at 20° C. Both isomers were methylated with retention of configuration at saturated carbon. 

Enantiocontrol of carbanion reactions of organolithium reagents has been the subject of a short review. ... 

Organolithium reagents in which the carbanion is delocalized are less subject to competing electron-transfer processes. Allyllithium and benzyllithium reagents can be alkylated by secondary alkyl bromides, and a high degree of inversion of configuration is observed.65... 

Deprotonation of t-Bu-BisP (BH3)2 with 1.2 equivalents of s-BuLi/( )-sparteine formed a mixture of mono- and dilithiated t-Bu-BisP (BH3)2 whose - intermolecular oxidative coupling with Cu(II) afforded a mixture of tetraphosphine borane 86 and hexaphosphine borane 87. The use of ( )-sparteine may surprise the reader, as the reaction does not involve any enantioselective deprotonation. However, it was found that its presence was beneficial to activate the -BuLi, showing that ( )-sp is not only a chiral inductor, but also modifies the reactivity of the organolithium reagents. After separation by column chromatography, 86 and 87 were obtained in 26% and 14% isolated yields respectively. Tetraphosphine borane 86 was subjected to similar reactions, affording compounds 88 (29% yield) and 90 (8% yield), which contain 8... 

Like other Lewis bases, Grignard reagents, organolithium reagents, and metal hydrides are also able to undergo addition to carbonyl-containing compounds. These additions lead directly to the next subject. 

Preparation of 2-substituted a-Alkenes. The reaction of trimethylsilylacetone with Grignard and organolithium reagents has been employed in the synthesis of 2-substituted propenes via the formation of a /3-hydroxysilane, which is then subjected to a Peterson elimination (eq 1). It was also used to prepare, y-unsaturated esters, nitriles, and amides (eq 2). ... 

RM can be a traditional Grignard reagent or an organolithium, 2inc, aluminum, or mercury compound. The Grignard route is employed commercially for production of tertiary phosphines, even though these reactions are subject to side reactions. Yields are often low, eg, 40—50% for (C4H )2P prepared via a Grignard reaction (18). A phosphoms—carbon bond can form from the metathetical reaction of a phosphoms haUde and a pseudohaUde salt. 

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