Organolithium reagents with aldehydes and ketones

Reaction of organolithium reagents with aldehydes and ketones (Section... 

Reaction of organolithium reagents with aldehydes and ketones (Section 14.7) Organolithium reagents react with aldehydes and ketones in a manner similar to that of Grignard reagents to form alcohols. 

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 ... 

These compounds are sources of the nucleophilic anion RC=C and their reaction with primary alkyl halides provides an effective synthesis of alkynes (Section 9 6) The nucleophilicity of acetylide anions is also evident m their reactions with aldehydes and ketones which are entirely analogous to those of Grignard and organolithium reagents... 

Organolithium and organomagnesium reagents are highly reactive toward most carbonyl compounds. With aldehydes and ketones, the tetrahedral adduct is stable, and alcohols are isolated after protonation of the adduct, which is an alkoxide ion. 

All that has been said in this section applies with equal force to the use of organo-lithium reagents in the synthesis of alcohols. Grignard reagents are one source of nucleophilic carbon organolithium reagents are another. Both have substantial carbanionic char acter in their- car bon-metal bonds and undergo the same kind of reaction with aldehydes and ketones. 

Similarly, organolithiums (or Grignard reagents) add to ester (26) to afford silyl enolates which are intercepted with aldehydes and ketones to give a,p-unsaturated esters (27),434 while addition of the bifunctional aryllithium (28) (MIRC protocol) affords the 2-(trimethylsilyl)tetrahydronaphthoate ester (29 Scheme 7).43b... 

Organolithium reagents reacts just like Grignard reagents. For example, reaction with aldehydes and ketones proceeds by nucleophilic addition to yield secondary and tertiary alcohols respectively. 

Organolithium reagents bearing a-trimethylsilyl substituents react with aldehydes and ketones to produce olefins in a manner similar to the Wittig reaction/ The presence of the silicon substituent may facilitate formation of the anionic carbon... 

The real value of this acid-base reaction is to transform a weak acid into an anion by using a powerful base the organolithium reagent. Such anions behave as nucleophiles in various reactions. In Chapter 11 (Section 11.3.6), alkyne anions underwent Sn2 reactions with alkyl halides. In Chapter 18 (Section 18.3.2), alkyne anions react with aldehydes and ketones. Both Grignard reagents and organolithium reagents react as nucleophiles with aldehydes and ketones (also described in Chapter 18, Section 18.4). Lithium amides such as 45 react as bases with aldehydes or ketones in Chapter 22 (Section 22.3). Many such examples are discussed in this book. 

Grignard reagents and organolithium reagents react as carban-ions with aldehydes and ketones to give alcohols in a two-step process (1) acyl addition and (2) hydrolysis. The organometallic reagent reacts as a nucleophile with epoxides at the less substituted carbon atom. 

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