Organolithium reagents, addition alkynes

It was observed that the metallation of terminal alkynes by organomagnesium (or organolithium) reagents considerably accelerated the rate of the subsequent addition of allylzinc bromide. The products resulting from a bis-addition predominate even in the case of sterically more demanding alkynes (equation 140). 

The reacuons of electrophihc tnflyl sources with nucleophiles were investi gated The reaction of tnfhc anhydride with an organolithium reagent is not synthetically promising because of ditnflylation and other side reactions [20] When phenyllithium reacts with tnfhc anhydnde, dimerization products and acetylenic Michael diadducts are observed [20] (equation 17), but using the sodium salt of the alkynes instead of the lithium salt provides the alkynyl tnfluoromethyl sulfones [21] (equation 18) (Table 7) Alkynyl tnfluoromethyl sulfones are of synthetic interest, because they show a pronounced reactivity toward nucleophiles in addition reactions and cyclopentadiene in Diels-Alder reactions [21] (Table 7)... 

Such nucleophilic additions of organolithiums to olefins are of limited use in laboratories. Nevertheless, there are certain categories of alkenes and alkynes that undergo ready addition [15]. A secondary organolithium reagent is easily transformed to the more stable primary reagent via the rapid equilibration [16]. 

G.ii. Intramolecular Addition to Alkenes and Alkynes. Organolithium reagents can react with alkenes or alkynes in an intramolecular reaction, although both are relatively inert to the analogous intermolecular reaction. Ward treated alkynyl bromide 263 with n-butyllithium and observed a 60% yield of... 

The reaction of carbon nucleophiles with ketones or aldehydes proceeds by acyl addition, as described in Chapter 18. The reaction of carbon nucleophiles with acid derivatives proceeds by acyl substitution, as described in Chapter 20. Carbon nucleophiles included cyanide, alkyne anions, Grignard reagents, organolithium reagents, and organocuprates. Alkyne anions are formed by an acid-base reaction with terminal alkynes (RC=C-H RCsCr). In this latter transformation, it is clear that formation of the alkyne anion relies on the fact that a terminal alkyne is a weak carbon acid. Other carbon acids specifically involve the proton on an a-carbon in aldehydes, ketones, or esters. With a siiitable base, these carbonyl compounds generate a new type of carbon nucleophile called an enolate anion. 

Acyl addition to aldehydes and ketones with Grignard reagents organolithium reagents enolate anions alkyne anions... 

Organolithium and terminal alkyne anions add to the carbonyl group of aldehydes and ketones to give alcohols according to a mechanism similar to addition of Grignard reagents. 

Grignard reagents are also synthesized by addition reactions of alkynes, addition reactions of unsaturated compounds having C=S groups, reactions of cycloalkanes, reactions with organolithium compounds or organomercury compounds, etc. [4,15,27,28],... 

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