Reaction of Organometallic Reagents with Other Compounds

This reaction results in nucleophilic substitution of an alkyl group R for the leaving group Cl, forming one new carbon-carbon bond. 

Problem 20.31 What organocuprate reagent is needed to convert CH3CH2COCI to each ketone  

Problem 20.32 What reagent is needed to convert (CH3)2CHCH2COCi into each compound  

A ketone with two different R groups bonded to the carbonyl carbon can be made by two different methods, as illustrated in Sample Problem 20.4. 

Sample Problem 20.4 Show two different ways to prepare 2-pentanone from an acid chioride and an organocuprate 

14 Reaction of Organometallic Reagents with Other Compounds 

Because organometallic reagents are strong nucleophiles, they react with many other electrophiles in addition to carbonyl groups. Because these reactions always lead to the formation of new carbon-carbon bonds, they are also valuable in organic synthesis. In Section 20.14, we examine the reactions of organometallic reagents with carbon dioxide and epoxides. 

14A Reaction of Grignard Reagents with Carbon Dioxide 

Grignard reagents react with CO2 to give carboxylic acids after protonation with aqueous acid. This reaction, called carboxylation, forms a carboxylic acid with one more carbon atom than the Grignard reagent from which it is prepared. 

Because Grignard reagents are made fiom alkyl halides, an alkyl halide can be converted to a carboxylic acid having one more carbon atom by a two-step reaction sequence formation of a Grignard reagent, followed by reaction with CO2. 

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Reaction of organometallic reagents with other compounds... 

Transmetallation reactions of Grignard reagents with other organometallic compounds are rare. An example is shown here [70] other transmetallations have been briefly reported [71]. 

In this chapter, the substitution reactions of organometallic reagents with organic halides and related electrophiles are reviewed. - The major portion of the chapter is devoted to a discussion of organocopper compounds, which first transformed the alkylation of nonstabilized carbanions into a reaction of general synthetic utility. More recently, transition metals other than copper have also found widespread application in such coupling reactions, and developments in this area are outlined in Section 1.5.3. 

Because of their nucleophilic character, organometallic compounds are widely utilized as reagents in reactions that produce new carbon-carbon bonds. For example, two typical reactions of organometallic reagents 1 with carbon electrophiles such as alkyl halides 2 and carbonyl compounds 3 are illustrated by the general transformations shown in Equations 19.1 and 19.2. In each of these reactions, the nucleophilic carbon atom of one reactant becomes attached to the electrophilic carbon atom of the other reactant with the resulting formation of a new carbon-carbon bond. Thus, like many bond-forming processes, these reactions may be viewed in the simple context of combinations of Lewis bases with Lewis acids. 

Before we describe the applications of organometallic reagents to organic synthesis let us examine their preparation Organolithium compounds and other Group I organometal he compounds are prepared by the reaction of an alkyl halide with the appropriate metal... 

Reactions of different organometallic species with thiocarbonyi compounds have been extensively investigated and been shown to proceed both in a carbophilic and a thiophilic fashion. However, other reactions can be observed simultaneously such as reduction, double addition, coupling, deprotonation and formation of enesulfides1,226,423. A complex pattern appears in the reactions of thioketones with lithium or Grignard reagents424. The first application of Reformatsky reagents in C—C bond formation by reaction with... 

Thiols and sulfides are occasionally prepared by treatment of Grignard reagents with sulfur." " Analogous reactions are known for selenium and tellurium compounds. Grignard reagents and other organometallic... 

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