OTHER ORGANOMETALLIC CARBANIONIC COMPOUNDS

Nucleophiles can be added to acceptor-substituted alkenes. In that case, enolates and other stabilized carbanions occur as intermediates. Reactions of this type are discussed in this book only in connection with 1,4-additions of organometallic compounds (Section 10.6), or enolates (Section 13.6) to a,/J-unsaturated carbonyl and carboxyl compounds. 

Carbanions arising from other organometallic compounds also react with phosphorus with the formation of organophosphorus compounds. Heating tetraphen-yltin with elemental phosphorus (1 2) for 16 h to 320 oC produced triphenyl-phosphine in 85% yield 5) ppoof for the intermediate formation of tin-phos-... 

These are very facile processes, and here this subject is divided into reaction of halides with (i) organometallic compounds, (ii) reaction with carbonyl stabilized anions and (iii) reaction with other carbanions. 

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. 

So far we have considered sulfur-containing carbanions obtained by metallation with appropriate bases of a to sulfur atom(s) acidic C-H bonds. For synthetic purposes this method has been by far the most used. Among the variety of other routes to such carbanions [203] we shall consider two methods which seem to be general and promising the reductive lithiation of phenyl thioethers and the thiophilie addition of organometallics to thiocarbonyl compounds (vide infra Section 4.1.2). 

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