Organolithium compounds, synthetic applications

Several chapters deal with the synthesis of and the synthetic applications of organolithium compounds such as orthometallation, arene catalysed lithiation, addition to carbon-carbon double bonds, their reaction with oxiranes, and asymmetric deprotonation with lithium (-)-sparteine. We gratefully acknowledge the contributions of ah the authors of these chapters. 

Having in mind the fact that lithium is the most electropositive metal among those with wide synthetic applications (Li, Mg, Zn, Cd, Cu), the preparation of an organolithium compound formally represents the access to any other of such classes of organometallic compounds by a transmetallation reaction (Scheme 88).240... 

The synthetic applications of acyllithiums, generated by reaction of organolithium compounds with carbon monoxide, by treatment with electrophiles started when Nudelman and coworkers found that phenyllithium reacted with carbon monoxide in the presence of alkyl bromides to yield diphenylalkylcarbinols24,27. a-Hydroxy-a-phenylacetophenone was also obtained resulting from the dimerization of the carbene intermediate of type 3. In the absence of electrophiles a,a-diphenylacetophenone was obtained in 94% yield, attributed to the dimerization of the corresponding aroyl anion radical28. 

Synthetic Application of (Benzyllithium —TMED A and Benzyl-lithium—TED. All the synthetic application studies were run with an aged (benzyllithium)2-TMEDA toluene solution that had 0.8% of the total organolithium compounds present as the tolyllithium isomers (only meta present) or with benzyllithium-TED crystalline complex free of ring isomers. 

In 1950, Renaud published a generally overlooked paper on the use of ultrasoimd in the preparation of organolithium, -magnesium, and -mercury compounds. For many years, these findings remained unapplied, probably because reliable, cheap generators were not easily available. This situation has changed now and many laboratories possess at least ultrasonic cleaning baths, which permit many synthetic applications (p. 304). 

The main synthetic application of Grignard and organolithium reagents is their reaction with carbonyl-containing compounds to produce alcohols. Carbon-carbon bond formation is rapid and exothermic when Grignard and organolithium reagents react with an aldehyde or ketone. 

Many interesting and important synthetic applications of 1,1-diphenylethylene and its derivatives in polymer chemistry are based on the addition reactions of polymeric organolithium compounds with 1,1-diphenylethylenes. Therefore, it is important to understand the scope and limitations of this chemistry. In contrast to the factors discussed with respect to the ability of 1,1-dipheny-lalkylcarbanions to initiate polymerization of styrenes and dienes, the additions of poly(styryl)lithium and poly(dienyl)lithium to 1,1-diphenylethylene should be very favorable reactions since it can be estimated that the corresponding 1,1-diphenylalkyllithium is approximately 64.5kJ/mol more stable than allylic and benzylic carbanions as discussed in Sect. 2.2 (see Table 2). Furthermore, the exothermicity of this addition reaction is also enhanced by the conversion of a tt-bond to a more stable a-bond [51]. However, the rate of an addition reaction cannot be deduced from thermodynamic (equilibrium) data an accessible kinetic pathway must also exist [3]. In the following sections, the importance of these kinetic considerations will be apparent. 

---