Metathesis s. Interchange

Metathesis s. Interchange Methane derivatives s. Diarylmethanes Methanesulfonic acid esters (s. a. Mesylation)... 

Olefin metathesis, an expression coined by Calderon in 1967,1 has been accurately described in Ivin and Mol s seminal text Olefin Metathesis and Metathesis Polymerization as the (apparent) interchange of carbon atoms between a pair of double bonds (ref. 2, p. 1). This remarkable conversion can be divided into three types of reactions, as illustrated in Fig. 8.1. These reactions have been used extensively in the synthesis of a broad range of both macromolecules and small molecules3 this chapter focuses on acyclic diene metathesis (ADMET) polymerization as a versatile route for the production of a wide range of functionalized polymers. 

Consider now the reactions of 1,1-disubstituted ethylenes. Since monosubstituted ethylenes react selectively to interchange their more highly substituted halves, 1,1-disubstituted ethylenes should react even more selectively in the same way [Eq. (22)]. This increased selectivity manifests itself in isobutylene s reaction with (Tol)2C=W(CO)5 yielding even less than the 0.06% of more highly substituted 1,1-ditolylethylene yielded by 1-pentene (23). But to demonstrate that metathesis catalysts will induce the reaction in Eq. (22) selectively is not easy, for the... 

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