Alkyne metathesis polymerization ADIMET

I 6 Alkyne Metathesis Polymerization (ADIMET) and Macrocyclization (ADIMAC)... 

The tungsten alkylidyne complex (t-BuO)3W(C-t-Bu) [130-132] is capable of catalyzing alkyne metathesis polymerization of cyclic alkynes. In addition, it can be used in acyclic diene metathesis (ADIMET) [133, 134]. The synthesis of the corresponding Mo-compound Mo(CCH2SiMe3)(OAd)3 (Ad=adamantyl) has been reported by C.C. Cummins et al. [135]. Though the active species is not known yet, a mixture of Mo(CO)6 and 4-chlorophenol is nowadays used for purposes of convenience [136]. 

Alkyne metathesis is generally restricted to internal alkynes, and is driven to completion by the evolution of gaseous 2-butyne. Representative examples of alkyne cross-metathesis are depicted in Scheme 33, and include (i) dimerization of alkynylbenzoic acid derivative 287, (ii) alkyne cross-metathesis of 289 and bis(trimethylsilyl)acetylene, (iii) cross-metathesis of enyne 291 and various alkynes and metathesis dimerization of 291, and (iv) formation of high molecular weight alkyne-containing polymers through acyclic diyne metathesis (ADIMET) polymerization of acyclic diynes (e.g., 293) " using the molybdenum hexacarbonyl/2-chlorophe-nol system. 

Scheme 33 Representative examples of alkyne cross-metathesis and acyclic diyne metathesis (ADIMET) polymerization.

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