Hetero-enyne metathesis

By use of Ru-based carbenes such as [Ru]-Ia, II, III, various carbo- and heterocycles can be synthesized from the corresponding enyne precursors. The metathesis is carried out not only by ring-closing enyne metathesis but also by dienyne metathesis, cross enyne metathesis, and ring-opening enyne metathesis.In this section, the synthetic applications of enyne metathesis reactions, including skeletal reorganization reactions and hetero-enyne metathesis, to natural products and related compounds are described. 

SCHEME 24.76. Formation of heterocyclic compounds via hetero-enyne metathesis. 

Diynes are also used to perform intermolecular enyne metathesis. With the objective of producing functionalized hetero- and carbocycles, a cascade diyne-alkene cross metathesis leading to five-membered cyclic products has recently been proposed [27] (Scheme 13). 

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