Abstract
Olefin metathesis using ruthenium carbene complexes is a useful method in synthetic organic chemistry. Enyne metathesis is also catalyzed by these complexes and various carbo- and heterocycles could be synthesized from the corresponding enynes. Dienyne metathesis, cross enyne metathesis and ring-opening enyne metathesis have been further developed. Various complicated compounds, such as the natural products and the related biologically active substances, could be synthesized using these metatheses reactions. Skeletal reorganization using the transition metals and metallotropic rearrangement are also discussed.
Highlights
Many researchers were able to use these catalysts, and various cyclic compounds were synthesized from dienes using ring-closing metathesis (RCM)
The first example of the total synthesis of a natural product using ring-closing enyne metathesis is the synthesis of (-)-stemoamide [57,58]. (-)-Pyroglutamic acid was converted into enyne 44 having an ester group on the alkyne, and RCM of enyne was carried out in the presence of 4 mol % of ruthenium-carbene complex 1c to afford bicyclic compound in 87% yield
Lee succeeded in the total synthesis of (-)-amphidinolide E, whose side chain was constructed using cross enyne metathesis [113,114]
Summary
Since the discovery of molybdenum and ruthenium carbene complexes by Schrock and Grubbs in 1990 [1] and 1992 [2], synthetic organic chemistry has made rapid progress using metathesis reactions. Ring-opening of this gives cyclic compound 3 and ruthenium carbene complex 7 is regenerated (Scheme 2, Route 2). Silicon-tethered ring closing enyne metathesis of 27b by ruthenium carbene catalyst 1c gave 25b, which was subjected to Tamao oxidation to afford diol 26b [44,45]. Metathesis of enyne 36a containing conjugated ene-yne using ruthenium catalyst 1k gave cycloheptene derivative 37a having a triene unit This reaction did not proceed by first or second-generation ruthenium catalyst 1c or 1g (Scheme 10) [52]. (-)-Pyroglutamic acid was converted into enyne 44 having an ester group on the alkyne, and RCM of enyne was carried out in the presence of 4 mol % of ruthenium-carbene complex 1c to afford bicyclic compound in 87% yield.
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