Alkyne metathesis

In addition to the decomposition pathways by bimolecular collision or hydrolysis, Schrock alkylidyne complexes degrade upon attempted metathesis of terminal alkynes.

After ring closure the new triple bond is stereoselectively reduced with hydrogen and the Lindlar catalyst in order to obtain the Z-alkene (cyclic E-alkenes are available through the Birch reduction).

For example, RCAM can serve as key step in total synthesis of marine prostanoid hybridalactone, where epoxide, internal olefin and ester are tolerated.

[14] Another example shows a highly functionalized enyne, which displays a rare thiazolidinone unit, can be metathesized under Mo(III) catalyst, neither this unusual sulfur-containing heterocycle nor the elimination-prone tertiary glycoside posed any problem in the ring-closing step.

[16] The molecular frame of this potent phosphatase inhibitor is decorated with no less than 21 stereogenic centers and features a labile skipped diene in the side chain.

Its macrocyclic core incorporates a tetrahydropyran ring, a spiroketal unit, as well as a highly unusual chlorinated bis-spiroketal motif.

Specifically, a sequence of RCAM coupled with a gold-catalyzed acetalization successfully build the polycyclic system at the late stage of the synthesis.