Ring-Closing Alkyne Metathesis (RCAM)

Dr. Josephine Nakhla

Alkyne metathesis has been a useful tool for C–C bond formation since the discovery of structurally well-defined metal alkylidynes by Schrock and coworkers.³ These complexes have found use in the synthesis of complex natural products and in material science.⁴ The limitations of these catalysts include air- and moisture-sensitivity as well as incompatibilities with substrates that contain donor sites. Fürstner and co-workers have recently developed an air-stable molybdenum catalyst for alkyne metathesis, which proved versatile and compatible with substrates containing donor sites.⁴ The authors also examined the use of this catalyst in the ring-closing cross metathesis (RCAM) of a variety of alkynes in generating various macrocycles in good yields (Scheme 1).

Scheme 1. Air-Stable molybdenum catalyst for alkyne metathesis.

References

1. Romero PE, Piers WE, McDonald R. 2004. Rapidly Initiating Ruthenium Olefin-Metathesis Catalysts. Angew. Chem. Int. Ed.. 43(45):6161-6165. https://doi.org/10.1002/anie.200461374

2. Romero PE, Piers WE. 2005. Direct Observation of a 14-Electron Ruthenacyclobutane Relevant to Olefin Metathesis. J. Am. Chem. Soc.. 127(14):5032-5033. https://doi.org/10.1021/ja042259d

3. Schrock RR. 2002. High Oxidation State Multiple Metal?Carbon Bonds. Chem. Rev.. 102(1):145-180. https://doi.org/10.1021/cr0103726

4. Fürstner A, Davies PW. 2005. Alkyne metathesis. Chem. Commun..(18):2307. https://doi.org/10.1039/b419143a

5. Schrock R, Czekelius C. 2007. Recent Advances in the Syntheses and Applications of Molybdenum and Tungsten Alkylidene and Alkylidyne Catalysts for the Metathesis of Alkenes and Alkynes. Adv. Synth. Catal.. 349(1-2):55-77. https://doi.org/10.1002/adsc.200600459

6. Bindl M, Stade R, Heilmann EK, Picot A, Goddard R, Fu?rstner A. 2009. Molybdenum Nitride Complexes with Ph3SiO Ligands Are Exceedingly Practical and Tolerant Precatalysts for Alkyne Metathesis and Efficient Nitrogen Transfer Agents. J. Am. Chem. Soc.. 131(27):9468-9470. https://doi.org/10.1021/ja903259g