Two Reactions for the Price of One Olefin Metathesis Catalyst

“In tandem or alone: a remarkably selective transfer hydrogenation of alkenes catalyzed by ruthenium olefin metathesis catalysts” G. K. Zieli?ski, C. Samoj?owicz, T. Wdowik and K. Grela, Org. Biomol. Chem., 2015, 13, 2684 DOI: 10.1039/C4OB02480J

Chemists are always searching for ways to rapidly construct complex molecules from relatively simple starting materials and avoid tedious purification steps. Something I‘d rather avoid if I can, high pressure hydrogenations. Transition-metal-catalyzed tandem bond formations are powerful methods that present an entry point to the aforementioned problems. At Materia we often do olefin metathesis followed by other functional group transformations. So the putting the two together in one pot sounds pretty attractive.

Recently, the Grela group reported a tandem reaction involving olefin metathesis followed by transfer hydrogenation by using commercially available ruthenium olefin metathesis catalysts. Although not the first report of such a transformation,  previously reported metathesis-hydrogenation sequences are typically conducted under high pressures of hydrogen, which is required to convert the ruthenium alkylidne complexes into a hydrogenation catalyst. In this report the transfer hydrogenation system is composed of a ruthenium metathesis catalyst and formic acid. The process is operationally simple and can be performed in a single pot.

step-wise-one-pot
The example shown in the scheme above starts with Ru-catalyzed double-RCM (ring closing metathesis) of tetraene 1 forming selectively product 2 bearing one five- and one six-membered unsaturated ring.  Then, only one of the two seemingly very similar C-C double bonds present in 2 was reduced by Grubbs second generation catalyst and formic acid selectively due to the increased ring strain of the cyclopentene, yielding monosaturated product 3 in good yield. This process can easily be conducted in a one-pot fashion, converting 1 directly into 3 in 90% yield. It should be mentioned that the reaction conditions are capable of reducing 6-membered rings, albeit over much longer reaction times. A variety of olefins bearing an assortment of functional groups can also be reduced by this method. The highly selective nature of this system provides a useful addition to the still expanding collection of hydrogenation methods in conjunction with Materia’s favorite reaction, olefin metathesis!

Olefin Metathesis in Self-Healing Materials

ATM self healing

Neal, J. A.; Mozhdehi, D.; Guan, Z. “Enhancing Mechanical Performance of a Covalent Self-Healing Material by Sacrificial Noncovalent Bonds” J. Am. Chem. Soc. 2015, 137, 4846-4850. Self-healing materials have been an objective of extensive research … [Continue reading]

New Remarkably Efficient Ethenolysis Catalysts

ethenolysis-1

Marx, V. M.; Sullivan, A. H.; Melaimi, M.; Virgil; S. C.; Keitz, B. K.; Weinberger, D. S.; Bertrand, G. and Grubbs, R. H. “Cyclic Alkyl Amino Carbene (CAAC) Ruthenium Complexes as Remarkably Active Catalysts for Ethenolysis” Angew. Chem. Int. Ed. … [Continue reading]

Olefin Metathesis at the 249th ACS Meeting

The 249th ACS National Meeting & Exposition is fast approaching with Denver, CO preparing to host the biannual event from March 22 – 26, 2015. The theme of this spring’s event is “Chemistry of Natural Resources” which is fitting for the … [Continue reading]

Yves Chauvin, One of Metathesis Greats, Dies at 84

Yves Chauvin, one of the “metathesis greats,” passed away on January 27, 2015 at the age of 84. Winner of the Nobel Prize in Chemistry in 2005, Chauvin was a key player in proposing the metallacyclobutane intermediate of the generally accepted … [Continue reading]

The Boomerang is Back in Olefin Metathesis

Boomerang

Bates, J. M.; Lummiss, J. A. M.; C.; Bailey; G. A., and Fogg, D. E. “Operation of the Boomerang Mechanism in Olefin Metathesis Reactions Promoted by the Second-Generation Hoveyda Catalyst” ACS Catal., 2014, 4 (7), 2387-94. No consensus has been … [Continue reading]

Olefin Metathesis at the 248th ACS Meeting

The 248th American Chemical Society National Meeting and Exposition will be held in San Francisco, California from August 10-14, 2014. The theme of this fall’s meeting is “Chemistry and Global Stewardship.” As olefin metathesis has made significant … [Continue reading]

Examining Polytopal Rearrangements around Ruthenium

fig_1r

Torker, S.; Khan, R.K.M.; Hoveyda, A.M. “The Influence of Anionic Ligands on Stereoisomerism of Ru Carbenes and Their Importance to Efficiency and Selectivity of Catalytic Olefin Metathesis Reactions” J. Am. Chem. Soc. 2014, 136, 3439-3455. For … [Continue reading]