Mo and W Alkylidene Chemistry

Schrock, R. R. Recent Advances in High Oxidation State Mo and W Imido Alkylidene Chemistry Chem. Rev. 2009, 109, 3211 The design of new molybdenum and tungsten-based olefin metathesis catalysts has resulted in a number of significant improvements over current systems. The high yield syntheses of bispyrrolide-ligated Mo and W alkylidene complexes have resulted in […]

Removing Oxygen and Peroxides for High Catalyst Efficiencies

It’s well known that olefins can build up peroxides over time, especially if stored at room temperature and exposed to light. Oxygen and peroxide impurities can accelerate the decomposition of an olefin metathesis catalyst and decrease the efficiency of the metathesis significantly. Of course higher catalyst loadings can fix that, but it’s not a perfect […]

High Density Reagent Scavengers

Throughput is a major concern for anyone trying to prepare even small libraries of compounds and a number of tools have been developed to help in making parallel synthesis faster and easier. When coupling two components together, you’ll generally use an excess of the cheaper component in order to drive the reaction to completion. This […]

2nd Generation Piers Catalyst

2nd Generation Piers Catalyst1 (PCy3 = tricyclohexylphosphine) – CAS#: [832146-68-6] – FW: 858.67 – Color: Brown – Initiation temperature: <0 °C Process Strengths Weaknesses CM -Synthesis of 1,2-disubstituted olefins from terminal olefins -Slower than 2nd Generation Grubbs Catalyst for CM of internal olefins RCM -Synthesis of 1,2-disubstituted and trisubstituted olefins -Reacts at low temperatures -Hindered […]

Benefits of Exploring Metathesis Catalyst Addition Methods

Metathesis catalysts can be added to the reaction mixture as a solid, a solution (methylene chloride, etc.) or as a suspension. If you’re not concerned with optimizing for the lowest catalyst loading, you can usually get away with whichever is easiest for your process. But if you have a challenging reaction or want to use […]

Running a Metathesis Reaction in Water

Burtscher, D.; Grela, K. “Aqueous Olefin Metathesis” Angew. Chem. Int. Ed. 2009, 48, 442-454. Q: If ruthenium-based olefin metathesis catalysts are tolerant of water, then can you run a metathesis reaction in water as a solvent? A: It depends. It’s true that the Grubbs-type catalyst systems aren’t particularly reactive with water. When it comes to […]

Convenient Route to Metal Alkylidenes: Grubbs 1st Gen Catalyst

Schwab, P.; France, M. B.; Ziller, J. W.; Grubbs, R. H. A Series of Well-Defined Metathesis Catalysts—Synthesis of [RuCl2(=CHR’)(PR3)2] and Its Reactions Angew. Chem. Int. Ed. Engl., 1995, 34, 2039. Schwab, P.; Grubbs, R. H.; Ziller, J. W.; Synthesis and Applications of RuCl2(=CHR’)(PR3)2: The Influence of the Alkylidene Moiety on Metathesis Activity J. Am. Chem. […]

1st Generation Grubbs Dimethylvinyl Alkylidene Catalyst

1st Generation Grubbs Dimethylvinyl Alkylidene Catalyst1 (PCy3 = tricyclohexylphosphine) – CAS#: [194659-03-9] – FW: 800.95 – Color: Purple – Initiation temperature: >20 °C Process Strengths Weaknesses CM2 -Synthesis of 1,2-disubstituted olefins from terminal olefins-Ethenolysis of internal olefins to make terminal olefins-ADMET of unhindered terminal olefins -Formation of trisubstituted olefins-Low reactivity with electron-deficient and hindered substrates RCM -1,2-Disubstituted olefin formation-Typically […]

Z-selective Metathesis Homocoupling of Terminal Olefins

Hoveyda and Schrock showed recently that monoaryloxide-pyrrolide Mo catalysts are Z selective for selected internal olefins and polymerization of norbornenes.1 In this new paper they show that similar Mo- or W-catalysts can be used to effect self-cross metathesis of terminal olefins with very high Z-selectivity.2 Highly Z-selective homocoupling of terminal olefins to make acyclic products […]