17344-59-1Relevant academic research and scientific papers
Olefin Metathesis in Confined Geometries: A Biomimetic Approach toward Selective Macrocyclization
Ziegler, Felix,Teske, Johannes,Elser, Iris,Dyballa, Michael,Frey, Wolfgang,Kraus, Hamzeh,Hansen, Niels,Rybka, Julia,Tallarek, Ulrich,Buchmeiser, Michael R.
supporting information, p. 19014 - 19022 (2019/11/28)
The synthesis of macrocycles is severely impeded by concomitant oligomer formation. Here, we present a biomimetic approach that utilizes spatial confinement to increase macrocyclization selectivity in the ring-closing metathesis of various dienes at elevated substrate concentration up to 25 mM using an olefin metathesis catalyst selectively immobilized inside ordered mesoporous silicas with defined pore diameters. By this approach, the ratio between macro(mono)cyclization (MMC) product and all undesired oligomerization products (O) resulting from acyclic diene metathesis polymerization was increased from 0.55, corresponding to 35% MMC product obtained with the homogeneous catalyst, up to 1.49, corresponding to 60% MMC product. A correlation between the MMC/O ratio and the substrate-to-pore-size ratio was successfully established. Modification of the inner pore surface with dimethoxydimethylsilane allowed fine-tuning the effective pore size and reversing surface polarity, which resulted in a further increase of the MMC/O ratio up to 2.2, corresponding to >68% MMC product. Molecular-level simulations in model pore geometries help to rationalize the complex interplay between spatial confinement, specific (substrate and product) interaction with the pore surface, and diffusive transport. These effects can be synergistically adjusted for optimum selectivity by suitable surface modification.
Stereoselective access to Z and e macrocycles by ruthenium-catalyzed Z-selective ring-closing metathesis and ethenolysis
Marx, Vanessa M.,Herbert, Myles B.,Keitz, Benjamin K.,Grubbs, Robert H.
supporting information, p. 94 - 97 (2013/04/10)
The first report of Z-selective macrocyclizations using a ruthenium-based metathesis catalyst is described. The selectivity for Z macrocycles is consistently high for a diverse set of substrates with a variety of functional groups and ring sizes. The same catalyst was also employed for the Z-selective ethenolysis of a mixture of E and Z macrocycles, providing the pure E isomer. Notably, an ethylene pressure of only 1 atm was required. These methodologies were successfully applied to the construction of several olfactory macrocycles as well as the formal total synthesis of the cytotoxic alkaloid motuporamine C.
