Sebastien Monfette

Equilibrium Ring-Closing Metathesis

Ring-closing metathesis (RCM) of dienes is one of the most important methodologies now in use for the assembly of cyclic organic compounds. First employed by Villemin and by Tsuji nearly three decades ago,1,2 the reaction has risen to astonishing prominence in organic synthesis over the past decade, owing largely to the development of easily handled catalysts that enable controlled reaction.3 RCM represents a key step in many synthetic sequences: recent reviews describe its use in, inter alia, construction of synthetically valuable building blocks such as heterocyclic rings containing phosphorus,4 sulfur,4 oxygen,5 or nitrogen,5,6 including aromatic heterocycles;7 spirocyclic,8,9 cyclophane,8 and polycyclic compounds;8,9 and compounds of biological and medicinal relevance such as peptidomimetics,10,11 carbohydrate derivatives,11-14 alkaloids,11,15-19 bioactive cyclic molecules,20,21 and polycyclic ethers,22 including macrocyclic aza-crown ethers23 and topologically interesting molecules and “molecular machines”.24,25 While the common rings of 5-7 members have historically been dominant, owing in part to their greater ease of access, important advances have been made in the synthesis of medium20,26-30 and macrocyclic16,17,23,27,31-35 targets. One aspect of this review will examine the increased tendency of many medium and large rings to participate in equilibrium metathesis, and the resulting implications for selectivity and yields.

Enantiopure C1-Symmetric Bis(imino)pyridine Cobalt Complexes for Asymmetric Alkene Hydrogenation

Enantiopure C(1)-symmetric bis(imino)pyridine cobalt chloride, methyl, hydride, and cyclometalated complexes have been synthesized and characterized. These complexes are active as catalysts for the enantioselective hydrogenation of geminal-disubstituted olefins.

A Ru-isocyanate initiator for fast, living, precisely controlled ring-opening metathesis polymerization at ambient temperatures

The new complex Ru(NCO)(2)(IMes)(py)(2)(=CHPh) is the first ruthenium metathesis initiator capable of fast, controlled living polymerization of functionalized norbornenes at room temperature, irrespective of monomer bulk.

Ring-Closing Metathesis Synthesis of Medium and Large Rings: Challenges and Implications for Sustainable Synthesis

Synthesis of medium-sized and macrocyclic rings by ring closing metathesis (RCM) reactions of dienes involves challenges not found in synthesis of the more common five- and six-membered rings. This review discusses factors that determine the probability and efficiency of cyclization, and experimental methods that have been used to increase selectivity for RCM products, with specific reference to the concentrations at which RCM can be achieved. These issues have important implications for the environmental and economic sustainability of large-scale synthetic processes utilizing RCM for assembly of rings larger than six members.