Oxygen-chelated indenylidene ruthenium catalysts for olefin metathesis

Steric and electronic effects in latent S-chelated olefin metathesis catalysts

In this work, the structure, latency, and activity of twelve sulfur-chelated ruthenium precatalysts were studied by systematically varying their ligand shell.

Fluorine-containing ruthenium-based olefin metathesis catalysts

The review summarizes literature data on the methods for the introduction of fluorine atoms and fluoralkyl groups into different ligands to construct metathesis-active ruthenium carbene complexes. It also analyzes the influence of fluorinated ligands on the catalytic activity of the complexes. The choice, structure and positions of fluorinated substituents in NHC ligands are generally dictated by the desire to increase the electrophilicity of the ruthenium atom due to the electron-withdrawing effect of fluorine atoms and fluoroalkyl groups, resulting, as a rule, in an increase in the activity of the ruthenium complex. In catalysts with unsymmetrical fluorine-containing NHC ligands, there is a possibility of additional Ru–F coordination, making the complexes much more stable and, consequently, more active. The presence of fluorine in chelating alkylidene ligands provides an increase in the catalyst initiation rate due to a weakening of the ruthenium – heteroatom bond. Besides, the introduction of polyfluoroalkyl groups into ligands solves the problem of catalyst recovery using fluorous biphasic systems for reuse.

The bibliography includes 172 references.

Ring Rearrangement Metathesis in 7-Oxabicyclo[2.2.1]heptene (7-Oxanorbornene) Derivatives. Some Applications in Natural Product Chemistry

Metathesis reactions is firmly established as a valuable synthetic tool in organic chemistry, clearly comparable with the venerable Diels-Alder and Wittig reactions and, more recently, with the metal-catalyzed cross-coupling reactions. Metathesis reactions can be considered as a fascinating synthetic methodology, allowing different variants regarding substrate (alkene and alkyne metathesis) and type of metathetical reactions. On the other hand, tandem metathesis reactions such Ring Rearrangement Metathesis (RRM) and the coupling of metathesis reaction with other reactions of alkenes such as Diels-Alder or Heck reactions, makes metathesis one of the most powerful and reliable synthetic procedure.

In particular, Ring-Rearrangement Metathesis (RRM) refers to the combination of several metathesis transformations into a domino process such as ring-opening metathesis (ROM)/ring-closing metathesis (RCM) and ROM-cross metathesis (CM) in a one-pot operation. RRM delivers complex frameworks that are difficult to assemble by conventional methods constitutingan atom economic process. RRM is applicable to mono- and polycyclic systems of varying ring sizes such as cyclopropene, cyclobutene, cyclopentene, cyclohexene, pyran systems, bicyclo[2.2.1]heptene derivatives, bicyclo[2.2.2]octene derivatives, bicyclo[3.2.1]octene derivatives and bicyclo[3.2.1]octene derivatives.

In this review our attention has focused on the RRM reactions in 7-oxabicyclo[2.2.1]heptene derivatives and on their application in the synthesis of natural products or significant subunits of them.

Effect of the bulkiness of indenylidene moieties on the catalytic initiation and efficiency of second-generation ruthenium-based olefin metathesis catalysts

Fast initiation and high efficiency of ruthenium indenylidene catalysts induced by steric repulsion between two ligands (SIMes ligand and bulky indenylidene ligand).