Macrocyclic lactones, ketones, and ethers can be obtained in the High-Concentration Ring-Closing Metathesis (HC-RCM) reaction in high yield and selectivity at concentrations 40 to 380 times higher than those typically used by organic chemists for similar macrocyclizations. The new method consists of using tailored ruthenium catalysts together with applying vacuum to distill off the macrocyclic product as it is formed by the metathetical backbiting of oligomers. Unlike classical RCM, no large quantities of organic solvents are used, but rather inexpensive nonvolatile diluents, such as natural or synthetic paraffin oils. Moreover, use of a protecting atmosphere or a glovebox is not needed, as the new catalysts are perfectly moisture and air stable. In addition, some other cyclic compounds previously reported as unobtainable by RCM in neat conditions, or in high dilutions even, can be formed with the help of the HC-RCM method.

Three new quinone‐containing Hoveyda‐type complexes have been synthesised and fully characterised. Their ability to suppress undesired double‐bond migration along the carbon chain during metathesis reactions was examined. It was proved that these catalysts decrease the amounts of undesired side‐products with a shifted double bond in the reaction mixture.

Recent advances in the synthesis of macrocycles with musk scent via catalytic olefin metathesis are presented with a particular emphasis on advantages offered by the metathesis technology. The review includes short historical background about musks and olefin metathesis to introduce the subject. Substantial emphasis is given on ring-closing metathesis (RCM) as a tool for the synthesis of cyclic compounds such as civetone, muscone, exaltolide, ambrettolide/isoambrettolide, and yuzu lactone. The bibliography includes 106 references.

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