Ruthenium-based olefin metathesis catalysts, known for their functional group tolerance and broad applicability in organic synthesis and polymer science, continue to evolve as an enabling technology in these areas. A discussion of recent mechanistic investigations is followed by an overview of selected applications.

Recent advances in ruthenium-based olefin metathesis

The proceedings of the Eleventh International Congress of Pure and Applied Chemistry, held in London from July 17 to 24, covered a wide variety of topics of medical interest. Joint meetings between sections primarily concerned with human beings, animals, and plants proved of special value. Sir Henry Dale's congress lecture on "The Part of Chemistry in the New Therapeutics " was published in our last issue (Aug. 2, p. 161). The report which follows excludes also discussions on bacterial chemotherapy, the principal points from which were summarized last week in a leading article (p. 179), and the reported discovery of a lactation vitamin which was the subject of an annotation (p. 181).

Pure and Applied Chemistry

Synthesis of coumarins via Pd-catalyzed oxidative cyclocarbonylation of 2-vinylphenols.

An efficient ZrCl4 catalyzed one-pot solvent free protocol for the synthesis of 4-substituted coumarins

Natural products and ring-closing metathesis: synthesis of sterically congested olefins.

Investigations into olefin ring-closing metathesis (RCM) have led to a general method for the synthesis of coumarins. Catalysts with higher activity, such as the second-gen- eration ruthenium catalyst, promote the intramolecular reaction between two-electron defi- cient olefins. This method allows for convenient access to a variety of coumarins substituted at both the 3- and 4-positions, as well as a tetrasubstituted example.

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F. D. Toste

Papers

Synthesis of coumarins by ring-closing metathesis*