A number of diversely substituted furans are synthesized via a cycloisomerization process that goes through a unique metal carbene species. Both ligand structure and the nature of the leaving group are evaluated. The characteristics of the carbene intermediate can be modulated, resulting in highly selective hydrogen or silicon group migrations.

A novel platinum-catalyzed double heterocyclization of propargylic ethers is described. The transformation exploits the intermediacy of a key α,β-unsaturated carbene. The reactivity of this carbene is such that systems can be developed which avoid a complicating 1,2-hydrogen migration, allowing remarkable versatility in the selective syntheses of oxygen- and nitrogen-containing vicinal bis-heterocyclic compounds.

A novel synthesis of regioisomeric isoxazoles is described. Using catalytic platinum, both propargylic N-hydroxycarbamates and N-alkoxycarbonyl amino ethers can be cyclized to form differentially substituted isoxazoles. Reaction conditions are developed that address specific aspects of the catalytic manifold. A unique mechanism involving a Pt-carbene intermediate is proposed, and deuterium labeling studies corroborate this hypothesis. This regiocomplementary approach to isoxazoles is highlighted in the syntheses of antirhinovirus analogues, illustrating the relevance of this science to medicinal chemistry.

Formal syntheses of tetracyclic terpenoids frondosin B and liphagal are described. Both synthetic routes rely on the use of platinum-catalyzed α,β-unsaturated carbene formation for the key C–C bond forming transformations. The successful route toward frondosin B utilizes a formal (4 + 3) cycloaddition, while the liphagal synthesis features the vinylogous addition of an enol nucleophile as a key step. Both synthetic routes are discussed, revealing insights into structural requirements in the catalytic α,β-unsaturated carbene reaction manifold.

A variety of substituted indoles and benzofurans are accessed via a platinum catalyzed annulation and vinylogous addition of enol nucleophiles. Several β-dicarbonyl compounds participate in the reaction, as do α-nitro and α-cyano carbonyl species. Subjecting the indole products to acidic conditions results in the formation of fused heterocycles.