A new synthetic method for the preparation of cyclic malonic acid monoesters in aqueous media was developed based on the combination of a metathesis reaction and subsequent biocatalytic hydrolysis with a pig liver esterase in a one-pot synthesis. Both reaction steps proceed smoothly under optimized conditions in aqueous media requiring only a low amount of the metal catalyst for the metathesis reaction. Notably, the applied biocatalyst turned out to be highly compatible with the metal catalyst showing no significant influence on the enzyme activity.

Functionalized furans are conveniently formed by a new silver(I)-catalyzed reaction of alk-1-ynyl oxiranes in the presence of p-toluenesulfonic acid and methanol. Evidence supported a cascade mechanism.

In the presence of alcohol Ag or Au salts or complexes catalyze the conversion of alkynyloxiranes to substituted furans. Both catalysts are effective, and a large furan diversity can be obtained in high yield with one or the other catalyst. Mechanistic studies revealed that a cascade pathway and not the sometimes reported direct intramolecular nucleophilic addition of oxirane oxygen atom to intermediate acetylene-metal pi-complex occurs. Under the defined conditions, the intermediate formation of epoxide opening products has been identified. Depending on the catalyst, one or both of the latter cyclized to dihydrofurans, and further elimination of the alcohol led to the corresponding furans. These results highlight the duality between oxophilicity and alkynophilicity of Ag or Au salts.