Hydration of Acetylenic Esters: Synthesis of β ββ ββ-Keto-Esters

Acetylenic esters, which are easily prepared by carbethoxylation of terminal acetylenes, can be hydrated regioselectively to β-keto-esters. In this paper, the terminal acetylenes were prepared by addition of lithium acetylide (complexed with ethylenediamine) to epoxides of cyclopentane derivatives to produce compounds oxygenated at the same position as certain natural products from Otoba parvifolia. The hydration was carried out by two different processes, producing either δ-oxygenated or γ,δ-unsaturated β-keto-esters.