Selective “One-Pot” Synthesis of Functionalized Cyclopentenones

Double addition (1,2–1,4) of vinyl magnesium bromide to squaric acid derivatives allows the preparation of polyoxygenated cyclopentenones (8) in a “one-pot” procedure. The reaction occurs through the intermediate formation of octatetraenes (6). Protonation of this latter intermediate at −78 °C with TFE occurs selectively at the vinyl CH₂ closer to the metallic centers. DFT studies of the cyclization step justify the observed diastereoselectivity.