1,2-Adducts of 5-Allyl-2,3,5-trichloro-4,4-dimethoxy-2-cyclopentenone with Ethyl Acetate Lithium Salt and Their Reactions with Iodine

The condensation of 5-allyl-2,3,5-trichloro-4,4-dimethoxy-2-cyclopentenone with ethyl acetate lithium salt generated in situ in THF at -78°C gave adducts at the carbonyl group, the corresponding cis- and trans-chlorohydrins. The steric structure of the products was determined by involving them into reaction with iodine. From the trans-adduct the expected bicyclic compound was obtained, while the cis-chlorohydrin underwent anomalous deacetalization to iodomethoxycyclopentenone. Spectral parameters of the adducts were discussed. Unusual diastereotopicity was observed for the remote methylene groups in the ester moiety.