Regiospecific Ring Opening of Some Methyl- and Phenyl-Substituted 1,1,2-Trihalocyclopropanes to Acetylenic Acetals or Ketals by Variation of Reaction Conditions.
摘要:
Regiospecific ring opening of six title compounds has been achieved under various reaction conditions. With dry sodium ethoxide in dry THF as reagent acetylenic diethyl ketals are obtained in 66-81% isolated yield. With DBU in dry ethanol, the corresponding acetylenic diethyl acetals are formed and isolated in 50-67% yield. Finally, treatment of the substrates with 50% aqueous sodium hydroxide in the presence of 2-propanol, triethylbenzylammonium chloride and dichloromethane gave acetylenic diisopropyl acetals, in 82% yield at the best. By-product formation was negligible in most cases.