Acid catalysis induces a total change from retention to inversion of configuration in CO2 elimination from β-lactones

Abstract

With increasing acidity of the reaction medium the stereochemistry of the CO₂ elimination from cis-3-t-butyl-4-(p-methoxyphenyl)oxetan-2-one (1a) and from cis-3-t-butyl-4-phenyloxetan-2-one (1b) gradually changes from total retention to total inversion of configuration, so that sterically pure (Z)- and (E)-3,3-dimethyl-1-(p-methoxyphenyl)but-1-ene (3a) and (7a) and (Z)- and (E)-3,3-dimethyl-1-phenylbut-1-ene (3b) and (7b) may be obtained from (1a) and (1b), respectively.