Conjugate addition to 3-arylsulfinylchromones as a synthetic route to homochiral 2-substituted chromanones: scope and limitations

A route to homochiral 2-substituted chromanones via the diastereoselective conjugate addition of organocopper reagents to 3-(p-tolylsulfinyl)chromones has been improved and used to prepare 2,6-dimethylchromanone (S)-4 and LL-D253α methyl ether (S)-6. The attempted preparation of a 2-phenylchromanone (flavanone) using this strategy was unsuccessful due to the lability of the intermediate 2-phenyl-3-(p-tolylsulfinyl)chromanone, which underwent sulfoxide elimination at room temperature to give the corresponding 2-phenylchromone (flavone).