Ring transformation of glycidic amides with ortho-metalated phenols to enantiopure 3-hydroxychromanones

A novel access to hitherto unknown enantiopure 2-alkylchroman-4-ones 10 was found by a reaction of ortho-metalated O-MOM-protected phenols with Weinre b amides 8 of enantiopure cis- or trans-glycidic acids, Upon acidic hydroly sis, the resulting o-MOMO-benzoyloxiranes 9 undergo ring transformation to 2-alkylchroman-4-ones 10. 2-Alkylidenecoumaran-3-ones 11 were formed as alt ernative products, depending on the configuration of the starting oxirane r ing and on the type of phenol used as starting material.