Ring Transformation of Glycidic Amides with <i>Ortho</i>-Metalated Phenols to Enantiopure 3-Hydroxychromanones

Abstract

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 Weinreb amides 8 of enantiopure cis- or trans-glycidic acids. Upon acidic hydrolysis, the resulting o-MOMO-benzoyloxiranes 9 undergo ring transformation to 2-alkylchroman-4-ones 10. 2-Alkylidenecoumaran-3-ones 11 were formed as alternative products, depending on the configuration of the starting oxirane ring and on the type of phenol used as starting material.