Photochemical type II reaction of atropchiral benzoylformamides to point chiral oxazolidin-4-ones. Axial chiral memory leading to enantiomeric resolution of photoproducts

Abstract

Atropisomeric benzoylformamides 1 undergo Type II reaction leading to cis-2 and trans-2 oxazolidin-4-one photoproducts. The N-C(Aryl) chiral axis is maintained during the course of the phototransformation in spite the reaction proceeding through a near planar intermediate(s). As the rotational barrier of the N-C(Aryl) chiral axis in the cis-2 and trans-2 photoproducts is lowered when compared with the reactant 1, the isolated optically pure trans-2 isomer is converted to the ent-cis-2 isomer without affecting the C-5 stereogenic center, resulting in resolution of the cis-2 enantiomers.