AN ASYMMETRIC SYNTHESIS OF CHIRAL PHTHALIDES VIA CHIRAL LITHIATED OXAZOLINES

Article abstract of DOI:10.1016/S0040-4020(01)91917-9

Chiral aromatic oxazolines were prepared for utilization in asymmetric C-C bonding reactions.Lithiation of aryloxazolines could not be accomplished directly but were efficiently lithiated via halogen metal exchange of the o-bromo derivative (16).The resulting lithio compound (9) reacted smoothly with carbonyls to give adducts 19 but with poor stereoselectivity.Hydrolysis gave the phthalides 4 in poor ee's (20-25percent).When the lithio-oxazolines 9 were transformed into 21, they now served as chiral electrophiles.Addition of organometallics to 21 gave, particularly with Grignard reagents, useful levels of asymmetric induction which, after hydrolysis, gave phthalides 4 in 40-80percent ee.