Highly stereoselective synthesis of optically active oxazolinyl oxiranes from azaenolates of a chiral 2-chloromethyloxazoline

Boron and titanium azaenolates 2 and 4, generated at 0°C and −100°C, respectively, from the optically active chloromethyloxazoline 1, have been found to couple with aliphatic ketones in a highly diastereoselective fashion ending up with the formation of optically active oxazolinyl oxiranes 3. Less stereoselective was the reaction with aromatic ketones.