Enantioselective Oxidation of Chiral Titanium Enolates Derived from Propiophenone by Dimethyldioxirane or 3‐Phenyl‐2‐phenylsulfonyloxazirdine

The stereoselective oxidation of the optically active titanium enolate complexes 2 of propiophenone by dimethyldioxirane ( 3 ) (as acetone solution) and 3‐Phenyl‐2‐phenylsulfonyloxaziridine ( 4 ) has been investigated. The chiral titanium enolates 2 were synthesized by the reaction of the lithium enolate of propiophenone and the respective optically active chlorotitanate complexes 1. For 3 as oxidant, the stereoselectivity of the α hydroxylation strongly depends on the substitution pattern at the central titanium atom and reached for the best case, namely 2e , an enantiomeric excess (ee) of 63%. Solvent and temperature exhibited only small effects on the stereoselectivity. Compound 4 as oxidant gave lower enantiomeric excesses than 3 .