Enantioselective chlorination and fluorination of (beta)-keto phosphonates catalyzed by chiral Lewis acids

The direct chiral Lewis acidic enantioselective chlorination and fluorination of (beta)-keto phosphonates is presented; the chlorination proceeds in high yields and with up to 94% ee using NCS as the chloro source, while the fluorination with (PhSO2)2NF (NFSI) gives the optically active (alpha)fluoro-(beta)-keto phosphonates in moderate to good yields and with up to 91% ee.