The complexed beta-hydroxysulfonamide 9 was obtained in 89% yield and as single diastereoisomer. The enantiomeric excess determined by 1H NMR with Eu(hfc)3 on product 11 was higher than 98%. The cyclization of 11 in DMF/NaH at 45°C affords the expected beta- sultam 12 in 98% yield and in e.e. 98% .
On the basis of accepted stereochemical model for the chromium arene derivative, we think that it is resonable to assign the 3R configuration to product 12.
A similar yield and e.e. purity was obtained when the complex of 2-OMe tricarbonylchromium benzaldehyde was used as starting material.