Stereoselective Halolactonization of $\alpha-Phenylsulfonyl-\gamma,\delta$ -Unsaturated Amides

Iodine-induced lactonization of -Phenylsulfonyl--Unsaturated Amides provided 2,4-trans-substitued -butyrolactones in high selectivity. NBS-or NCS-induced lactonization of N,N-dimethyl-2-(phenylsulfonyl)-4-pentenamide in DME- gave 2-halo-4-(halomethyl)-2-(phenylsulfonyl)--butyrolactone.