New cyclization of N‐hydroxyiminoyl chlorides with N‐alkyl ethynesulfonamides: Synthesis of 4‐alkyl‐3‐aryl‐4,5‐dihydro‐1,5,2,4‐oxathiadiazepine‐5,5‐diones

N‐Hydroxyiminoyl chlorides reacted with N‐alkyl ethynesulfonamides in the presence of triethylamine in CH₂Cl₂ to afford the 4‐alkyl‐3‐aryl‐4,5‐dihydro‐1,5,2,4‐oxathiadiazepine‐5,5‐diones (3) as the major products together with N‐alkyl‐3‐aryl‐5‐isoxazolesulfonamides (4). © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 461–464, 1999