Herein, we report the preparation of 1,2,4-thiadiazinane 1,1-dioxides from reaction of β-aminoethane sulfonamides with dichloromethane, dibromomethane and formaldehyde as methylene donors. The β-aminoethane sulfonamides were obtained through sequential Michael addition of amines to α,β-unsaturated ethenesulfonyl fluorides followed by further DBU mediated sulfur(VI) fluoride exchange (SuFEx) reaction with amines at the S–F bond.