A straightforward synthesis of 4-substituted 3,4-dihydro-1H-2,1,3-benzothiadiazine 2,2-dioxides

4-Substituted 3,4-dihydro-1H-2,1,3-benzothiadiazine 2,2-dioxides 11 have been efficiently prepared in two steps from the suphamide 9 by condensation of anion II, derived from 9 by metal–halogen exchange, with aromatic and aliphatic aldehydes and cyclodehydration of the so-formed alcohols 10 under acidic conditions.