A new procedure for the synthesis of 4-substituted-2H-1,2,3-benzothiadiazine 1,1-dioxides via directed ortho-lithiation of N1-arylsulfonylhydrazonates

N1-Arylsulfonylhydrazonates, which are readily available from commercial N1-arylsulfonylhydrazides, undergo directed ortho-lithiation with an excess of lithium diisopropylamide and tetramethylethylenediamine to provide new 2H-1,2,3-benzothiadiazine 1,1-dioxide derivatives in yields ranging from 43% to 85%.