An investigation of the application of nucleophilic aromatic substitution by the
SRN 1 mechanism of halobenzenesulfonamides and related compounds towards the
synthesis of 1,2-benzothiazine I,I-dioxides is reported. 3-Substituted and 3,4-
disubstituted 2H-l,2-benzothiazine l,l-dioxides were prepared in moderate to good yields
via the photostimulated reaction of 2-halobenzenesulfonamides with ketone enolates. It
was observed that with certain ketone enolates reduction to yield benzene sulfonamide
competed with the substitution reaction. The presence of β-hydrogen atoms was a
common structural feature of ketones used in reactions in which reduction competed with
substitution. It was also observed that the amount of reduction product isolated increased
as a function of the number of β-hydrogen atoms present on the ketone enolate. It was
found that 2-bromo and 2-iodobenzenesulfonamide exhibit comparable reactivity with
ketone enolates that do not possess β-hydrogen atoms. However, a marked decrease in the
reactivity of 2-bromobenzenesulfonamide was observed when β-hydrogen atoms were
present on the ketone enolate.
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