1,2,3-Benzoxathiazole 2,2-Dioxides: Synthesis, Mechanism of Hydrolysis, and Reactions with Nucleophiles

Article abstract of DOI:10.1021/jo00023a012

The rate of base-induced hydrolysis of some five-membered cyclic sulfamates, X-3-(p-tolylsulfonyl)-1,2,3-benzoxathiazole 2,2-dioxides (1a, X = H; 1b, X = 5-Me; 1c, X = 5-t-Bu; 1d, X = 5-Br; 1e, X = 5-Cl; 1f, X = 5-Ac; 1g, X = 5-NO2; 8a, X = 6-NO2) were measured in aqueous acetonitrile.The hydrolyses occurred with cleavage of the endocyclic N-SO2 bond.A Hammett plot using ?_m values for 1a-g and ?_p for 8a had ρ = +2.20.Activation enthalpies and entropies were measured for 1a and for 3-methyl-1,2,3-benzoxathiazole 2,2-dioxide (10).Volumes of activation weredetermined for 1g and for 8a.The mechanistic profile for hydrolysis resembled that for the saponification of the analogous sultones and cyclic sulfates.These first examples of 1,2,3-benzoxathiazole 2,2-dioxides (1a-g, 8a) were prepared by treating N-(2-hydroxyphenyl)-p-toluenesulfonamides with sulfuryl chloride and triethylamine or by oxidizing the monoxide precursors using m-chloroperbenzoic acid.Treatment of 1a with potassium fluoride gave 1,2,3-benzoxathiazole 2,2-dioxide (9), which was methylated to give 10.Sulfamate 1a was treated with various nucleophilic reagents: phenyllithium, methyllithium, potassium fluoride, methylamine, tert-butylamine, and sodium methoxide.The first three attacked the tosyl sulfur atom and cleaved the exocyclic N-SO2 bond.The amines attacked the endocyclic sulfonyl sulfur atom and cleaved the endocyclic N-SO2 bond.Sodium methoxide attacked both sulfonyl groups.