Acid-catalysed hydrolysis and protonation behaviour of N-arylpropane-1,3-sultams

Abstract

The acid-catalysed hydrolyses of some N-(para-substituted pheny1)propane-I ,3-sultams have been studied in aqueous acidic solutions. The rate maxima observed are shown to be consistent with an A-2 mechanism in which extensive protonation of the substrate occurs. Values of pK,,+ for the sultams have been determined.Whilst the acid-catalysed hydrolysis of sulfonamides has been studied in some detail because of its relevance to the Hinsberg method for the separation of amines, very few studies of the hydrolyses of sultams (the corresponding cyclic sulfonamides) have been recorded.' Erman and Kretschmar reported that a number of five-membered N-alkyl sultams undergo hydrolysis in methanolic HCl or HBr or in glacial acetic acid.2 They suggested that acid catalysed cleavage of the ring proceeds via an A-1 mechanism by analogy to the mechanism proposed earlier for the acid-catalysed hydrolysis of sulfonamides3 although Klamann and his co-workers subsequently changed this view.4 In order to clarify the situation for the hydrolysis of sultams, we now report a detailed study of the protonation behaviour and kinetics of hydrolysis of a series of fivemembered N-arylpropane-1,3-sultams 1 in aqueous solutions of mineral acids.

Investigation of the acid-catalyzed hydrolysis and reaction mechanisms ofN,N′-diarylsulfamides using various criteria

“…10.00–11.00 M), and finally increase again (after 11.00 M). Similar rate maxima have been observed for acid‐catalyzed hydrolysis of other compounds such as sultams, amides, hydroxamic acids, primary acetate esters, and N ‐acetylsulfonimidic esters . These rate maxima were attributed to an A2 mechanism in which extensive protonation of the sulfamides occurs in the regions of acidity in which the activity of the water is falling.…”

“…In the literature, the mechanism of the acid‐catalyzed hydrolysis of the sulfonamides and the sultams (the corresponding cyclic sulfonamides) has been studied in some detail . Both classes of compounds are very stable and so their S–N bond cleavage occurs in strong acid media at elevated temperatures.…”

“…In the literature, the mechanism of the acid-catalyzed hydrolysis of the sulfonamides [1] and the sultams (the corresponding cyclic sulfonamides) has been studied in some detail. [2] Both classes of compounds are very stable and so their S-N bond cleavage occurs in strong acid media at elevated temperatures. Protonation of these compounds in aqueous acid solutions takes place on the nitrogen [3] and then, in slow steps, a water molecule attacks the sulfur atom.…”

Acid‐catalyzed hydrolysis of 5‐substituted‐1H,3H‐2,1,3‐benzothiadiazole 2,2‐dioxides (5‐substituted benzosulfamides): kinetic behavior and mechanistic interpretations

“…The slightly downward curvature of this region allows easy distinction of A2 reactions involving water in the rate‐determining step. Similar behavior has been observed for the hydrolysis of iminosulfonate esters, benzohydroxamic acids, sultams, sulfinylphthalimides, and N,N'‐diarylsulfamides …”

“…However, the protonation behaviors of the sultams and sulfamate esters were studied. The values of pK BH + of the substituted sultams = 5.96–8.3 . Sulfamate esters have pK a values of ≈ 8 in water‐organic media .…”