Aminolysis and hydrolysis of sulphamate esters: Substantial NS bonding in the transition state leading to Nsulfonylamines

The aminolysis and hydrolysis of several sulphamate esters, RNHSO₂ONp (R = PhCH₂, Ph, 4‐MeC₆H₄4, 3‐MeC₆H₄, 4‐FC₆H₄, 4‐ClC₆H₄, 3‐ClC₆H₄, H; Np = 4‐NO₂C₆H₄) were been studied in 50% (v/v) aqueous acetonitrile at various temperatures. Reaction of the esters with an amine (R¹NH₂) gives ⁻ONp and both sulphamide, (RNHSO₂NHR¹) and sulphamate (RNHSO₂O⁻R¹NH₃⁺) products. First‐order rates were determined by the appearance of ⁻ONp and sometimes also by the disapperance of ester. The reaction was found to be independent of amine type and concentration and at the high pHs that obtain the substrate esters are fully ionized. A Hammett ρ_acyl of −;1·8 was obtained for the decomposition of the sulphamate anions and this is consistent with substantial NS bonding in the transition state leading to N‐sulphonylamine, RNSO₂. This intermediate then partitions very rapidly, reacting with R¹NH₂ and H₂O respectively. ΔH‡, ΔS‡ and a deuterium solvent isotope effect were determined and were also interpreted in favour of the proposed mechanism. The dimethyl sulphamate ester (Me₂NSO₂ONp) does not react under the conditions used.