AMINOLYSIS AND HYDROLYSIS OF SULPHAMATE ESTERS: SUBSTANTIAL N=S BONDING IN THE TRANSITION STATE LEADING TO N=SULFONYLAMINES

Article abstract of DOI:10.1002/poc.610080907

The aminolysis and hydrolysis of several sulphamate esters, RNHSO2ONp (R = PhCH2, Ph, 4-MeC6H4, 3-MeC6H4, 4-FC6H4, 4-ClC6H4, 3-ClC6H4, H; Np = 4-NO2C6H4) were been studied in 50 percent (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 disappearance 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.