An Investigation of the Reactivity and Mutagenicity of Alkyl N-acyloxybenzohydroxamates

Abstract

A new class of relatively stable compounds, alkyl N-acyloxybenzohydroxamates, were synthesised and found to he excellent sources of alkoxy stabilised nitrenium ions under acidic conditions. Under basic conditions the alkyl N acyloxybenzohydroxamates are rapidly consumed in bimolecular reactions. All precursors were determined to he mutagenic. In aqueous acetonitrile, butyl N-acetoxybenzohydroxamate decomposes via an AA11 mechanism to an N-acyl-N-hutoxynitrenium ion and the progress of the reaction was monitored by ¹H NMR across the temperature range 298-338K. The acid-catalysed solvolysis was repeated with a number of electron-donating and electron-withdrawing Para substituents and the Arrhenius data was obtained, which determined that nitrenium ion formation proceeds with positive entropy of activation and negative heat of enthalpy. Analysis of the Hammett plot revealed an excellent a+ relationship with moderate slope that reflected the separation between the ring and the developing positive charge of the nitrenium ion.