The key to high yield preparation of I1 compounds (which can be considered as N- acyloxyimides or triacylhydroxylamines) is the use of steam-bath heat rather than reflux, as used by Urbans1i3 Thus, Urbanslii isolated only IIb as the main product, no matter what R was present in I. Indeed, we found that, if the reaction mixture is heated to reflux, a selfsustaining exothermic react4ion takes place which results in complete conversion of ...
