Base-catalysed rearrangements involving ylide intermediates. Part 8. The preparation and some reactions of stable ammonium ylides

Abstract

The carbonyl-stabilised ammonium ylides (3), (12a–n), and (14a–c) were obtained from the reaction of the corresponding ammonium halides (1), (13a–n), and (15a–c) with sodium hydroxide in water or aqueous methanol. The ylides, which were characterised by their molecular formulae and spectroscopic properties, regenerated quaternary ammonium bromides on treatment with hydrobromic acid. In general the reactions of the ammonium ylides resemble those of the corresponding sulphonium ylides. Thus ylides having a suitable migrating group (ArCH₂) undergo a Stevens [1,2] rearrangement on heating, and other ylides fragment to give a tertiary amine and products containing the PhCOCH grouping. A number of ylides reacted with dimethyl acetylenedicarboxylate to give the furans (32). The ylides (14b and c) with phenyl isocyanate gave the phenylcarbamoyl-substituted ylides (35).