Base catalysed rearrangements involving ylide intermediates. Part 14. Rearrangements of 4-oxidoanilinium ylides and 3-oxidoanilinium betaines

The N-allyl-4-oxidoanilinium ylides (11a–c) undergo a [3,2] sigmatropic rearrangement at 0 °C to give initially the products (9a–c), which undergo a further [3,3] rearrangement to give the isolated reaction products (8a–c). The N-(3,3-dimethylallyl)-4-oxidoanilinium ylide (11d) reacts at 0 °C by the alternative pathway involving homolysis and radical pair recombination to give a mixture of the products (8d) and (13d). The ylides (15a–c) rearrange by a similar radical pair mechanism. The N-pentadienyl-4-oxidoanilinium ylides derived from the salts (24a and b) also rearrange at 0 °C by a sequence of [3,2] and [3,3] sigmatropic rearrangements to give in each case the product (26b). The N-allyl-3-oxidoanilinium betaines (29a and b) undergo [3,3] rearrangements on heating at 40 °C to give mixtures of the products (32) and (33) whereas the N-pentadienyl-3-oxidoanilinium ylide (30) gives only the product (35) of a [5,5] rearrangement followed by aromatisation.