Under acidic conditions, methylenedioxy-substituted ortho-(pivaloylaminomethyl)benzaldehyde
underwent a surprising rearrangement reaction leading to the regioisomer of the starting
compound as the major product and a dimer-type aldehyde as the minor one. The supposed
reaction mechanisms are given below providing a feasible explanation for the formation
of both products. Isoindole, proposed as the key intermediate for the formation of
the products, was trapped in a Diels–Alder cycloaddition carried out with N-phenylmaleimide.
