Interesting Transformations of Methylenedioxy-Substituted Ortho-(Pivaloylaminomethyl)benzaldehyde

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.