Versatile reactivity of 3-chloro-2-phenyl-isoindole-1-carbaldehyde: hydrolysis and alkylating rearrangement to 1-amino-4-isochromanones

3-Chloro-2-phenyl-isoindole-1-carbaldehyde has been prepared from N-phenylisoindolinone under Vilsmeier–Hack conditions. This electrophilic isoindole proved to be stable under the basic conditions used in the final treatment (KOH/MeOH), and for weeks under air in the solid state. Nevertheless, the double bond; length as m-dashC–Cl bond proved highly sensitive to any treatment with reducing or alkylating agents targeted towards the pendant carbaldehyde group, giving various phthalimide derivatives. This unique reactivity is exploited for the selective synthesis of new aminoisochromanones.