An efficient route to N-alkylated 3,4-dihydroisoquinolinones with substituents at the 3-position.

A facile synthetic procedure for the production of N-alkylated 3,4-dihydroisoquinolinone derivatives is described. The desired products were obtained by N-alkylation of 3,3'-dimethyl-3,4-dihydroisoquinoline derivatives followed by oxidation of the resulting iminium salts. Reaction conditions for both steps were very mild and the desired cyclization products could be obtained in good yield. This strategy allows the generation of N-substituted 3,4-dihydroisoquinolinone derivatives with substituents at the 3-position.