A novel 3,4-dihydroisoquinoline annulation: expedient access to isoquinoline heterocycles

Abstract 3,4-Dihydroisoquinoline carboxylate 1 undergoes a smooth annulation with ω-bromopropionate, butyrate or ortho -bromomethyl benzoate 2 to afford the isoquinoline heterocycle 3 upon treatment with potassium tert -butoxide in DMF at −60 °C. This novel annulation constitutes a formal direct synthesis of cyclic Reissert equivalent compounds, thus offers an expedient access towards certain medicinally important isoquinoline heterocycles and relevant natural alkaloids, that is, of berberine and erythrina types.