The synthesis of 8‐oxoberbines containing a heterocyclic D‐ring by enamide photocyclizations

The photocyclization of 2‐heteroyl‐1‐methyleneyl‐3,4‐dihydro‐6,7‐dimethoxyisoquinolines, where heteroyl = benzofuran, benzo[b]thiophene, coumarin and nicotinoyl, leads to the corresponding 8‐oxoberbines containing a heterocyclic D‐ring. Dehydrogenation can accompany photocyclization depending on the reaction conditions employed, or alternatively DDQ can be used to effect this dehydrogenation.