New Approach of Ethyl Substituted Isoquinoline-3-Carboxylate Synthesis

The application of palladium catalysis for carbon-carbon bond formation is particularly attractive owing to the mild reaction conditions and high reaction yields. The synthesis of ethyl 1,4-disubstitued isoquinoline-3-carboxylate derivatives was achieved in four steps utilizing readily available N-substituted phthalimide by employing Suzuki reaction as a key step. In the Pd(0)-catalyzed cross coupling step, a regioselectivity was observed between a triflate-enol ether and a triflate-imino ether. The present methodology can provide an expedient access to diversely substituted isoquinolines.