From high-throughput catalyst screening to reaction optimization : Detailed investigation of regioselective suzuki coupling of 1,6-naphthyridone dichloride

Efficient catalyst systems and reaction protocols were discovered for the regioselective Suzuki coupling of 1,6-naphthyridone dichloride through high-throughput experimentation. With Pd2(dba)3·CHCl3 as the precatalyst, either (2-MeO-Ph)3P or IMes·HCl afforded greater than 95% conversion to the coupling products with up to 92% desired regioselectivity. DMF/K3PO4 was found to be the most effective combination of solvent and base. The concentration profiles of reactants and products indicated that, with the regioselective catalyst, the first coupling step at one of the two competitive reactive centers was 10 times faster than the second coupling step at the other reactive center, resulting in high regioselectivity of the desired monoadduct.