Regioselective Suzuki Cross-Coupling Route to 3,4-Disubstituted Quinolin-2(1H)-ones

Significance

Reported is a regioselective method for the synthesis of 3,4-disubstituted quinolin-2(1H)-ones via Pd-catalyzed Suzuki cross-coupling reactions. The starting 3-bromo-4-tosyl-quinolin-2(1H)-one is easily synthesized from the commercially available 4-hydroxyquinolin-2(1H)-one. Selective Suzuki coupling occurs, as expected, at the more reactive bromo substituent to give 3-substituted products (route i). A second tosylate coupling (route ii) may be achieved under more vigorous conditions to afford 3,4-disubstituted quinolones. Alternatively, excess of a single boronic acid coupling partner leads to a 3,4-disubstituted product (route iii). The conditions for the tosylate coupling were extensively optimized and only the conditions shown provided the expected product. The reaction scope was moderately studied.