General and efficient route for the synthesis of 3,4-disubstituted coumarins via Pd-catalyzed site-selective cross-coupling reactions

Palladium-catalyzed site-selective cross-coupling reactions of 3-bromo-4-trifloxycoumarin or 3-bromo-4-tosyloxycoumarin provide an efficient and facile route for the synthesis of 3,4-disubstituted coumarins, which include 3,4-diarylcoumarins, 3-amino-4-arylcoumarins, and 3-aryl-4-aminocoumarins. The order of reactivity of the (pseudo)halide substituents in the coumarins was found to be 4-OTf > 3-Br > 4-OTs.