Synthesis of neoflavones by Suzuki arylation of 4-substituted coumarins

Palladium-catalysed coupling of the 4-chloro- or 4-bromo-coumarins 1–4 with arylboronic acids 5–13 under the Suzuki reaction conditions constitutes an efficient access to 4-arylcoumarins. These 4-arylcoumarins can also be obtained in good yields (70–97%) by treatment of 4-trifluoromethyl-sulfonyloxycoumarins 35–38 with arylboronic acids under modified Suzuki reaction conditions, involving the use of copper(I) iodide as a co-catalyst.