Synthesis of unsymmetrical 2,4-diaryl substituted and 3-bromo-2-(4-bromoalkoxy)-derived pyranocoumarins

A series of unsymmetrical 2,4-disubstituted pyranocoumarins and 3-bromo-2-(4-bromoalkoxy)-derived pyranocoumarins were synthesized via the palladium-catalyzed C-H arylation of 4-phenyl-4 H ,5 H -pyrano[3,2- c ]chromen-5-ones with aryl iodide and the three-component reaction of 4-phenyl-4 H ,5 H -pyrano[3,2- c ]chromen-5-one with bromine and cyclic ether, respectively. 4-Arylpyranocoumarins were prepared as precursors to construct unsymmetrical 2,4-disubstituted and dibromo-derived pyranocoumarins via Heck coupling and a three-component reaction, respectively.