Synthesis of chromeno[4,3-b]quinolines and spirobenzofuran-3,3′-quinolines through silver-mediated Appel reaction/C–Br bond cleavage/double selective rearrangement sequence

Various chromeno[4,3-b]quinolines and spirobenzofuran-3,3 '-quinolines were prepared in good to excellent yields through a reduction and silver-mediated Appel reaction/sequential C-Br bond cleavage/double selective rearrangement cascade strategy from easily available chromeno[4,3-b]indolecarbaldehydes. Cross-over experiments revealed that the group migration occurred intramolecularly and the electronic effect on styrenyl groups had a little effect on the migration step. Two novel quinoline scaffolds were easily prepared on a gram scale by simple operation.