Two efficient cascade reactions to synthesize substituted furocoumarins

We have developed two efficient one-pot reactions to generate furo[3,2-c]coumarins and chlorofuro[3,2-c]coumarins through addition/cyclization/oxidation and chlorination. One cascade addition/cyclization/oxidation sequence of 1 with H2O in the presence of 20% CuCl as Lewis acid under an air atmosphere generated the 2-substituted-4H-furo[3,2-c]chromen-4-one 2. Another sequence in the presence of 10% CuBr and excess CuCl2 as the oxidant afforded the 3-chloro2-substituted-4H-furo[3,2-c]chromen-4-one 3.