Regiocontrolled benzannulation of diaryl (gem-dichlorocyclopropyl) methanols for the synthesis of unsymmetrically substituted alpha-arylnaphthalenes: Application to total synthesis of natural lignan lactones

An efficient synthesis of highly substituted alpha-arylnaphthalene analogues is developed utilizing Lewis acid-promoted regicontrolled benzannulation of aryl(aryl')-2,2-dichlorocyclopropylmethanols. Application of the method to the total synthesis for unsymmetrically substituted natural lignan lactones, justicidin B, retrojusticidin B, dehydrodesoxypodophyllotoxin, and a related analogue, 5'-methoxy-retrochinensin, was demonstrated.