LEWIS-ACID CATALYZED CYCLIZATION AND HALOGEN EXCHANGE-REACTIONS OF 1,1'-BIPHENYL-2-YL ISOCYANIDE DIHALIDES

1,1'-Biphenyl-2-yl isocyanide dichloride and dibromide undergo unprecedented intramolecular Friedel-Crafts type cyclisation reactions catalysed by various Lewis acids affording useful synthetic methods for otherwise difficult to access 6-chloro- and 6-bromo-phenanthridines; nucleophilic displacement reactions of the latter and halogen; exchange reactions of 1,1'-biphenyl-2-yl isocyanide dichloride and dibromide are also described.