Intramolecular addition of aryl radicals to the azo-group. Part 2. Production of some N-(carbazol-9-yl)arylaminyl radicals and their reactivity

Abstract

The N-(carbazol-9-yl)arylaminyl radicals (2a–d) have been produced by intramolecular addition of the 2′-arylazobiphenyl-2-yl radicals (1a–d) generated by reduction of the corresponding arenediazonium tetrafluoroborates (3a–d) and their reactivity has been investigated. N-(Carbazol-9-yl)-4-tolylaminyl (2a) and N-(carbazol-9-yl)4-chiorophenylaminyl (2b) exhibit N,N-coupling at –20° C, whereas hydrogen abstraction and C_ortho,N-coupling appear to be the main reaction paths at room temperature. A comparable trend has been observed with 1-(4-chlorophenyl)-2,2-diphenylhydrazyl radicals (14) generated by oxidation of the corresponding hydrazine (13) with lead dioxide. From the N-(carbazol-9-yl)biphenyl-2-ylaminyl radicals (2c) and (2d) some evidence has been obtained that they are capable of undergoing intramolecular addition to aromatic rings.