Reactions of electron‐rich heterocycles with orthocarboxylic acid derivatives. 11. Reactions of carbazole and 4‐methoxycarbazole with triethyl orthoformate: Regiospecific functionalization of the carbazole nucleus

Carbazole ( 1a ) and 4‐methoxycarbazole ( 1b ) can be regioselectively functionalized by reaction with triethyl orthoformate. Whereas the reaction of 1a with the ortho ester furnishes the amide acetal 2 , the new carbazole derivatives 4–10 are formed, depending on the reaction conditions, in the electrophilic substitution of 1b . The products of this reaction sequence provide a contribution to studies on the mechanism of the transformation of 1b to tris‐carbazolylmethane 5 . Compound 5 represents a new, three‐bladed propeller in the triheteroarylmethane series.