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ChemInform Abstract

Vicarious nucleophilic substitution is shown to be a versatile tool for the introduction of several O-, N-, or S-substituents into the azulene skeleton. Hydroxylation of azulene derivatives (I) with tert-butylhydroperoxide proceeds smoothly in the presence of electron-withdrawing substituents to furnish the 6-hydroxyazulenes (II) with absolute regioselectivity. These hydroxy derivatives can be used to introduce, via several sulfonyloxy analogues (VII), nucleophiles into position 6 [cf. (VIII) and (X)]. Additionally, allylation of 6-hydroxy derivatives (II) in the presence of K₂CO₃ affords the corresponding O-allyl derivatives (IV), which readily undergo Claisen rearrangement to provide access to C-allylated azulenes. Amination of azulenes (I) also proceeds smoothly and regiospecifically even in the case of unsubstituted azulene (Ia).