Mono-substituted azulenes

Azulenes are halocienated by jy-bromosuccinimide or iV-chlorosuccinimide [42,47], or by copper(II) bromide or chloride [94], to give mixtures of 1- and 1,3-substituted azulenes. Pyridinium perbromide produces the dibromo derivative [95]. Mono- and di-iodo derivatives have been obtained by reaction with iodine monochloride [95], T -iodosuccinimide [42] or iodine in the presence of copper(II) acetate [94]. Iodine in the presence of sodium iodide reacts with azulene at room temperature to give a good yield of 1-iodoazulene the kinetics of this reaction are comparable to those of a reactive benzene derivative such as aniline [96]. 

The Ullmann reaction was used in the coupling of a wide variety of aryl halides, Ar-X, where the Ar includes mono-, di-, poly-substituted phenyl [4,5,14], naphthalene [4,5,15,16], azulene [17], pyridine [18], pyrimidine [19], thiophene [4,5,20], carbazole [21], and even ferrocene [22], while X = I, Br, Cl. The reaction was successfully used in the intramolecular cyclization reactions affording four- [23], five- [24], six-membered [25], and some other larger rings [6]. Selected examples where halides 10-13 were converted to biaryls 14-17 are given in the Scheme 2 [14,16,17,19]. 

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