Azulenes, sulphonation

Aerial oxidation of this affords anthraquinone in 37% yield. Both 1-naphthyl and 2,4-dimethylbenzene sulphonates follow the same path but yield only traces of the corresponding quinone. In the last case, 2,4-dimethylbenzenesulphonate, the quinone is accompanied by 0.8% of 2,4-dimethylphenol. The second path involves loss of sulphur trioxide to yield aryl radicals which afford the products, the arene and/or the biaryl, shown in Scheme 17212,213. Other studies have shown that anthraquinone-1-sulphonic acid (256)214,215 and anthraquinone-2-sulphonate216 are also photochemically labile. A study of the photochemical reactivity of azulene sulphonic acids has also been reported217. Photochromism has been studied with respect to the stilbene derivative 257218. 

When azulene is heated with sulphuric acid and acetic anhydride a sulphonic acid, soluble in water, is formed. This acid forms a fine violet sodium salt. This sodium salt is not very stable when kept for three months it decomposes into a mixture of oil and resin. Its aqueous solution gives blue precipitates with calcium and barium salts. 

Synthesis of sodium 6-isopropyl-3-[4-(p-chlorobenzenesulphonylamino)butyl]-[2-14C] azulene-1-sulphonate... 

Sulphur.—Desulphurizations. Pyrolyses of cyclic bis-sulphones can be used to obtain large-ring cyclophanes (e.g. Scheme 24)/ Sulpholenes undergo pyrolysis or LiAlH4-promoted SO2 elimination to give dienes, and this approach has been used in the synthesis of azulenes. A related reaction gives Dewar-benzene derivatives. ... 

Hono-sulphonation of azulene has been achieved by using sulphur trioxide in dioxan [105,106]. 

Methane- and benzene-sulphinyl chlorides react with azulene to give - ulphoxides [107], Methanesulphonyl chloride, but not benzcnesulphonyl chloride, gives a -sulphone [107], Sulphur di-diloride reacts with azulene to give a bis( 1-azulcnyl) sulphide [ 108]. 

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