Benzene, alkylation disulfonation

The manufacture of a dye from primary raw materials involves a number of prior synthetic stages and transformations, commonly referred to as unit processes. Such processes include nitration, sulfona-tion, diazotization, oxidation, reduction, chlorination, and others. The products, precursors of the dyes themselves, are collectively known as intermediates. Intermediates are produced by a variety of reactions. Many dye intermediates are manufactured by repeated, and often difficult, chemical reactions to obtain the desired product. Such conversion may be exemplified by the manufacture of a relatively simple intermediate, for example, N,-N-diabenzylaniline disulfonic acid. This conversion requires a number of unit processes, namely the nitration of benzene, the reduction of nitrobenzene, to give aniline, the alkylation of aniline leading to N,N-dibenzylaniline the sulfonation of which gives, finally, the disulfonic acid [11]. 

Inhibiting Side Reactions. As stated in a preceding section, undesired by-product sulfone formation is pronounced in the mono- and disulfonation of ai matic hydrocarbons such as benzene, toluene, or xylene with SO or strong oleum. The addition of acetic acid (about 5 per cent by weight of the hydrocarbon) inhibits, but does not eliminate, sulfone formation. Sodium sulfate and sodium benzenesulfonate are also said to inhibit sulfone formation from benzene. In sul nating dodecylbenzene detergent alkylate with SO3, sulfone formation does not occur as it does with benzene or toluene, but sulfonic anhydride formation does occur. This objection-... 

The use of dry aryldiazonium salts of naphthalene-1-sulfonic [70], naphthalene-1,5-disulfonic [70], ZnCl2 complex [70], hexafluorophosphoric or tetrafluoroboric acid [61] in non-aqueous medium under as mild as possible reaction conditions is substantial to reach higher yields of biaryls. An alternative method for non-aqueous GBH reaction is the aprotic diazotation of aromatic amines with alkyl nitrites such as butyl or pentyl nitrite with subsequent arylation of aromatic compound, as demonstrated by Cadogan [71,72]. This method is realized by simple heating the mixture of aromatic amine, alkyl nitrite and liquid arene at an elevated temperature. When a mixture of 3-aminopyridine (46), benzene and pentyl nitrite is heated at reflux, 3-phenylpyridine (47) is obtained with a 55% yield [71], Scheme 16. 

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