Diaryl azines, chlorosulfonation

Several diaryl azines have been successfully chlorosulfonated by reaction with a large excess of chlorosulfonic acid under forcing conditions. For instance, benzaldehyde azine 435 reacted with the reagent (12 equivalents) at 120 C (4 hours) to give the 3,3 -disulfonyl chloride 436, 39% (Equation 134). ... 

The criss-cross cycloadducts from the reaction of isocyanates and diaryl azines have been chlorosulfonated by treatment with a mixture of chlorosulfonic acid and thionyl chloride. ... 

An alternative synthetic route to these sulfonyl criss-cross cycloadducts involved performing the cycloaddition reaction using sulfonyl aryl azines obtained by chlorosulfonation of the appropriate diaryl azine as described in Chapter 4, p 119. 

Criss-cross cycloadducts may also be prepared by reaction of diaryl azines with either maleimides or maleic anhydride and these may also be chlorosulfonated by treatment with chlorosulfonic acid. The cycloadduct 76 (from the reaction of benzaldehyde azine and maleimide) reacts with chlorosulfonic acid at RT (1 week) to give the corresponding 4,4 -disulfonyl chloride 77, 70%. ... 

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