11.1 N-Arylmaleimides

N-Arylimides are generally chlorosulfonated by treatment with chlorosulfonic acid. Thus, several N-arylmaleimides have been successfully chlorosulfonated by reaction with excess chlorosulfonic acid at 10 30 C without opening the imido ring.355 N-Phenylmaleimide 396 reacted with excess reagent (six equivalents) at 45 50 C (1 hour) to give an excellent yield of the p-sulfonyl chloride 397, (83%)356 (Equation 124). 3,4-Dichloromaleimide also reacted rapidly with the reagent to give the corresponding p-sulfonyl chloride (80%).357

(124)

3-Chloro-4-phenoxy- N-phenylmaleimide 398 reacted with a large excess of chlorosulfonic acid (10 equivalents) to give a high yield (88%) of the disulfonyl chloride 399 (Equation 125).356

(125)

In this reaction sulfonation occurred, as expected, para to both the imino nitrogen atom and the oxygen atom of the phenoxy group.

N-( p-Chlorosulfonylphenyl) maleimide 397 can be employed as a dienophile in Diels-Alder reactions without affecting the chlorosulfonyl group, even when the cycloaddition required prolonged refluxing in boiling o-xylene (16 hours) as occurred with hexachlorocyclopentadiene.358

The reaction of N-( p-chlorosulfonylphenyl) maleimide 397 with amines R ¹R ²NH (two equivalents), gave the corresponding maleimidosulfonamides 400 which resulted from nucleophilic substitution by the amine at the electron deficient sulfur atom.

On the other hand, reaction of the sulfonyl chloride 397 with excess morpholine, pyrrolidine and piperidine (three equivalents) afforded a mixture of the sulfonamides 400 and 401. The succinimidosulfonamide 401 was formed by simultaneous...