TABLE OF CONTENTS Phenylurea344 and N, N-dimethylphenylurea345 ( 380 and 381) reacted easily with hot chlorosulfonic acid (four equivalents) at 60 80 C (2 hours) to give the corresponding ureidobenzenesulfonyl chlorides 382 and 383 (Equation 120).
| (120) |  |
The conversion of phenylurea 380 into the p-ureidobenzenesulfonyl chloride 382 by the action of excess chlorosulfonic acid at 55 C was first reported by Travagli,346 although when less reagent (one equivalent) was used at 60 C a water-soluble product was formed.344 This was probably the p-sulfonic acid resulting from acid-catalysed migration of the initial N-sulfonic acid ( cf. the analogous reaction with amines see Section 9, p 98). The chlorosulfonation of 2-substituted phenylureas occurs under similar conditions: for instance, 2-chloro- and 2-methylphenylurea by heating with chlorosulfonic acid (four equivalents) at 70 80 C for 4 hours afforded the corresponding 4-sulfonyl chlorides (55% yield).347 On the other hand, chlorosulfonation of 2-methoxyphenylurea under similar conditions gave a higher yield (80%) of 4-methoxy-3-ureidobenzenesulfonyl chloride, in which the orientation of sulfonation is now controlled by the more powerful electron-donating methoxy group.348
When the substituents were in the m- or p-positions, the chlorosulfonation was more difficult and much lower yields of the sulfonyl chlorides were obtained.347 For instance, 3-methylphenylurea reacts with chlorosulfonic acid (four equivalents, 70 80 C, 4 hours) to yield only 15% of the corresponding 4-sulfonyl chloride (sulfonation p to the ureido group). With 4-methylphenylurea 384, chlorosulfonation resulted in an...
