Isoxazole and Derivatives

Isoxazole reacts with 20% oleum at 90 °C to give a low yield of the 4-sulfonic acid (17%). The isoxazole ring is found to be rather resistant to sulfonation with the 4-position the most favoured site of attack. The action of boiling excess chlorosulfonic acid on 3- and 5-methylisoxazole gave a mixture of the 4-sulfonic acid and the 4-sulfonyl chloride, whereas 3,5-dimethylisoxazole on similar treatment afforded only the 4-sulfonic acid derivative. However, 3,5-dimethylisoxazole, by dropwise treatment with chlorosulfonic acid at 80 °C, heating at 110 °C (2 hours), followed by further heating with thionyl chloride at 60-110 °C for 2 hoins, afforded an excellent yield of the 4-sulfonyl chloride (81.7%).  

5-Phenylisoxazole 150 by prolonged heating with chlorosulfonic acid at 100 C (30 hours) yields a mixture of the m- and / -chlorosulfonyl derivatives 151 and 152 in a ratio of 2 1 in this substrate only the phenyl ring is attacked (Equation 

3-Phenyl-1,2-benzisoxazole is reported to react with 40% oleum to give a disulfonic acid of unknown structure and l,2-benzisoxazole-3-acetic acid 153 with excess chlorosulfonic acid, followed by treatment with ammonia afforded a mixture of the sulfonamides 154 and 155 (Equation 39). In this reaction, the major sulfonation occurred in the 5-position of the benzisoxazole nucleus, which is para to the electron-donating hetero oxygen atom leading to the formation of the disulfonamide 155. 

---

With 0 heterocyclic ligands With isoxazole and derivatives Ni(C3H3NO)2(SCN-)2 0.5 H2O ==) 298 2.90 Gouy octahedral coordination suggested probably polymeric, bridging thiocyanate groups 74C25... 

---