Isoxazole ring opening

Sprio et al. reported the preparation of 6-acetylimidazo[2,l-Z)]thiazoles derivatives 57 (74JHC91). TTie synthesis involves substituted 4-(2-thiazo-lyl)aminoisoxazoles 56, which were obtained in good yield by the reaction of N-(3,5-dimethylisoxazol-4-yl) thiourea 55 with a-chloro ketones. Subsequent isoxazole ring opening led to intermediates which readily underwent cyclization by refluxing in acetic acid or ethanol/hydrochloric acid. 

Pyrazolo[l,5-a]pyrimidines are obtained via catalytic hydrogenation of the pyrazolylisoxazoles 88 with W2/Raney nickel. The reagent caused isoxazole ring opening to give the intermediate aminopyrazole derivatives,... 

Host-catalyzed isoxazole ring opening A rationally designed artificial enzyme. J. Am. Chem. Soc., 118 (12). 3027-3028. 

In many synthetic pathways, isoxazoles have been used as latent /3-ketonitrile functionalities. Reactions of 5-ribofuranosylisoxazole-4-carbaldehyde 52 with 1,2-diaminobenzenes led to Schiffs bases 53, converted to 3-cyano-l,5-benzodiazepine C-nucleosides 54 through isoxazole ring opening (Scheme 13) <2000CAR681>. 

The reactions of AI that start with isoxazole ring opening often proceed with cyclization of intermediates to give diverse heterocyclic systems. In this review, the... 

Isoxazoles 27 were converted into bis(silyloxy) butadienes 28 by ring cleavage and subsequent silylation. In the case of the 4-acetyl compound 27a, C-3 deprotonation by LDA caused the isoxazole ring-opening with formation of a P-cyanoenolate intermediate whieh was trapped with TMSCl. Under the reaction conditions, the acetyl group was changed into... 

Irradiation triethy lamine Reductive isoxazole ring opening mEtjN c... 

Sodium methoxide Isoxazole ring opening a, -EthyIene- -hydroxynitriIes... 

Kennan Whitlock HW. Host-catalyzed isoxazole ring opening a rationally designed artificial enzyme, y Hm Chem Soc. 1996 118 3027—3028. 

---