The synthesis of 3‐substituted 5‐arylisoxazoles from oximes of α,β‐unsaturated ketones is studied. The formation of the isoxazole derivatives takes place by cyclization of oximes in the presence of iodine and potassium iodide. The presence of isoxazoline is detected. On the basis of the results a plausible mechanism is suggested.
A comparative study of reactions of 3‐methyl‐5‐phenylisoxazole and 3‐methyl‐5‐phenylisothiazole with electrophilic compounds in the presence of n‐BuLi, LICA or LICA‐TMEDA is reported. By using LICA‐TMEDA, regioselective reactions of the heterocyclic compounds at the C‐3 methyl group are obtained. With n‐BuLi or LICA and the isoxazole derivative a product mixture at the C‐4 position and the C‐3 methyl group is found. In the case of isothiazole compound, only with methyl iodide and n‐BuLi, the dialkylated product at both positions is formed.
The reactivity of 3‐methyl‐5‐phenylisothiazole with carbonyl compounds in the presence of n‐butyllithium and the system lithium isopropylcyclohexylamide‐N,N,N',N'‐tetramethylethylendiamine (LICA‐TMEDA) is studied. n‐Butyllithium is found to lead to higher yields of the hydroxy derivatives of the isothiazole compound than LICA‐TMEDA. Ring opening products are not detected under the reaction conditions used.
Synthesis of 3-Substituted 5-Arylisoxazoles from α,β-Unsaturated Oximes.-Ten examples of title compounds such as (II) are prepared by cyclization of the oximes (I) in the presence of iodine and KI. The compounds (III) are prepared analogously from α,β-unsaturated cyclic oximes. The results are used to suggest a plausible reaction mechanism. -(ALBEROLA, A.; BANEZ, J. M.; CALVO, L.; RODRIGUEZ RODRIGUEZ, M. T.; SANUDO, M. C.; J.
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