ChemInform Abstract: Novel Methods for the Synthesis of 4‐(Azol‐5‐yl)isoxazoles.

Abstract

Novel Methods for the Synthesis of 4-(Azol-5-yl)isoxazoles. -Three title compounds of type (V) are prepared by the [3 + 2] cycloaddition reaction of enamines (III) and nitrile oxides generated in situ from hydroxamoyl chlorides. -(BAKULEV*, V. A.; EFIMOV, I. V.; BELYAEV, N. A.; ZHIDOVINOV, S. S.; ROZIN, Y. A.; VOLKOVA, N. N.; KHABAROVA, A. A.; EL'TSOV, O. S.; Chem. Heterocycl.

Synthesis of 4‐Hetarylisoxazoles from Amino Acid‐Derived Halogenoximes and Push‐Pull Enamines

“…The starting chloroximes 5 – 9 [both ( R )‐ and ( S )‐isomers were used in the case of chiral compounds] and enamines 10 – 18 were prepared according to the known procedures. Existing literature protocols for the [3+2] cycloaddition of halogenoximes and “push‐pull“ enamines varied in the reaction conditions, including AcOH in dioxane–H 2 O, neat Et 3 N, NaHCO 3 in EtOAc,, , and no promoter in dioxane , . In this work, we have used the conditions described in our previous works for similar transformations of the chloroximes 5 – 9 , , .…”

“…The known methods for the synthesis of 4‐(het)arylisoxazoles include palladium‐catalyzed C–C couplings,, , various heterocyclizations and recyclizations, diazotative deamination of the corresponding 5‐aminoisoxazoles, and formal [3+2] cycloaddition of alkynes, electron‐deficient enamines or their synthetic equivalents with halogenoximes , . The latter approach can be considered as the most convenient since generally, the target products are obtained in good yields with high regioselectivity.…”