The reaction of enamines with isoxazol-5-ones unsubstituted at the 4-position takes place in a manner similar to that with oxazol5-ones to give, in this case, the 4-alkenylisoxazol-5-olate salts of the appropriate amine. These salts are readily converted into the 4-alkylideneisoxazolones with hydrogen chloride. By using a mixture of ketone and base rather than the enamine, the same salts are obtained
Knoevenagel type condensation of 4-unsubstituted isoxazolinones with ketones or aldehydes followed by Michael addition of a nucleophile — hydride, cyanide, or phosphite— and exposure of the adduct to sodium nitrite/aqueous acetic acid and ferrous sulfate gives variously functionalised alkynes.
A variety of a-branched alkynes can be easily assembled by a Knoevenagel type condensation of 4-unsubstituted isoxazolin-5-ones with aldehydes or ketones, followed by conjugate addition of an organometallic reagent and nitrosative cleavage of the heterocyclic ring.
Selective Reduction of the Exocyclic Double Bond of Isoxazolones and Pyrazolones by Hantzsch 1,4-Dihydropyridine
作者:Wei Yu、Zhengang Liu、Bing Han、Qiang Liu、Wei Zhang、Li Yang、Zhong-Li Liu
DOI:10.1055/s-2005-869860
日期:——
Hantzsch 1,4-dihydropyridine (HEH) was used to realize the selective reduction of the exocyclic double bond of 4-arylmethylene- and 4-alkylidene-4H-isoxazol-5-ones and 4-arylmethylene-4H-pyrazol-5-ones.