Transformation of 3-isoxazolecarboxylic acids into pyrazole derivatives. IV was written by Cusmano, Sigismondo. And the article was included in Gazzetta Chimica Italiana in 1940.Safety of Ethyl 1,5-diphenyl-1H-pyrazole-3-carboxylate The following contents are mentioned in the article:
cf. C. A. 34, 7903.8. The transformation of 3-isoxazolecarboxylic acids into pyrazolonimines by fusion with PhNHNH2 may proceed by decarboxylation followed by ring closure of the resulting cyano ketone phenylhydrazone. To test this hypothesis the fusion was repeated in the presence of Natur Kupfer C (I) (or ordinary reduced Cu) so that, at the lower decarboxylation temperatures it might be possible to isolate the phenylhydrazone prior to ring closure and so shed some light on the mechanism of the reaction. A mixture of 1 g. of 5-phenyl-3-isoxazolecarboxylic acid (II), 1 g. I and 1 g. PhNHNH2 in 20 cc. alc. was boiled for a few min. over a free flame, filtered, alkalinized with Na2CO3, extracted free from PhNHNH2 with ether, acidified with dilute H2SO4, and extracted with ether. The residue from the evaporated extract gave 1,5-diphenyl-3-pyrazolecarboxylic acid (III), m. 185° (Et ester, m. 98°), decarboxylated by fusion to give 1,5-diphenylpyrazole, m. 55°, and identical with the known acid prepared by the action of PhNHNH2 on BzCH2COCO2H. A similar transformation of 5-methyl-3-isoxazolecarboxylic acid (IV) gave 1-phenyl-5-methyl-3-pyrazolecarboxylic acid, m. 136° (Me ester, m. 55°), decarboxylated to 1-phenyl-5-methylpyrazole, transformed into the known picrate, m. 98°. In these transformations alc. can be replaced by other solvents. In the absence of I or in the presence of PhNH2 instead of PhNHNH2 the isoxazolecarboxylic acid is recovered unchanged. This study involved multiple reactions and reactants, such as Ethyl 1,5-diphenyl-1H-pyrazole-3-carboxylate (cas: 17355-75-8Safety of Ethyl 1,5-diphenyl-1H-pyrazole-3-carboxylate).
Ethyl 1,5-diphenyl-1H-pyrazole-3-carboxylate (cas: 17355-75-8) belongs to pyrazole derivatives. The strategies for the synthesis of pyrazoles generally can be applied for the construction of indazoles. Protonation of pyrazole in strong acid leads to pyrazolium cations, which undergo electrophilic substitution preferentially at C3 rather than C4. The pyrazole anion is not reactive toward nucleophiles but is mostly reactive to electrophiles.Safety of Ethyl 1,5-diphenyl-1H-pyrazole-3-carboxylate
Referemce:
Pyrazole – Wikipedia,
Pyrazoles – an overview | ScienceDirect Topics