Synthesis of 3-substituted arylpyrazole-4-carboxylic acids
A method was suggested for preparing previously unknown 3-aryl-substituted pyrazole-4-carboxylic acids, involving Vilsmeier formylation of semicarbazones of 26 available mono- and disubstituted acetophenones and 2-acetylthiophene followed by oxidation of
Stobbe condensation of 3-alkyl- or aryl-4-formylpyrazoles 3a-f with diethyl succinate in the presence of potassium f-butoxide, followed by intramolecular ring closure (Ac2O-NaOAc), afforded the corresponding indazole derivatives 5a-f in 65-85% overall yield. These compounds are good starting materials for transformation to biologically active molecules, such as new pyrazole analogs of the left-hand segment of the potent natural antineoplastic agent CC-1065.
Baraldi, Pier Giovanni,Cacciari, Barbara,Spalluto, Giampiero,Romagnoli, Romeo,Braccioli, Giovanni,Zaid, Abdel Naser,De Pineda Las Infantas, Maria J.
p. 1140 - 1142
(2007/10/03)
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