Synthesis and transformations of 1-phenyl-5-hydroxy-1H-pyrazole-4-carboxylic acid

V tem diplomskem delu smo poskušali na različne načine sintetizirati 1-fenil-5-hidroksi-1H-pirazol-4-karboksilno kislino (spojina 4). Najprej smo jo poskusili sintetizirati iz etil 5-hidroksi-1-fenil-1H-pirazol-4-karboksilata (spojina 1) z encimsko in bazično hidrolizo. Za encimsko hidrolizo smo uporabili osem različnih encimov, ki pri naših pogojih niso hidrolizirali estrov. Bazično hidrolizo smo izvedli pod različnimi pogoji (čas, temperatura), vendar nam je uspelo dobiti le zmes želene spojine 4 in dekarboksiliranega produkta (spojina 5). Nato smo poskušali spojino 4 sintetizirati s hidrogenolizo iz benzil 5-hidroksi-1-fenil-1H-pirazol-4-karboksilata (spojina 3), kjer pa smo dobili le dekarboksilirano spojino 5. Ugotovili smo, da je spojina 1-fenil-5-hidroksi-1H-pirazol-4-karboksilna kislina zaradi hidroksi substituente na β-mestu zelo neobstojna in dekarboksilira tudi pri sobni temperaturi pri nevtralnem pH.In this diploma thesis we made an attempt to synthesize 1-phenyl-5-hydroxy-1H-pyrazole-4-carboxylic acid (compound 4) in different ways. Firstly, we tried to synthesize the desired compound from ethyl 5-hydroxy-1-phenyl-1H-pyrazole-4-carboxylate (compound 1) by enzymatic and basic hydrolysis. The enzymatic hydrolysis was done with eight different enzymeshowever, the hydrolysis was unsuccessful. The basic hydrolysis was done under various conditions (reaction time, temperature) but only a mixture of the compound 4 and a decarboxylated compound (compound 5) was obtained. Then we tried to synthesize the compound 4 by hydrogenolysis of benzyl 5-hydroxy-1-phenyl-1H-pyrazole-4-carboxylate (compound 3). However, only the decarboxylated compound 5 was obtained. We found out that 1-phenyl-5-hydroxy-1H-pyrazole-4-carboxylic acid is very unstable because of the hydroxy group at β position and undergoes decarboxylation also at room temperature and neutral pH