Pyrazole Carboxylic Acid Research Articles

Synthesis and tranformations of trinitroethyl esters of pyrazoline-carboxylic acids

Trinitroethyl esters of pyrazolinecarboxylic acids were synthesized by the reaction of trinitroethyl sters of unsaturated carboxylic acids with diazomethane. The reaction is stereospecific. The trinitroethyl esters of pyrazolecarboxylic acids and N-acyl derivatives of pyrazolines were isolated during a study of the chemical properties of the compounds obtained.

The Ring Contraction of Pyridazinones to Pyrazoles. VI

In order to explore the scope of the ring contraction of pyridazinone to pyrazole, 2-phenyl-3 (2H)-pyridazinones (IIIa-f) and (IVa-e) having 4 and 5 substituents other than chlorine were prepared and examined their behavior against sodium hydroxide. Amongthem, (Ma, b) and (IVa, b, e) undergothe ring contraction to afford the corresponding pyrazole carboxylic acid, (V), (VII), and (VIII). From available data, substituent effects and mechanisms for these ring contractions were discussed.In the course of this study, an unusual displacement reaction was observed in the reaction of 2-phenyl-4-chloro-5-methylthio-3 (2H)-pyridazinone (IIIa) with sodium hydroxide and sodium ethoxide.