Pyrazolidinones, hydrolysis

The susceptibility of the sydnone ring to acid-catalyzed hydrolysis at elevated temperature is exploited for the preparation of hydrazines <2000MI227>. Primary amines are first converted to sydnones, which are then hydrolyzed to give hydrazines that may be isolated or reacted further without isolation <1996CHEC-II(4)165>. As masked hydrazines, 3-arylsydnones are firstly subjected to acid-catalyzed ring opening and then allowed to react further in situ with 2-(4-chlorophenyl)hydrazono-3-oxo-butyric acid to form substituted pyrazolidinones (Equation 2) <2005SC2169>. 

J. M. Indelicato, C. E. Pasini, The Acylating Potential of y-Lactam Antibacterials Base Hydrolysis of Bicyclic Pyrazolidinones , J. Med. Chem. 1988, 31, 1227-1230. 

A complete study of the basic hydrolysis of pyrazolidinone (196) by ab initio calculations at RHF/6-31+GV/RHF/6-31-fG" and MP2/6-31-bGV/MP2/6-31- -G levels has been carried out. The alkaline hydrolysis has been studied through a Z ac2 mechanism, characterized by a nucleophilic attack of the hydroxyl group on the carbonyl of the y-lactam ring, formation of the tetrahedral intermediate, and cleavage of the C(2)-N(3) bond to yield the final reaction product. ... 

Coll M, Frau J, Munoz F, Donoso J. Ab initio study of the basic hydrolysis of the pyrazolidinone ring. J Phys Chem A 1998 102 5915-5922. 

The 5-oxo-3-pyrazolincarboxylic acids react normally. A number of their reactions have already been discussed in connection with the synthesis of analogous aldehydes and ketones. The Curtius rearrangement of the azide will be discussed in more detail in the section concerning 5-imino-3-pyrazolidinones. Both the 3- and 4-carboxylic acids decarboxylate at elevated temperatures.107,108,370 Hydrolysis of 4-carboxanilides with hydrochloric acid first forms the acid which then loses carbon dioxide.826... 

Synthetic methods involving conversion of other, but similar, ring systems to 3,5-pyrazolidinediones have been reduction of 1,2-diphenyl-3,4,5-pyrazolidinetrione with tin and hydrochloric acid63 and hydrolysis of 5-imino-3-pyrazolidinones (3-amino-2-pyrazolin-5-ones) with acid.1339,1596... 

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