3-Pyrazolidinones oxidation

The oxidation of 3-pyrazolidinones to 2-pyrazolin-5-ones has been mentioned (eq. 22). The 3-pyrazolidinones are also oxidized by Feh-ling s solution1550 and cupric sulfate.581 The oxidation of l-aryl-3-pyrazolidinones to 3-pyrazolin-5-ones has been mentioned.56,888... 

Substitution in the 3-pyrazolidinone molecule occurs preferentially on one of the nitrogen atoms,"irthia ii possible, although reagents such a3 bromme may oxidize the 3-pyrazolidinone to a 2-pyrazolin-5-one, and then substitute at C-4. Alkylation of 3-pyrazolidinones with alkyl halides and alkyl sulfates and bases usually occurs at N-2,335,1029 but if substituents are present here, alkylation occurs at I1j 1.888.126i... 

Alkylation of 4-methyl-3-pyrazolidinone with butyl ethylenesulfonate gave alkylation at N-l with addition of nitrogen at the /3-position of the a,/3-unsaturated system.1209 Earlier workers have claimed that nitrosation of 3-pyrazolidinones leads to either substitution at C-4446 or oxidation to 2-pyrazolin-5-ones followed by substitution at q 4 sis, 1550 However, later workers uniformly report that nitrosation occurs at N-l (eq. 247).911-1342,1491 Treatment of 3-pyrazolidinones... 

Amino-5-imino-3-pyrazolidinones have been synthesized by reduction of the corresponding oximes.644,1339 Such amines form ureas and thioureas by reaction with potassium cyanate in acid solution and with phenyl isothiocyanate.644 4-Arylimino-5-imino-3-pyrazolidinones have been prepared by reaction of the 5-imino-3-pyrazolidinones with p-amino-A.-AT-diethylaniline in the presence of silver salts as oxidizing agents (eq. 172).244,519,1255,1538 4-Arylazo-5-imino-3-pyrazolidinones have most frequently been prepared by reaction of 5-imino-3-pyrazoli-dinones with aryldiazonium chlorides, as is usual for the preparation of similar compounds.591,594,920,1087,1255,1339,1539,1649 One such compound has been prepared by the Curtius rearrangement of the corresponding 4-arylazo azide.594... 

The azo-compound (248) rearranges thermally to the pyrazole (249). The 1-pyrazoline (250) is formed from the thioketen 5-oxide Bu Pr C=C=SO and 2-diazopropane.The allyl chloride H2C=C(COPh)CH2Cl reacts with 1,1-dimethylhydrazine to yield the pyrazolidine derivative (251). Numerous betaines (252 R, R, R = H or Me) have been prepared by the action of aromatic aldehydes on the appropriate pyrazolidinones. Treatment of diethyl acetylmalonate with 1,1-dimethylhydrazine affords the amine-imide (253). ... 

A most unusual photochemical oxidation occurred on 5-methyl-2-phenyl-3-pyrazolidinone (158) in acetone to give the spiroepoxide product (159). The structure of the epoxide (159) was confirmed by MCPBA epoxidation of the olefin (160). The oxidation of salicyl alcohol with sodium periodate... 

On irradiation in acetone solution, the pyrazolidinone (304) gives the spiro-epoxide (305), whereas its isomer (306) undergoes oxidative dimerization to (307).2 ... 

In 2004, an elegant example of nitrile oxide cycloaddition to pyrazolidinone cro-tonates catalyzed by a chiral Lewis acid was described by Sibi and coworkers [17a]. 

Sibi et al. reported that substoichiometric chiral Mg(II) complexes catalyzed regio- and enantioselective nitrile oxide cycloadditions to electron-deficient alkenes (Scheme 4.8) [6]. For an achiral template, bulky pyrazolidinone (20) was essential for high regio- and enantioselectivity in (22) and (23), while oxazolidinone crotonate and 3,5-dimethylpyrazole gave the adducts, but with poor results. In particular, mesityl nitrile oxide (21), a stable dipole, was chosen as the reagent due to steric interactions of that group with either a bulky achiral template and/or a bulky Lewis acid center. Aliphatic (t-Bu and i-Bu) nitrile oxides also provided cycloaddition... 

TABLE 7.16 Asymmetric Cycloadditions of Several Nitrile Oxides with l-Benzyl-2-crotonoyl-5,5-dimethyl-3-pyrazolidinone Catalyzed by (/ )-BINIM-Ni(ll) Complex"... 

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