3-Pyrazolidinones alkylation

Dimethyl acetylenedicarboxylate with several pyrazolidinones (142 R1, R2, R3 = H or alkyl) gives131 the normal Michael adducts 143 and the diazepinones 144 the crystal structure was determined for one diazepinone. 

One of the syntheses mentioned there started with 3-pyrazolidinone 236, which was protected as the benzyloxycarbonyl derivative 237 in order to obtain selective N-alkylation at position 8 yielding compound 238 after removal of the protecting group. Addition of the resulting amine 238 to l-octyne-3-one 239 formed the enone 240 with the complete diazaprostanoid skeleton. Katalytic... 

Alkylation of hydrazine with a, 3-unsaturated carbonyl derivatives or carbonyl derivatives with a leaving group in the p-position provides pyrazole derivatives. For example, treatment of the tosylate (77), obtained from L-serine, with anhydrous hydrazine gives racemic pyrazolidinone (78). It appears that py-razolidinone (78) or one of the intermediates suffers base-catalyzed racemization (equation 32). Starting from P-lactam (79) seven-membered cyclic hydrazine (80) has been formed by ring closure in an unusually high (84%) yield (equation 33). Reaction of ( ir-allyl)palladium complex (81) with dimethyl-hydrazine produces exocyclic diene (82) in a modest (29%) yield, but this is still more efficient than the reaction of 2,3-bis(chloromethyl)butadiene (83) with dimethylhydrazine (equation 34). ... 

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... 

The most frequently used procedures for preparation of 5-imino-3-pyrazolidines can all be considered as variations of cyclization of malonic acid derivatives. Various hydrazines react with ethyl /3-amino-/ -ethoxyacrylate to form 2-substituted-5-imino-3-pyrazolidinones (eq. 261). Complex alkyl groups,706 aryl groups693,695,922,1140,1601 and... 

In compounds which have no substituents at N-l or N-2 nuclear acylation also occurs and under some conditions acylation occurs at C-4. The use of 2-alkyl- or aryl-5-imino-3-pyrazolidinones, which exist as the 3-amino-2-pyrazolin-5-one isomer, with an equivalent of acid chloride, either aliphatic or aryl, leads to 3-acylamides (eq. 266),14,67,594,695,1247,1594,1595 although in some cases a side-reaction gives both N- and O-acylation.1595 Under the same conditions 3-hydroxy-5-imino-2-pyrazolinones give O-acylation.1599 The reaction of... 

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