3 Imino 1 pyrazolidine

Imidazole, purification of, 48, 45 reaction with phosgene, 48, 44 Imldazole, 1,1 -carbonyldi-, 48, 44 Imidazolium chloride, 48, 46 3-Imino-l-( -tolylsulfonyl)pyrazolidine, from 3-amino-3-pyrazoline sulfate and / -toluenesulfonyl chloride, 48, 9... 

Aminopyrazole may also be obtained by hydrolysis of 3-imino-l-(/>-tolylsulfonyl)pyrazolidine with aqueous alkali. In this case the pyrazolidine (239 g., 1.00 mole) is added to a solution of 40 g. (1.0 mole) of sodium hydroxide in 250 ml. of water at 75°, the resulting solution is stirred briefly, and the water is removed at reduced pressure. 3(5)-Aminopyrazole is separated from the sodium />-toluenesulfinate by several extractions with isopropyl alcohol. 

Replacement of carbon atoms in the cyclic aliphatic side chain of proline with nitrogen leads to the azaprolines where incorporation of an additional imino group may affect molecular recognition processes via electrostatic interactions. While the proline analogues imidazoli-dine-2-carboxylic acid (3-azaproline, 15) and pyrazolidine-3-carboxylic acid (5-azaproline, 16) allow for additional side-chain modifications in peptidomimetic structures, with pyr-azolidine-2-carboxylic acid (2-azaproline, 17) (Table 2), where the a-CH is replaced by nitrogen, the peptide backbone is modified with consequently strong conformational effects. 

Pentafulven 6,6-Bis-[dimethyl-amino]-2-cyan- V/2c, 582 Piperidin 1-Phenylazo- X/3, 719 Pyrazin 2-Cyan-3,6-diisopropyl-E9b/2, 336 (Cl - CN) Pyrazolidin 3-Imino-l-(2-phenyl-ethyl)- X/2, 63... 

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... 

TABLE XLVI. Miscellaneous Bis(3,5-pyrazolidinediones), Bis(5-imino-3-pyrazolidin-ones), and Bis(4-imino-3-pyrazolidinones)... 

C, HuBrNg4A 3 -Broin-l-bantaiiiino-2-[4 iipan 9II260. C,H NA4.5-Dime b xy l8ithalons6mre-[4-bram-pheiqrlhydrazon] 16II167. C,H rN,OS 3-Oxo.4-[aniliiiotiiiaformyl imino]-5.methyl.l-[4-bnmi- enyI]-pyrazolidin 24, 273. 

---