3-Amino-3 pyrazoline, reaction with

Ketene dithioacetal 130 reacts with 3-amino-2-pyrazolin-5-one 129 to give the highly functionalized pyrazolopyridine 131, which is converted into the bispyrazolopyridine 132 by reaction with hydrazine hydrate (Scheme 9) <1997JCM256>. 

Arenes, polyalkyl, oxidation with per-oxytrifluoroacetic acid and boron trifluoride, 48, 89, 90 Arenesulfonyl chlorides, reaction with 3-amino-3-pyrazoline, 48, 11 Aromatic aldehydes. Mesitalde-HYDE, 47, 1... 

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... 

The amino group of 4-amino-3-pyrazolin-5-ones reacts normally. Acylation occurs readily with a wide variety of acylating agents. Amides are formed by reaction with acid chlorides,50,533,984,1414,1473 acids618,984,1471 and esters in the presence of phosphorus pentoxide.1471 Thioformamides have been prepared by reaction with dithioformic acid and its salts.472,556,1374 Sulfonyl chlorides react to form sulfonamides.98,489,984,1249,1504 Chlorophosphates react with 4-amino-3-pyrazolin-5-ones to form phosphoramide derivatives.509,1498... 

The reaction of 2-amino-4-methyl-l,l,l-trifluoromethyl-2-butene-4-one with thiosemicarbazide forms 5-hydroxy-5-trifluoromethyl-2-pyrazoline, and with derivatives 3-amine-1,2,4-triazoles forms derivatives triazolo[l,5-a]pyrimidine (02IZV332) (Scheme 75). 

Pyrazoles such as 2.159 are formed by a [3+2]-cycloaddition reaction of an alkene with a diazoalkane7 Basic hydrolysis of such pyrazolines leads to an amino acid. Reaction of 2.159 with aqueous sodium hydroxide, for example, gave 2-methyl-3-aminopropanoic acid 2.160) Similarly, 2-methyl-3-aminobutanoic acid was prepared in 52% yield 2-ethyl-3-aminopropanoic acid in 81% yield and, 2-methyl-3-aminopentanoic acid in 52% yield, all from the appropriate pyrazoline. ... 

Zhao and coworkers reported the use of 2-pyrazolin-5-ones as suitable nitrogen nucleophiles for the Michael reaction with enones [108]. In this report the use of 32 mol% of 9-epi-9-amino-9-deoxyquinine and 40mol% of benzoic add was necessary to obtain high yields and enantioselectivities. 

A mechanism has been proposed to rationalize the results shown in Figure 23. The relative proportion of the A -pyrazolines obtained by the reduction of pyrazolium salts depends on steric and electronic effects. When all the substituents are alkyl groups, the hydride ion attacks the less hindered carbon atom for example when = Bu only C-5 is attacked. The smaller deuterohydride ion is less sensitive to steric effects and consequently the reaction is less selective (73BSF288). Phenyl substituents, both on the nitrogen atom and on the carbon atoms, direct the hydride attack selectively to one carbon atom and the isolated A -pyrazoline has the C—C double bond conjugated with the phenyl (328 R or R = Ph). Open-chain compounds are always formed during the reduction of pyrazolium salts, becoming predominant in the reduction of amino substituted pyrazoliums. 

The reaction of 3-amino-2-pyrazolin-5-one with diketene afforded 2-hy-droxy-7-methyl-1,2-dihydropyrazolo[ 1,5-a]pyrimidine-5-one (49US2481466) (Scheme 1). 

Amino polystyrene pyrazolone linker resin 58 provided various amide products 59 with a high conversion rate and good purity under mild conditions the resin linker was stable under the reaction conditions, resistant to hydrolysis, and reused repeatedly without loss of activity <03TL8063>. The preparation of pyrazoline derivatives 61 was accomplished with traceless solid-phase sulfone linker 60 with phenylhydrazine <030L1067>. Aniline cellulose-bound enaminones 62 reacted with phenylhydrazine under microwave irradiation to produce pyrazolocarboxylic acid derivatives 63 in high yields <03JCO465>. 

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