Pyrazole-4-carboxylic acids

Another possibility is observed upon cyclization of hydrazides of pyrazole-carboxylic acids in the presence of CuCl in an inert atmosphere in DMF. When acetylenylcarboxylic acids are heated in the presence of CuCl in DMF, the orientation of the cycloaddition of the hydrazide group differs from that observed for cyclization in basic conditions. The cycloisomerization of hydrazides 78 in boiling DMF leads to the corresponding pyrazolopyridazines 79 in 60-71 % yields (Scheme 134 Table XXIX) (85IZV1367 85MI2). 

Preparation of one of the analogues in which benzene is replaced by pyrazole starts by nitration of pyrazole carboxylic acid The product, is then converted to... 

On the other hand, imidazoquinoxalines 94 or pyrazoloquinoxalines 95 have been built starting from orf/ o-fluoroanilines 91 and imidazol- or pyrazol-carboxylic acids 92 and 93. Interestingly, the presence of an electron-withdrawing group as the substituent is not needed in most entries was just hydrogen. Cyclization by... 

A study of the pA s of a series of l-phenylthieno[2,3-c]pyrazole-carboxylic acids with different 3-substituents (479) showed that substituent effects in bicyclic type A systems are transmitted less strongly (p — 1.17) than in the corresponding benzolb thiophenes (p = 2.5).94... 

For solid-phase synthesis various linker molecules were constructed on the ULTRA resin 15. To determine the optimal spacer length, ULTRA resins were coupled with spacers of variable length. With 4-(4 -acetoxy-methyl-3 -methoxy-phenoxy) butyrate and a loading of 2.5 mmol/g the synthesis of heterocycles and peptides was investigated. A pyrazole carboxylic acid was prepared using a procedure established for Wang polystyrene... 

The catalytic activity of Ag/Pd bimetallic nanoparticles immobilized on quartz surfaces was tested for 4-nitro-3-pyrazole carboxylic acid with help from surface plasmon resonance, scanning electron microscopy, and surface-enhanced Raman scattering (SERS) measurements [1417], The SERS spectra showed that the nitro group reduces to amino group. 

Solid-phase synthesis of substituted pyrazolones 550 from polymer-bound /3-keto esters 549 has been described (Scheme 68) <2001EJ01631>. Trisubstituted pyrazole carboxylic acids were prepared by reaction of polymer-bound arylidene- or alkylidene-/3-oxo esters with phenylhydrazines <1999S1961>. 2-(Pyrazol-l-yl)pyrimi-dine derivatives were prepared by cyclocondensation of ethyl acetoacetate and (6-methyl-4-oxo-3,4-dihydropyrimi-din-2-yl)hydrazine with aromatic aldehydes <2004RJC423>. Reactions of acylated diethyl malonates with hydrazine monohydrochloride in ethanol afforded 3,4-disubstituted-pyrazolin-5-ones <2002T3639>. Reactions of hydrazines with A -acetoacetyl derivatives of (45 )-4-benzyloxazolidin-2-one (Evans oxazolidinone) and (2R)-bornane-10,2-sultam (Oppolzer sultam) in very acidic media gave pyrazoles retaining the 3(5)-chiral moiety <1999S157>. 

HIF-la prolyl hydroxylase (EGLN-1) The X-ray analysis of EGLN-1 in complex with an isoquinoline derivative inspired the design of a series of pyridine carboxyamide derivatives which could then be further improved by replacing the flexible carboxyamide substituent with a constrained isostere, pyrazole carboxylic acid. 139 ... 

This index was applied in a structure-activity studies on anti-inflammatory activity of pyrazole carboxylic acid hydrazide analogs. It was demonstrated that, despite the overall classification accuracy was above 80%, this descriptor did not perform better than the popular valence... 

Goel, A. and Madan, A.K. (1995) Structure-activity study on antiinflammatory pyrazole carboxylic acid hydrazide analogs using molecular connectivity indices./. Chem. Inf. Comput. Sci., 35, 510-514. 

Based on the high levels of activity obtained for DIO, a series of N-pyridyl analogs were explored. We also wished to study the effect of substituents R4 on the aryl portion of the anthranilic diamide. Figures 4-6 illustrate the routes by which these compounds were prepared [2]. The method presented in Figure 4 was used to prepare the 3-trifluoromethyl-5-pyrazolecarboxylic acid 26. This method involves regioselective lithiation of 3-trifluoromethylpyrazole 25 followed by reaction with carbon dioxide, to afford the pyrazole carboxylic acid 26 in good yield. 

---