Preparation and reactions Pyrazole

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1 preparation , reactions

1.1 history
1.2 conversion scorpionates
1.3 3,5-diphenyl-1h-pyrazole





preparation , reactions

pyrazoles synthesized reaction of α,β-unsaturated aldehydes hydrazine , subsequent dehydrogenation:





substituted pyrazoles prepared condensation of 1,3-diketones hydrazine. example, acetylacetone , hydrazine gives 3,5-dimethylpyrazole:



ch3c(o)ch2c(o)ch3   +   n2h4   →   (ch3)2c3hn2h   +   2 h2o

history

the term pyrazole given class of compounds german chemist ludwig knorr in 1883. in classical method developed german chemist hans von pechmann in 1898, pyrazole synthesized acetylene , diazomethane.


conversion scorpionates

pyrazoles react potassium borohydride form class of ligands known scorpionate. pyrazole reacts potassium borohydride @ high temperatures (~200 °c) form tridentate ligand known tp ligand:





3,5-diphenyl-1h-pyrazole

3,5-diphenyl-1h-pyrazole produced when (e)-1,3-diphenylprop-2-en-1-one reacted hydrazine hydrate in presence of elemental sulfur or sodium persulfate, or using hydrazone in case azine produced by-product.








^ schmidt, andreas; dreger, andrij (2011). recent advances in chemistry of pyrazoles. properties, biological activities, , syntheses . curr. org. chem. 15 (9): 1423–1463. doi:10.2174/138527211795378263. 
^ johnson, william s.; highet, robert j. (1963). 3,5-dimethylpyrazole . organic syntheses. ; collective volume, 4, p. 351 
^ von pechmann, hans (1898). pyrazol aus acetylen und diazomethan . berichte der deutschen chemischen gesellschaft (in german). 31 (3): 2950–2951. doi:10.1002/cber.18980310363. 
^ outirite, moha; lebrini, mounim; lagrenée, michel; bentiss, fouad (2008). new 1 step synthesis of 3,5-disubstituted pyrazoles under microwave irradiation , classical heating . journal of heterocyclic chemistry. 45 (2): 503–505. doi:10.1002/jhet.5570450231. 
^ zhang, ze; tan, ya-jun; wang, chun-shan; wu, hao-hao (2014). one-pot synthesis of 3,5-diphenyl-1h-pyrazoles chalcones , hydrazine under mechanochemical ball milling . heterocycles. 89 (1): 103–112. doi:10.3987/com-13-12867. 
^ lasri, jamal; ismail, ali i. (2017, in press). metal-free , fecl3-catalyzed synthesis of azines , 3,5-diphenyl-1h-pyrazole hydrazones and/or ketones monitored high resolution esi-ms . indian journal of chemistry b.  check date values in: |date= (help)






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