Synthesis of 4-Aryl-3(5)-(2-hydroxyphenyl)pyrazoles by Reaction of Isoflavones and their 4-Thio Analogues with Hydrazine Derivatives

2007 ◽  
Vol 60 (12) ◽  
pp. 905 ◽  
Author(s):  
Albert Lévai ◽  
Artur M. S. Silva ◽  
José A. S. Cavaleiro ◽  
José Elguero ◽  
Ibon Alkorta ◽  
...  

4-Aryl-3(5)-2-(hydroxyphenyl)pyrazoles have been prepared by the reaction of isoflavones and their 4-thio analogues with hydrazine hydrate and phenylhydrazine in hot pyridine. The reaction mechanism for the formation of these pyrazoles is discussed. All the new compounds have been fully characterized by NMR spectroscopy. In [D6]DMSO, a 1H NMR study allows observation of the presence of both pyrazole annular tautomers, due to the presence of intramolecular hydrogen bonds in each tautomer (OH···N and NH···O). Theoretical calculations have been carried out on tautomers and conformers of compounds 20 (3(5)-(2-hydroxy-4-methoxyphenyl)-5(3)-methyl-4-phenylpyrazole) and 21 (3(5)-(2-hydroxy-4-methoxyphenyl)-4-(2-methoxyphenyl)-5(3)-methylpyrazole), including the absolute shieldings (GIAO/B3 LYP/6–311++G**) of 21.

1992 ◽  
Vol 230 (1) ◽  
pp. 41-61 ◽  
Author(s):  
Bas R. Leeflang ◽  
Johannes F.G. Vliegenthart ◽  
Loes M.J. Kroon-Batenburg ◽  
Bouke P. van Eijck ◽  
Jan Kroon

2012 ◽  
Vol 10 (1) ◽  
pp. 241-247 ◽  
Author(s):  
Ibrahim Mamedov ◽  
Uwe Eichhoff ◽  
Abel Maharramov ◽  
Musa Bayramov ◽  
Yegana Mamedova

AbstractThe formation of hydrogen bonds and the molecular dynamics for molecules (Z)-1-(2-hydroxy-5-methyl-3-nitrophenyl)ethanone oxime and (E)-2-hydroxy-5-methylacetophenone thiosemicarbazone, (E)-4-bromoacetophenone thiosemicarbazone have been investigated in solution using NMR. The results confirm the formation of different O-H…O type intramolecular hydrogen bonds in the oxime molecule. The rotational barrier energy and energy of intramolecular hydrogen bonds have been determined.


2005 ◽  
Vol 41 (10) ◽  
pp. 1516-1521 ◽  
Author(s):  
A. V. Afonin ◽  
I. A. Ushakov ◽  
D. E. Simonenko ◽  
E. Yu. Shmidt ◽  
N. V. Zorina ◽  
...  

Author(s):  
Elena Gaggelli ◽  
Nicola Gaggelli ◽  
Antonella Maccotta ◽  
Gianni Valensin ◽  
Domenico Marini ◽  
...  

2015 ◽  
Vol 17 (23) ◽  
pp. 15226-15235 ◽  
Author(s):  
Sandeep Kumar Mishra ◽  
N. Suryaprakash

The rare examples of intramolecular hydrogen bonds (HB) of the type the N–H⋯F–C, detected in a low polarity solvent in the derivatives of hydrazides, by utilizing one and two-dimensional solution state multinuclear NMR techniques, are reported.


2012 ◽  
Vol 476-478 ◽  
pp. 1897-1900 ◽  
Author(s):  
Shu Xiao ◽  
Lin Dai ◽  
Jing He

Dissolution and homogeneous graft copolymerization of cellulose were performed in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) with L-lactide. The best synthetic condition of the cellulose-graft-poly (L-) (cellulose-g-PLLA) was that cellulose 0.6g, L-lactide 5.34g and 4-dimethylaminopyri lactide dine (DMAP) as an organic catalyst 0.69g reacted for 12 hours at 80°C. The synthesized AmimCl and cellulose graft copolymers were characterized by FT-IR, 1H-NMR, GPC, TG and WAXD. The results indicated that AmimCl dissolved cellulose directly by destroying intermolecular and intramolecular hydrogen bonds in cellulose and the grafting rate of the polymer reached 4.44, which was higher than that reported in AmimCl with Sn(oct)2 as a catalyst.


2017 ◽  
Vol 24 (2) ◽  
pp. 492-498 ◽  
Author(s):  
Eliška Procházková ◽  
Lucie Čechová ◽  
Jonas Kind ◽  
Zlatko Janeba ◽  
Christina M. Thiele ◽  
...  

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