Synthesis of 4-(5-Aryl-2-oxo-2,3-dihydro-3-furanyliden)- amino-2,3-dimethyl-5-oxo-1-phenylpyrazolines [1]

Full text of DOI:10.1023/A:1012756105415

Chemistry of Heterocyclic Compounds, Vol. 37, No. 8, 2001
LETTERS TO THE EDITOR
SYNTHESIS OF 4-(5-ARYL-2-OXO-
2,3-DIHYDRO-3-FURANYLIDEN)-
AMINO-2,3-DIMETHYL-5-OXO-
1-PHENYLPYRAZOLINES
A. E. Rubtsov and V. V. Zalesov
Keywords: 4-amino-2,3-dimethyl-1-phenyl-5-pyrazolone, acid anils, 4-aryl-2-hydroxy-4-oxo-Z-2-
butenoic acids, substituted 3-imino-2-furanones, cyclization.
In previous work, we were unable to cyclize 2-amino-4-aryl-4-oxobutenoic acids to give 2-furanone
derivatives. However, we established that 4-aryl-2-(2,3-dimethyl-5-oxo-1-phenyl-4-pyrazolinyl)amino-2-
butenoic acids 2, obtained in 70-99% yield in the reaction of 4-amino-2,3-dimethyl-1-phenyl-5-pyrazolone with
4-aryl-2-hydroxy-4-oxo-Z-2-butenoic acids 1, undergo intramolecular cyclization by the action of acetic
anhydride to give 4-(5-aryl-2-oxo-2,3-dihydro-3-furanyliden)amino-2,3-dimethyl-5-oxo-1-phenylpyrazolines 3.
Ph
N
O
O
Me
O
N
Ar
Ar
OH
OH
Me
N
H2NAnt
–H2O
Ac2O
–H2O
O
O
O
N
Ant
H
H
Ar
O
O
1a–e
3a–e
2a–e
1–3 a Ar = Ph, b Ar = 4-MeC6H4, c Ar = 4-MeOC6H4,
d Ar = 4-ClC6H4, e Ar = 4-BrC6H4
Me
Ant =
N
O
Me
N
Ph
This heterocyclization is selective in nature and the low yields of 3 are attributed not to the formation of
side-products but rather the hydrolysis of the 2-furanones to the starting acids 2 upon isolation. The presence of
the bulky heterocyclic substituent apparently facilitates the cyclization in our case.
1
The H NMR spectra of 3 lack the signals for the NH group proton in starting 2a, while the IR spectra
show a band for the lactone carbonyl at 1780-1790 cm-1 in addition to the band for the lactam carbonyl at
1660-1680 cm-1.
____________________________________________________________________________________________
A. M. Gorky Perm State University, 614600 Perm, Russia; e-mail: info@psu.ru. Translated from
Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1130-1131, August, 2001. Original article submitted
December 13, 2000.
1038
0009-3122/01/3708-1038$25.00©2001 Plenum Publishing Corporation

4-(5-Aryl-2-oxo-2,3-dihydro-3-furanyliden)amino-2,3-dimethyl-5-oxo-1-phenylpyrazolines (3a-e).
A solution of acid 2 (0.01 mol) in acetic anhydride (5 ml) was heated at 80-90°C for 1 h. After cooling, the
precipitate formed was filtered off, washed with anhydrous ether, and recrystallized from anhydrous toluene.
Yields 40-80%. Products 3 melt with decomposition. The mp of 3a 235-236°C. Found, %: C 69.8; N 11.5.
C21H17N3O3. Calculated, %: C 70.2; N 11.7. The mp of 3b 206-208°C. Found, %: C 70.6; N 11.0. C22H19N3O3.
Calculated, %: C 70.8; N 11.3. The mp of 3c 246-247°C. Found, %: C 67.5; N 10.8. C22H19N3O4. Calculated, %:
C 67.9; N 10.8. The mp of 3d 230-232°C. Found, %: C 66.5; N 11.2; Cl 9.7. C21H16ClN3O3. Calculated, %:
C 66.7; N 11.1; Cl 9.4. The mp of 3e 225-226°C. Found, %: C 59.5; N 9.9; Br 19.1. C21H16BrN3O3.
Calculated, %: C 59.7; N 10.0; Br 18.9.
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