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Synlett 2005(3): 485-486  
DOI: 10.1055/s-2005-862353
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthesis of 5-Hydroxy- and 5-Amino-1-tosyl-5-phenyl-3-(2-arylvinyl)-4,5-­dihydropyrazoles

Nina M. Kuz’menok, Tatyana A. Koval’chuk*, Alexander M. Zvonok
Department of Organic Chemistry, Belarusian State Technologycal University, 13A, Sverdlova str., Minsk, 220050, Belarus
Fax: +375(17)2276217; e-Mail: kovtatale@yahoo.com;
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Publication History

Received 28 October 2004
Publication Date:
17 January 2005 (online)

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Abstract

The reaction of β-arylacryloyloxiranes with tosylhydrazine leads to unexpected 5-hydroxysubstituted Δ2-pyrazolines. A series of 3-styryl substituted pyrazoles and 5-amino-Δ2-pyrazolines were synthesized from the 5-hydroxy-Δ2-pyrazolines. The mechanism of this process has been proposed based on current and previous results.

Key words

epoxy enones - hydrazones - rearrangements

    References

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6

Typical Procedure:
Tosylhydrazine (1.02 g, 5.5 mmol) and catalytic amount of the concentrated HCl were added to a solution of 3-aryl-1-(3-phenyloxiran-2-yl)prop-2-en-1-one (1, 5 mmol) in 20 mL THF. The reaction was carried out at r.t. for 12-18 h (control by TLC). After evaporation of the solvent in vacuo the residue was diluted with a mixture of Et2O-benzene (1:3). Further solid pyrazoline 2 was filtered off and purified by recrystallization using EtOH or benzene. The residue mixture was divided on a column and pyrazole 3 and additional pyrazolines 2 were taken.

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Selected physical and spectroscopic data.
Compound 2a: yield 77%, mp 169-172 °C (EtOH). IR (KBr): νmax = 3504 (OH), 1600 (C=N), 1364, 1168 (S=O), 960 (HC=) cm-1. 1H NMR (400 MHz, CDCl3): δ = 2.39 (3 H, s, CH3), 3.23 (1 H, d, J = 17.6 Hz, CH 2), 3.51 (1 H, d, J = 17.6 Hz, CH 2), 6.63 (1 ,H d, J = 16.4 Hz, CH=), 7.02 (1 H, d, J = 16.4 Hz, CH =), 7.23 (2 H, d, J = 8.3 Hz, C6H4), 7.29-7.50 (10 H, m, arom.), 7.69 (2 H, d, J = 8.3 Hz, C6H4). MS: m/z (%) = 418 (5.4) [M+], 91 (100).
Compound 2c: yield 83%, mp 98-100 °C (C6H6). 1H NMR (400 MHz, CDCl3): δ = 2.39 (3 H, s, CH3), 3.21 (1 H, d, J = 17.6 Hz, CH 2), 3.49 (1 H, d, J = 17.6 Hz, CH 2), 6.55 (1 H, d, J = 16.4 Hz, CH =), 7.00 (1 H, d, J = 16.4 Hz, CH=), 7.22 (2 H, d, J = 8.3 Hz, C6H4), 7.25 (5 H, m, C6H5), 7.32-7.50 (4 H, m, C6H4), 7.68 (2 H, d, J = 8.3 Hz, C6H4). 13C NMR (125.77 MHz, CDCl3): δ = 21.61 (CH3), 50.50 (CH2), 97.82 (C-OH), 121.91 (CH=), 125.02 (CH=), 125.05, 126.90, 127.96, 128.33, 128.59, 128.94, 129.38, 130.08, 135.15, 137.6, 142.8 (arom.),153.02 (C-3).
Compound 3a: yield 12%, mp 122-124 °C (EtOH). IR (KBr): νmax = 1383, 1176 (S=O), 970 (HC=) cm-1. 1H NMR (400 MHz, CDCl3): δ = 2.37 (3 H, s, CH 3), 6.53 (1 H, s, 4-H), 7.08 (1 H, d, J = 16.6 Hz, CH=), 7.16 (1 H, d, J = 16.6 Hz, CH =), 7.20 (2 H, d, J = 8.2 Hz, arom.), 7.27-7.52 (10 H, m, arom.), 7.56 (2 H, d, J = 8.2 Hz, C6H4).
Compound 4i: yield 79%, mp 190-192 °C (MeOH). IR (KBr): νmax = 3385 (NH), 2928, 2856 (CH), 1344, 1160 (S=O) cm-1. 1H NMR (400 MHz, CDCl3): δ = 1.20-2.25 (10 H, m, C6H11), 2.38 (3 H, s, CH3), 2.81 (1 H, m, C6H11), 3.17 (1 H, d, J = 18.0 Hz, CH2), 3.56 (1 H, d, J = 18.0 Hz, CH2), 6.60 (1 H, d, J = 16.4 Hz, CH=), 7.10 (1 H, d, J = 16.4 Hz, CH=), 7.12-7.45 (14 H, m, arom.).

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Amine (propyl-, cyclohexyl- or benzylamines) (1 mmol) was added to the colorless solution of the pyrazoline 2 (1 mmol) in 10 mL THF or MeOH (the color of the solution becomes brightly orange). Reaction mixture was left at r.t. for 12 h. After evaporation of the solvent in vacuo, the residue was diluted with a mixture of CHCl3-MeOH. Further solid 5-aminopyrazoline 4 was filtered off or taken as an oil.

13

Pyrazoline 2 (1 mmol) was dissolved in 10 mL THF with catalytic amount of the concentrated HCl and left at 50 °C for 6 h. After solvent evaporation in vacuo, the oil was diluted with Et2O from which pyrazole 3 was crystallized.