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Domino one-pot multicomponent synthesis of 3,5-disubstituted isoxazoles; 3-(4-Methoxyphenyl)-5-phenylisoxazole

SyntheticPage 728
DOI: 10.1039/SP728
Submitted Mar 15, 2014, published Mar 24, 2014
Rammohan R. Yadav (rammohanryadav@gmail.com), Sandip Bharate (sbharate@iiim.ac.in), Anil Padala (anil.p.iiim@gmail.com)
A contribution from Bharate Group, CSIR-IIIM


			Reaction Scheme: <img src="/images/empty.gif" alt="" /><img src="/images/empty.gif" alt="" /><img src="/images/empty.gif" alt="" />Domino one-pot multicomponent synthesis of 3,5-disubstituted isoxazoles<img src="/images/empty.gif" alt="" /><img src="/images/empty.gif" alt="" /><img src="/images/empty.gif" alt="" />

Chemicals Used

p-Anisaldehyde (Sigma Aldrich), 98%, A88107
Hydroxylamine hydrochloride (SD Fine Chemicals Ltd)
Sodium hydroxide (SD Fine Chemicals Ltd)
N-Chlorosuccinimide (Sigma Aldrich), 98%, 109681
Phenyl acetylene (Sigma Aldrich), 98%, 117706
Clay-Cu(II) catalyst (preparation provided below)
Sodium azide (Sigma Aldrich), ReagentPlus, ≥99.5%, S2002

Procedure

Preparation of Clay-Cu(II) catalyst:  To the solution of copper(II) chloride (0.1 g, 10% w/w) in 100 ml of water was added montmorillonite KSF (1 g). The resulting mixture was stirred for 15 h at room temperature. Mixture was then filtered, followed by washing with distilled water (several times) to remove chlorides. The cake so formed was dried, kept overnight in hot-air oven at 110 °C and then powdered and calcined at 425 °C for 3 h to get clay-Cu(II) catalyst (1.046 g). This catalyst was used in the experiment without further activation. (For details, see; Bharate, S. B.; Padala, A.; Dar, B. A.; Yadav, R. R.; Singh, B.; Vishwakarma, R. A. Tetrahedron Lett. 2013, 54, 3558-3561. http://dx.doi.org/10.1016/j.tetlet.2013.04.102).
Synthesis of 3-(4-methoxyphenyl)-5-phenylisoxazole: The aqueous solution of p-anisaldehyde (100 mg, 1 mmol) and hydroxylamine hydrochloride (61 mg, 1.2 mmol) was stirred at room temperature for 30 minutes. After complete conversion of aldehyde to oxime (monitored by TLC), N-chlorosuccinimide (127 mg, 1.3 mmol) was added to the reaction mixture and was allowed to stir for 3 hours. The clay-Cu(II)/NaN3 mixture [prepared by stirring 15 mol% clay-Cu catalyst (15 mg) and 7.5 mol% NaN3 (4 mg) in water (3 ml) until the color changes from brown to black] and phenyl acetylene (104 µl, 1.3 mmol) was added and the reaction mixture was further stirred for another 3 hours. After completion of reaction, the reaction mixture was filtered through filter paper, and residue was washed with EtOAc. Organic layer was dried over anhydrous sodium sulfate and concentrated in vacuo. The crude product was purified by silica gel (mesh 100-200) column chromatography using EtOAc: hexane as eluting solvent to get 3-(4-methoxyphenyl)-5-phenylisoxazole (71 mg, 55% yield). The product was characterized by comparison of NMR data with literature values (Himo, F.; Lovell, T.; Hilgraf, R.; Rostovtsev, V. V.; Noodleman, L.; Sharpless, K. B.; Fokin, V. V.  J. Am. Chem. Soc. 2005, 127, 210-216. http://dx.doi.org/10.1021/ja0471525)

Author's Comments

In this domino one-pot MCR protocol, the key reaction intermediate nitrile oxide is obtained directly from oxime and thus the isolation and handling of potentially harmful and unstable hydroximoyl chloride is avoided.

Data

3-(4-methoxyphenyl)-5-phenylisoxazole: White solid; m.p. 121-123 °C; Rf (5% EtOAc: n-hexane): 0.2;
1H NMR (CDCl3, 400 MHz) δ ppm: 7.85-7.80 (m, 4H), 7.51-7.45 (m, 3H), 7.00 (d, J = 8.0 Hz, 2H), 6.78 (s, 1H), 3.87 (s, 3H);
13C NMR (CDCl3, 125 MHz) δ ppm: 170.16, 162.61, 161.01, 130.18, 129.02, 128.23, 127.55, 125.84, 121.62, 114.33, 97.29, 55.40;
IR (neat)): 3400, 3115, 2921, 2851, 1613, 1570, 1529, 1494, 1447, 1430, 1299, 1253, 1178, 1116, 1073, 1032 cm-1;
ESI-MS: m/z 252.00 [M+H]+. 


Lead Reference

Bharate, S. B.; Padala, A.; Dar, B. A.; Yadav, R. R.; Singh, B.; Vishwakarma, R. A. Montmorrillonite clay Cu(II) catalyzed domino one-pot multicomponent synthesis of 3,5-disubstituted isoxazoles. Tetrahedron Lett2013543558-3561. http://dx.doi.org/10.1016/j.tetlet.2013.04.102

Other References

Supplementary Information

1H NMR Scan (1H NMR_3-(4-Methoxyphenyl)-5-phenylisoxazole.doc)
13C NMR Scan (13C NMR_3-(4-Methoxyphenyl)-5-phenylisoxazole.doc)

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Keywords: 1, 3-dipolar cycloaddition, aldehydes, heterocyclic compounds, heterogeneous, isoxazoles, Montmorillonite clay, multicomponent

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