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Synlett 2009(8): 1326-1330  
DOI: 10.1055/s-0028-1088135
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

ZnO Nanoparticles as an Efficient Catalyst for the One-Pot Synthesis of α-Amino Phosphonates

Mohammad Zaman Kassaee*, Farnaz Movahedi, Hassan Masrouri
Department of Chemistry, Tarbiat Modares University, P. O. Box 14155-4838, Tehran, Iran
Fax: +98(21)8006544; e-Mail: kassaeem@modares.ac.ir;
Further Information

Publication History

Received 21 December 2008
Publication Date:
08 April 2009 (online)

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Abstract

Zinc oxide nanoparticles (ZnO NPs, ca. 22 nm) were used as an effective catalyst in the solvent-free, three-component couplings of aldehydes, aromatic amines and dialkyl phosphites at room temperature to produce various α-amino phosphonates. Compared to known methods, satisfactory results were obtained with high yields through a simple experimental procedure. The catalyst was recycled and reused five times with minor decrease in its catalytic activity.

Key words

ZnO nanoparticles - α-amino phosphonates - hetero­geneous catalyst - solvent-free - three-component reaction

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General Procedure for the Synthesis of α-Amino Phosphonate Derivatives: ZnO nanoparticles (20% mol) were added to a mixture of aldehyde (1 mmol), amine (1 mmol) and dialkyl phosphite (1 mmol), at r.t., followed
by 8-18 h of stirring. The progress of the reaction was monitored by TLC (eluent: EtOAc-n-hexane, 30:70). After the reaction completion, CH2Cl2 (10 mL) was added to the reaction mixture and the mixture was centrifuged at 2000-3000 rpm, at 10 ˚C for 5 min to remove the catalyst. Evaporation of the reaction solvent, followed by column chromatography, afforded the pure α-amino phosphonates. Spectral data for selected products, 4b: white solid; mp 89-90 ˚C. ¹H NMR (500 MHz, CDCl3): δ = 1.14 (t, ³ J = 7.0 Hz, 3 H), 1.29 (t, ³ J = 7.1 Hz, 3 H), 3.66-3.68 (m, 1 H), 3.90-3.93 (m, 1 H), 4.11-4.12 (m, 2 H), 4.79 (d, ² J HP = 24.3 Hz, 1 H), 4.81 (br, 1 H), 6.58-6.67 (m, 3 H), 7.07-7.08 (m, 2 H), 7.29-7.31 (m, 3 H), 7.45-7.46 (m, 2 H). ¹³C NMR (125 MHz, CDCl3): δ = 16.12 (d, ³ J PC = 5.6 Hz, Me), 16.26 (d, ³ J PC = 5.7 Hz, Me), 56.71 (d, ¹ J PC = 151.3 Hz, CH), 63.21 (d, ² J PC = 7.0 Hz, OCH2), 63.97 (d, ² J PC = 6.9 Hz, OCH2), 114.28 (CH), 117.27 (CH), 127.34 (d, ³ J PC = 5.6 Hz, CH), 128.51 (d, 4 J PC = 2.9 Hz, CH), 128.84 (CH), 130.04 (CH), 134.11 (C), 146.73 (d, ³ J PC = 14.3 Hz, C). 4d: white solid; mp 59-60 ˚C. ¹H NMR (500 MHz, CDCl3): δ = 1.15 (t, ³ J = 6.9 Hz, 3 H), 1.28 (t, ³ J = 7.0 Hz, 3 H), 3.71-3.74 (m, 1 H), 3.79-3.83 (m, 1 H), 4.06-4.10 (m, 2 H), 4.79 (d, ² J HP = 24.3 Hz, 1 H), 4.88 (br, 1 H), 6.49 (d, ³ J = 7.6 Hz, 2 H), 6.73 (t, ³ J = 7.2 Hz, 1 H), 7.07 (t, ³ J = 7.4 Hz, 2 H), 7.33 (dd, ³ J = 2.3, 8.0 Hz, 2 H), 7.43 (d, ³ J = 8.0 Hz, 2 H). ¹³C NMR (125 MHz, CDCl3): δ = 16.44 (d, ³ J PC = 5.5 Hz, Me), 16.61 (d, ³ J PC = 5.6 Hz, Me), 63.05 (d, ² J PC = 7.1 Hz, OCH2), 63.27 (d, ² J PC = 6.9 Hz, OCH2), 63.65 (d, ¹ J PC = 151.1 Hz, CH), 116.09 (CH), 116.89 (CH), 128.27 (d, 4 J PC = 2.6 Hz, CH), 128.46 (CH), 130.63 (C), 131.03 (d, ³ J PC = 5.9 Hz, CH), 135.43 (C), 147.29 (d, ³ J PC = 14.3 Hz, C). 4h: white solid; mp 60 ˚C. ¹H NMR (500 MHz, CDCl3): δ = 1.13 (t, ³ J = 7.0 Hz, 3 H), 1.28 (t, ³ J = 7.0 Hz, 3 H), 2.30 (s, 3 H), 3.68-3.70 (m, 1 H), 3.92-3.94 (m, 1 H), 4.08-4.13 (m, 2 H), 4.73 (d, ² J HP = 24.1 Hz, 1 H), 4.96 (br, 1 H), 6.69 (d, ³ J = 7.5 Hz, 2 H), 6.65-6.69 (m, 1 H), 7.07-7.13 (m, 4 H), 7.31-7.34 (m, 2 H). ¹³C NMR (125 MHz, CDCl3): δ = 16.45 (d, ³ J PC = 5.5 Hz, Me), 16.63 (d, ³ J PC = 5.6 Hz, Me), 20.79 (Me), 58.65 (d, ¹ J PC = 151.7 Hz, CH), 63.43 (d, ² J PC = 7.0 Hz, OCH2), 63.97 (d, ² J PC = 6.9 Hz, OCH2), 115.08 (CH), 118.19 (CH), 128.04 (d, 4 J PC = 2.9 Hz, CH), 128.93 (d, ³ J PC = 5.7 Hz, CH), 128.84 (CH), 132.52 (C), 137.36 (C), 146.73 (d, ³ J PC = 14.1 Hz, C). 4q: white solid; mp 117-119 ˚C. ¹H NMR (500 MHz, CDCl3): δ = 1.11 (t, J = 7.0 Hz, 3 H), 1.25 (t, J = 7.0 Hz, 3 H), 3.41 (s, 3 H), 3.43 (s, 3 H), 3.59-3.64 (m, 1 H), 3.81-3.85 (m, 1 H), 4.00-4.08 (m, 2 H), 4.61 (d, ² J HP = 24.4 Hz, 1 H), 4.78 (br, 1 H), 6.50 (d, ³ J = 7.6 Hz, 2 H), 6.63 (d, ³ J = 7.2 Hz, 2 H), 6.91 (d, ³ J = 8.4 Hz, 2 H), 7.23 (d, ³ J = 8.5 Hz, 2 H). 4r: white solid; mp 106-108 ˚C. ¹H NMR (500 MHz, CDCl3): δ = 1.12 (t,
J = 7.1 Hz, 3 H), 1.21 (t, J = 7.1 Hz, 3 H), 3.53 (s, 3 H), 3.52-3.54 (m, 1 H), 3.58-3.69 (m, 1 H), 3.88-3.93 (m, 2 H), 4.45 (d, ² J HP = 23.9 Hz, 1 H), 4.65 (br, 1 H), 6.26 (d, ³ J = 8.4 Hz, 2 H), 6.64 (d, ³ J = 8.3 Hz, 2 H), 6.91 (d, ³ J = 8.6 Hz, 2 H), 7.11 (d, ³ J = 8.6 Hz, 2 H).