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Synlett 2003(6): 0801-0804
DOI: 10.1055/s-2003-38730
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

The Alkylation of Aminophosphanes: A New Synthesis of Iminophosphoranes

Mateo Alajarín*, Carmen López-Leonardo, Pilar Llamas-Lorente
Departamento de Química Orgánica, Facultad de Química, Universidad de Murcia, Campus de Espinardo, 30100 Murcia, Spain
Fax: +34(968)364149; e-Mail: alajarin@um.es;
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Publication History

Received 11 February 2003
Publication Date:
17 April 2003 (online)

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Abstract

Iminophosphoranes are prepared by P-alkylation of easily available N,P,P-trisubstituted aminophosphanes with reactive alkyl halides and further deprotonation.

Key words

alkyl halides - alkylation - phosphorus - ylides - iminophosphoranes

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Typical Procedure for the Synthesis of Bromides 1: To a solution of 4-tolylaminodiphenylphosphane (0.3 g, 1.03 mmol) in dry Et2O (15 mL) was added benzyl bromide (0.25 g, 1.5 mmol). The mixture was stirred for 6 h under N2 atmosphere. The appearance of a white precipitate of 1j was observed, which was filtered, washed with Et2O (5 mL) and dried under reduced pressure. An analytically pure sample was obtained by recrystallization from CH2Cl2-Et2O (white prisms). Yield (0.37 g, 77%); mp 176-178 ºC. IR (nujol): 2758, 1515, 1437, 1386, 1116, 750, 698 cm-1. 1H NMR (400 MHz, CDCl3): δ = 2.15 (s, 3 H, CH3), 4.72 (d, 2 H, 2 J HP = 16.2 Hz, CH2P), 6.84 (d, 2 H, 3 J HH = 8.2 Hz, Harom), 6.91-6.93 (m, 4 H, Harom), 7.11 (t, 2 H, 2 J HH = 7.4 Hz, Harom), 7.22 (m, 1 H, Harom), 7.51-7.56 (m, 4 H, Harom), 7.63-7.74 (m, 6 H, Harom), 10.07 (d, 1 H, 2 J HH = 8.6 Hz, NH). 13C {1H} NMR (75 MHz, CDCl3): δ = 20.60 (CH3), 34.45 (d, 1 J CP = 61.6 Hz, CH2P), 118.87 (d, 1 J CP = 95.7 Hz, q, C i ), 120.17 (d, 3 J CP = 7.1 Hz, Carom), 127.00 (d, 2 J CP = 7.4 Hz, q, Carom), 128.37 (d, 5 J CP = 4.2 Hz, Carom), 128.78 (d, 4 J CP = 3.5 Hz, Carom), 129.71 (d, 3 J CP = 12.9 Hz, C m ), 129.73 (Carom), 131.01 (d, 3 J CP = 5.7 Hz, Carom), 132.96 (q, Carom), 133.57 (d, 2 J CP = 10.1 Hz, C o ), 134.93 (d, 4 J CP = 3.0 Hz, C p ), 135.63 (d, 2 J CP = 3.8 Hz, q, Carom). 31P {1H} NMR (121 MHz, CDCl3): δ = 35.36. MS (EI): m/z (rel. intensity) = 383 (4) [M+ + 1 - Br], 382 (29) [M+ - Br], 381 (100) [M+ - HBr], 183 (46). Anal. Calcd for C26H25BrNP: C, 67.54; H, 5.45; N, 3.03. Found: C, 67.62; H, 5.62; N, 3.21.

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Typical Procedure for the Synthesis of Iminophos-phoranes 2: To a suspension of 1j (0.3 g, 0.65 mmol) in dry C6H6 (20 mL) was added Et3N (0.08 g, 0.8 mmol). The mixture was stirred for 1 h under N2 atmosphere and the precipitate of Et3N〈HBr was filtered. The solvent from the filtrate was removed under vacuum and the residue was triturated with dry Et2O (10 mL). White crystalline 2j was isolated by filtration and dried under reduced pressure. An analytically pure sample was obtained by recrystallization from CH2Cl2-Et2O (white prisms). Yield (0.24 g, 97%); mp 138-140 ºC. IR(nujol): 1506, 1438, 1329, 1109, 1026, 910, 822 cm-1. 1H NMR (400 MHz, CDCl3): δ = 2.20 (s, 3 H, CH3), 3.91 (d, 2 H, 2 J HP = 14.2 Hz, CH2P), 6.67 (d, 2 H, 3 J HH = 8.1 Hz, Harom), 6.84-6.86 (m, 4 H, Harom), 7.08-7.15 (m, 3 H, Harom), 7.37-7.44 (m, 4H, Harom), 7.49-7.53 (m, 2H, Harom), 7.62-7.67 (m, 4H, Harom). 13C {1H} NMR (CDCl3, 100 MHz): δ 20.61 (CH3), 35.71 (d, 1 J CP = 64.7 Hz, CH2P), 122.81 (d, 3 J CP = 18.0 Hz, Carom), 126.84 (d, 5 J CP = 2.1 Hz, Carom), 128.13 (d, 4 J CP = 2.6 Hz, Carom), 128.40 (q, Carom), 128.66 (d, 3 J CP = 11.5 Hz, C m ), 129.43 (Carom), 130.57 (d, 3 J CP = 5.0 Hz, Carom), 130.67 (d, 1 J CP = 90.7 Hz, q, C i ), 131.91 (br s, C p ), 132.26 (d, 2 J CP = 8.9 Hz, C o ), 134.88 (d, 2 J CP = 10.27.4 Hz, q, Carom), 148.63 (d, 2 J CP = 2.9 Hz, q, Carom). 31P {1H} NMR (161 MHz, CDCl3): δ = 7.08. MS (EI): m/z (rel. intensity) = 382 (24) [M+ + 1], 381 (79) [M+], 380 (25) [M+ - 1), 290 (100). Anal. Calcd for C26H24NP: C, 81.87; H, 6.34; N, 3.67. Found: C, 81.75; H, 6.50; N, 3.75.

12

Compound 6: Colorless prisms (from CH2Cl2-Et2O), mp 181-183 ºC. IR (nujol): 3390, 1515, 1439, 1182, 1121, 778, 721 cm- 1. 1H NMR (400 MHz, CDCl3): δ = 2.24 (s, 3 H, CH3), 3.76 (d, 2 H, 2 J HP = 13.2 Hz, CH2P), 4.18 (s, 2 H, CH2N), 6.60 (d, 2 H, 3 J HH = 8.5 Hz, Harom), 6.80 (dt, 1 H, 4 J HH = 1.7 Hz, 3 J HH = 7.7 Hz, Harom), 6.98 (d, 2 H, 3 J HH = 8.5 Hz, Harom), 7.05 (dd, 1 H, 4 J HH = 1.1 Hz, 3 J HH = 7.5 Hz, Harom), 7.16 (dt, 1 H, 4 J HH = 1.7 Hz, 3 J HH = 7.5 Hz, Harom), 7.32 (m, 1 H, Harom), 7.38-7.57 (m, 6 H, Harom), 7.62-7.74 (m, 4 H, Harom), NH proton obscured. 13C {1H} NMR (100 MHz, CDCl3): δ = 20.49 (CH3), 34.70 (d, 1 J CP = 65.8 Hz, CH2P), 47.47 (CH2N), 113.16 (Carom), 126.49 (q, Carom), 127.41 (d, J CP = 6.6 Hz, Carom), 127.42 (Carom), 128.65 (d, 3 J CP = 11.7 Hz, C m ), 129.71 (Carom), 130.15 (d, 3 J CP = 8.4 Hz, q, Carom), 130.34 (d, J CP = 2.6 Hz, Carom), 131.06 (d, J CP = 4.5 Hz, Carom), 131.37 (d, 2 J CP = 9.2 Hz, C o ), 132.02 (d, 4 J CP = 2.8 Hz, C p ), 132.24 (d, 1 J CP = 97.3 Hz, q, C i ), 138.46 (d, 2 J CP = 5.2 Hz, q, Carom), 146.22 (q, Carom). 31P {1H} NMR (161 MHz, CDCl3): δ = 30.74. Anal. Calcd for C27H26NOP: C, 78.81; H, 6.37; N, 3.40. Found: C, 78.62; H, 6.32; N, 3.23.

15

Compound 8: Colorless prisms (from CHCl3-Et2O), mp 227-229 ºC. IR (nujol): 1437, 1182, 1099, 1029, 751, 693 cm-1. 1H NMR (400 MHz, CDCl3): δ = 1.49 (s, 3 H, CH3), 3.95 (d, 2 H, 2 J HP = 13.8 Hz, CH2P), 7.37-7.42 (m, 4 H, Harom), 7.44-7.48 (m, 2 H, Harom), 7.50-7.80 (m, 4 H, Harom). 13C {1H} NMR (100 MHz, CDCl3): δ = 19.89 (CH3), 38.30 (d, 1 J CP = 50.4 Hz, CH2P), 128.52 (d, 3 J CP = 12.4 Hz, C m ), 129.18 (m, q, Carom), 131.45 (C p ), 131.68 (d, 2 J CP = 9.9 Hz, C o ), 133.34 (d, 1 J CP = 76.6 Hz, q, C i ), 137.17 (m, q, Carom). 31P {1H} NMR (161 MHz, CDCl3): δ = 38.84. MS (FAB+): m/z (rel. intensity) = 812 (45) [M+ + 1].