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Synlett 2007(11): 1767-1770  
DOI: 10.1055/s-2007-984501
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© Georg Thieme Verlag Stuttgart · New York

Gold-Catalyzed Intermolecular Hydroamination of Allenes: First Example of the Use of an Aliphatic Amine in Hydroamination

Naoko Nishina, Yoshinori Yamamoto*
Department of Chemistry, Faculty of Science, Tohoku University, Sendai 980-8578, Japan
Fax: +81(22)7956784; e-Mail: yoshi@mail.tains.tohoku.ac.jp;
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Publication History

Received 1 March 2007
Publication Date:
25 June 2007 (online)

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Abstract

Treatment of allenes with morpholine in the presence of cationic gold(I) catalyst in toluene at 80 °C gave the corresponding allylic amines in good to moderate yields. To the best of our knowledge, this is the first example for carrying out the gold-catalyzed ­intermolecular hydroamination with an aliphatic amine.

Keywords

hydroamination - gold catalyst - aliphatic amine - allenes - gold-phosphine complex

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  • 14 General Procedure for Preparation of Catalysts These complexes were prepared following a literature procedure, and characterized by comparison of the NMR data with literature values, except for 4c, 4d, and 4h. A solution of SMe2 (1.2 mL, 16 mmol) in MeOH (6 mL) was added to a solution of NaAuCl4·2H2O (2.19 g, 5.5 mmol) in MeOH (30 mL) with minimum light exposure. The white precipitate was recovered by filtration, washed (MeOH, Et2O, and pentane), and dried under vacuum. Then, [AuCl(SMe2)] was obtained in 99% yield (1.60 g) and used without further purification. 1H NMR (300 MHz, CDCl3): δ = 2.73 (s, 6 H). A solution of diphenyl(o-tolyl)phosphine (0.589 g, 2 mmol) in acetone (50 mL) was added to a solution of [AuCl(SMe2)] (0.553 g) in acetone (150 mL). The mixture was stirred for 2 h and concentrated, recrystallized from toluene, and dried under vacuum; [AuClPPh2(o-Me-C6H4)](4h) was obtained in 83% (0.83 g). See: Brandys M.-C. Jennings MC. Puddephatt RJ. J. Chem. Soc., Dalton Trans.  2000,  4601 
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8

We examined the following complexes, but all attempts resulted in failure: AuCl, AuCl3, AuBr3, AuI, Au(CO)Cl, NaAuCl4·2H2O. It is known that the hydroamination of olefins with tosylamides is accelerated by TfOH, [9] so we examined the TfOH-catalyzed (10 mol%) hydroamination of 1a with 2 in toluene at 80 °C. However, the desired product (allylic amine) was not obtained at all. The allene 1a was decomposed gradually in the presence of TfOH at 80 °C, and only 30% of 1a was recovered after 12 h. It is clear that the present hydroamination is catalyzed by the gold complexes.

13

This reaction could not be checked by TLC nor GC-MS, because of its low boiling point (ca. 80 °C). Thus, reactions were stopped at 24 h.

15

ClAuPPh2(o-MeOC6H4)(4c): 1H NMR (600 MHz, CDCl3): δ = 3.71 (3 H, s), 6.82 (1 H, ddd, J = 13.2, 7.8, 1.8 Hz), 6.97 (1 H, dd, J = 8.4, 5.1 Hz), 6.93-6.97 (1 H, m), 7.42-7.47 (4 H, m), 7.49-7.57 (7 H, m). 13C NMR (75.5 Hz, CDCl3): δ = 55.9, 111.6 [d, J(13C-31P) = 4.1 Hz], 116.4 [d, J(13C-31P) = 57.0 Hz], 121.1 [d, J(13C-31P) = 10.8 Hz], 128.4, 128.9 [d, J(13C-31P) = 11.6 Hz], 131.5 [d, J(13C-31P) = 2.5 Hz], 133.9 [d, J(13C-31P) = 1.7 Hz], 134.0 [d, J(13C-31P) = 14.9 Hz], 134.2 [d, J(13C-31P) = 7.5 Hz], 160.7 [d, J(13C-31P) = 5.0 Hz]. 31P NMR (121.5 Hz, CDCl3): δ = 25.0. IR (neat, ATR): 1584, 1572, 1473, 1459, 1435, 1278, 1247, 1101, 1011, 764, 747 cm-1. Anal. Calcd for C19H17AuClOP: C, 43.49; H, 3.27; Cl, 6.76. Found: C, 43.62; H, 3.32; Cl, 6.75. ESI-HRMS: m/z calcd for C19H17AuClOP [M + Na]: 547.0263; found: 547.0267.
ClAuPPh2(p-F3CC6H4) (4d): 1H NMR (600 MHz, CDCl3): δ = 7.48-7.60 (10 H, m), 7.64 (2 H, dd, J = 12.6, 7.8 Hz), 7.72 (2 H, dd, J = 7.8, 1.5 Hz). 13C NMR (75.5 Hz, CDCl3): δ = 121.4 [d, J(13C-31P) = 1.2 Hz], 126.0 [dq, J(13C-31P) = 11.8 Hz, J(13C-19F) = 3.7 Hz], 126.7 [q, J(13C-19F) = 81.3 Hz], 128.0, 129.5 [d, J(13C-31P) = 11.8 Hz], 132.4 [d, J(13C-31P) = 2.5 Hz], 134.2 [d, J(13C-31P) = 8.8 Hz], 134.3 [d, J(13C-31P) = 14.3 Hz]. 31P NMR (121.5 Hz, CDCl3): δ = 33.3. IR (neat, ATR): 1436, 1395, 1322, 1125, 1103, 1061, 1014, 838, 748, 708 cm-1. ESI-HRMS: m/z calcd for C19H14AuClF3P [M + Na]: 585.0031; found: 585.0032.
ClAuPPh2(o-MeC6H4) (4h): 1H NMR (600 MHz, CDCl3): δ = 2.53 (3 H, s), 6.74 (1 H, ddd, J = 12.7, 7.7, 1.2 Hz), 7.18 (1 H, dd, J = 7.5, 7.5 Hz), 7.29-7.33 (1 H, m), 7.43 (1 H, ddd, J = 7.5, 7.5, 1.4 Hz), 7.46-7.51 (4 H, m), 7.53-7.60 (6 H, m). 13C NMR (75.5 Hz, CDCl3): δ = 22.6 [d, J(13C-31P) = 12.2 Hz], 126.3 [d, J(13C-31P) = 10.0 Hz], 126.8 [d, J(13C-31P) = 60.2 Hz], 128.0 [d, J(13C-31P) = 63.8 Hz], 129.4 [d, J(13C-31P) = 12.2 Hz], 131.8 [d, J(13C-31P) = 2.2 Hz], 132.0 [d, J(13C-31P) = 9.3 Hz], 132.1 [d, J(13C-31P) = 2.2 Hz], 133.0 [d, J(13C-31P) = 8.6 Hz], 134.5 [d, J(13C-31P) = 14.3 Hz], 142.0 [d, J(13C-31P) = 12.2 Hz]. 31P NMR (121.5 Hz, CDCl3): δ = 32.1. IR (neat, ATR): 1589, 1479, 1436, 1101, 997, 804, 751, 714 cm-1. Anal. Calcd for C19H17AuClP: C, 44.86; H, 3.37; Cl, 6.97. Found: C, 45.00; H, 3.60; Cl, 6.93. ESI-HRMS: m/z calcd for C19H17AuClP [M + Na]: 531.0314; Found: 531.0314.
1H, 13C, and 31P NMR chemical shifts are reported relative to CDCl3 and 85% H3PO4.

16

General Procedure for Hydroamination of Allenes
To a suspension of [AuClPPh2(o-tolyl)] (25.4 mg, 0.05 mmol) in toluene (0.5 mL) was added morpholine (43.7 mg, 0.502 mmol). To the reaction mixture was added 4-methyl-phenylallene (1a, 79.3 mg, 0.6 mmol) and the resulting mixture was stirred at 80 °C under an Ar atmosphere. The reaction mixture was colorless and heterogeneous at the beginning, but it turned yellow to brown as the reaction progressed. After the reaction was completed (12 h), the reaction mixture was filtered through short Florisil® gel pad with EtOAc as an eluent and the resulting filtered solution was concentrated. The product was purified by column chromatography (basic silica gel, hexane-EtOAc = 100:1 to 10:1) to give 3a in 83% yield (90.8 mg).

17

(E)-4-(3-p-Tolylallyl)morpholine (3a): 1H NMR (300 MHz, CDCl3): δ = 2.31 (3 H, s), 2.40-2.59 (4 H, m), 3.12 (2 H, dd, J = 6.8, 1.3 Hz), 3.72 (4 H, dd, J = 4.7, 4.7 Hz), 6.18 (1 H, dt, J = 15.8, 6.8 Hz), 6.48 (1 H, d, J = 15.8 Hz), 7.10 (2 H, d, J = 8.1 Hz), 7.25 (2 H, d, J = 8.1 Hz). 13C NMR (75.5 Hz, CDCl3): δ = 21.2, 53.7, 61.5, 67.0, 124.9, 126.2, 129.3, 133.3, 134.0, 137.4. IR (neat): 1712, 1512, 1452, 1116, 1006, 968, 869, 809, 776 cm-1. HRMS (EI): m/z calcd for C14H19NO [M+]: 217.1462; found: 217.1464. 4-Cinnamylmorpholine (3b): 1H NMR (300 MHz, CDCl3): δ = 2.45 (4 H, dd, J = 4.6, 4.6 Hz), 3.10 (2 H, dd, J = 6.8, 1.3 Hz), 3.68 (4 H, dd, J = 4.6, 4.6 Hz), 6.19 (1 H, dt, J = 15.8, 6.8 Hz), 6.47 (1 H, d, J = 15.8 Hz), 7.11-7.38 (5 H, m). 13C NMR (75.5 Hz, CDCl3): δ = 53.7, 61.5, 66.9, 125.8, 126.3, 127.6, 128.6, 133.5, 136.7. IR (neat): 1598, 1496, 1451, 1277, 1115, 1006, 966, 868, 741 cm-1. HRMS (EI): m/z calcd for C13H17NO [M+]: 203.1305; found: 203.1308.
(E)-4-(4-Phenylbut-2-enyl)morpholine (3c): 1H NMR (300 MHz, CDCl3): δ = 2.30-2.54 (4 H, m), 2.95 (2 H, dd, J = 6.6, 0.9 Hz), 3.36 (2 H, d, J = 6.6 Hz), 3.70 (4 H, dd, J = 4.8, 4.8 Hz), 5.54 (1 H, dtt, J = 15.2, 6.6, 1.3 Hz), 5.76 (1 H, dtt, J = 15.2, 6.6, 1.3 Hz), 7.11-7.23 (3 H, m), 7.23-7.33 (2 H, m). 13C NMR (75.5 Hz, CDCl3): δ = 38.9, 53.5, 61.1, 67.0, 126.1, 127.3, 128.4, 128.5, 133.4, 140.2. IR (neat): 1603, 1495, 1453, 1116, 1003, 975, 865, 745 cm-1. HRMS (EI): m/z calcd for C14H19NO [M+]: 217.1462; found: 217.1464.
(E)-4-(Undec-2-enyl)morpholine (3d): 1H NMR (300 MHz, CDCl3): δ = 0.81 (3 H, t, J = 6.6 Hz), 1.03-1.43 (12 H, m), 1.95 (2 H, dt, J = 7.0, 6.6 Hz), 2.26-2.48 (4 H, m), 2.86 (2 H, d, J = 6.6 Hz), 3.65 (4 H, dd, J = 4.6, 4.6 Hz), 5.39 (1 H, dt, J = 15.2, 6.6 Hz), 5.54 (1 H, dt, J = 15.2, 6.6 Hz). 13C NMR (75.5 Hz, CDCl3): δ = 14.1, 22.7, 29.2, 29.2, 29.3, 29.4, 31.9, 32.3, 53.5, 61.4, 67.0, 125.6, 135.3. IR (neat): 1720, 1454, 1004, 972, 867 cm-1. HRMS (EI): m/z calcd for C15H29NO [M+]: 239.2244; found: 239.2246.
(E)-4-(3-Cyclohexylallyl)morpholine (3e): 1H NMR (300 MHz, CDCl3): δ = 0.98-1.31 (5 H, m), 1.55-1.85 (5 H, m), 1.85-2.03 (1 H, m), 2.34-2.55 (4 H, m), 2.93 (2 H, d, J = 6.8 Hz), 3.71 (4 H, dd, J = 4.7, 4.7 Hz), 5.40 (1 H, dtd, J = 15.4, 6.6, 0.9 Hz), 5.55 (1 H, dd, J = 15.4, 6.6 Hz). 13C NMR (75.5 Hz, CDCl3): δ = 26.0, 26.1, 32.9, 40.5, 53.5, 61.5, 67.0, 123.0, 141.1. IR (neat): 1718, 1449, 1118, 1005, 971, 866 cm-1. HRMS (EI): m/z calcd for C13H23NO [M+]: 209.1775; found: 209.1779.
(E)-4-(4,4-Dimethylpent-2-enyl)morpholine (3f): 1H NMR (300 MHz, CDCl3): δ = 0.94 (9 H, s), 2.27-2.44 (4 H, m), 2.87 (2 H, dd, J = 6.8, 1.0 Hz), 3.66 (4 H, dd, J = 4.7, 4.7 Hz), 5.32 (1 H, dt, J = 15.6, 6.8 Hz), 5.56 (1 H, d, J = 15.6 Hz). 13C NMR (75.5 Hz, CDCl3): δ = 29.6, 29.7, 53.5, 61.5, 67.0, 120.3, 146.2. IR (neat): 1732, 1454, 1260, 1119, 1005, 975, 868 cm-1. ESI-HRMS: m/z calcd for C11H21NO [M + H]: 184.1696; found: 184.1696.
(E)-4-(4-Phenylbut-3-en-2-yl)morpholine (3g): 1H NMR (300 MHz, CDCl3): δ = 1.24 (3 H, d, J = 6.6 Hz), 2.54 (4 H, dt, J = 4.8, 4.4 Hz), 3.00 (2 H, dq, J = 8.1, 6.6 Hz), 3.71 (4 H, dd, J = 4.4, 4.4 Hz), 6.15 (1 H, dt, J = 15.8, 8.1 Hz), 6.44 (1 H, d, J = 15.8 Hz), 7.14-7.42 (5 H, m). 13C NMR (75.5 Hz, CDCl3): δ = 17.8, 50.8, 63.1, 67.2, 126.2, 127.5, 128.6, 131.2, 132.1, 136.9. IR (neat): 1600, 1494, 1447, 1265, 1116, 963, 864, 747 cm-1. HRMS (EI): m/z calcd for C14H19NO [M+]: 217.1462; found: 217.1465.
(E)-4-(1-Phenylbut-2-enyl)morpholine (3g′): 1H NMR (300 MHz, CDCl3): δ = 1.59 (3 H, dd, J = 6.0, 1.1 Hz), 2.15-2.31 (2 H, m), 2.33-2.56 (2 H, m), 3.48 (1 H, d, J = 8.6 Hz), 3.61 (4 H, dd, J = 4.4, 4.4 Hz), 5.45 (1 H, ddd, J = 15.0, 8.6, 1.1 Hz), 5.58 (1 H, dq, J = 15.0, 6.0 Hz), 7.11-7.31 (5 H, m). 13C NMR (75.5 Hz, CDCl3): δ = 17.8, 52.0, 67.2, 74.6, 127.0, 127.7, 127.9, 128.5, 132.7, 142.3. IR (neat): 1492, 1449, 1271, 1116, 1003, 967, 875, 755 cm-1. ESI-HRMS: m/z calcd for C14H19NO [M + H]: 218.1539; found: 218.1539.
4-(3-Phenylbut-2-enyl)morpholine (3h): inseparable stereoisomeric mixture. 1H NMR (300 MHz, CDCl3): δ = 2.05 (E- and Z-3 H, s), 2.25-2.42 (Z-4 H, m), 2.44-2.60 (E-4 H, m), 2.91 (Z-2 H, d, J = 6.8 Hz), 3.17 (E-2 H, d, J = 6.8 Hz), 3.70 (Z-4 H, dd, J = 4.6, 4.6 Hz), 3.72 (E-4 H, dd, J = 4.6, 4.6 Hz), 5.55 (Z-1 H, td, J = 6.8, 1.3 Hz), 5.86 (E-1 H, td, J = 6.8, 1.3 Hz), 7.09-7.45 (E- and Z-5 H, m).
NOE Experiment for 3h: Two signals were observed by irradiation for Me peak (δ = 2.05 ppm); 0.52% for allyl-H peak of E-isomer (δ = 3.17 ppm) and 1.64% for vinyl-H peak of Z-isomer (δ = 5.55 ppm). From this experiment, we determined that the major product was E-isomer and the E:Z ratio was 5: 4.