Synlett 2009(7): 1167-1171  
DOI: 10.1055/s-0028-1088151
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Zirconium-Catalyzed Intermolecular Hydroamination of Unactivated Olefins

Lei Yanga, Li-Wen Xu*a,b, Wei Zhoua, Yue-Hua Gaoa, Wei Suna, Chun-Gu Xia*a
a State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, and Graduate School of the Chinese Academy of Sciences, Lanzhou 730000, P. R. of China
Fax: +86(931)8277088; e-Mail: lyang@lzb.ac.cn; e-Mail: cgxia@lzb.ac.cn;
b Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Hangzhou Normal University, Hangzhou 310012, P. R. of China
Further Information

Publication History

Received 3 November 2008
Publication Date:
26 March 2009 (online)

Abstract

Highly efficient hydroamination reactions of sulfon­amides, carboxamides, and carbamates with unactivated olefins catalyzed by simple and inexpensive zirconium salts under mild reaction conditions were presented for the practical preparation of various amines. These processes gave good to excellent yields of the addition products in Markovnikov addition fashion.

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During the preparation of our manuscript, several related papers using other metal salts dealing with the intermolecular hydroamination of styrenes have appeared in the literature, see ref. 10a-c.

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Typical Procedure for Intermolecular Addition Reactions of Olefins
Into a test tube were placed Zr(OTf)4 (0.05 mmol) and NH2Ts (1 mmol). After the test tube was sealed, it was purged three times with argon, then n-heptane (2 mL) and cyclohexene (2 mmol) were injected. The reaction mixture was heated at 85 ˚C and stirred vigorously for 20 h. After the reaction was completed, the mixture was directly applied to column chromatography using SiO2 (EtOAc-PE, 1:10 to 1:5) to afford a analytically pure product (93% isolated yield). All the compounds are known and NMR or GC-MS data for some representative products are given below.
N -(1-Phenylethyl)benzamide ¹H NMR (400 MHz, CDCl3): δ = 7.77 (d, J = 7.2 Hz, 2 H), 7.50-7.46 (t, 1 H), 7.42-7.35 (m, 6 H), 7.33-7.25 (m, 1 H), 6.44 (br, 1 H), 5.34 (dt, J = 7.2, 7.2 Hz, 1 H), 1.60 (d, J = 6.8 Hz, 3 H). ¹³C NMR (100 MHz, CDCl3): δ = 166.56, 143.08, 134.51, 131.42, 128.70, 128.50, 127.40, 126.89, 126.21, 49.17, 21.68. GC-MS: m/z = 225.
N -[1-(4-Bromophenyl)ethyl]-4-methylbenzenesulfon-amide
¹H NMR (400 MHz, CDCl3): δ = 7.57 (d, J = 8.4 Hz, 2 H), 7.27 (d, J = 8.4 Hz, 2 H,), 7.16 (d, J = 8.0 Hz, 2 H), 6.97 (d, J = 8.0 Hz, 2 H), 5.42 (d, J = 7.2 Hz, 1 H), 4.41 (quint, J = 6.8 Hz, 1 H), 2.39 (s, 3 H), 1.37 (d, J = 6.8 Hz, 3 H). ¹³C NMR (100 MHz, CDCl3): δ = 143.32, 140.00, 137.33, 131.43, 129.42, 127.92, 127.00, 121.16, 53.06, 23.35, 21.47. GC-MS: m/z = 354. Cyclohex-2-enyl- p -toluenesulfonamide
¹H NMR (400 MHz, CDCl3): δ = 7.75 (d, J = 7.6 Hz, 2 H), 7.27 (d, J = 8.0 Hz, 2 H), 5.71 (d, J = 10.0 Hz, 1 H), 5.31 (d, J = 10.4 Hz, 1 H), 4.84 (d, J = 8.4 Hz, 1 H), 3.77 (s, 1 H), 2.39 (s, 3 H), 1.94-1.77 (m, 2 H), 1.74-1.61 (m,1 H), 1.57-1.50 (m, 3 H). ¹³C NMR (100 MHz, CDCl3): δ = 143.14, 138.24, 131.39, 129.60, 126.95, 126.91, 48.89, 30.12, 24.38, 21.45, 19.22. GC-MS: m/z = 251.