Synlett 2008(9): 1331-1334  
DOI: 10.1055/s-2008-1072631
LETTER
© Georg Thieme Verlag Stuttgart · New York

Electrophilic Addition to 1-Cyclopropylallenes: A Highly Efficient and Stereoselective Method for the Preparation of 6-Substituted-1,3-hexadienes

Lei Yua, Bo Menga, Xian Huang*a,b
a Department of Chemistry, Zhejiang University (Campus Xixi), Hangzhou 310028, P. R. of China
Fax: +86(571)88807077; e-Mail: huangx@zju.edu.cn;
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, P. R. of China
Further Information

Publication History

Received 13 January 2008
Publication Date:
07 May 2008 (online)

Abstract

Electrophilic additions to 1-cyclopropylallenes were investigated, providing an efficient and stereoselective method for the synthesis of 6-substituted-1,3-hexadienes.

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Preparation of ( Z )-2,6-Diiodo-3-phenyl-1,3-hexadiene (11a); Typical Procedure 1-Phenyl-1-cyclopropylallene (3a, 0.3mmol) was first dissolved in CH2Cl2 (1 mL). Under a nitrogen-atmosphere protection, a solution of I2 (0.3 mmol) in CH2Cl2 (5 mL) was slowly added. The reaction proceeded very rapidly and color of I2 disappeared immediately. The reaction liquid was stirred for an extra 1 min. Then, the solvent was evaporated under vacuum and residue was separated by preparation TLC (eluent: PE) to give 11a in 85% yield. The other 2,6-diiodo-1,3-hexadienes were prepared in a similar way.

Selected Spectroscopic Data of 11a IR (film): 3055, 3024, 2956, 2923, 1602, 1444, 1235, 1171, 1104, 908, 762, 696 cm-1. 1H NMR (400 MHz, CDCl3): δ = 7.25-7.45 (m, 5 H), 6.24 (s, 1 H), 6.21 (s, 1 H), 5.83 (t, J = 7.2 Hz, 1 H), 3.26 (t, J = 7.2 Hz, 2 H), 2.86-2.91 (m, 2 H). 13C NMR (100 MHz, CDCl3): δ = 3.6, 33.4, 102.6, 126.6, 127.4, 128.1, 128.5, 130.6, 137.4, 145.8. MS (EI, 70 eV): m/z (%) = 410 (13) [M+], 283 (100). HRMS (EI): m/z calcd for C12H12I2: 409.9029; found: 409.9038.

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Spectroscopic Data of Compound 12a IR (film): 3352, 2924, 2876, 1603, 1444, 1088, 1047, 907, 763, 697cm-1. 1H NMR (400 MHz, CDCl3): δ = 7.26-7.44 (m, 5 H), 6.23 (s, 1 H), 6.21 (s, 1 H), 5.93 (t, J = 7.6 Hz, 1 H), 3.79 (t, J = 6.4 Hz, 2 H), 2.55-2.60 (m, 2 H), 1.60 (s, 1 H). 13C NMR (100 MHz, CDCl3): δ = 33.4, 61.8, 103.1, 125.3, 126.5, 127.9, 128.4, 130.6, 137.6, 146.2. MS (EI, 70 eV): m/z (%) = 300 (10) [M+], 173 (44), 141 (100). HRMS (EI): m/z calcd for C12H13OI: 300.0011; found: 300.0019.

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Preparation of ( E )-3-Phenyl-6-chloro-1,3-hexadiene (13c); Typical Procedure Under a nitrogen-atmosphere protection, 1-phenyl-1-cyclopropylallene (3a, 0.3 mmol) and NaCl (0.6 mmol) were dissolved in AcOH (1 mL). The mixture was stirred at 80 °C for 4 h. Then, the solvent was evaporated under vacuum and residue was separated by preparation TLC (eluent: PE) to give 13c in 75% yield. The other 6-halo-1,3-hexadienes could be prepared in the similar way.
Selected Spectroscopic Data of 13c IR (film): 3057, 3024, 2959, 1492, 1444, 990, 919, 767, 702 cm-1. 1H NMR (400 MHz, CDCl3): δ = 7.24-7.34 (m, 5 H), 6.77-6.82 (m, 1 H), 5.56 (t, J = 7.2 Hz, 1 H), 5.32 (d, J = 11.2 Hz, 1 H), 5.13 (d, J = 17.2 Hz, 1 H), 3.61 (t, J = 7.2 Hz, 2 H), 2.76-2.81 (m, 2 H). 13C NMR (100 MHz, CDCl3): δ = 31.4, 43.9, 118.9, 127.2, 128.0, 128.7, 129.4, 132.7, 140.9, 142.4. MS (EI, 70 eV): m/z (%) = 192 (32) [M+], 143 (80), 128 (100). HRMS (EI): m/z calcd for C12H13Cl: 192.0706; found: 192.0712.

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Spectroscopic Data of Compound 14a
E-Isomer: 1H NMR (400 MHz, CDCl3): δ = 7.13-7.39 (m, 5 H), 6.83-6.90 (m, 1 H), 5.59 (t, J = 7.2 Hz, 1 H), 5.28 (d, J =
11.2 Hz, 1 H), 5.10 (d, J = 17.2 Hz, 1 H), 3.50-3.59 (m, 4 H), 2.59-2.65 (m, 2 H), 1.24 (t, J = 7.2 Hz, 3 H).
Z-Isomer: 1H NMR (400 MHz, CDCl3): δ = 7.13-7.39 (m, 5 H), 6.54-6.61 (m, 1 H), 5.77 (t, J = 7.6 Hz, 1 H), 5.01 (d, J = 10.8 Hz, 1 H), 4.70 (d, J = 17.2 Hz, 1 H), 3.36-3.45 (m, 4 H), 2.21-2.26 (m, 2 H), 1.16 (t, J = 7.2 Hz, 3 H).
Mixture of Z- and E-isomers: IR (film): 2974, 2863, 1491, 1443, 1377, 1112, 911, 768, 703 cm-1. MS (EI, 70 eV): m/z (%) = 202 (10) [M+], 201 (17), 156 (96), 129 (100). HRMS (EI): m/z calcd for C14H18O: 202.1358; found: 202.1356.