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Synlett 2007(18): 2919-2921  
DOI: 10.1055/s-2007-991094
LETTER
© Georg Thieme Verlag Stuttgart · New York

Reaction of 1-Cyclopropylallenes with Phenylselenyl Bromide: A Highly Efficient and Stereoselective Method for the Preparation of 2-Phenylselenyl-6-bromo-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
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, P. R. of China
Fax: +86(571)88807077; e-Mail: huangx@mail.hz.zj.cn;
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Publication History

Received 6 July 2007
Publication Date:
12 October 2007 (online)

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Abstract

Reaction of 1-cyclopropylallenes with phenylselenyl bromide, which provided a highly efficient and stereoselective method for the preparation of 2-phenylselenyl-6-bromo-1,3-hexadienes, was investigated.

Key words

cyclopropyl - allene - selenium - 1,3-hexadiene - ionic ­reaction

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Preparation of 2-Phenylselenyl-3-phenyl-6-bromo-1,3-hexadiene (9a); Typical Procedure: 1-Phenyl-1-cyclopropylallene (3a; 0.33 mmol) was first dissolved in CH2Cl2 (1 mL) and the reaction was kept at 0 °C under ice-bath cooling. Under a nitrogen atmosphere protection, a solution of phenylselenyl bromide (0.3 mmol) in CH2Cl2 (6 mL) was slowly added. The reaction proceeded very rapidly and the color of phenylselenyl bromide disappeared immediately. The reaction liquid was stirred for an extra 1 min. Then, the solvent was evaporated under vacuum and the residue was separated by preparation TLC (eluent: PE) to give 9a in 78% yield. The other 2-phenylselenyl-6-bromo-1,3-hexadienes could be prepared in the similar way. Selected Data of 9a: IR (film): 3056, 3024, 1597, 1440, 1126, 882, 762, 740, 694 cm-1. 1H NMR (400 MHz, CDCl3): δ = 7.29-7.55 (m, 10 H), 5.88 (t, J = 6.8 Hz, 1 H), 5.63 (s, 1 H), 5.53 (s, 1 H), 3.32 (t, J = 7.2 Hz, 2 H), 2.78-2.83 (m, 2 H). 13C NMR (100 MHz, CDCl3): δ = 32.2, 33.0, 118.2, 126.6, 126.9, 127.6, 127.9, 128.2, 128.6, 129.0, 136.6, 138.7, 139.8, 142.9. MS (EI, 70 eV): m/z (%) = 392 (26) [M+], 236 (22), 155 (100). HRMS (EI): m/z calcd for C18H17SeBr: 391.9679; found: 391.9675.

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Spectral Data of Compound 11: IR (film): 2973, 2924, 1441, 1068, 1025, 740, 699 cm-1. 1H NMR (400 MHz, CDCl3): δ = 7.28-7.59 (m, 10 H), 6.01 (s, 1 H), 5.09 (s, 1 H), 3.67-3.79 (m, 2 H), 1.54-1.57 (m, 1 H), 1.35 (t, J = 6.8 Hz, 3 H), 0.43-0.55 (m, 2 H), 0.14-0.24 (m, 2 H). 13C NMR (100 MHz, CDCl3): δ = 0.7, 3.5, 15.7, 16.6, 58.4, 85.7, 115.1, 127.2, 127.3, 127.8, 128.2, 129.2, 129.3, 136.7, 140.0, 152.1. MS (EI, 70 eV): m/z (%) = 358 (5) [M+], 317 (26), 105 (100). HRMS (EI): m/z calcd for C20H22OSe: 358.0836; found: 358.0844.