Molecules 1998, 3, M66

(Z)-2-Bromo-5-phenyl-2-pentene

Martin J. Stoermer* and John T. Pinhey

Division of Organic Chemistry, School of Chemistry F11, The University of Sydney, N.S.W 2006, Australia.
* Current address: Victorian College of Pharmacy, Monash University (Parkville Campus), 381 Royal Parade, Parkville, Victoria 3052, Australia. Phone: +61 3 990 39000, Fax: +61 3 99039582, e-mail: [email protected], http://synapse.vcp.monash.edu.au/martin/

Received: 27 February 1998 / Published: 6 March 1998

The general part of the experimental section [1] has been presented elsewhere. 2,3-Dibromo-2-methyl-5-phenyl-2-pentanoic acid (1.95 g, 5.6 mmol) was refluxed with potassium carbonate (1.93 g, 14.0 mmol) in acetone (50 ml) for 3 hours. The solvent was removed by distillation and the residue was partitioned between ether (100 ml) and water (100 ml). The ether extract was washed with brine (50 ml), dried (Na2SO4), filtered and evaporated under reduced pressure. The crude product was Kugelrohr distilled to yield (Z)-2-bromo-5-phenyl-2-pentene (1.10 g, 88%) as a colourless oil.

B.p. 91°/0.8 mmHg

UV (ethanol) 260 (259), 255 (378) nm.

IR (CDCl3) 3063, 3027(s), 2919(s), 2857, 1644, 1603, 1496(s), 1453, 1427, 1367, 1283, 1167, 1096, 1031, 746, 698 cm-1.

1H-NMR (400 MHz, CDCl3) 2.25 (3H, dt, J 1.4, 1.3 Hz, CH3), 2.45 (2H, m, CH2), 2.69 (2H, bt, J 7.9 Hz, Ph-CH2), 5.62 (1H, tq, J 6.9, 1.4 Hz, =CH), 7.14-7.31 (5H, m, ArH). Stereochemistry confirmed by n.O.e. difference spectroscopy. Irradiation at 5.62 produced a 6% n.O.e. at 2.25 (also 3% at 2.45, 3% at 2.69). Irradiation at 2.25 produced an 2% n.O.e. at 5.62.

13C-NMR (15 MHz, CDCl3) 28.70 (CH3), 33.11, 34.54 (CH2), 123.0 (quat, C2), 125.9 (ArCH), 127.9 (=CH), 128.0 (2xArCH), 141.4 (quat, C1'.

EI-MS 226(M++2, 7%), 224(M+, 7), 146(37), 145(72), 135(26), 133(27), 92(56), 91(100), 77(21), 65(52), 63(22).

Acknowledgment: The authors gratefully acknowledge financial support from the Australian Research Council and The University of Sydney.

References and Notes

1. Moloney, M.G.; Pinhey, J.T.; Stoermer, M.J. "Vinyl Cation Formation by Decomposition of Vinyl-lead Triacetates. The reactions of Vinylmercury and Vinyltin Compounds with Lead Tetraacetate." J. Chem. Soc. Perkin Trans. 1 1990, 10, 2645.

Sample Availability: No sample available.

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