(Z)-1-Bromo-2-methyl-4-phenyl-1-butene

Molecules 1998, 3, M57

(Z)-1-Bromo-2-methyl-4-phenyl-1-butene

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(S,R),3(R,S)-2,3-Dibromo-3-methyl-5-phenyl-2-pentanoic acid (4.18 g, 12 mmol) was refluxed with potassium carbonate (4.13 g, 30 mmol) in acetone (100 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 (40 ml), dried (Na₂SO₄), filtered and evaporated under reduced pressure. The crude product was purified by flash chromatography (light petroleum) and then Kugelrohr distilled to yield (Z)-1-bromo-2-methyl-4-phenyl-1-butene (1.445 g, 54%) as a colourless oil.

B.p. 95°/0.7 mmHg

UV (ethanol) 271 (259) nm.

IR (CDCl₃) 3027, 2938, 1630, 1496(s), 1031, 719 cm^-1.

¹H-NMR (400 MHz, CDCl₃) 1.77 (3H, d, J 1.6 Hz, CH₃), 2.52 (2H, m, CH₂), 2.74 (2H, m, CH₂), 5.90 (1H, m, =CH), 7.14-7.33 (5H, m, ArH). Stereochemistry confirmed by n.O.e. difference spectroscopy. Irradiation at 1.77 produced a 2% n.O.e. at 5.90. Irradiation at 5.90 produced an 3% n.O.e. at 1.77.

¹³C-NMR (15 MHz, CDCl₃) 22.27 (CH₃), 33.11, 34.30 (CH₂), 101.4 (=CH), 126.0, 128.4, 128.4 (ArCH), 140.9 (quat, C1' or C2), 141.4 (quat, C1' or C2).

EI-MS 226(M⁺+2, 6%), 224(M⁺, 10), 146(12), 145(87), 129(11), 92(13), 91(100).

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.